software.amazon.disco.agent.reflect

Class ReflectiveCall<T>

java.lang.Object

software.amazon.disco.agent.reflect.ReflectiveCall<T>

Type Parameters:

T - - the return type of the method being called

public class ReflectiveCall<T>
extends java.lang.Object

Everything in disco.agent.reflect basically works the same way - attempting to reflectively invoke methods, usually static ones, that reside within the Agent. Any failures are degraded gracefully to no-ops in the case that the Agent is not loaded, making it safe for clients to use the reflect library in their Prod code.

Method Summary

Modifier and Type	Method and Description
T	call(java.lang.Object... args) Invoke the given method with the given args.
void	dispatchException(java.lang.Throwable t, java.lang.Object... args) Tries to dispatch an exception to the installed UncaughtExceptionHandler.
java.lang.Class[]	getArgTypes() Get the array of argument types specified in this ReflectiveCall
java.lang.String	getClassName() Get the class name specified in this ReflectiveCall
java.lang.String	getMethodName() Get the name of the method specified in this ReflectiveCall
java.lang.Class	getReturnType() Get the class return type of the method specified in this ReflectiveCall
static void	installUncaughtExceptionHandler(UncaughtExceptionHandler handler) Install an UncaughtExceptionHandler, to receive a notification whe any exception is thrown by any method in the DiSCo reflect APIs.
static boolean	isAgentPresent() Test if a DiSCo agent is present
boolean	methodFound() Test if the method about to be called exists or not
ReflectiveCall<T>	ofClass(java.lang.String className) Set the partial class name which declares the method to be called as it appears after software.amazon.disco.agent e.g.
ReflectiveCall<T>	ofMethod(java.lang.String methodName) Set the name of the method to be called
ReflectiveCall<T>	onInstance(java.lang.Object thiz) For non-static methods, set the instance object on which to invoke the method
static <T> ReflectiveCall<T>	returning(java.lang.Class<T> clazz) Factory method to create a new ReflectiveCall which is on a method returning the given type
static ReflectiveCall	returningVoid() Factory method to create a new ReflectiveCall which is on a void method
java.lang.String	toString()
ReflectiveCall<T>	withArgTypes(java.lang.Class... argTypes) Declare the expected method signature by its arguments
ReflectiveCall<T>	withDefaultValue(T defaultValue) Set the default value to return in case no DiSCo agent is present.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

returningVoid

public static ReflectiveCall returningVoid()

Factory method to create a new ReflectiveCall which is on a void method

Returns:

a new ReflectiveCall to continue building/calling

returning

public static <T> ReflectiveCall<T> returning(java.lang.Class<T> clazz)

Factory method to create a new ReflectiveCall which is on a method returning the given type

Type Parameters:

T - the class of the method's return type

Parameters:

clazz - the class of the method's return type

Returns:

a new ReflectiveCall to continue building/calling

withDefaultValue

public ReflectiveCall<T> withDefaultValue(T defaultValue)

Set the default value to return in case no DiSCo agent is present. If none is provided, then null it returns null.

Parameters:

defaultValue - The default value

Returns:

the ReflectiveCall to continue building/calling

ofClass

public ReflectiveCall<T> ofClass(java.lang.String className)

Set the partial class name which declares the method to be called as it appears after software.amazon.disco.agent e.g. '.config.Config' including the prefixing '.'

Parameters:

className - the class name which declares the method

Returns:

the ReflectiveCall to continue building/calling

ofMethod

public ReflectiveCall<T> ofMethod(java.lang.String methodName)

Set the name of the method to be called

Parameters:

methodName - the name of the method to be called

Returns:

the ReflectiveCall to continue building/calling

onInstance

public ReflectiveCall<T> onInstance(java.lang.Object thiz)

For non-static methods, set the instance object on which to invoke the method

Parameters:

thiz - the instance object on which to invoke the method

Returns:

the ReflectiveCall to continue building/calling

withArgTypes

public ReflectiveCall<T> withArgTypes(java.lang.Class... argTypes)

Declare the expected method signature by its arguments

Parameters:

argTypes - array of types for method lookup

Returns:

the ReflectiveCall to continue building/calling

methodFound

public boolean methodFound()

Test if the method about to be called exists or not

Returns:

true if the method configured exists

call

public T call(java.lang.Object... args)

Invoke the given method with the given args. If a DiSCo agent is present the call will proceed. In the case that building the method was not possible, due to the agent being absent, this method will have no side effects.

Parameters:

args - any arguments to pass to the method invocation.

Returns:

any value which the method returns, or null if the call could not be made

isAgentPresent

public static boolean isAgentPresent()

Test if a DiSCo agent is present

Returns:

true if a DiSCo agent is present

installUncaughtExceptionHandler

public static void installUncaughtExceptionHandler(UncaughtExceptionHandler handler)

Install an UncaughtExceptionHandler, to receive a notification whe any exception is thrown by any method in the DiSCo reflect APIs. Without such a handler installed, all exceptions - even unchecked ones - will be suppressed

Parameters:

handler - a callback to receive any unhandled exceptions in client code

dispatchException

public void dispatchException(java.lang.Throwable t,
                              java.lang.Object... args)

Tries to dispatch an exception to the installed UncaughtExceptionHandler. Does nothing if no such handler is installed

Parameters:

t - the throwable to notify the calling code, via any installed UncaughtExceptionHandler

args - any arguments to notify the UncaughtExceptionHandler of

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

getClassName

public java.lang.String getClassName()

Get the class name specified in this ReflectiveCall

Returns:

the class name

getReturnType

public java.lang.Class getReturnType()

Get the class return type of the method specified in this ReflectiveCall

Returns:

the return type of this method

getMethodName

public java.lang.String getMethodName()

Get the name of the method specified in this ReflectiveCall

Returns:

the name of this method

getArgTypes

public java.lang.Class[] getArgTypes()

Get the array of argument types specified in this ReflectiveCall

Returns:

the argument types of this method