Java tutorial
package com.ekingsoft.core.utils; /** * Copyright (c) 2005-2009 springside.org.cn * * Licensed under the Apache License, Version 2.0 (the "License"); * * $Id: ReflectionUtils.java 384 2009-08-28 14:50:14Z calvinxiu $ */ import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import java.util.ArrayList; import java.util.Collection; import java.util.Date; import java.util.List; import org.apache.commons.beanutils.ConvertUtils; import org.apache.commons.beanutils.PropertyUtils; import org.apache.commons.beanutils.converters.DateConverter; import org.apache.commons.lang.StringUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.util.Assert; /** * ??Utils?. * * ?????,?Class,????Utils. * * @author calvin */ public class ReflectionUtils { private static Logger logger = LoggerFactory.getLogger(ReflectionUtils.class); /** * ?,private/protected,??getter. */ public static Object getFieldValue(final Object object, final String fieldName) { Field field = getDeclaredField(object, fieldName); if (field == null) throw new IllegalArgumentException( "Could not find field [" + fieldName + "] on target [" + object + "]"); makeAccessible(field); Object result = null; try { result = field.get(object); } catch (IllegalAccessException e) { logger.error("??{}", e.getMessage()); } return result; } /** * ,private/protected,??setter. */ public static void setFieldValue(final Object object, final String fieldName, final Object value) { Field field = getDeclaredField(object, fieldName); if (field == null) throw new IllegalArgumentException( "Could not find field [" + fieldName + "] on target [" + object + "]"); makeAccessible(field); try { field.set(object, value); } catch (IllegalAccessException e) { logger.error("??:{}", e.getMessage()); } } /** * ,private/protected. */ public static Object invokeMethod(final Object object, final String methodName, final Class<?>[] parameterTypes, final Object[] parameters) throws InvocationTargetException { Method method = getDeclaredMethod(object, methodName, parameterTypes); if (method == null) throw new IllegalArgumentException( "Could not find method [" + methodName + "] on target [" + object + "]"); method.setAccessible(true); try { return method.invoke(object, parameters); } catch (IllegalAccessException e) { logger.error("??:{}", e.getMessage()); } return null; } /** * ?,?DeclaredField. */ protected static Field getDeclaredField(final Object object, final String fieldName) { Assert.notNull(object, "object?"); Assert.hasText(fieldName, "fieldName"); for (Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass .getSuperclass()) { try { return superClass.getDeclaredField(fieldName); } catch (NoSuchFieldException e) { // Field??,? } } return null; } /** * ?,?DeclaredField. */ protected static void makeAccessible(final Field field) { if (!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers())) { field.setAccessible(true); } } /** * ?,?DeclaredMethod. */ protected static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes) { Assert.notNull(object, "object?"); for (Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass .getSuperclass()) { try { return superClass.getDeclaredMethod(methodName, parameterTypes); } catch (NoSuchMethodException e) { // Method??,? } } return null; } /** * ??,Class?. * eg. * public UserDao extends HibernateDao<User> * * @param clazz The class to introspect * @return the first generic declaration, or Object.class if cannot be determined */ @SuppressWarnings("unchecked") public static <T> Class<T> getSuperClassGenricType(final Class clazz) { return getSuperClassGenricType(clazz, 0); } /** * ??,Class?. * * public UserDao extends HibernateDao<User,Long> * * @param clazz clazz The class to introspect * @param index the Index of the generic ddeclaration,start from 0. * @return the index generic declaration, or Object.class if cannot be determined */ @SuppressWarnings("unchecked") public static Class getSuperClassGenricType(final Class clazz, final int index) { Type genType = clazz.getGenericSuperclass(); if (!(genType instanceof ParameterizedType)) { logger.warn(clazz.getSimpleName() + "'s superclass not ParameterizedType"); return Object.class; } Type[] params = ((ParameterizedType) genType).getActualTypeArguments(); if (index >= params.length || index < 0) { logger.warn("Index: " + index + ", Size of " + clazz.getSimpleName() + "'s Parameterized Type: " + params.length); return Object.class; } if (!(params[index] instanceof Class)) { logger.warn(clazz.getSimpleName() + " not set the actual class on superclass generic parameter"); return Object.class; } return (Class) params[index]; } /** * ????(getter),??List. * * @param collection ???. * @param propertyName ??????. */ @SuppressWarnings("unchecked") public static List fetchElementPropertyToList(final Collection collection, final String propertyName) { List list = new ArrayList(); try { for (Object obj : collection) { list.add(PropertyUtils.getProperty(obj, propertyName)); } } catch (Exception e) { convertToUncheckedException(e); } return list; } /** * ????(getter),??. * * @param collection ???. * @param propertyName ??????. * @param separator . */ @SuppressWarnings("unchecked") public static String fetchElementPropertyToString(final Collection collection, final String propertyName, final String separator) { List list = fetchElementPropertyToList(collection, propertyName); return StringUtils.join(list, separator); } /** * ?clazzproperty. * * @param value ? * @param clazz ???Class * @param propertyName ???Class. */ public static Object convertValue(Object value, Class<?> toType) { try { DateConverter dc = new DateConverter(); dc.setUseLocaleFormat(true); dc.setPatterns(new String[] { "yyyy-MM-dd", "yyyy-MM-dd HH:mm:ss" }); ConvertUtils.register(dc, Date.class); return ConvertUtils.convert(value, toType); } catch (Exception e) { throw convertToUncheckedException(e); } } /** * ??checked exception?unchecked exception. */ public static IllegalArgumentException convertToUncheckedException(Exception e) { if (e instanceof IllegalAccessException || e instanceof IllegalArgumentException || e instanceof NoSuchMethodException) return new IllegalArgumentException("Refelction Exception.", e); else return new IllegalArgumentException(e); } }