Package javassist.tools.reflect

Class Metaobject

java.lang.Object
javassist.tools.reflect.Metaobject
All Implemented Interfaces:
Serializable
public class Metaobject extends Object implements Serializable
A runtime metaobject.

A Metaobject is created for every object at the base level. A different reflective object is associated with a different metaobject.

The metaobject intercepts method calls on the reflective object at the base-level. To change the behavior of the method calls, a subclass of Metaobject should be defined.

To obtain a metaobject, calls _getMetaobject() on a reflective object. For example, 

 Metaobject m = ((Metalevel)reflectiveObject)._getMetaobject();
See Also:

  • Constructor Details

    • Metaobject

      public Metaobject(Object self, Object[] args)
      Constructs a Metaobject. The metaobject is constructed before the constructor is called on the base-level object.
      Parameters:
      self - the object that this metaobject is associated with.
      args - the parameters passed to the constructor of self.

  • Method Details

    • getClassMetaobject

      public final ClassMetaobject getClassMetaobject()
      Obtains the class metaobject associated with this metaobject.
      See Also:

    • getObject

      public final Object getObject()
      Obtains the object controlled by this metaobject.

    • setObject

      public final void setObject(Object self)
      Changes the object controlled by this metaobject.
      Parameters:
      self - the object

    • getMethodName

      public final String getMethodName(int identifier)
      Returns the name of the method specified by identifier.

    • getParameterTypes

      public final Class<?>[] getParameterTypes(int identifier)
      Returns an array of Class objects representing the formal parameter types of the method specified by identifier.

    • getReturnType

      public final Class<?> getReturnType(int identifier)
      Returns a Class objects representing the return type of the method specified by identifier.

    • trapFieldRead

      public Object trapFieldRead(String name)
      Is invoked when public fields of the base-level class are read and the runtime system intercepts it. This method simply returns the value of the field.

      Every subclass of this class should redefine this method.

    • trapFieldWrite

      public void trapFieldWrite(String name, Object value)
      Is invoked when public fields of the base-level class are modified and the runtime system intercepts it. This method simply sets the field to the given value.

      Every subclass of this class should redefine this method.

    • trapMethodcall

      public Object trapMethodcall(int identifier, Object[] args) throws Throwable
      Is invoked when base-level method invocation is intercepted. This method simply executes the intercepted method invocation with the original parameters and returns the resulting value.

      Every subclass of this class should redefine this method.

      Note: this method is not invoked if the base-level method is invoked by a constructor in the super class. For example, 

       abstract class A {
   abstract void initialize();
   A() {
       initialize();    // not intercepted
   }
 }

 class B extends A {
   void initialize() { System.out.println("initialize()"); }
   B() {
       super();
       initialize();    // intercepted
   }
 }

      if an instance of B is created, the invocation of initialize() in B is intercepted only once. The first invocation by the constructor in A is not intercepted. This is because the link between a base-level object and a metaobject is not created until the execution of a constructor of the super class finishes.

      Throws:
      Throwable