8.2 Parts Developed by Wombat

Wombat Inc. is an ISV specializing in the development of applications for enterprises to use to administer benefits plans, such as medical and dental insurance plans. One Wombat application is a Web-based self-service Benefits Enrollment application. Employees of an enterprise use the application to make selections from multiple medical and dental plans offered to them by their employer.

Wombat's goal is to develop a single, generic Benefits Enrollment application and sell it to many customer enterprises. The Benefits Enrollment application is not an isolated application: It uses data provided by other applications or databases that exist in the customers' operational environment. This presents a challenge for Wombat: Every customer is likely to have a different implementation of the application or data with which the Benefits Enrollment application needs to integrate. For example, the enrollment application needs access to a database that contains information about employees, as well as access to the payroll system so that it can update benefits-related paycheck deductions. In addition, the enrollment application needs to have access to the plan-specific information provided by the insurance companies.

8.2.1 Overview of the Wombat Parts

Wombat develops the Web applications and enterprise beans, which are illustrated in Figure 8.3.

Figure 8.3. Web Applications and Enterprise Beans Developed by Wombat

Each of the following applications and enterprise beans is detailed throughout this section:

• EnrollmentWeb A Web application that implements the presentation logic for the benefits enrollment process. A customer's employees use EnrollmentWeb to enroll into the offered medical and dental plans.

• BenefitsAdminWeb A Web application that implements the presentation logic for business processes used by the customer's benefits administration department to configure and customize the medical and dental plans offered to the employees.

• EnrollmentEJB A stateful session bean that implements the benefits enrollment business process.

• EmployeeEJB An entity bean with CMP that encapsulates access to a customer's employee information so that it can accommodate the different representations of employee databases at different customer sites. CMP allows deployment binding with the customer's employee database. CMP also allows customers to implement their own database access code by writing a BMP entity bean that subclasses the CMP entity bean class.

• SelectionEJB A CMP entity bean that encapsulates the benefits selections chosen by each employee.

• PlanEJB A CMP entity bean that stores information about medical and dental plans and provides operations to search through plans.

• DoctorEJB A CMP entity bean that stores information about physicians and dentists and provides operations to search for doctors, based on specified criteria.

The enterprise beans developed by Wombat store information in BenefitsDatabase. Wombat designed the BenefitsDatabase schema, and at deployment the customer creates the database at the customer site. Wombat also allows the customer to choose a different schema as a deployment option.

The following describe in greater detail the parts developed by Wombat.

8.2.2 EnrollmentEJB Session Bean

EnrollmentEJB is a stateful session bean that implements the benefits enrollment business process. EnrollmentEJB's home and component interfaces are the same as in the example in Chapter 4, Working with Session Beans. However, although an IT developer at Star Enterprise defined the interfaces in that chapter, Wombat defined the home and component interfaces shown in this chapter's alternative approach. Code Example 8.1 shows the EnrollmentEJB's home interface definition:

Code Example 8.1 The EnrollmentHome Home Interface Defined by Wombat

 package com.wombat.benefits; import javax.ejb.*; import java.rmi.RemoteException; public interface EnrollmentHome extends EJBHome {    Enrollment create(int emplnum) throws RemoteException,    CreateException, EnrollmentException; } 

Code Example 8.2 shows the definition of the EnrollmentEJB's remote component interface:

Code Example 8.2 The Enrollment Remote Interface Defined by Wombat

    package com.wombat.benefits;    import javax.ejb.*;    import java.rmi.RemoteException;    public interface Enrollment extends EJBObject {       EmployeeInfo getEmployeeInfo()              throws RemoteException, EnrollmentException;       Options getCoverageOptions()              throws RemoteException, EnrollmentException;       void setCoverageOption(int choice)              throws RemoteException, EnrollmentException;       Options getMedicalOptions()              throws RemoteException, EnrollmentException;       void setMedicalOption(int choice)              throws RemoteException, EnrollmentException;       Options getDentalOptions()              throws RemoteException, EnrollmentException;       void setDentalOption(int choice)              throws RemoteException, EnrollmentException;       boolean isSmoker()              throws RemoteException, EnrollmentException;       void setSmoker(boolean status)              throws RemoteException, EnrollmentException;       Summary getSummary()              throws RemoteException, EnrollmentException;       void commitSelections()              throws RemoteException, EnrollmentException;    } 

The Enrollment and EnrollmentHome interfaces presented in this chapter are similar to those presented in Chapter 4. However, the interfaces presented here are implemented as remote interfaces, extending javax.ejb.EJBObject and javax.ejb.EJBHome, respectively. (The interfaces in Chapter 4 extended javax.ejb.EJBLocalObject and javax.ejb.EJBLocalHome.)

Wombat's developers consciously decided to make these interfaces remote instead of local when they designed the EnrollmentEJB entity bean. Wombat chose to use remote interfaces because they provide a location-independent client view. As a result, Wombat's customers, such as Star Enterprise, can deploy the EnrollmentEJB in a server other than the EnrollmentWeb application, thus allowing more flexible deployment choices. Moreover, the Benefits Enrollment application can be accessed by "rich client" applications and other enterprise applications, regardless of their location on the network. Such deployment and client access flexibility was critical for Wombat to achieve its goal of selling its benefits application to as many customers as possible.

However, the use of remote interfaces introduces new issues that need to be reflected in the design of the interfaces themselves:

• Remote access is expensive. Remote calls require more resources and use more overhead: They may traverse a network, they require client-side and server-side software to provide the distributed object invocation infrastructures, and they require arguments to be "deep copied" even when the client is in the same Java virtual machine. Hence, the cost of a remote call may be a hundred to a thousand times more than the cost of a local call.

  Accordingly, the Enrollment remote interface must be designed to avoid a large number of fine-grained calls from the client and instead use a small number of large- or coarse-grained calls. Hence, the Enrollment interface defines the getEmployeeInfo method, which returns all employee information to the client in one call, using the serializable value class EmployeeInfo. Similarly, the getSummary method returns all benefits summary information in one method call, using the serializable value class Summary.

• Remote access can lead to errors that are not encountered in local calls. Because remote calls make requests on another computer over the network, any number of reasons can cause the remote call to fail, including network problems, resource/memory limits on the target computer, software errors, and so forth. The client must always be prepared to receive such exceptions and handle them if necessary. (For example, a Web component might handle an error by sending a meaningful error page to the browser.) To help identify these remote errors, the methods of the Enrollment and EnrollmentHome interface throw java.rmi.RemoteException as required for all remote interfaces.

• State cannot be shared directly. Because remote calls involve copying all arguments and return values, both the bean and the client code cannot assume that they have a reference to the actual Java object used by the other side. Thus, the bean and the client never share any state directly; they can have only copies of each other's state.

• Remote references behave slightly differently from local references. In particular, casting a remote reference to a derived type requires the use of the javax.rmi.PortableRemoteObject.narrow operation. Thus, the EnrollmentEJB's client the EnrollmentWeb application must use this narrow operation to cast EJBHome reference objects that are obtained through JNDI lookup to the EnrollmentHome interface.

EnrollmentBean Implementation Class

The implementation of the EnrollmentBean session bean class is similar to the implementation illustrated in Chapter 4. However, there are some key differences, as follows:

• EnrollmentEJB in Chapter 4 uses command beans to access the employee's database. EnrollmentEJB in this chapter uses the EmployeeEJB entity bean to encapsulate access to the employee information. Because the EmployeeEJB entity bean is implemented with CMP, the deployer can bind the EmployeeEJB bean with the customer's employee database in a standard way.

• EnrollmentEJB in Chapter 4 uses command beans to access the benefits selections in BenefitsDatabase. EnrollmentEJB in this chapter uses the SelectionEJB entity bean to encapsulate the access to the employees' current selections. In addition, because Wombat provides a CMP version of the SelectionEJB entity bean the SelectionBean class a customer can customize the format in which the selections are stored or even store them in a nonrelational database.

• EnrollmentEJB uses the PlanEJB entity bean to access the medical and dental plans offered to the employees. PlanEJB allows the medical and dental plan information to be dynamically updated by Wombat's customers through the BenefitsAdmin Web application. The EnrollmentEJB implementation in Chapter 4 relied on Java classes that hard-coded the plan information. This hard-coding prevented the dynamic update of plan information after the benefits application was deployed.

• EnrollmentEJB uses a command bean to update an employee's payroll with the deduction based on his or her benefits choices. Because each customer of Wombat may have a different payroll system, Wombat defines only a command bean interface: DeductionUpdateBean. The actual implementation class for this bean is provided by Wombat's customer, such as Star Enterprise. The class name is then set in the EnrollmentEJB's environment by the deployer.

Code Example A.4 on page 382 illustrates the source code for the EnrollmentBean session bean class as it has been implemented for the example in this chapter. (Note that this implementation of EnrollmentBean differs from that in Chapter 4.)

Using Entity Bean Client-View Interfaces

The EnrollmentBean class illustrates how applications typically use the entity bean client-view interfaces. Recall that EnrollmentEJB is a client of the EmployeeEJB, SelectionEJB, and PlanEJB entity beans.

For example, let's look at how EnrollmentEJB uses the SelectionEJB entity bean. In the ejbCreate method, note that EnrollmentEJB uses the findByPrimaryKey method to look up an existing Selection object, as follows:

 selection = selectionHome.findByPrimaryKey(                       new Integer(employeeNumber)); 

After obtaining an object reference to the Selection object, EnrollmentEJB invokes a business method on the object. Here, it invokes the Selection object's getCopy method to read the current benefits selection values:

 selCopy = selection.getCopy(); 

In the commitSelections method, EnrollmentEJB either creates a new Selection object by invoking the create method on the SelectionHome interface, or it updates the existing Selection object by invoking the updateFromCopy business method on the Selection object, as follows:

 if (recordDoesNotExist) {     selection = selectionHome.create(selCopy);     recordDoesNotExist = false; } else {     selection.updateFromCopy(selCopy); } 

Note that EnrollmentEJB does not need to remove Selection objects. If it did, however, it would use the following code fragment:

 selection.remove(); 

Alternatively, EnrollmentEJB could use the SelectionHome interface to remove a Selection object identified by its primary key:

 selectionHome.remove(new Integer(employeeNumber)); 

EnrollmentEJB uses the other entity beans in much the same manner.

8.2.3 EmployeeEJB Entity Bean

EmployeeEJB is an entity bean that uses the container-managed persistence model defined in the EJB 2.0 and 2.1 specifications. EmployeeEJB provides an object-oriented view of the employee data used by the Benefits Enrollment application. The main role of this entity bean is to allow the integration between the benefits application and the customer's employee data.

Because Wombat does not impose rules about how a customer stores the information about its employees, customers must have the means to integrate the application with their employee data. Wombat uses the CMP mechanism to allow the deployer to bind EmployeeEJB with an existing employee database.

Wombat's customers have two choices while deploying the EmployeeEJB bean:

• Using an object-relational mapping tool A customer can use an object-relational mapping tool to create a mapping from the Employee bean's abstract persistence schema that is, its CMP and CMR fields to the physical database schema in the preexisting employee database. In this case, the object-relational mapping tool generates the database access code.

• Using bean-managed persistence Alternatively, a customer could develop a BMP entity bean that subclasses the CMP EmployeeBean class. The customer then would write the database access code.

However, Wombat designs the Employee and EmployeeHome interfaces to meet the needs of the Benefits Enrollment application.

EmployeeEJB's Primary Key

Wombat uses the employee number as the primary key for the EmployeeEJB entity bean. Its type is the class java.lang.Integer. Note that it would be an error if the employee number were the Java primitive int, because the EJB specification requires that the primary key type for an entity bean be a Java class. Furthermore, this requirement implies that primitive types that are not serializable Java classes cannot be used directly for the primary key type.

Employee Local Interface

Because EmployeeEJB is accessed only from EnrollmentEJB and both are packaged in the same benefits application, EmployeeEJB defines only local interfaces. Code Example 8.3 shows the Employee local interface definition:

Code Example 8.3 The Employee Local Interface

 public interface Employee extends EJBLocalObject {    Integer getEmployeeNumber();    String getFirstName();    String getLastName();    Date getBirthDate(); } 

The Employee local interface defines methods that allow its client, the EnrollmentEJB bean, to access each employee's employee number, first and last names, and date of birth. Note that these methods are fine-grained: One method returns one piece of data rather than a single method returning an aggregation of all the pieces of data. Typically, the EnrollmentEJB bean would make several calls on the Employee interface to eventually retrieve all fields for an employee. Making multiple method calls, with each method call retrieving individual data fields, is effective because local EJB calls are very efficient in typical application server implementations.

Note that the Employee local interface does not define any methods that allow clients to modify EmployeeBean's state. This implies that the EmployeeEJB is a read-only bean. Most EJB containers are designed to efficiently manage such read-only beans.

The EmployeeHome Home Interface

Code Example 8.4 shows the EmployeeHome interface definition:

Code Example 8.4 The EmployeeHome Home Interface

 package com.wombat.benefits; import javax.ejb.*; public interface EmployeeHome extends EJBLocalHome {    // find methods    Employee findByPrimaryKey(Integer employeeNumber)           throws FinderException; } 

The EmployeeHome interface defines only the mandatory findByPrimaryKey method. It defines no create methods, because the Wombat Benefits Enrollment application does not need to create new employee objects in the customer databases.

The EmployeeBean Entity Bean Class

The EmployeeBean class illustrates how simple it is to develop an entity bean with CMP. Note that the entity bean contains no database operations. Section 8.3.1, The Employee Database and Deployment of EmployeeEJB, on page 286 explains how the deployer binds the container-managed fields with the columns of the preexisting EmployeeDatabase at Star Enterprise. Note also that the entity bean class contains no implementations of any find methods, although the home interface defines the findByPrimaryKey method. Because EmployeeEJB is an entity bean with CMP, the EJB container supplies the implementations of its find methods. Code Example 8.5 shows the source code of the EmployeeBean entity bean class:

Code Example 8.5 EmployeeBean Class Implementation

 package com.wombat.benefits; import javax.ejb.*; import java.util.Date; import com.wombat.AbstractEntityBean; public abstract class EmployeeBean extends AbstractEntityBean {    // Container-managed fields    public abstract Integer getEmployeeNumber(); // primary key field    public abstract void setEmployeeNumber(Integer n);    public abstract String getFirstName();    public abstract void setFirstName(String s);    public abstract String getLastName();    public abstract void setLastName(String s);    public abstract Date getBirthDate();    public abstract void setBirthDate(Date d); } 

The EmployeeBean class, essentially a pure data object that models a business entity, is one of the simplest examples of a CMP entity bean class. The EmployeeBean class contains only CMP fields, and these fields define the persistent state of the employee. The class has no create methods and no relationships with other beans.

The AbstractEntityBean class, which EmployeeBean imports, is a utility class developed by Wombat. This class contains default implementations of the javax.ejb.EntityBean methods. The class was developed to make it easy to implement entity bean classes that do not need to use methods in the EntityBean interface.

There are some important things to note about the implementation of an entity bean class, particularly concerning container-managed fields and the primary key. The employeeNumber, lastName, firstName, and birthDate fields are container-managed fields of the entity bean class and are declared as such in the EmployeeEJB's deployment descriptor. These fields are also virtual fields. Virtual fields are represented in the EmployeeBean class as pairs of get and set methods. The method names are derived from the CMP field names and follow the JavaBeans design pattern. The EJB specification mandates that the get and set methods be defined as public, even though a client program never directly accesses them. The container uses these methods to synchronize the content of the fields they represent with the information in the database. These methods must be public so that the container can move the data between the fields and the database to keep them synchronized.

8.2.4 SelectionEJB Entity Bean

The SelectionEJB entity bean stores an employee's benefits selections, using CMP. By using CMP, the bean can be developed with no database dependences: Wombat's customers can use any database of their choice, including nonrelational databases, to store the persistent state of the bean.

SelectionEJB's Primary Key

Wombat uses the employee number as the primary key for the SelectionEJB entity bean. The type of the primary key is java.lang.Integer.

Selection Local Interface

Wombat designed SelectionEJB's local interface to meet the needs of its client, the EnrollmentEJB session bean. The local interface uses the SelectionCopy value object to pass the information between the SelectionEJB entity bean and its client, through its getCopy and updateFromCopy business methods. Code Example 8.6 shows the Selection interface definition:

Code Example 8.6 The Selection Interface Definition

 package com.wombat.benefits; import javax.ejb.*; public interface Selection extends EJBLocalObject {    SelectionCopy getCopy()       throws SelectionException;    void updateFromCopy(SelectionCopy copy)       throws SelectionException; } 

The Selection interface defines methods that its clients use to obtain and update an employee's benefits selection. In the Wombat benefits application, the EnrollmentEJB session bean is the client of SelectionEJB. EnrollmentEJB uses the Selection interface's getCopy method to obtain a transient copy of the employee's benefits selection. The SelectionCopy object stores this data in memory while the employee selects the benefits options. When the employee commits those selections, EnrollmentEJB uses the updateFromCopy method to write the contents of the SelectionCopy object to the persistent fields of the SelectionEJB entity bean, thus saving the selection information to the database. Code Example 8.7 shows the code for the SelectionCopy class:

Code Example 8.7 The SelectionCopy Value Object

 package com.wombat.benefits; import com.wombat.plan.Plan; public class SelectionCopy {    private Employee employee;    private int coverage;    private Plan medicalPlan;    private Plan dentalPlan;    private boolean smokerStatus;    public Employee getEmployee() { return employee; }    public int getCoverage() { return coverage; }    public Plan getMedicalPlan() { return medicalPlan; }    public Plan getDentalPlan() { return dentalPlan; }    public boolean isSmoker() { return smokerStatus; }    public void setEmployee(Employee v) { employee = v; }    public void setCoverage(int v) { coverage = v; }    public void setMedicalPlan(Plan v) { medicalPlan = v; }    public void setDentalPlan(Plan v) { dentalPlan = v; }    public void setSmoker(boolean v) { smokerStatus = v; } } 

You might wonder why an entity bean with a local client view uses a value object such as SelectionCopy. Value objects are a useful way to avoid fine-grained data access, something you might want to consider when access is across a distributed network. A bean can also use a value object to temporarily hold information that the bean collects in the course of its processing but that the bean may not ultimately save to a database.

SelectionHome Home Interface

Code Example 8.8 shows the definition for the SelectionHome home interface:

Code Example 8.8 The SelectionHome Home Interface

 package com.wombat.benefits; import javax.ejb.*; public interface SelectionHome extends EJBLocalHome { Selection create(SelectionCopy copy)       throws CreateException; Selection findByPrimaryKey(Integer emplNumber)       throws FinderException; } 

Note how the SelectionHome interface uses the SelectionCopy object as the argument of the create method. A client uses this method to create an entity object that stores an employee's benefits selections from a copy of the information passed by the client.

The SelectionHome interface also defines the mandatory findByPrimaryKey method. This method finds the Selection object by using the primary key, which is the employee number.

SelectionBean Entity Bean Class

Code Example 8.9 shows the abstract schema portion of the SelectionBean entity bean implementation:

Code Example 8.9 Abstract Schema for the SelectionBean Entity Bean Class

 public abstract class SelectionBean extends AbstractEntityBean {     // Container-managed persistence fields     public abstract Integer getEmployeeNumber(); // primary key field     public abstract void setEmployeeNumber(Integer n);     public abstract int getCoverage();     public abstract void setCoverage(int c);     public abstract boolean getSmokerStatus();     public abstract void setSmokerStatus(boolean s);     // Container-managed relationship fields     public abstract Plan getMedicalPlan();     public abstract void setMedicalPlan(Plan p);     public abstract Plan getDentalPlan();     public abstract void setDentalPlan(Plan p);     ...... } 

The abstract schema defines the bean's persistent state. (For the complete listing of the source code for the SelectionBean entity bean class implementation, see Code Example A.5 on page 392.)

The SelectionBean class has three CMP fields: coverage, smokerStatus, and employeeNumber. These CMP fields are declared by using pairs of set and get methods.

The SelectionBean class also has two container-managed relationships, represented as CMR fields: medicalPlan and dentalPlan. Like CMP fields, CMR fields are declared by using pairs of set and get methods. The argument and return value types for CMR fields are the local interfaces of the related beans. The medicalPlan and dentalPlan CMR fields provide references to different instances of the PlanEJB bean. In the deployment descriptor, these fields are declared to be many-to-one relationships because many instances of a SelectionEJB bean are associated with a single medical plan or dental plan bean instance. Also in the deployment descriptor, the medicalPlan and dentalPlan relationships are declared to be unidirectional, implying that no corresponding CMR field in the PlanEJB bean refers to a SelectionEJB instance.

Using CMR fields to manage references to other enterprise beans has two benefits:

1. It simplifies the development of the SelectionBean methods because they can work directly with object references rather than having to convert object references to primary keys.

2. It avoids hard-coding into the SelectionBean class the database representation of the relationships to the other entity beans. As a result, a deployer is free to choose how to represent the relationships in the underlying database schema.

Note that although it could have done so, the SelectionEJB class does not define a container-managed relationship with the EmployeeEJB bean. At first glance, it seems natural to define this relationship as container managed because there is a SelectionEJB instance for each EmployeeEJB instance. In addition, SelectionEJB and EmployeeEJB use the same primary key: the employee number.

However, Wombat's developers want to give their customers the flexibility to store instances of these two beans in separate databases and not be compelled to store them together in the same database. To allow customers this flexibility, Wombat's developers chose not to define the relationship between the SelectionEJB and EmployeeEJB beans as a container-managed relationship. Generally, when two beans are related using a container-managed relationship, they must be stored in the same database. Keeping related beans in the same database allows it to manage the relationship more efficiently; for example, a relational database might use a foreign key to model the relationship. Because Wombat knows that its customers are likely to have two separate databases an employee database managed by the human resources department and a benefits database managed by the benefits department the developers decided to keep the EmployeeEJB and SelectionEJB beans independent. By doing so, Wombat customers can store these bean instances in separate databases or together in one database. (Although CMP allows multiple databases to be used, EJB products that permit multiple databases are still evolving.)

Let's take a closer look at the implementation of the SelectionBean methods. The SelectionBeanCMP class implements three sets of methods:

1. The business methods defined in the Selection local interface

2. The ejbCreate and ejbPostCreate methods that correspond to the create method defined in the SelectionHome interface

3. The container callbacks defined in the EntityBean interface

The SelectionBean class follows the EJB specification rules and does not implement the ejbFind methods corresponding to the find methods defined in the SelectionHome interface.

Business Methods

The business methods getCopy and updateFromCopy read and write the container-managed fields. The container loads and stores the contents of the container-managed fields according to the rules defined in the EJB specification. The business methods can assume that the contents of the container-managed fields are always up-to-date, even if other transactions change the underlying selection record in the database.

The code for the business methods demonstrates how an enterprise might implement simple business rules. For example, the updateCoverage helper method checks that the value of the coverage field is an allowed value, whereas the updateMedicalPlan helper method optionally checks that the value of medicalPlan is indeed a medical plan rather than a dental plan.

The ejbCreate and ejbPostCreate Methods

The ejbCreate method sets values into SelectionBean's container-managed persistence fields from the values passed to it in the method parameter. In particular, the method sets the primary key by using the setEmployeeNumber method. Setting the primary key establishes the identity of the bean instance. After the ejbCreate method completes, the container extracts the values of the container-managed fields and creates a representation of the selection object in the database. Note that ejbCreate returns a null value even though the return value type is declared to be the primary key type. According to the EJB 2.1 specification, the container ignores the value returned from an ejbCreate method of an entity bean with container-managed persistence. However, the EJB 2.1 specification requires that the type of the ejbCreate method be the primary key type to allow a subclass of the SelectionBean class to be an entity bean with bean-managed persistence.

The ejbPostCreate method sets values of the CMR fields medicalPlan and dentalPlan. The EJB 2.1 specification does not allow CMR fields to be set in the ejbCreate method. Thus, CMR fields should be set either in the ejbPostCreate method or in a business method.

Life-Cycle Methods

The SelectionBean class inherits most of the default EntityBean life-cycle method implementations from the AbstractEntityBean class, providing an implementation only of the setEntityContext method. Entity bean classes typically use the setEntityContext method to query their environment and customize their business logic as part of their initialization. SelectionBean's setEntityContext method calls the readEnvironment helper method, which accesses the environment entry available with the key java:comp/env/checkPlanType to do the lookup operation in Code Example 8.10:

Code Example 8.10 SelectionBean's readEnvironment Method

 private void readEnvironment() {    try {       Context ictx = new InitialContext();       Boolean val = (Boolean)ictx.lookup(              "java:comp/env/checkPlanType");       checkPlanType = val.booleanValue();       employeeHome = (EmployeeHome)ictx.lookup(              "java:comp/env/ejb/EmployeeEJB");    } catch (Exception ex) {       throw new EJBException(ex);    } } 

The value of the entry parameterizes the business logic of the bean. If the value of the environment entry is true, the setMedicalPlan and setDentalPlan methods check that the value of the plan to be set is indeed of the expected plan type. If the value is false, they do not perform these checks. The application assembler sets the value of the environment entry at application assembly. Wombat made the plan type checks optional to allow the application assembler to improve performance by omitting them if the clients of SelectionEJB are known to set the plan types correctly. We added this somewhat artificial optional check to illustrate how to use the enterprise bean environment entries to parameterize the business logic at application assembly or deployment.

8.2.5 PlanEJB Entity Bean

The PlanEJB entity bean represents medical and dental plan information that is obtained from insurance providers. This entity bean has been implemented to use container-managed persistence. PlanEJB is accessed from the EnrollmentEJB bean, as well as from the benefits administration Web application. This entity bean allows client applications to obtain details of medical and dental plans, as well as to run queries on all existing plan objects. The bean also has a facility, which uses the timer service, to e-mail to administrators on a daily basis statistics of employee enrollment in each plan.

The primary key for the PlanEJB entity bean is a unique plan identifier that is a java.lang.String type. The benefits department assigns unique identifiers to plan instances.

Plan Local Interface

Code Example 8.11 shows the methods defined by the Plan local interface:

Code Example 8.11 The Plan Local Interface

 public interface Plan extends EJBLocalObject {     // values of planType CMP field    public final int MEDICAL_PLAN = 1;    public final int DENTAL_PLAN = 2;    int getPlanType() throws PlanException;    String getPlanId();    String getPlanName();    double getAgeFactor();    void setAgeFactor(double a);    double getCoverageFactor();    void setCoverageFactor(double c);    double getSmokerCost();    void setSmokerCost(double cost);    double getCost(int coverage, int age, boolean smokerStatus)       throws PlanException;    void addDoctor(Doctor doctor) throws PlanException;    boolean removeDoctor(Doctor doctor) throws PlanException;    Collection getAllDoctors() throws PlanException;    Collection getDoctorsByName(Doctor template)       throws PlanException;    Collection getDoctorsBySpecialty(String specialty)       throws PlanException; } 

The Plan local interface methods perform the following operations:

• The getPlanType method returns an integer value that indicates the type of benefits plan. The value is equal to Plan.MEDICAL_PLAN if the plan is a medical plan and to Plan.DENTAL_PLAN if the plan is a dental plan.

• The getPlanId method returns the unique identifier the primary key of the plan.

• The getPlanName method returns the name of the medical or dental plan.

• The getCost method returns the monthly premium charged by the plan provider. The premium is determined by the benefits enrollee's coverage category, age, and smoker status.

• The set/getSmokerCost, set/getAgeFactor, set/getCoverageFactor methods retrieve and update the smoker cost, age factor, and coverage factor of the plan.

• The addDoctor method adds a doctor to the plan.

• The removeDoctor method removes a doctor from the plan.

• The getAllDoctors method returns a collection of Doctor objects that participate in the plan. The Doctor class is described later.

• The getDoctorsByName method returns a collection of participating doctors whose names match the information in the template supplied as a method argument.

• The getDoctorsBySpecialty method returns all the doctors of a given specialty.

PlanHome Home Interface

Code Example 8.12 shows the definition of the PlanHome home interface:

Code Example 8.12 The PlanHome Home Interface

 public interface PlanHome extends EJBLocalHome {    // create methods    Plan create(String planId, String planName, int planType,       double coverageFactor, double ageFactor, double smokerCost)       throws CreateException;    // find methods    Plan findByPrimaryKey(String planID) throws FinderException;    Collection findMedicalPlans() throws FinderException;    Collection findDentalPlans() throws FinderException;    Collection findByDoctor(String firstName, String lastName)       throws FinderException;    // home business methods    void updateSmokerCosts(double cost) throws FinderException;    String[] getMedicalPlanNames() throws FinderException;    String[] getDentalPlanNames() throws FinderException; } 

The PlanHome interface defines one create method. The benefits administration Web application uses this create method to add a new medical or dental plan to the benefit options provided to employees. The PlanHome interface also defines the find methods used by the benefits application. The find methods that can potentially return more than one object return these objects as a Java Collection and are also implemented as EJB QL queries in the deployment descriptor for PlanEJB.

• The findByPrimaryKey method returns the Plan object for a given plan identifier. The plan identifier is the primary key that uniquely identifies the plan.

• The findMedicalPlans method returns as a Collection all the medical plans configured in this home interface. Each object in the returned Collection implements the Plan interface. The EJB QL query for this method is provided in PlanEJB's deployment descriptor. The query is as follows:

   SELECT DISTINCT OBJECT(p) FROM PlanBean p WHERE p.planType = 1 

• The findDentalPlans method returns all the dental plans configured in this home interface. Each object in the returned Collection implements the Plan interface. The EJB QL query for this method is as follows:

   SELECT DISTINCT OBJECT(p) FROM PlanBean p WHERE p.planType = 2 

• The findByDoctor method returns configured in this home interface all the plans that include a specified doctor in their doctors list. This find method is implemented with an EJB QL query that navigates from the PlanEJB bean to the DoctorEJB bean. The EJB QL query for the findByDoctor method is as follows:

   SELECT DISTINCT OBJECT(p) FROM PlanBean p, IN(p.doctors) d    WHERE d.firstName = ?1 AND d.lastName = ?2 

In this query, the FROM clause declares an identification variable d whose values are DoctorEJB instances belonging to PlanEJB's one-to-many CMR field doctors. The WHERE clause restricts the set of doctors to those having the requested first and last names. The SELECT clause thus returns PlanEJB instances containing doctors satisfying the condition in the WHERE clause.

In addition, the PlanHome interface defines the home business methods, whose operations are not restricted to a particular bean instance. Instead, home business methods are used to implement aggregate operations or queries on an entire set of benefits plans. The home business methods are

• updateSmokerCost updates the smoker cost for all plans

• getMedicalPlanNames returns an array of medical plan names

• getDentalPlanNames returns an array of dental plan names

PlanBean Implementation Class

The PlanBean class is an abstract class that follows the requirements for an entity bean class with container-managed persistence. Code Example A.6 on page 396 lists the complete source code for the PlanBean entity bean class implementation.

Code Example 8.13 shows just the abstract schema for PlanBean. The abstract schema defines the bean's persistent state:

Code Example 8.13 Abstract Schema for the PlanBean Entity Bean Class

 public abstract class PlanBean extends AbstractEntityBean implements        TimedObject {    // Container-managed persistence fields    public abstract String getPlanId();    public abstract void setPlanId(String s);    public abstract String getPlanName();    public abstract void setPlanName(String s);    public abstract int getPlanType();    public abstract void setPlanType(int s);    public abstract double getCoverageFactor();    public abstract void setCoverageFactor(double s);    public abstract double getAgeFactor();    public abstract void setAgeFactor(double s);    public abstract double getSmokerCost();    public abstract void setSmokerCost(double s);    // container-managed relationships (CMR fields)    public abstract Collection getDoctors();    public abstract void setDoctors(Collection doctors);       ... } 

PlanBean has six CMP fields that represent the persistent state of PlanEJB. These fields, declared in the deployment descriptor, are planId, planName, planType, coverageFactor, ageFactor, and smokerCost. In the PlanBean class, the CMP fields are represented as pairs of get and set methods.

PlanBean also has one CMR field, doctors, which represents a container-managed relationship to the DoctorEJB bean. This relationship is a many-to-many relationship: Each plan is associated with multiple doctors, and each doctor may participate in several plans. As a result, the setDoctors and getDoctors methods have argument and return types that are java.util.Collection types. The doctor/plan relationship is also declared as a bidirectional relationship. In a bidirectional relationship between two entity beans, each bean has a CMR field referencing the other bean. For the doctor/plan bidirectional relationship, PlanEJB declares a CMR field doctors that references DoctorEJB, which in turn has a CMR field referencing back to PlanEJB. Section 8.2.6, DoctorEJB Entity Bean, on page 279 discusses this in more detail.

Remember from the previous section that SelectionEJB declared two one-to-one relationships to PlanEJB. However, those were declared as unidirectional relationships from SelectionEJB to PlanEJB. Hence the PlanBean class does not declare a CMR field referencing back to SelectionEJB.

PlanBean has five types of methods:

• Business methods PlanBean implements the business methods declared in the local interface.

• Home business methods PlanBean implements the home business methods from the home interface.

• Select methods PlanBean includes ejbSelect methods that are used to declare and invoke EJB QL queries from other methods of PlanBean.

• ejbTimeout method PlanBean includes the ejbTimeout method, which is called when the bean's timer expires.

• Life-cycle methods PlanBean includes the life-cycle methods ejbCreate and ejbPostCreate.

Business Methods

The business methods implement the operations declared in the local interface. The business methods getCost, addDoctor, removeDoctor, getAllDoctors, getDoctorsByName, and getDoctorsBySpecialty are called from EnrollmentEJB and from the benefits administration Web application.

The addDoctor and removeDoctor methods operate on the Collection returned from the getDoctor method. The code for these methods is shown in Code Example 8.14:

Code Example 8.14 Implementation of the addDoctor and removeDoctor Methods

 public void addDoctor(Doctor doctor) throws PlanException {    Collection doctors = getDoctors();    doctors.add(doctor); } public boolean removeDoctor(Doctor doctor) throws PlanException {    Collection doctors = getDoctors();    return doctors.remove(doctor); } 

The addDoctor method first obtains the doctors managed Collection, a live Collection; any changes made to the Collection cause the bean's persistent state to be changed. The addDoctor method simply adds the new DoctorEJB instance represented by the doctor argument to the managed Collection. Note that it is not necessary to add the PlanEJB instance to the corresponding plans Collection held by the DoctorEJB instance; the container automatically sets the other side of a bidirectional relationship when the first side is set.

The removeDoctor method obtains the doctors managed Collection and removes the doctor argument from the Collection. Again, it is not necessary to remove this PlanEJB instance from the corresponding Collection held by the DoctorEJB instance, because the container automatically does this for you.

The getAllDoctors method returns a Collection of all DoctorEJB instances related to a PlanEJB instance that is, all the doctors participating in a particular insurance plan. Code Example 8.15 shows the code for getAllDoctors:

Code Example 8.15 Implementation of the getAllDoctors Method

 public Collection getAllDoctors() throws FinderException {         Collection doctors = getDoctors();         Collection doctorsCopy = new ArrayList(doctors);    return doctorsCopy; } 

You might wonder why the Plan local interface does not expose the getDoctors method. You might also wonder why the getAllDoctors method returns a new Collection rather than returning the doctors managed collection directly. The answer lies in the behavior of managed collections and transactions.

Managed collections are live collections whose state needs to be saved to the database when the transaction to which they are involved commits. Thus, managed collections are valid only in the transaction in which they were obtained. If a client of PlanEJB does not have an active transaction, the container starts a new transaction before calling the getAllDoctors method and commits the transaction immediately after the getAllDoctors method ends. In this situation, if it were given the doctors managed collection directly, the client would not be able to access the collection, as the transaction would have already committed. Operations on the collection at this point, such as obtaining an iterator, are out of the context of a transaction and would throw IllegalStateException.

To avoid such problems, Wombat's developers instead return a copy of the managed collection doctors to the client. The doctorsCopy collection is an unmanaged collection. A client can access an unmanaged collection at any time, without having to be within the context of a transaction, and changes to the unmanaged collection are not saved to the persistent state of the PlanEJB instance.

The getDoctorsByName method returns all doctors with the given first name and last name. To do this, the method invokes the ejbSelectDoctorsByName method. Similarly, the getDoctorsBySpecialty method returns all doctors with the given specialty. The method invokes the ejbSelectDoctorsBySpecialty method to accomplish this.

Home Business Methods

The home business methods implement the methods declared in the home interface. These methods execute on an instance that is not associated with a specific identity. As a result, they can perform only the logic that does not operate on a specific bean instance. They cannot access the identity of the bean instance that is executing the method through the getPrimaryKey, getEJBObject, and getEJBLocalObject methods on the EntityContext interface. Usually, the home business methods implement aggregate operations or queries on an entire set of beans.

The ejbHomeUpdateSmokerCosts method implements the updateSmokerCosts method declared in the PlanHome home interface (Code Example 8.16):

Code Example 8.16 Implementation of the ejbHomeUpdateSmokerCosts Method

 public void ejbHomeUpdateSmokerCosts(double cost)            throws FinderException {    Collection allPlans = ejbSelectAllPlans();    Iterator itr = allPlans.iterator();    while ( itr.hasNext() ) {       Plan plan = (Plan)itr.next();       plan.setSmokerCost(cost);    } } 

This method uses the cost argument value to set one smoker cost for all plans. The method first obtains a Collection of all plans, using the ejbSelectAllPlans method, and then iterates over all the plans, setting the cost for each plan.

Two other home business methods the ejbHomeGetMedicalPlanNames and the ejbHomeGetDentalPlanNames methods are shown in Code Example 8.17:

Code Example 8.17 Implementation of Home Business Methods

 // get all medical plan names public String[] ejbHomeGetMedicalPlanNames()            throws FinderException {    Collection names = ejbSelectPlanNames(Plan.MEDICAL_PLAN);    return (String[])names.toArray(new String[names.size()]); } // get all dental plan names public String[] ejbHomeGetDentalPlanNames()            throws FinderException {    Collection names = ejbSelectPlanNames(Plan.DENTAL_PLAN);    return (String[])names.toArray(new String[names.size()]); } 

Depending on the application's needs, it can be more efficient to use a home business method than a find method. For example, a client can use the home business method ejbHomeGetMedicalPlanNames to retrieve an array of all medical plan names in one operation. The home business method returns a Collection or array of fields of a bean. This is often more efficient than using a find method, which can return only a Collection of enterprise bean local or remote interfaces. If the client instead uses the PlanHome findMedicalPlans method, the client gets back a Collection of enterprise bean interfaces. The client then has to iterate over the Collection and extract each plan name one at a time.

Select Methods

The ejbSelect methods declare EJB QL queries that are used internally by a bean class. The queries themselves are defined in the deployment descriptor. The PlanBean class declares five ejbSelect methods, shown in Code Example 8.18:

Code Example 8.18 The ejbSelect Method Declarations in the PlanBean Class

 public abstract Collection ejbSelectAllPlans()        throws FinderException; public abstract Collection ejbSelectPlanNames(int planType)        throws FinderException; public abstract Collection ejbSelectDoctorsByName        (String planId, String fname, String lname)        throws FinderException; public abstract Collection ejbSelectDoctorsBySpecialty        (String planId, String specialty) throws FinderException; public abstract long ejbSelectNumEmployeesInPlan(Plan plan)        throws FinderException; 

The ejbSelectAllPlans method returns all PlanEJB instances. The EJB QL query for this select method does not have a WHERE clause:

 SELECT DISTINCT OBJECT(p) FROM PlanBean p 

The ejbSelectPlanNames method returns the names of all plans of a given plan type. The EJB QL query for this method is

 SELECT p.planName FROM PlanBean p WHERE p.planType = ?1 

The ejbSelectDoctorsByName method returns for a given plan all participating doctors whose first and last names match the specified name parameters. The EJB QL query for this method is

 SELECT DISTINCT OBJECT(d) FROM PlanBean p, IN(p.doctors) d WHERE p.planId = ?1 AND d.firstName = ?2 AND d.lastName = ?3 

The ejbSelectDoctorsBySpecialty method returns for a given plan all participating doctors with a particular specialty. The returned Collection of doctors is ordered by each doctor's last name. The EJB QL query for this method is

 SELECT DISTINCT OBJECT(d) FROM PlanBean p, IN(p.doctors) d WHERE p.planId = ?1 AND d.specialty = ?2 ORDER BY d.lastName 

The ejbSelectNumEmployeesInPlan method returns the number of employees who have chosen a given plan. The EJB QL query for this method is

 SELECT COUNT(s) FROM SelectionBean s WHERE s.medicalPlan = ?1 OR s.dentalPlan = ?1 

Life-Cycle Methods

There are two life-cycle methods in the PlanEJB bean. The ejbCreate method initializes the container-managed persistence fields of PlanBean, using arguments that the client passes to the method. The ejbPostCreate initializes the timer that provides daily statistics to plan administrators. Code Example 8.19 shows the code used to create a timer:

Code Example 8.19 Creating a Timer

 TimerService timerService = entityContext.getTimerService(); timerService.createTimer(midnight, interval, null); 

To create a timer, the entity bean's identity its primary key needs to be available, because a Timer object is associated with the instance of the entity bean that created it. Hence, the timer can be created in the ejbPostCreate method but not in the ejbCreate method.

The TimerService.createTimer method used in Code Example 8.19 takes three parameters, two of which have values:

• midnight A java.util.Date object whose value corresponds to midnight on the day the bean instance was created

• interval A long type whose value represents the number of milliseconds in one day

Together, these parameters indicate that the timer will first expire at midnight on the first day and then at midnight every day thereafter. Let's now look at what happens when the timer expires.

ejbTimeout Method

The PlanBean class has an ejbTimeout method. This method is defined in the TimedObject interface, which the PlanBean class implements. This method is called by the EJB container when the timer expires at midnight every day. The code in the ejbTimeout method gets statistics about the PlanBean instances the number of employees who have subscribed to each plan and sends them to the administrators. It obtains these numbers by calling the select method ejbSelectNumEmployeesInPlan. Code Example 8.20 shows the code for the ejbTimeout method:

Code Example 8.20 The ejbTimeout Method

 public void ejbTimeout(javax.ejb.Timer timer) {    try {        // get the number of employees who have subscribed to        // this plan        long numEmployeesInThisPlan = ejbSelectNumEmployeesInPlan(               (Plan)entityContext.getEJBLocalObject());        String emailText = "Plan " + getPlanName() + " has "               + numEmployeesInThisPlan +" employees.";        // email the text        InitialContext ic = new InitialContext();        Session session = (Session)ic.lookup(               "java:comp/env/MailSession");        String toAddress = (String)ic.lookup(               "java:comp/env/toAddress");        String fromAddress = (String)ic.lookup(               "java:comp/env/fromAddress");        Message msg = new MimeMessage(session);        msg.setFrom(new InternetAddress(fromAddress));        msg.addRecipient(Message.RecipientType.TO,               new InternetAddress(toAddress));        msg.setSubject("Statistics");        msg.setText(emailText);        Transport.send(msg);     } catch ( Exception ex ) {        throw new EJBException(ex);     } } 

The ejbTimeout method obtains the statistics by calling a select method and composing a text message string to be sent by e-mail to the plan administrator. It sends the e-mail message using the JavaMail™ APIs. Because these APIs are a standard part of the J2EE platform, they are available in all application servers that support J2EE. Typically, application servers provide an implementation of these APIs, which can send messages using SMTP (Simple Mail Transfer Protocol). The ejbTimeout method first looks up a JavaMail Session object using JNDI and then uses that object to create a JavaMail MimeMessage, which represents an e-mail message with MIME (Multipurpose Internet Mail Extensions) attachments. Next, the method sets in the MimeMessage object the sender, receiver, subject, and content text of the e-mail message. Finally, it sends the message using the default mail transport, usually SMTP. For more information about JavaMail, refer to http://java.sun.com/products/javamail.

8.2.6 DoctorEJB Entity Bean

The DoctorEJB entity bean, like PlanEJB, manages its state and relationships by using container-managed persistence. This entity bean essentially functions as a data object that stores information about physicians and dentists.

DoctorEJB Primary Key

The DoctorEJB primary key sets this bean apart from other entity beans in the benefits application. The DoctorEJB entity bean has a composite primary key consisting of two CMP fields firstName and lastName and also uses a special primary key class, DoctorPkey, created by Wombat's developers. Code Example 8.21 shows the code for DoctorPkey:

Code Example 8.21 The DoctorPkey Primary Key Class

 public class DoctorPkey implements java.io.Serializable {    public String firstName;    public String lastName;    public boolean equals(Object other) {       if ( other instanceof DoctorPkey ) {          DoctorPkey pkey = (DoctorPkey)other;          return (firstName.equals(pkey.firstName) &&                 lastName.equals (pkey.lastName));       }       return false;     }    public int hashCode() {       return (firstName.hashCode() | lastName.hashCode());    } } 

Because it uses a composite primary key, DoctorEJB needs to declare these two CMP fields as public Java fields in its DoctorPkey primary key class. The names of the fields in the primary key class need to be a subset of the names of the CMP fields in the bean class. In addition, the DoctorPkey class needs to provide implementations of the equals and hashCode methods, which allow the EJB container to use DoctorPkey as a key into the container's internal data structures, such as hash tables.

Doctor Local Interface

The DoctorEJB entity bean is accessed from EnrollmentEJB and from the benefits administration Web application, both of which are packaged in the same benefits application. This copackaging of the bean with its clients ensures that only local access is required. As a result, the DoctorEJB entity bean defines only local interfaces. Code Example 8.22 shows the Doctor local interface definition:

Code Example 8.22 The Doctor Local Interface

 public interface Doctor extends EJBLocalObject {    String getLastName();    String getFirstName();    String getSpecialty();    String[] getHospitals();    int getPracticeSince(); } 

The Doctor local interface defines methods that allow clients to view its persistent fields but does not define any other business methods. Note that the local interface does not allow clients to modify any information in the bean. Because the DoctorEJB bean is a read-only bean, the EJB container can manage it more efficiently.

DoctorHome Home Interface

The DoctorHome interface defines a create method that allows the benefits administration Web application to create DoctorEJB instances when doctors are added to a plan. This interface also defines the mandatory findByPrimaryKey method, which takes the DoctorPkey primary key class as its argument. Code Example 8.23 shows the DoctorHome interface definition:

Code Example 8.23 The DoctorHome Home Interface

 public interface DoctorHome extends EJBLocalHome {    Doctor create(String firstName, String lastName,           String specialty, String hospital, int practiceSince)           throws CreateException;    Doctor findByPrimaryKey(DoctorPkey pkey) throws FinderException; } 

DoctorBean Entity Bean Class

Code Example 8.24 shows the source code of the DoctorBean entity bean class:

Code Example 8.24 The DoctorBean Class Implementation

 public abstract class DoctorBean extends AbstractEntityBean {    public abstract String getFirstName();    public abstract void setFirstName(String v);    public abstract String getLastName();    public abstract void setLastName(String v);    public abstract String getSpecialty();    public abstract void setSpecialty(String v);    public abstract String[] getHospitals();    public abstract void setHospitals(String[] v);    public abstract int getPracticeSince();    public abstract void setPracticeSince(int v);    // CMR fields    public abstract Collection getPlans();    public abstract void setPlans(Collection c);        // Life-cycle methods    public DoctorPkey ejbCreate(String firstName, String lastName,           String specialty, String[] hospitals, int practiceSince)           throws CreateException {       setFirstName(firstName);       setLastName(lastName);       setSpecialty(specialty);       setHospitals(hospitals);       setPracticeSince(practiceSince);       return null;    }    public void ejbPostCreate(String firstName, String lastName,           String specialty, String[] hospitals, int practiceSince)           throws CreateException {} } 

The DoctorBean class is a simple entity bean class that uses container-managed persistence: CMP fields define the persistent state of each DoctorEJB instance. The CMP fields, declared in the deployment descriptor, are firstName, lastName, specialty, hospitals, and practiceSince. Each field is represented as a pair of get and set methods in the DoctorBean class.

The DoctorBean class also defines a CMR field for its relationship with the PlanEJB entity bean. This CMR field, plans, is represented by the methods setPlans and getPlans. (Recall that the description of the PlanBean class discussed this relationship. See the section PlanBean Implementation Class on page 270.) The relationship between DoctorBean and PlanBean is bidirectional; hence, both classes have a CMR field to refer to each other. Because this relationship is many-to-many, the get and set methods in DoctorBean operate on a Collection of Plan objects.

The DoctorBean class defines an ejbCreate method that initializes the values of the CMP fields, including the two primary key fields firstName and lastName. The class also has an empty ejbPostCreate method.

8.2.7 EnrollmentWeb Web Application

The EnrollmentWeb Web application is a set of JSPs. See the example in Chapter 4, Working with Session Beans, for a description of the EnrollmentWeb Web application.

8.2.8 BenefitsAdminWeb Web Application

The BenefitsAdminWeb Web application is a set of JSPs used by the customer's benefits administration department to administer its benefits plans. The BenefitsAdminWeb Web application does the following work:

• Uses the find methods on the PlanHome interface to find the deployed plan beans from the respective insurance companies

• Allows the plan administrator to use the business methods on the Plan interface to query the doctors associated with a plan

• Uses the business methods on the Plan interface to allow doctors to be added and removed from a plan

• Allows the plan administrator to add or remove plans from the set of configured plans

Code Example 8.25 shows the skeleton code for adding an insurance plan to the set of configured plans. (Note that the example shows only those parts relevant to using the PlanEJB entity bean.)

Code Example 8.25 Code for Adding a Plan

 ... // Create an entity object for the new plan. InitialContext initialContext = new InitialContext(); PlanHome planHome = (PlanHome)initialContext.lookup    ("java:comp/env/ejb/Plan"); Plan plan = planHome.create    (planId, planName, planType, coverageFactor, ageFactor,    smokerCost); ... 

After the create method completes, the created plan entity object is saved to the database and becomes available to the Benefits Enrollment application. A plan administrator wanting to remove a plan from the list of configured plans invokes the remove method on the PlanHome interface and passes it the plan identifier, planId, which is PlanEJB's primary key:

 ... planHome.remove(planId); ... 

8.2.9 The Benefits Database

BenefitsDatabase stores the persistent state of the three entity beans SelectionEJB, PlanEJB, and DoctorEJB. All three beans use container-managed persistence, so Wombat does not need to specify a schema for this database. The schema is created by Wombat's customer, which in this case is Star Enterprise, using the object-relational mapping tools provided by the J2EE application server product on which these CMP entity beans are deployed.

8.2.10 Packaging of Parts

This section describes how Wombat packages its benefits application for distribution to customers.

benefits.ear File

Wombat packages the benefits application as a single J2EE enterprise application archive file, which it names benefits.ear. (An .ear file is an enterprise application archive resource file.) Figure 8.4 depicts the contents of the benefits.ear file.

Figure 8.4. Contents of the benefits.ear File

The benefits.ear file contains

• The enrollment.war file with the EnrollmentWeb Web application. (A .war file is a Web archive file.) The EnrollmentWeb Web application consists of several JSPs.

• The benefits_admin.war file with the BenefitsAdminWeb Web application. The BenefitsAdminWeb Web application consists of several JSPs.

• The benefits_ejb.jar file. This is the ejb-jar file that contains the enterprise beans developed by Wombat.

benefits_ejb.jar File

The benefits_ejb.jar file contains the enterprise beans developed by Wombat. Code Example 8.26 lists the classes that the file contains:

Code Example 8.26 Contents of the benefits_ejb.jar File

 com/wombat/AbstractEntityBean.class com/wombat/benefits/DeductionUpdateBean.class com/wombat/benefits/Employee.class com/wombat/benefits/EmployeeBean.class com/wombat/benefits/EmployeeHome.class com/wombat/benefits/EmployeeInfo.class com/wombat/benefits/Enrollment.class com/wombat/benefits/EnrollmentBean.class com/wombat/benefits/EnrollmentException.class com/wombat/benefits/EnrollmentHome.class com/wombat/benefits/Options.class com/wombat/benefits/Selection.class com/wombat/benefits/SelectionBean.class com/wombat/benefits/SelectionCopy.class com/wombat/benefits/SelectionException.class com/wombat/benefits/SelectionHome.class com/wombat/benefits/Summary.class com/wombat/plan/Doctor.class com/wombat/plan/DoctorBean.class com/wombat/plan/DoctorHome.class com/wombat/plan/DoctorPkey.class com/wombat/plan/Plan.class com/wombat/plan/PlanBean.class com/wombat/plan/PlanException.class com/wombat/plan/PlanHome.class