13.2 Portlets

We introduced the concept of a portlet in the previous section. Basically, a portlet is a reusable program that delivers information. This information can come from a variety of sources. A portlet works with and leverages the services provided by the OracleAS Portal runtime to integrate its information into the overall OracleAS Portal environment. The portlet is one of the key enablers for OracleAS Portal's display of information.

A portlet displays information that is collected from a source, known as a portlet provider . The portlet provider collects the information and then passes it to the portlet, which displays the information. This architecture, and the two types of portlet providers, are shown in Figure 13-3.

Figure 13-3. Portlet architecture and provider types

A portlet provider can provide information to many different portlets. Portlet providers can be organized into Provider Groups, which combine related providers. A Database Provider, described later, can be shared between multiple instances of OracleAS Portal.

Each portlet is registered in the Portlet Repository, which is a part of the overall OracleAS Infrastructure. When you build a page, you can select any of the portlets in the repository for inclusion in a region.

An individual instance of a portlet can be shared across multiple pages in a page group . By sharing a portlet, you both ensure a consistent view of the information the portlet is providing and reduce the resources required to retrieve the information and create the portlet for the end user .

13.2.1 Providers

Portal providers act as the link between a content source and an OracleAS Portal page via portlets. OracleAS Portal includes many portal providers and can create additional providers to run within the OracleAS Portal environment or to register external providers. There are two basic types of providers, Web Providers and Database Providers, described in the following sections.

13.2.1.1 Web Providers

A Web Provider collects information from someplace on the Web and delivers information to its portlets using SOAP over HTTP. Because it uses the common protocol of SOAP, a Web Provider can be written in virtually any language. A Web Provider runs in its own environment, while a Database Provider, written in PL/SQL, runs in the Oracle database that holds the Portal Repository.

The OracleAS Portal Development Kit (PDK), described later in this chapter, comes with a Java framework that makes it easier to create Web Providers in Java. This framework includes interfaces to use such Oracle Application Server features as OracleAS Single Sign-On.

13.2.1.2 Database Providers

Database Providers, as their name implies, retrieve information from an Oracle database and are written in PL/SQL. These Database Providers supply information for portlets based on PL/SQL or JSPs.

Database Providers run in the Oracle database that is also used for the OracleAS Portal Repository. You can access Database Providers running on other OracleAS Portal instances through a feature called the Federated Portal Adapter.

13.2.2 Using Prebuilt Portlets

Although the overall thrust of OracleAS Portal is now to provide a consolidated interface to many sources of information, earlier versions of OracleAS Portal put a lot of effort into making it easy to create your own portlets using a set of portlet wizards .

These wizards prompt you for information and then create PL/SQL packages to implement the portlet. The wizards are entirely HTML-based, so you can build portlets from any browser.

You can build a number of different types of portlets with OracleAS Portal wizards:

Form portlets

These portlets include simple forms, master detail sets of forms, and forms based on PL/SQL procedures.

Report portlets

These portlets can be built using the Query Wizard, which doesn't require knowledge of SQL or can be based on an SQL query. You can also create a Query-By-Example report, which provides a form interface for users to implement their own selection criteria. An item in a report can be used as a link to another portlet page with detailed information about the item.

Chart portlets

These portlets can include links from chart values to more detailed information.

Hierarchy portlets

These portlets display multiple levels of related information.

Frame driver portlets

These portlets create a page with two frames , with the content of one frame driving the display of information in the other frame.

URL page portlets

These portlets display the content of a URL.

Data component portlets

These portlets display data in a spreadsheet format.

Calendar portlets

These portlets include links to underlying information based on date.

Dynamic page portlets

These portlets display dynamically created HTML pages.

XML page portlets

These portlets are based on XML.

The most recent version of OracleAS Portal includes two new prebuilt portlets that give a broader range of functionality:

OmniPortlet

This portlet can access data from a variety of sources, including a database, an XML file, a comma-separated variable file, web pages, or Web Services. The OmniPortlet can display the information in a variety of ways. OmniPortlet provides some of the same functionality as some of the prebuilt portlets mentioned previously, such as reports , charts , and forms.

Web Clipping portlet

This portlet makes it easy for a developer to select a web page and have some or all of its content displayed in a portlet. With the Web Clipping portlet, any web page can be a data source.

These two new portlets are also Web Provider portlets, which means they can exist outside the Oracle database.

OracleAS Portal also includes wizards that help you build portlets that are meant to be part of a page, such as menus , links, and list-of-values portlets.

Once you have created a portlet, you can use the OracleAS Portal environment to edit the portlet and make changes to its look, feel, or functionality. For Database Provider portlets, Portal automatically stores each version of a portlet, and you can recall earlier versions if necessary.

The end result of building a prebuilt portlet with one of the development wizards is a PL/SQL package that is stored in the OracleAS Portal Repository and run when the portlet is called. The OracleAS Portal development environment includes an option to compile the PL/SQL package to ensure that any code you may have added to the package compiles without errors.

In addition to the prebuilt portlets that come with OracleAS Portal, you can download third-party portlets from the Portal Studio site; it's described in a later subsection.

The development wizards make building portlets fairly easy, and you can include a lot of functionality in these declaratively created portlets. You can even go so far as to include PL/SQL routines to run at various times during the processing of a page.

You can access any of the data values on a page, or session values for the page, in PL/SQL code.

Although you probably shouldn't think about creating mission-critical OLTP applications with portlets, the ease of creation makes them a viable option for helping users to interact with information in the database through a browser interface. Also, the Database Provider portlets require that the data they are accessing exist within the Portal Repository Database, which is frequently not the case. You can use OmniPortlet to access data outside the Portal Repository Database, because OmniPortlet is a Web Provider.

13.2.3 OracleAS Portal Development Kit

The wizard-driven interface that comes with OracleAS Portal is powerful and productive, but there may be times when you want to implement some type of functionality that is beyond the scope of these built-in wizards. For these occasions, the OracleAS Portal team has created the OracleAS Portal Development Kit.

The PDK contains all the information and APIs you need to create your own customized portlets, in either PL/SQL or Java. Using the PDK is significantly more complex than the simple creation of portlets with the built-in wizards, but it offers almost unlimited flexibility.

13.2.4 Java Portlets

Two new Java standards, Web Services for Remote Portlets (WSRP) and Java Specification Request 168 (JSR 168), provide the Java world with specifications for portlets to run in different portal environments.

OracleAS Portal comes with an Oracle JDeveloper Portlet Wizard, which helps you create a portlet out of Java code in Oracle JDeveloper. This wizard is an add-on for Oracle JDeveloper that allows you to create Java portlet code. This code can be run against any JSR 168-compliant portal, which includes OracleAS Portal. Portal Studio, described in the next section, has a section that lets you test a Java portlet to make sure it can properly interoperate with a JSR 168-compliant portal.

The Oracle JDeveloper Portlet Wizard can also create portlets that use the Oracle PDK, rather than JSR 168, as the basic API for the portlet. Regardless of which type of Java portlet you create, the portlet is run in the Java Portlet Container servlet.

13.2.5 Portal Studio

To encourage the creation and sharing of portlets and providers, Oracle Corporation provides the Portal Studio site (http://portalstudio.oracle.com). Portal Studio is intended to be a full-service support site, containing the latest versions of the PDK, a discussion area for developers, integration tools for other applications, and even a way to register and test your own portlets. Portal Studio includes third-party portlets and providers in its Portal Catalog. The OracleAS Portal development team and product managers are continually updating this site with new explanations , tutorials, and sample code.