Java tutorial
/* ==================================================================== Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You 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.apache.poi.util; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * <p> Utility reflection methods focussed on methods in general rather than properties in particular. </p> * * <h3>Known Limitations</h3> * <h4>Accessing Public Methods In A Default Access Superclass</h4> * <p>There is an issue when invoking public methods contained in a default access superclass. * Reflection locates these methods fine and correctly assigns them as public. * However, an <code>IllegalAccessException</code> is thrown if the method is invoked.</p> * * <p><code>MethodUtils</code> contains a workaround for this situation. * It will attempt to call <code>setAccessible</code> on this method. * If this call succeeds, then the method can be invoked as normal. * This call will only succeed when the application has sufficient security privilages. * If this call fails then a warning will be logged and the method may fail.</p> * * @author Craig R. McClanahan * @author Ralph Schaer * @author Chris Audley * @author Rey François * @author Gregor Raýman * @author Jan Sorensen * @author Robert Burrell Donkin */ public class MethodUtils { // --------------------------------------------------------- Private Methods /** * Only log warning about accessibility work around once. * <p> * Note that this is broken when this class is deployed via a shared * classloader in a container, as the warning message will be emitted * only once, not once per webapp. However making the warning appear * once per webapp means having a map keyed by context classloader * which introduces nasty memory-leak problems. As this warning is * really optional we can ignore this problem; only one of the webapps * will get the warning in its logs but that should be good enough. */ private static boolean loggedAccessibleWarning = false; /** * Indicates whether methods should be cached for improved performance. * <p> * Note that when this class is deployed via a shared classloader in * a container, this will affect all webapps. However making this * configurable per webapp would mean having a map keyed by context classloader * which may introduce memory-leak problems. */ private static boolean CACHE_METHODS = true; /** An empty class array */ private static final Class[] EMPTY_CLASS_PARAMETERS = new Class[0]; /** An empty object array */ private static final Object[] EMPTY_OBJECT_ARRAY = new Object[0]; // --------------------------------------------------------- Public Methods /** * <p>Invoke a named method whose parameter type matches the object type.</p> * * <p>The behaviour of this method is less deterministic * than <code>invokeExactMethod()</code>. * It loops through all methods with names that match * and then executes the first it finds with compatable parameters.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> class * would match a <code>boolean</code> primitive.</p> * * <p> This is a convenient wrapper for * {@link #invokeMethod(Object object,String methodName,Object [] args)}. * </p> * * @param object invoke method on this object * @param methodName get method with this name * @param arg use this argument * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeMethod(Object object, String methodName, Object arg) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { Object[] args = { arg }; return invokeMethod(object, methodName, args); } /** * <p>Invoke a named method whose parameter type matches the object type.</p> * * <p>The behaviour of this method is less deterministic * than {@link #invokeExactMethod(Object object,String methodName,Object [] args)}. * It loops through all methods with names that match * and then executes the first it finds with compatable parameters.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> class * would match a <code>boolean</code> primitive.</p> * * <p> This is a convenient wrapper for * {@link #invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}. * </p> * * @param object invoke method on this object * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeMethod(Object object, String methodName, Object[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = EMPTY_OBJECT_ARRAY; } int arguments = args.length; Class[] parameterTypes = new Class[arguments]; for (int i = 0; i < arguments; i++) { parameterTypes[i] = args[i].getClass(); } return invokeMethod(object, methodName, args, parameterTypes); } /** * <p>Invoke a named method whose parameter type matches the object type.</p> * * <p>The behaviour of this method is less deterministic * than {@link * #invokeExactMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}. * It loops through all methods with names that match * and then executes the first it finds with compatable parameters.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> class * would match a <code>boolean</code> primitive.</p> * * * @param object invoke method on this object * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @param parameterTypes match these parameters - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeMethod(Object object, String methodName, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (parameterTypes == null) { parameterTypes = EMPTY_CLASS_PARAMETERS; } if (args == null) { args = EMPTY_OBJECT_ARRAY; } Method method = getMatchingAccessibleMethod(object.getClass(), methodName, parameterTypes); if (method == null) { throw new NoSuchMethodException( "No such accessible method: " + methodName + "() on object: " + object.getClass().getName()); } return method.invoke(object, args); } /** * <p>Invoke a method whose parameter type matches exactly the object * type.</p> * * <p> This is a convenient wrapper for * {@link #invokeExactMethod(Object object,String methodName,Object [] args)}. * </p> * * @param object invoke method on this object * @param methodName get method with this name * @param arg use this argument * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeExactMethod(Object object, String methodName, Object arg) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { Object[] args = { arg }; return invokeExactMethod(object, methodName, args); } /** * <p>Invoke a method whose parameter types match exactly the object * types.</p> * * <p> This uses reflection to invoke the method obtained from a call to * <code>getAccessibleMethod()</code>.</p> * * @param object invoke method on this object * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeExactMethod(Object object, String methodName, Object[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = EMPTY_OBJECT_ARRAY; } int arguments = args.length; Class[] parameterTypes = new Class[arguments]; for (int i = 0; i < arguments; i++) { parameterTypes[i] = args[i].getClass(); } return invokeExactMethod(object, methodName, args, parameterTypes); } /** * <p>Invoke a method whose parameter types match exactly the parameter * types given.</p> * * <p>This uses reflection to invoke the method obtained from a call to * <code>getAccessibleMethod()</code>.</p> * * @param object invoke method on this object * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @param parameterTypes match these parameters - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeExactMethod(Object object, String methodName, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = EMPTY_OBJECT_ARRAY; } if (parameterTypes == null) { parameterTypes = EMPTY_CLASS_PARAMETERS; } Method method = getAccessibleMethod(object.getClass(), methodName, parameterTypes); if (method == null) { throw new NoSuchMethodException( "No such accessible method: " + methodName + "() on object: " + object.getClass().getName()); } return method.invoke(object, args); } /** * <p>Invoke a static method whose parameter types match exactly the parameter * types given.</p> * * <p>This uses reflection to invoke the method obtained from a call to * {@link #getAccessibleMethod(Class, String, Class[])}.</p> * * @param objectClass invoke static method on this class * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @param parameterTypes match these parameters - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeExactStaticMethod(Class objectClass, String methodName, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = EMPTY_OBJECT_ARRAY; } if (parameterTypes == null) { parameterTypes = EMPTY_CLASS_PARAMETERS; } Method method = getAccessibleMethod(objectClass, methodName, parameterTypes); if (method == null) { throw new NoSuchMethodException( "No such accessible method: " + methodName + "() on class: " + objectClass.getName()); } return method.invoke(null, args); } /** * <p>Invoke a named static method whose parameter type matches the object type.</p> * * <p>The behaviour of this method is less deterministic * than {@link #invokeExactMethod(Object, String, Object[], Class[])}. * It loops through all methods with names that match * and then executes the first it finds with compatable parameters.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> class * would match a <code>boolean</code> primitive.</p> * * <p> This is a convenient wrapper for * {@link #invokeStaticMethod(Class objectClass,String methodName,Object [] args)}. * </p> * * @param objectClass invoke static method on this class * @param methodName get method with this name * @param arg use this argument * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeStaticMethod(Class objectClass, String methodName, Object arg) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { Object[] args = { arg }; return invokeStaticMethod(objectClass, methodName, args); } /** * <p>Invoke a named static method whose parameter type matches the object type.</p> * * <p>The behaviour of this method is less deterministic * than {@link #invokeExactMethod(Object object,String methodName,Object [] args)}. * It loops through all methods with names that match * and then executes the first it finds with compatable parameters.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> class * would match a <code>boolean</code> primitive.</p> * * <p> This is a convenient wrapper for * {@link #invokeStaticMethod(Class objectClass,String methodName,Object [] args,Class[] parameterTypes)}. * </p> * * @param objectClass invoke static method on this class * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeStaticMethod(Class objectClass, String methodName, Object[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = EMPTY_OBJECT_ARRAY; } int arguments = args.length; Class[] parameterTypes = new Class[arguments]; for (int i = 0; i < arguments; i++) { parameterTypes[i] = args[i].getClass(); } return invokeStaticMethod(objectClass, methodName, args, parameterTypes); } /** * <p>Invoke a named static method whose parameter type matches the object type.</p> * * <p>The behaviour of this method is less deterministic * than {@link * #invokeExactStaticMethod(Class objectClass,String methodName,Object [] args,Class[] parameterTypes)}. * It loops through all methods with names that match * and then executes the first it finds with compatable parameters.</p> * * <p>This method supports calls to methods taking primitive parameters * via passing in wrapping classes. So, for example, a <code>Boolean</code> class * would match a <code>boolean</code> primitive.</p> * * * @param objectClass invoke static method on this class * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @param parameterTypes match these parameters - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeStaticMethod(Class objectClass, String methodName, Object[] args, Class[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (parameterTypes == null) { parameterTypes = EMPTY_CLASS_PARAMETERS; } if (args == null) { args = EMPTY_OBJECT_ARRAY; } Method method = getMatchingAccessibleMethod(objectClass, methodName, parameterTypes); if (method == null) { throw new NoSuchMethodException( "No such accessible method: " + methodName + "() on class: " + objectClass.getName()); } return method.invoke(null, args); } /** * <p>Invoke a static method whose parameter type matches exactly the object * type.</p> * * <p> This is a convenient wrapper for * {@link #invokeExactStaticMethod(Class objectClass,String methodName,Object [] args)}. * </p> * * @param objectClass invoke static method on this class * @param methodName get method with this name * @param arg use this argument * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeExactStaticMethod(Class objectClass, String methodName, Object arg) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { Object[] args = { arg }; return invokeExactStaticMethod(objectClass, methodName, args); } /** * <p>Invoke a static method whose parameter types match exactly the object * types.</p> * * <p> This uses reflection to invoke the method obtained from a call to * {@link #getAccessibleMethod(Class, String, Class[])}.</p> * * @param objectClass invoke static method on this class * @param methodName get method with this name * @param args use these arguments - treat null as empty array * @return The value returned by the invoked method * * @throws NoSuchMethodException if there is no such accessible method * @throws InvocationTargetException wraps an exception thrown by the * method invoked * @throws IllegalAccessException if the requested method is not accessible * via reflection */ public static Object invokeExactStaticMethod(Class objectClass, String methodName, Object[] args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException { if (args == null) { args = EMPTY_OBJECT_ARRAY; } int arguments = args.length; Class[] parameterTypes = new Class[arguments]; for (int i = 0; i < arguments; i++) { parameterTypes[i] = args[i].getClass(); } return invokeExactStaticMethod(objectClass, methodName, args, parameterTypes); } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) with given name and a single parameter. If no such method * can be found, return <code>null</code>. * Basically, a convenience wrapper that constructs a <code>Class</code> * array for you.</p> * * @param clazz get method from this class * @param methodName get method with this name * @param parameterType taking this type of parameter * @return The accessible method */ public static Method getAccessibleMethod(Class clazz, String methodName, Class parameterType) { Class[] parameterTypes = { parameterType }; return getAccessibleMethod(clazz, methodName, parameterTypes); } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) with given name and parameters. If no such method * can be found, return <code>null</code>. * This is just a convenient wrapper for * {@link #getAccessibleMethod(Method method)}.</p> * * @param clazz get method from this class * @param methodName get method with this name * @param parameterTypes with these parameters types * @return The accessible method */ public static Method getAccessibleMethod(Class clazz, String methodName, Class[] parameterTypes) { try { MethodDescriptor md = new MethodDescriptor(clazz, methodName, parameterTypes, true); Method method = getAccessibleMethod(clazz, clazz.getMethod(methodName, parameterTypes)); return method; } catch (NoSuchMethodException e) { return (null); } } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) that implements the specified Method. If no such method * can be found, return <code>null</code>.</p> * * @param method The method that we wish to call * @return The accessible method */ public static Method getAccessibleMethod(Method method) { // Make sure we have a method to check if (method == null) { return (null); } return getAccessibleMethod(method.getDeclaringClass(), method); } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) that implements the specified Method. If no such method * can be found, return <code>null</code>.</p> * * @param clazz The class of the object * @param method The method that we wish to call * @return The accessible method */ public static Method getAccessibleMethod(Class clazz, Method method) { // Make sure we have a method to check if (method == null) { return (null); } // If the requested method is not public we cannot call it if (!Modifier.isPublic(method.getModifiers())) { return (null); } boolean sameClass = true; if (clazz == null) { clazz = method.getDeclaringClass(); } else { sameClass = clazz.equals(method.getDeclaringClass()); if (!method.getDeclaringClass().isAssignableFrom(clazz)) { throw new IllegalArgumentException( clazz.getName() + " is not assignable from " + method.getDeclaringClass().getName()); } } // If the class is public, we are done if (Modifier.isPublic(clazz.getModifiers())) { if (!sameClass && !Modifier.isPublic(method.getDeclaringClass().getModifiers())) { setMethodAccessible(method); // Default access superclass workaround } return (method); } String methodName = method.getName(); Class[] parameterTypes = method.getParameterTypes(); // Check the implemented interfaces and subinterfaces method = getAccessibleMethodFromInterfaceNest(clazz, methodName, parameterTypes); // Check the superclass chain if (method == null) { method = getAccessibleMethodFromSuperclass(clazz, methodName, parameterTypes); } return (method); } // -------------------------------------------------------- Private Methods /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) by scanning through the superclasses. If no such method * can be found, return <code>null</code>.</p> * * @param clazz Class to be checked * @param methodName Method name of the method we wish to call * @param parameterTypes The parameter type signatures */ private static Method getAccessibleMethodFromSuperclass(Class clazz, String methodName, Class[] parameterTypes) { Class parentClazz = clazz.getSuperclass(); while (parentClazz != null) { if (Modifier.isPublic(parentClazz.getModifiers())) { try { return parentClazz.getMethod(methodName, parameterTypes); } catch (NoSuchMethodException e) { return null; } } parentClazz = parentClazz.getSuperclass(); } return null; } /** * <p>Return an accessible method (that is, one that can be invoked via * reflection) that implements the specified method, by scanning through * all implemented interfaces and subinterfaces. If no such method * can be found, return <code>null</code>.</p> * * <p> There isn't any good reason why this method must be private. * It is because there doesn't seem any reason why other classes should * call this rather than the higher level methods.</p> * * @param clazz Parent class for the interfaces to be checked * @param methodName Method name of the method we wish to call * @param parameterTypes The parameter type signatures */ private static Method getAccessibleMethodFromInterfaceNest(Class clazz, String methodName, Class[] parameterTypes) { Method method = null; // Search up the superclass chain for (; clazz != null; clazz = clazz.getSuperclass()) { // Check the implemented interfaces of the parent class Class[] interfaces = clazz.getInterfaces(); for (int i = 0; i < interfaces.length; i++) { // Is this interface public? if (!Modifier.isPublic(interfaces[i].getModifiers())) { continue; } // Does the method exist on this interface? try { method = interfaces[i].getDeclaredMethod(methodName, parameterTypes); } catch (NoSuchMethodException e) { /* Swallow, if no method is found after the loop then this * method returns null. */ } if (method != null) { return method; } // Recursively check our parent interfaces method = getAccessibleMethodFromInterfaceNest(interfaces[i], methodName, parameterTypes); if (method != null) { return method; } } } // If we found a method return it if (method != null) { return (method); } // We did not find anything return (null); } /** * <p>Find an accessible method that matches the given name and has compatible parameters. * Compatible parameters mean that every method parameter is assignable from * the given parameters. * In other words, it finds a method with the given name * that will take the parameters given.<p> * * <p>This method is slightly undeterminstic since it loops * through methods names and return the first matching method.</p> * * <p>This method is used by * {@link * #invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}. * * <p>This method can match primitive parameter by passing in wrapper classes. * For example, a <code>Boolean</code> will match a primitive <code>boolean</code> * parameter. * * @param clazz find method in this class * @param methodName find method with this name * @param parameterTypes find method with compatible parameters * @return The accessible method */ public static Method getMatchingAccessibleMethod(Class clazz, String methodName, Class[] parameterTypes) { // trace logging Log log = LogFactory.getLog(MethodUtils.class); if (log.isTraceEnabled()) { log.trace("Matching name=" + methodName + " on " + clazz); } MethodDescriptor md = new MethodDescriptor(clazz, methodName, parameterTypes, false); // see if we can find the method directly // most of the time this works and it's much faster try { Method method = clazz.getMethod(methodName, parameterTypes); if (log.isTraceEnabled()) { log.trace("Found straight match: " + method); log.trace("isPublic:" + Modifier.isPublic(method.getModifiers())); } setMethodAccessible(method); // Default access superclass workaround return method; } catch (NoSuchMethodException e) { /* SWALLOW */ } // search through all methods int paramSize = parameterTypes.length; Method bestMatch = null; Method[] methods = clazz.getMethods(); float bestMatchCost = Float.MAX_VALUE; float myCost = Float.MAX_VALUE; for (int i = 0, size = methods.length; i < size; i++) { if (methods[i].getName().equals(methodName)) { // log some trace information if (log.isTraceEnabled()) { log.trace("Found matching name:"); log.trace(methods[i]); } // compare parameters Class[] methodsParams = methods[i].getParameterTypes(); int methodParamSize = methodsParams.length; if (methodParamSize == paramSize) { boolean match = true; for (int n = 0; n < methodParamSize; n++) { if (log.isTraceEnabled()) { log.trace("Param=" + parameterTypes[n].getName()); log.trace("Method=" + methodsParams[n].getName()); } if (!isAssignmentCompatible(methodsParams[n], parameterTypes[n])) { if (log.isTraceEnabled()) { log.trace(methodsParams[n] + " is not assignable from " + parameterTypes[n]); } match = false; break; } } if (match) { // get accessible version of method Method method = getAccessibleMethod(clazz, methods[i]); if (method != null) { if (log.isTraceEnabled()) { log.trace(method + " accessible version of " + methods[i]); } setMethodAccessible(method); // Default access superclass workaround myCost = getTotalTransformationCost(parameterTypes, method.getParameterTypes()); if (myCost < bestMatchCost) { bestMatch = method; bestMatchCost = myCost; } } log.trace("Couldn't find accessible method."); } } } } if (bestMatch == null) { // didn't find a match log.trace("No match found."); } return bestMatch; } public static <T> Constructor<T> getMatchingAccessibleConstructor(Class<T> clazz, Class[] parameterTypes) { // trace logging Log log = LogFactory.getLog(MethodUtils.class); MethodDescriptor md = new MethodDescriptor(clazz, "dummy", parameterTypes, false); // see if we can find the method directly // most of the time this works and it's much faster try { Constructor<T> constructor = clazz.getConstructor(parameterTypes); if (log.isTraceEnabled()) { log.trace("Found straight match: " + constructor); log.trace("isPublic:" + Modifier.isPublic(constructor.getModifiers())); } setMethodAccessible(constructor); // Default access superclass workaround return constructor; } catch (NoSuchMethodException e) { /* SWALLOW */ } // search through all methods int paramSize = parameterTypes.length; Constructor<T> bestMatch = null; Constructor<?>[] constructors = clazz.getConstructors(); float bestMatchCost = Float.MAX_VALUE; float myCost = Float.MAX_VALUE; for (int i = 0, size = constructors.length; i < size; i++) { // compare parameters Class[] methodsParams = constructors[i].getParameterTypes(); int methodParamSize = methodsParams.length; if (methodParamSize == paramSize) { boolean match = true; for (int n = 0; n < methodParamSize; n++) { if (log.isTraceEnabled()) { log.trace("Param=" + parameterTypes[n].getName()); log.trace("Method=" + methodsParams[n].getName()); } if (!isAssignmentCompatible(methodsParams[n], parameterTypes[n])) { if (log.isTraceEnabled()) { log.trace(methodsParams[n] + " is not assignable from " + parameterTypes[n]); } match = false; break; } } if (match) { // get accessible version of method Constructor<T> cons = (Constructor<T>) constructors[i]; myCost = getTotalTransformationCost(parameterTypes, cons.getParameterTypes()); if (myCost < bestMatchCost) { bestMatch = cons; bestMatchCost = myCost; } } } } if (bestMatch == null) { // didn't find a match log.trace("No match found."); } return bestMatch; } /** * Try to make the method accessible * @param method The source arguments */ private static void setMethodAccessible(Object method) { try { // // XXX Default access superclass workaround // // When a public class has a default access superclass // with public methods, these methods are accessible. // Calling them from compiled code works fine. // // Unfortunately, using reflection to invoke these methods // seems to (wrongly) to prevent access even when the method // modifer is public. // // The following workaround solves the problem but will only // work from sufficiently privilages code. // // Better workarounds would be greatfully accepted. // if (method instanceof Method) { ((Method) method).setAccessible(true); } else if (method instanceof Constructor) { ((Constructor) method).setAccessible(true); } else { throw new RuntimeException("invalid parameter"); } } catch (SecurityException se) { // log but continue just in case the method.invoke works anyway Log log = LogFactory.getLog(MethodUtils.class); if (!loggedAccessibleWarning) { boolean vulnerableJVM = false; try { String specVersion = System.getProperty("java.specification.version"); if (specVersion.charAt(0) == '1' && (specVersion.charAt(2) == '0' || specVersion.charAt(2) == '1' || specVersion.charAt(2) == '2' || specVersion.charAt(2) == '3')) { vulnerableJVM = true; } } catch (SecurityException e) { // don't know - so display warning vulnerableJVM = true; } if (vulnerableJVM) { log.warn("Current Security Manager restricts use of workarounds for reflection bugs " + " in pre-1.4 JVMs."); } loggedAccessibleWarning = true; } log.debug("Cannot setAccessible on method. Therefore cannot use jvm access bug workaround.", se); } } /** * Returns the sum of the object transformation cost for each class in the source * argument list. * @param srcArgs The source arguments * @param destArgs The destination arguments * @return The total transformation cost */ private static float getTotalTransformationCost(Class[] srcArgs, Class[] destArgs) { float totalCost = 0.0f; for (int i = 0; i < srcArgs.length; i++) { Class srcClass, destClass; srcClass = srcArgs[i]; destClass = destArgs[i]; totalCost += getObjectTransformationCost(srcClass, destClass); } return totalCost; } /** * Gets the number of steps required needed to turn the source class into the * destination class. This represents the number of steps in the object hierarchy * graph. * @param srcClass The source class * @param destClass The destination class * @return The cost of transforming an object */ private static float getObjectTransformationCost(Class srcClass, Class destClass) { float cost = 0.0f; while (destClass != null && !destClass.equals(srcClass)) { if (destClass.isInterface() && isAssignmentCompatible(destClass, srcClass)) { // slight penalty for interface match. // we still want an exact match to override an interface match, but // an interface match should override anything where we have to get a // superclass. cost += 0.25f; break; } cost++; destClass = destClass.getSuperclass(); } /* * If the destination class is null, we've travelled all the way up to * an Object match. We'll penalize this by adding 1.5 to the cost. */ if (destClass == null) { cost += 1.5f; } return cost; } /** * <p>Determine whether a type can be used as a parameter in a method invocation. * This method handles primitive conversions correctly.</p> * * <p>In order words, it will match a <code>Boolean</code> to a <code>boolean</code>, * a <code>Long</code> to a <code>long</code>, * a <code>Float</code> to a <code>float</code>, * a <code>Integer</code> to a <code>int</code>, * and a <code>Double</code> to a <code>double</code>. * Now logic widening matches are allowed. * For example, a <code>Long</code> will not match a <code>int</code>. * * @param parameterType the type of parameter accepted by the method * @param parameterization the type of parameter being tested * * @return true if the assignement is compatible. */ public static final boolean isAssignmentCompatible(Class parameterType, Class parameterization) { // try plain assignment if (parameterType.isAssignableFrom(parameterization)) { return true; } if (parameterType.isPrimitive()) { // this method does *not* do widening - you must specify exactly // is this the right behaviour? Class parameterWrapperClazz = getPrimitiveWrapper(parameterType); if (parameterWrapperClazz != null) { return parameterWrapperClazz.equals(parameterization); } } return false; } /** * Gets the wrapper object class for the given primitive type class. * For example, passing <code>boolean.class</code> returns <code>Boolean.class</code> * @param primitiveType the primitive type class for which a match is to be found * @return the wrapper type associated with the given primitive * or null if no match is found */ public static Class getPrimitiveWrapper(Class primitiveType) { // does anyone know a better strategy than comparing names? if (boolean.class.equals(primitiveType)) { return Boolean.class; } else if (float.class.equals(primitiveType)) { return Float.class; } else if (long.class.equals(primitiveType)) { return Long.class; } else if (int.class.equals(primitiveType)) { return Integer.class; } else if (short.class.equals(primitiveType)) { return Short.class; } else if (byte.class.equals(primitiveType)) { return Byte.class; } else if (double.class.equals(primitiveType)) { return Double.class; } else if (char.class.equals(primitiveType)) { return Character.class; } else { return null; } } /** * Gets the class for the primitive type corresponding to the primitive wrapper class given. * For example, an instance of <code>Boolean.class</code> returns a <code>boolean.class</code>. * @param wrapperType the * @return the primitive type class corresponding to the given wrapper class, * null if no match is found */ public static Class getPrimitiveType(Class wrapperType) { // does anyone know a better strategy than comparing names? if (Boolean.class.equals(wrapperType)) { return boolean.class; } else if (Float.class.equals(wrapperType)) { return float.class; } else if (Long.class.equals(wrapperType)) { return long.class; } else if (Integer.class.equals(wrapperType)) { return int.class; } else if (Short.class.equals(wrapperType)) { return short.class; } else if (Byte.class.equals(wrapperType)) { return byte.class; } else if (Double.class.equals(wrapperType)) { return double.class; } else if (Character.class.equals(wrapperType)) { return char.class; } else { Log log = LogFactory.getLog(MethodUtils.class); if (log.isDebugEnabled()) { log.debug("Not a known primitive wrapper class: " + wrapperType); } return null; } } /** * Find a non primitive representation for given primitive class. * * @param clazz the class to find a representation for, not null * @return the original class if it not a primitive. Otherwise the wrapper class. Not null */ public static Class toNonPrimitiveClass(Class clazz) { if (clazz.isPrimitive()) { Class primitiveClazz = MethodUtils.getPrimitiveWrapper(clazz); // the above method returns if (primitiveClazz != null) { return primitiveClazz; } else { return clazz; } } else { return clazz; } } /** * Represents the key to looking up a Method by reflection. */ private static class MethodDescriptor { private Class cls; private String methodName; private Class[] paramTypes; private boolean exact; private int hashCode; /** * The sole constructor. * * @param cls the class to reflect, must not be null * @param methodName the method name to obtain * @param paramTypes the array of classes representing the paramater types * @param exact whether the match has to be exact. */ public MethodDescriptor(Class cls, String methodName, Class[] paramTypes, boolean exact) { if (cls == null) { throw new IllegalArgumentException("Class cannot be null"); } if (methodName == null) { throw new IllegalArgumentException("Method Name cannot be null"); } if (paramTypes == null) { paramTypes = EMPTY_CLASS_PARAMETERS; } this.cls = cls; this.methodName = methodName; this.paramTypes = paramTypes; this.exact = exact; this.hashCode = methodName.length(); } /** * Checks for equality. * @param obj object to be tested for equality * @return true, if the object describes the same Method. */ public boolean equals(Object obj) { if (!(obj instanceof MethodDescriptor)) { return false; } MethodDescriptor md = (MethodDescriptor) obj; return (exact == md.exact && methodName.equals(md.methodName) && cls.equals(md.cls) && java.util.Arrays.equals(paramTypes, md.paramTypes)); } /** * Returns the string length of method name. I.e. if the * hashcodes are different, the objects are different. If the * hashcodes are the same, need to use the equals method to * determine equality. * @return the string length of method name. */ public int hashCode() { return hashCode; } } }