InvocationHandler (Java Platform SE 8 )
Keywords: java.lang.reflect.InvocationHandler interface
Date: 2016-10-23

compact1, compact2, compact3
java.lang.reflect

## Interface InvocationHandler

- All Known Implementing Classes:
    CompositeDataInvocationHandler, EventHandler, MBeanServerInvocationHandler, RemoteObjectInvocationHandler

      public interface InvocationHandler

  `InvocationHandler` is the interface implemented by the invocation handler of a proxy instance.

  Each proxy instance has an associated invocation handler. When a method is invoked on a proxy instance, the method invocation is encoded and dispatched to the `invoke` method of its invocation handler.

  Since:
    1.3
  See Also:
    `Proxy`

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `Object` | `invoke(Object proxy, Method method, Object[] args)` Processes a method invocation on a proxy instance and returns the result.

- - ### Method Detail

    - #### invoke

          Object invoke(Object proxy,
                        Method method,
                        Object[] args)
                 throws Throwable

      Processes a method invocation on a proxy instance and returns the result. This method will be invoked on an invocation handler when a method is invoked on a proxy instance that it is associated with.
      Parameters:
        `proxy` - the proxy instance that the method was invoked on
        `method` - the `Method` instance corresponding to the interface method invoked on the proxy instance. The declaring class of the `Method` object will be the interface that the method was declared in, which may be a superinterface of the proxy interface that the proxy class inherits the method through.
        `args` - an array of objects containing the values of the arguments passed in the method invocation on the proxy instance, or `null` if interface method takes no arguments. Arguments of primitive types are wrapped in instances of the appropriate primitive wrapper class, such as `java.lang.Integer` or `java.lang.Boolean`.
      Returns:
        the value to return from the method invocation on the proxy instance. If the declared return type of the interface method is a primitive type, then the value returned by this method must be an instance of the corresponding primitive wrapper class; otherwise, it must be a type assignable to the declared return type. If the value returned by this method is `null` and the interface method's return type is primitive, then a `NullPointerException` will be thrown by the method invocation on the proxy instance. If the value returned by this method is otherwise not compatible with the interface method's declared return type as described above, a `ClassCastException` will be thrown by the method invocation on the proxy instance.
      Throws:
        `Throwable` - the exception to throw from the method invocation on the proxy instance. The exception's type must be assignable either to any of the exception types declared in the `throws` clause of the interface method or to the unchecked exception types `java.lang.RuntimeException` or `java.lang.Error`. If a checked exception is thrown by this method that is not assignable to any of the exception types declared in the `throws` clause of the interface method, then an `UndeclaredThrowableException` containing the exception that was thrown by this method will be thrown by the method invocation on the proxy instance.
      See Also:
        `UndeclaredThrowableException`

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