Juixe Techknow

I recently had to work with the Jakarta BeanUtils project and found it really useful. I think of it as BeanUseful. The BeanUtils project allows you to easily manipulate a JavaBean object using the static methods from the PropertyUtils class. Here is a simple example of how to update a property value of a JavaBean. Imagine I have a simple Greeting JavaBean class with a single property message.

Greeting object = new Greeting();
object.setMessage("Hello");
// ...
String greeting = (String)PropertyUtils
   .getSimpleProperty(object, "message");
PropertyUtils.setSimpleProperty(
   object, "message", greeting+", World!");

Of course, object is an instance of a JavaBean with a property named message.

PropertyUtils can also access an indexed method. Here is how you define an indexed property for a JavaBean:

public Item getItem(int index);
public void setItem(int index, Item item);

And here is how you would access an index property using PropertyUtils:

int index = ...;
String name = "item[" + index + "]";
Item item = (Item)PropertyUtils
   .getIndexedProperty(object, name);

In similar fashion, you can access a property that is mapped. Here is an example of how you define a mapped property in a JavaBean:

public Object getValue(String key);
public void setValue(String key, Object item);

And here is how you would access a mapped property using PropertyUtils:

PropertyUtils.setMappedProperty(
   object, "value("+key+")", value);

The BeanUtils project and Java Reflection in general, is best used in a dynamic setting when you do not know the type of a bean at compile time; that is the strength of Java Reflection, which BeanUtils builds on.