Learning Java

Hand-Coding with Beans

So far, we’ve seen how to create and use Beans within a Bean application builder environment. That is the primary role of a Java Bean in development. But Beans are not limited to being used by automated tools. There’s no reason we can’t use Beans in handwritten code. You might use a builder to assemble Beans for the user interface of your application and then load that serialized Bean collection in your own code. We’ll give an example of that in a moment.

Bean Instantiation and Type Management

Beans are an abstraction over simple Java classes. They add, by convention, features that are not part of the Java language. To enable these additional capabilities of JavaBeans we have to use some special tools that take the place of basic language operations. Specifically, when working with Beans, we need replacements for three basic Java operations: creating an object with new, checking the type of an object with the instanceof operator, and casting a type with a cast expression. In place of these, use the corresponding static methods of the java.beans.Beans class, shown in Table 19.1.

Table 19-1. Methods of the java.beans.Beans Class

Operator	Equivalent
New	Beans.instantiate(classloader, name)
Instanceof	Beans.isInstanceOf(object, class)
Explicit cast	Beans.getInstanceOf(object, class)

Beans.instantiate( ) is the new operation for Beans. It takes a class loader and the name of a Bean class or serialized Bean as arguments. Its advantage over ...