Question

Can anoyne recommend a good library that will let me easily read/write private member fields of a class? I was looking through apache commons, but couldnt see it. I must be getting blind ?

Edit: Asking questions on the border of legalities always give these questions of ‘why’? I am writing several javarebel plugins for hotswapping classes. Accessing private variables is only step 1, I might even have to replace implementations of some methods.

Answer 1

In most of the cases java reflection solves the problem:

Example:

public class Foo {      /**      * Gets the name Field.      *       * @return the name      */     public final String getName() {         return name;     }      /**      * Sets the name Field with the name input value.      *       * @param name the name to set      */     public final void setName(String name) {         this.name = name;     }      private String name;  } 

Now the Reflection Code:

import java.lang.reflect.Field; ....  Foo foo = new Foo(); foo.setName('old Name'); String fieldName = 'name'; Class class1 = Foo.class;  try {      System.out.println(foo.getName());      Field field = class1.getDeclaredField(fieldName);      field.setAccessible(true);      field.set(foo, 'My New Name');      System.out.println(foo.getName());  } catch (NoSuchFieldException e) {     System.out.println('FieldNotFound: ' + e); } catch (IllegalAccessException e) {     System.out.println('Ilegal Access: ' + e); } 

UPDATE:

It’s worth mentioning that this approach can be thwarted by a SecurityManager. – Dan Dyer