Understanding BeanUtils

In many ways, BeanUtils can be considered a metadata wrapper that makes it as easy to work with a JavaBean as a Map. The properties are the keys, and property values can be set by simply setting the property as a value. For example:

 myUser.setName("Bob"); 

...can instead be written:

 BeanUtils.setProperty(myUser, "name", "Bob"); 

Similarly, an array of the properties available for myUser can be simply retrieved:

 DynaProperty[] properties = WrapDynaClass. createDynaClass(myUser.class).getDynaProperties(); 

This offers two key advantages: it allows you to decouple components of your application, and it allows you to build frameworks and tools to take advantage of the JavaBeans framework.

As shown in Figure 7-1, the BeanUtils package draws a distinction between a DynaClass, which describes a class, and a DynaBean, which describes a particular object instance. This notion can actually be extended a bita DynaClass can be used as a wrapper for a JDBC ResultSet, for example (in which the properties correspond to the returned results), and individual records can be returned as DynaBeans.

Figure 7-1. BeanUtils class diagram.

One aspect of the BeanUtils package worth calling out is the notion of a Converter. This provides a generic way to retrieve and set values across a suite of properties using String values, regardless of the type of the property. For example, you may want to set a property with a type of int using a String such as "2". The Converter package takes care of these details for you.

The following types are supported by built-in converters:

BigDecimal

BigInteger

Boolean

Byte

Character

Class

Double

File

Float

Integer

Long

Short

SqlDate

SqlTime

SqlTimestamp

String

URL

Abstract array

Boolean array

Byte array

Character array

Double array

Float array

Integer array

Long array

Short array

String array