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InvocationHandler
public
interface
InvocationHandler
| java.lang.reflect.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.
Summary
Public methods
invoke
public abstract Object invoke (Object proxy,
Method method,
Object[] args)
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 |
Object: the proxy instance that the method was invoked on |
method |
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 |
Object: 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 |
|---|
Object |
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. |
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Last updated 2025-02-10 UTC.
[null,null,["Last updated 2025-02-10 UTC."],[],[],null,["# InvocationHandler\n\nAdded in [API level 1](/guide/topics/manifest/uses-sdk-element#ApiLevels) \n\nInvocationHandler\n=================\n\n\n`\npublic\n\n\ninterface\nInvocationHandler\n`\n\n\n`\n\n\n`\n\n|-------------------------------------|\n| java.lang.reflect.InvocationHandler |\n\n\u003cbr /\u003e\n\n*** ** * ** ***\n\n`InvocationHandler` is the interface implemented by\nthe *invocation handler* of a proxy instance.\n\nEach proxy instance has an associated invocation handler.\nWhen a method is invoked on a proxy instance, the method\ninvocation is encoded and dispatched to the `invoke`\nmethod of its invocation handler. \n**See also:**\n\n- [Proxy](/reference/java/lang/reflect/Proxy)\n\nSummary\n-------\n\n| ### Public methods ||\n|---------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| ` abstract `[Object](/reference/java/lang/Object) | ` `[invoke](/reference/java/lang/reflect/InvocationHandler#invoke(java.lang.Object,%20java.lang.reflect.Method,%20java.lang.Object[]))`(`[Object](/reference/java/lang/Object)` proxy, `[Method](/reference/java/lang/reflect/Method)` method, `[Object[]](/reference/java/lang/Object)` args) ` Processes a method invocation on a proxy instance and returns the result. |\n\nPublic methods\n--------------\n\n### invoke\n\nAdded in [API level 1](/guide/topics/manifest/uses-sdk-element#ApiLevels) \n\n```\npublic abstract Object invoke (Object proxy, \n Method method, \n Object[] args)\n```\n\nProcesses a method invocation on a proxy instance and returns\nthe result. This method will be invoked on an invocation handler\nwhen a method is invoked on a proxy instance that it is\nassociated with.\n\n\u003cbr /\u003e\n\n| Parameters ||\n|----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| `proxy` | `Object`: the proxy instance that the method was invoked on \u003cbr /\u003e |\n| `method` | `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. \u003cbr /\u003e |\n| `args` | `Object`: 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`. \u003cbr /\u003e |\n\n| Returns ||\n|---------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| [Object](/reference/java/lang/Object) | 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. \u003cbr /\u003e |\n\n| Throws ||\n|---------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| [Throwable](/reference/java/lang/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](/reference/java/lang/reflect/UndeclaredThrowableException) containing the exception that was thrown by this method will be thrown by the method invocation on the proxy instance. |\n\n**See also:**\n\n- [UndeclaredThrowableException](/reference/java/lang/reflect/UndeclaredThrowableException)"]]
