reflectionutils.java

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/*
 * 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.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Simple utility class for working with the reflection API and handling
 * reflection exceptions.
 *
 * <p>Only intended for internal use.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rod Johnson
 * @author Costin Leau
 * @author Sam Brannen
 * @since 1.2.2
 */
public abstract class ReflectionUtils {

	/**
	 * Attempt to find a {@link Field field} on the supplied {@link Class} with
	 * the supplied <code>name</code> and {@link Class type}. Searches all
	 * superclasses up to {@link Object}.
	 * @param clazz the class to introspect
	 * @param name the name of the field
	 * @param type the type of the field
	 * @return the corresponding Field object, or <code>null</code> if not found
	 * @throws IllegalArgumentException if the class or field type is
	 * <code>null</code> or if the field name is <em>empty</em>
	 */
	public static Field findField(final Class clazz, final String name, final Class type) {
		Assert.notNull(clazz, "The 'class to introspect' supplied to findField() can not be null.");
		Assert.hasText(name, "The field name supplied to findField() can not be empty.");
		Assert.notNull(type, "The field type supplied to findField() can not be null.");
		Class searchType = clazz;
		while (!Object.class.equals(searchType) && searchType != null) {
			final Field[] fields = searchType.getDeclaredFields();
			for (int i = 0; i < fields.length; i++) {
				Field field = fields[i];
				if (name.equals(field.getName()) && type.equals(field.getType())) {
					return field;
				}
			}
			searchType = searchType.getSuperclass();
		}
		return null;
	}

	/**
	 * Set the field represented by the supplied {@link Field field object} on
	 * the specified {@link Object target object} to the specified
	 * <code>value</code>. In accordance with
	 * {@link Field#set(Object, Object)} semantics, the new value is
	 * automatically unwrapped if the underlying field has a primitive type.
	 * <p>Thrown exceptions are handled via a call to
	 * {@link #handleReflectionException(Exception)}.
	 * @param field the field to set
	 * @param target the target object on which to set the field
	 * @param value the value to set; may be <code>null</code>
	 */
	public static void setField(Field field, Object target, Object value) {
		try {
			field.set(target, value);
		}
		catch (IllegalAccessException ex) {
			handleReflectionException(ex);
			throw new IllegalStateException("Unexpected reflection exception - " + ex.getClass().getName() + ": " +
					ex.getMessage());
		}
	}

	/**
	 * Attempt to find a {@link Method} on the supplied class with the supplied name
	 * and no parameters. Searches all superclasses up to <code>Object</code>.
	 * <p>Returns <code>null</code> if no {@link Method} can be found.
	 * @param clazz the class to introspect
	 * @param name the name of the method
	 * @return the Method object, or <code>null</code> if none found
	 */
	public static Method findMethod(Class clazz, String name) {
		return findMethod(clazz, name, new Class[0]);
	}

	/**
	 * Attempt to find a {@link Method} on the supplied class with the supplied name
	 * and parameter types. Searches all superclasses up to <code>Object</code>.
	 * <p>Returns <code>null</code> if no {@link Method} can be found.
	 * @param clazz the class to introspect
	 * @param name the name of the method
	 * @param paramTypes the parameter types of the method
	 * @return the Method object, or <code>null</code> if none found
	 */
	public static Method findMethod(Class clazz, String name, Class[] paramTypes) {
		Assert.notNull(clazz, "Class must not be null");
		Assert.notNull(name, "Method name must not be null");
		Class searchType = clazz;
		while (!Object.class.equals(searchType) && searchType != null) {
			Method[] methods = (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods());
			for (int i = 0; i < methods.length; i++) {
				Method method = methods[i];
				if (name.equals(method.getName()) && Arrays.equals(paramTypes, method.getParameterTypes())) {
					return method;
				}
			}
			searchType = searchType.getSuperclass();
		}
		return null;
	}

	/**
	 * Invoke the specified {@link Method} against the supplied target object
	 * with no arguments. The target object can be <code>null</code> when
	 * invoking a static {@link Method}.
	 * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
	 * @param method the method to invoke
	 * @param target the target object to invoke the method on
	 * @return the invocation result, if any
	 * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
	 */
	public static Object invokeMethod(Method method, Object target) {
		return invokeMethod(method, target, null);
	}

	/**
	 * Invoke the specified {@link Method} against the supplied target object
	 * with the supplied arguments. The target object can be <code>null</code>
	 * when invoking a static {@link Method}.
	 * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
	 * @param method the method to invoke
	 * @param target the target object to invoke the method on
	 * @param args the invocation arguments (may be <code>null</code>)
	 * @return the invocation result, if any
	 */
	public static Object invokeMethod(Method method, Object target, Object[] args) {
		try {
			return method.invoke(target, args);
		}
		catch (Exception ex) {
			handleReflectionException(ex);
		}
		throw new IllegalStateException("Should never get here");
	}

	/**
	 * Invoke the specified JDBC API {@link Method} against the supplied
	 * target object with no arguments.
	 * @param method the method to invoke
	 * @param target the target object to invoke the method on
	 * @return the invocation result, if any
	 * @throws SQLException the JDBC API SQLException to rethrow (if any)
	 * @see #invokeJdbcMethod(java.lang.reflect.Method, Object, Object[])
	 */
	public static Object invokeJdbcMethod(Method method, Object target) throws SQLException {
		return invokeJdbcMethod(method, target, null);
	}

	/**
	 * Invoke the specified JDBC API {@link Method} against the supplied
	 * target object with the supplied arguments.
	 * @param method the method to invoke
	 * @param target the target object to invoke the method on
	 * @param args the invocation arguments (may be <code>null</code>)
	 * @return the invocation result, if any
	 * @throws SQLException the JDBC API SQLException to rethrow (if any)
	 * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
	 */
	public static Object invokeJdbcMethod(Method method, Object target, Object[] args) throws SQLException {
		try {
			return method.invoke(target, args);
		}
		catch (IllegalAccessException ex) {
			handleReflectionException(ex);
		}
		catch (InvocationTargetException ex) {
			if (ex.getTargetException() instanceof SQLException) {
				throw (SQLException) ex.getTargetException();
			}
			handleInvocationTargetException(ex);
		}
		throw new IllegalStateException("Should never get here");
	}

	/**
	 * Handle the given reflection exception. Should only be called if
	 * no checked exception is expected to be thrown by the target method.
	 * <p>Throws the underlying RuntimeException or Error in case of an
	 * InvocationTargetException with such a root cause. Throws an
	 * IllegalStateException with an appropriate message else.
	 * @param ex the reflection exception to handle
	 */
	public static void handleReflectionException(Exception ex) {
		if (ex instanceof NoSuchMethodException) {
			throw new IllegalStateException("Method not found: " + ex.getMessage());
		}
		if (ex instanceof IllegalAccessException) {
			throw new IllegalStateException("Could not access method: " + ex.getMessage());
		}
		if (ex instanceof InvocationTargetException) {
			handleInvocationTargetException((InvocationTargetException) ex);
		}
		if (ex instanceof RuntimeException) {
			throw (RuntimeException) ex;
		}
		handleUnexpectedException(ex);
	}

	/**
	 * Handle the given invocation target exception. Should only be called if
	 * no checked exception is expected to be thrown by the target method.
	 * <p>Throws the underlying RuntimeException or Error in case of such
	 * a root cause. Throws an IllegalStateException else.
	 * @param ex the invocation target exception to handle
	 */
	public static void handleInvocationTargetException(InvocationTargetException ex) {
		rethrowRuntimeException(ex.getTargetException());
	}

	/**
	 * Rethrow the given {@link Throwable exception}, which is presumably the
	 * <em>target exception</em> of an {@link InvocationTargetException}.
	 * Should only be called if no checked exception is expected to be thrown by
	 * the target method.
	 * <p>Rethrows the underlying exception cast to an {@link RuntimeException}
	 * or {@link Error} if appropriate; otherwise, throws an
	 * {@link IllegalStateException}.
	 * @param ex the exception to rethrow
	 * @throws RuntimeException the rethrown exception
	 */
	public static void rethrowRuntimeException(Throwable ex) {
		if (ex instanceof RuntimeException) {
			throw (RuntimeException) ex;
		}
		if (ex instanceof Error) {
			throw (Error) ex;
		}
		handleUnexpectedException(ex);
	}

	/**
	 * Rethrow the given {@link Throwable exception}, which is presumably the
	 * <em>target exception</em> of an {@link InvocationTargetException}.
	 * Should only be called if no checked exception is expected to be thrown by
	 * the target method.
	 * <p>Rethrows the underlying exception cast to an {@link Exception} or
	 * {@link Error} if appropriate; otherwise, throws an
	 * {@link IllegalStateException}.
	 * @param ex the exception to rethrow
	 * @throws Exception the rethrown exception (in case of a checked exception)
	 */
	public static void rethrowException(Throwable ex) throws Exception {
		if (ex instanceof Exception) {
			throw (Exception) ex;
		}
		if (ex instanceof Error) {
			throw (Error) ex;
		}
		handleUnexpectedException(ex);