Jakarta Commons Cookbook

3.9. Determining the Type of a Bean Property

Problem

You need to determine the type of a bean property.

Solution

Use PropertyUtils.getPropertyType( ) to determine the type of a bean property. This utility will return a Class object that represents the return type of the property’s getter method. The following example uses this method to obtain the return type for the author property on the Book bean:

import org.apache.commons.beanutils.PropertyUtils

Book book = new Book( );

Class type = PropertyUtils.getPropertyType( book, "author" );

System.out.println( "book.author type: " + type.getName( ) );

This example retrieves and displays the type of the author property on Book, which happens to be a Person object. The type of the property is returned and printed to the console:

book.author type: org.test.Person

Discussion

PropertyUtils.getPropertyType() also works for a complex bean property. Passing a nested, indexed, or mapped bean property to this utility will return the type of the last property specified. The following code retrieves the type of a nested, indexed property—chapters[0].name:

import org.apache.commons.beanutils.PropertyUtils;

Chapter chapter = new Chapter( );
chapter.setName( "Chapter 3 BeanUtils" );
chapter.setLength( new Integer(40) );

List chapters = new ArrayList( );
chapters.add( chapter );

Book book = new Book( );
book.setName( "Jakarta Commons Cookbook" );
book.setAuthor( "Dude" );
book.setChapters( chapters );

String property = "chapters[0].name";
               Class propertyType ...