Spring Framework example source code file (MethodInvoker.java)

This example Spring Framework source code file (MethodInvoker.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

class, class, classnotfoundexception, illegalargumentexception, illegalstateexception, method, method, methodinvoker, nosuchmethodexception, object, object, reflection, string, string, target

The Spring Framework MethodInvoker.java source code

/*
 * Copyright 2002-2008 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.util;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

/**
 * Helper class that allows for specifying a method to invoke in a declarative
 * fashion, be it static or non-static.
 *
 * <p>Usage: Specify "targetClass"/"targetMethod" or "targetObject"/"targetMethod",
 * optionally specify arguments, prepare the invoker. Afterwards, you may
 * invoke the method any number of times, obtaining the invocation result.
 *
 * <p>Typically not used directly but via its subclasses
 * {@link org.springframework.beans.factory.config.MethodInvokingFactoryBean} and
 * {@link org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean}.
 *
 * @author Colin Sampaleanu
 * @author Juergen Hoeller
 * @since 19.02.2004
 * @see #prepare
 * @see #invoke
 * @see org.springframework.beans.factory.config.MethodInvokingFactoryBean
 * @see org.springframework.scheduling.quartz.MethodInvokingJobDetailFactoryBean
 */
public class MethodInvoker {

	private Class targetClass;

	private Object targetObject;

	private String targetMethod;

	private String staticMethod;

	private Object[] arguments = new Object[0];

	/** The method we will call */
	private Method methodObject;


	/**
	 * Set the target class on which to call the target method.
	 * Only necessary when the target method is static; else,
	 * a target object needs to be specified anyway.
	 * @see #setTargetObject
	 * @see #setTargetMethod
	 */
	public void setTargetClass(Class targetClass) {
		this.targetClass = targetClass;
	}

	/**
	 * Return the target class on which to call the target method.
	 */
	public Class getTargetClass() {
		return this.targetClass;
	}

	/**
	 * Set the target object on which to call the target method.
	 * Only necessary when the target method is not static;
	 * else, a target class is sufficient.
	 * @see #setTargetClass
	 * @see #setTargetMethod
	 */
	public void setTargetObject(Object targetObject) {
		this.targetObject = targetObject;
		if (targetObject != null) {
			this.targetClass = targetObject.getClass();
		}
	}

	/**
	 * Return the target object on which to call the target method.
	 */
	public Object getTargetObject() {
		return this.targetObject;
	}

	/**
	 * Set the name of the method to be invoked.
	 * Refers to either a static method or a non-static method,
	 * depending on a target object being set.
	 * @see #setTargetClass
	 * @see #setTargetObject
	 */
	public void setTargetMethod(String targetMethod) {
		this.targetMethod = targetMethod;
	}

	/**
	 * Return the name of the method to be invoked.
	 */
	public String getTargetMethod() {
		return this.targetMethod;
	}

	/**
	 * Set a fully qualified static method name to invoke,
	 * e.g. "example.MyExampleClass.myExampleMethod".
	 * Convenient alternative to specifying targetClass and targetMethod.
	 * @see #setTargetClass
	 * @see #setTargetMethod
	 */
	public void setStaticMethod(String staticMethod) {
		this.staticMethod = staticMethod;
	}

	/**
	 * Set arguments for the method invocation. If this property is not set,
	 * or the Object array is of length 0, a method with no arguments is assumed.
	 */
	public void setArguments(Object[] arguments) {
		this.arguments = (arguments != null ? arguments : new Object[0]);
	}

	/**
	 * Return the arguments for the method invocation.
	 */
	public Object[] getArguments() {
		return this.arguments;
	}


	/**
	 * Prepare the specified method.
	 * The method can be invoked any number of times afterwards.
	 * @see #getPreparedMethod
	 * @see #invoke
	 */
	public void prepare() throws ClassNotFoundException, NoSuchMethodException {
		if (this.staticMethod != null) {
			int lastDotIndex = this.staticMethod.lastIndexOf('.');
			if (lastDotIndex == -1 || lastDotIndex == this.staticMethod.length()) {
				throw new IllegalArgumentException(
						"staticMethod must be a fully qualified class plus method name: " +
						"e.g. 'example.MyExampleClass.myExampleMethod'");
			}
			String className = this.staticMethod.substring(0, lastDotIndex);
			String methodName = this.staticMethod.substring(lastDotIndex + 1);
			this.targetClass = resolveClassName(className);
			this.targetMethod = methodName;
		}

		Class targetClass = getTargetClass();
		String targetMethod = getTargetMethod();
		if (targetClass == null) {
			throw new IllegalArgumentException("Either 'targetClass' or 'targetObject' is required");
		}
		if (targetMethod == null) {
			throw new IllegalArgumentException("Property 'targetMethod' is required");
		}

		Object[] arguments = getArguments();
		Class[] argTypes = new Class[arguments.length];
		for (int i = 0; i < arguments.length; ++i) {
			argTypes[i] = (arguments[i] != null ? arguments[i].getClass() : Object.class);
		}

		// Try to get the exact method first.
		try {
			this.methodObject = targetClass.getMethod(targetMethod, argTypes);
		}
		catch (NoSuchMethodException ex) {
			// Just rethrow exception if we can't get any match.
			this.methodObject = findMatchingMethod();
			if (this.methodObject == null) {
				throw ex;
			}
		}
	}

	/**
	 * Resolve the given class name into a Class.
	 * <p>The default implementations uses ClassUtils.forName,
	 * using the thread context class loader.
	 * @param className the class name to resolve
	 * @return the resolved Class
	 * @throws ClassNotFoundException if the class name was invalid
	 */
	protected Class resolveClassName(String className) throws ClassNotFoundException {
		return ClassUtils.forName(className);
	}

	/**
	 * Find a matching method with the specified name for the specified arguments.
	 * @return a matching method, or <code>null if none
	 * @see #getTargetClass()
	 * @see #getTargetMethod()
	 * @see #getArguments()
	 */
	protected Method findMatchingMethod() {
		String targetMethod = getTargetMethod();
		Object[] arguments = getArguments();
		int argCount = arguments.length;

		Method[] candidates = ReflectionUtils.getAllDeclaredMethods(getTargetClass());
		int minTypeDiffWeight = Integer.MAX_VALUE;
		Method matchingMethod = null;

		for (int i = 0; i < candidates.length; i++) {
			Method candidate = candidates[i];
			if (candidate.getName().equals(targetMethod)) {
				Class[] paramTypes = candidate.getParameterTypes();
				if (paramTypes.length == argCount) {
					int typeDiffWeight = getTypeDifferenceWeight(paramTypes, arguments);
					if (typeDiffWeight < minTypeDiffWeight) {
						minTypeDiffWeight = typeDiffWeight;
						matchingMethod = candidate;
					}
				}
			}
		}

		return matchingMethod;
	}

	/**
	 * Return the prepared Method object that will be invoked.
	 * <p>Can for example be used to determine the return type.
	 * @return the prepared Method object (never <code>null)
	 * @throws IllegalStateException if the invoker hasn't been prepared yet
	 * @see #prepare
	 * @see #invoke
	 */
	public Method getPreparedMethod() throws IllegalStateException {
		if (this.methodObject == null) {
			throw new IllegalStateException("prepare() must be called prior to invoke() on MethodInvoker");
		}
		return this.methodObject;
	}

	/**
	 * Return whether this invoker has been prepared already,
	 * i.e. whether it allows access to {@link #getPreparedMethod()} already.
	 */
	public boolean isPrepared() {
		return (this.methodObject != null);
	}

	/**
	 * Invoke the specified method.
	 * <p>The invoker needs to have been prepared before.
	 * @return the object (possibly null) returned by the method invocation,
	 * or <code>null if the method has a void return type
	 * @throws InvocationTargetException if the target method threw an exception
	 * @throws IllegalAccessException if the target method couldn't be accessed
	 * @see #prepare
	 */
	public Object invoke() throws InvocationTargetException, IllegalAccessException {
		// In the static case, target will simply be <code>null.
		Object targetObject = getTargetObject();
		Method preparedMethod = getPreparedMethod();
		if (targetObject == null && !Modifier.isStatic(preparedMethod.getModifiers())) {
			throw new IllegalArgumentException("Target method must not be non-static without a target");
		}
		ReflectionUtils.makeAccessible(preparedMethod);
		return preparedMethod.invoke(targetObject, getArguments());
	}


	/**
	 * Algorithm that judges the match between the declared parameter types of a candidate method
	 * and a specific list of arguments that this method is supposed to be invoked with.
	 * <p>Determines a weight that represents the class hierarchy difference between types and
	 * arguments. A direct match, i.e. type Integer -> arg of class Integer, does not increase
	 * the result - all direct matches means weight 0. A match between type Object and arg of
	 * class Integer would increase the weight by 2, due to the superclass 2 steps up in the
	 * hierarchy (i.e. Object) being the last one that still matches the required type Object.
	 * Type Number and class Integer would increase the weight by 1 accordingly, due to the
	 * superclass 1 step up the hierarchy (i.e. Number) still matching the required type Number.
	 * Therefore, with an arg of type Integer, a constructor (Integer) would be preferred to a
	 * constructor (Number) which would in turn be preferred to a constructor (Object).
	 * All argument weights get accumulated.
	 * @param paramTypes the parameter types to match
	 * @param args the arguments to match
	 * @return the accumulated weight for all arguments
	 */
	public static int getTypeDifferenceWeight(Class[] paramTypes, Object[] args) {
		int result = 0;
		for (int i = 0; i < paramTypes.length; i++) {
			if (!ClassUtils.isAssignableValue(paramTypes[i], args[i])) {
				return Integer.MAX_VALUE;
			}
			if (args[i] != null) {
				Class paramType = paramTypes[i];
				Class superClass = args[i].getClass().getSuperclass();
				while (superClass != null) {
					if (paramType.equals(superClass)) {
						result = result + 2;
						superClass = null;
					}
					else if (ClassUtils.isAssignable(paramType, superClass)) {
						result = result + 2;
						superClass = superClass.getSuperclass();
					}
					else {
						superClass = null;
					}
				}
				if (paramType.isInterface()) {
					result = result + 1;
				}
			}
		}
		return result;
	}

}