Package google.registry.util

Class ComparingInvocationHandler<T>

java.lang.Object

google.registry.util.ComparingInvocationHandler<T>

All Implemented Interfaces:

InvocationHandler

Direct Known Subclasses:

ComparatorKeyring

public abstract class ComparingInvocationHandler<T>
extends Object
implements InvocationHandler

Abstract InvocationHandler comparing two implementations of some interface.

Given an interface, and two instances of that interface (the "original" instance we know works, and a "second" instance we wish to test), creates an InvocationHandler that acts like an exact proxy to the "original" instance.

In addition, it will log any differences in return values or thrown exception between the "original" and "second" instances.

This can be used to create an exact proxy to the original instance that can be placed in any code, while live testing the second instance.

Constructor Summary

Constructors

Constructor	Description
ComparingInvocationHandler(Class<T> interfaceClass, T actualImplementation, T secondImplementation)	Creates a new InvocationHandler for the given interface.

Method Summary

Modifier and Type	Method	Description
protected boolean	compareResults(Method method, Object actual, Object second)	Checks whether the method results are as similar as we expect.
protected boolean	compareThrown(Method method, Throwable actual, Throwable second)	Checks whether the thrown exceptions are as similar as we expect.
final Object	invoke(Object proxy, Method method, Object[] args)
protected abstract void	log(Method method, String message)	Called when there was a difference between the implementations.
final T	makeProxy()	Returns the proxy to the actualImplementation.
protected String	stringifyResult(Method method, Object object)	Implements toString for specific types.
protected String	stringifyThrown(Method method, Throwable throwable)	Implements toString for thrown exceptions.

Methods inherited from class java.lang.Object

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

Constructor Details

ComparingInvocationHandler

public ComparingInvocationHandler(Class<T> interfaceClass,
 T actualImplementation,
 T secondImplementation)

Creates a new InvocationHandler for the given interface.

Parameters:

interfaceClass - the interface we want to create.

actualImplementation - the resulting proxy will be an exact proxy to this object

secondImplementation - Only used to log difference compared to actualImplementation. Otherwise has no effect on the resulting proxy's behavior.

Method Details

makeProxy

public final T makeProxy()

Returns the proxy to the actualImplementation.

The return value is a drop-in replacement to the actualImplementation, but will log any difference with the secondImplementation during normal execution.

log

protected abstract void log(Method method,
 String message)

Called when there was a difference between the implementations.

Parameters:

method - the method where the difference was found

message - human readable description of the difference found

stringifyResult

protected String stringifyResult(Method method,
 @Nullable
 Object object)

Implements toString for specific types.

By default objects are logged using their .toString. If .toString isn't implemented for some relevant classes (or if we want to use a different version), override this method with the desired implementation.

Parameters:

method - the method whose return value is given

object - the object returned by a call to method

compareResults

protected boolean compareResults(Method method,
 @Nullable
 Object actual,
 @Nullable
 Object second)

Checks whether the method results are as similar as we expect.

By default objects are compared using their .equals. If .equals isn't implemented for some relevant classes (or if we want change what is considered "not equal"), override this method with the desired implementation.

Parameters:

method - the method whose return value is given

actual - the object returned by a call to method for the "actual" implementation

second - the object returned by a call to method for the "second" implementation

compareThrown

protected boolean compareThrown(Method method,
 Throwable actual,
 Throwable second)

Checks whether the thrown exceptions are as similar as we expect.

By default this returns 'true' for any input: all we check by default is that both implementations threw something. Override if you need to actually compare both throwables.

Parameters:

method - the method whose return value is given

actual - the exception thrown by a call to method for the "actual" implementation

second - the exception thrown by a call to method for the "second" implementation

stringifyThrown

protected String stringifyThrown(Method method,
 Throwable throwable)

Implements toString for thrown exceptions.

By default exceptions are logged using their .toString. If more data is needed (part of stack trace for example), override this method with the desired implementation.

Parameters:

method - the method whose return value is given

throwable - the exception thrown by a call to method

invoke

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

Specified by:

invoke in interface InvocationHandler

Throws:

Throwable