Class Metaobject
- java.lang.Object
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- javassist.tools.reflect.Metaobject
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- All Implemented Interfaces:
java.io.Serializable
public class Metaobject extends java.lang.Object implements java.io.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:
ClassMetaobject
,Metalevel
, Serialized Form
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Constructor Summary
Constructors Constructor Description Metaobject(java.lang.Object self, java.lang.Object[] args)
Constructs aMetaobject
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description ClassMetaobject
getClassMetaobject()
Obtains the class metaobject associated with this metaobject.java.lang.String
getMethodName(int identifier)
Returns the name of the method specified byidentifier
.java.lang.Object
getObject()
Obtains the object controlled by this metaobject.java.lang.Class<?>[]
getParameterTypes(int identifier)
Returns an array ofClass
objects representing the formal parameter types of the method specified byidentifier
.java.lang.Class<?>
getReturnType(int identifier)
Returns aClass
objects representing the return type of the method specified byidentifier
.void
setObject(java.lang.Object self)
Changes the object controlled by this metaobject.java.lang.Object
trapFieldRead(java.lang.String name)
Is invoked when public fields of the base-level class are read and the runtime system intercepts it.void
trapFieldWrite(java.lang.String name, java.lang.Object value)
Is invoked when public fields of the base-level class are modified and the runtime system intercepts it.java.lang.Object
trapMethodcall(int identifier, java.lang.Object[] args)
Is invoked when base-level method invocation is intercepted.
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Constructor Detail
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Metaobject
public Metaobject(java.lang.Object self, java.lang.Object[] args)
Constructs aMetaobject
. 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 ofself
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Method Detail
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getClassMetaobject
public final ClassMetaobject getClassMetaobject()
Obtains the class metaobject associated with this metaobject.- See Also:
ClassMetaobject
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getObject
public final java.lang.Object getObject()
Obtains the object controlled by this metaobject.
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setObject
public final void setObject(java.lang.Object self)
Changes the object controlled by this metaobject.- Parameters:
self
- the object
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getMethodName
public final java.lang.String getMethodName(int identifier)
Returns the name of the method specified byidentifier
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getParameterTypes
public final java.lang.Class<?>[] getParameterTypes(int identifier)
Returns an array ofClass
objects representing the formal parameter types of the method specified byidentifier
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getReturnType
public final java.lang.Class<?> getReturnType(int identifier)
Returns aClass
objects representing the return type of the method specified byidentifier
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trapFieldRead
public java.lang.Object trapFieldRead(java.lang.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.
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trapFieldWrite
public void trapFieldWrite(java.lang.String name, java.lang.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.
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trapMethodcall
public java.lang.Object trapMethodcall(int identifier, java.lang.Object[] args) throws java.lang.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:
java.lang.Throwable
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