methodmatcher.java

Java/J2EE application framework based on [Expert One-on-One J2EE Design and Development] by Rod John

/*
 * Copyright 2002-2004 the original author or authors.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */ 

package org.springframework.aop;

import java.lang.reflect.Method;

/**
 * Part of a Pointcut. Checks whether the target method is eligible for advice.
 *
 * <p>A MethodMatcher may be evaluated <b>statically</b> or at <b>runtime</b> (dynamically).
 * Static matching involves method and (possibly) method attributes. Dynamic matching
 * also makes arguments for a particular call available, and any effects of running
 * previous advice applying to the joinpoint.
 *
 * <p>If an implementation returns false in its isRuntime() method, evaluation can be performed
 * statically, and the result will be the same for all invocations of this method,
 * whatever their arguments. If the isRuntime() method returns false, the 3-arg matches()
 * method will never be invoked.
 *
 * <p>If an implementation returns true in its 2-arg matches() method, and its isRuntime()
 * method returns true, the 3-argument matches() method will be invoked <i>immediately before
 * each potential execution of the related advice</i>, to decide whether the advice should run.
 * All previous advice, such as earlier interceptors in an interceptor chain, will have run,
 * so any state changes they have produced in parameters or ThreadLocal state, will be
 * available at the time of evaluation.
 * 
 * @author Rod Johnson
 * @since 11-Nov-2003
 */
public interface MethodMatcher {
	
	/**
	 * Perform static checking. If this returns false, or if the isRuntime() method
	 * returns false, no runtime check will be made.
	 * @param m candidate method
	 * @param targetClass target class (may be null, in which case the candidate
	 * class must be taken to be the method's declaring class)
	 * @return whether or not this method matches statically
	 */
	boolean matches(Method m, Class targetClass);
	
	/**
	 * Is this MethodMatcher dynamic?
	 * Must a final call be made on the matches(Method, Class, Object[]) method at runtime
	 * even if the 2-arg matches method returns true?
	 * Can be invoked when an AOP proxy is created, and need not be invoked
	 * again before each method invocation,
	 * <p>Note: Could be pulled up into a Matcher super-interface to apply to
	 * fields also.
	 * @return whether or not a runtime matche via the 3-arg matches() method is
	 * required if static matching passed.
	 */
	boolean isRuntime();
	
	/**
	 * Is there a runtime (dynamic) match for this method, which must have matched
	 * statically. This method is
	 * invoked only if the 2-arg matches method returns true for the given method
	 * and target class, and if the isRuntime() method returns true.
	 * Invoked immediately before potentially running of the advice, after any
	 * advice earlier in the advice chain has run.
	 * @param m candidate method
	 * @param targetClass target class
	 * @param args arguments to the method
	 * @return whether there's a runtime match
	 * @see MethodMatcher#matches(Method, Class)
	 */
	boolean matches(Method m, Class targetClass, Object[] args);
	
	
	/**
	 * Canonical instance that matches all methods.
	 */
	MethodMatcher TRUE = TrueMethodMatcher.INSTANCE;

}