ReflectionUtils.java

/**
 * Copyright 2013-2014 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 com.iflytek.edu.cloud.frame.utils;


import org.apache.commons.beanutils.PropertyUtils;
import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.Assert;

import java.lang.reflect.Field;
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.List;

/**
 * 反射的Utils函数集合. 提供访问私有变量,获取泛型类型Class,提取集合中元素的属性等Utils函数.
 *
 * @author dsliu
 */
@SuppressWarnings("rawtypes")
public class ReflectionUtils {

    private static Logger logger = LoggerFactory.getLogger(ReflectionUtils.class);

    private ReflectionUtils() {
    }

    /**
     * 直接读取对象属性值,无视private/protected修饰符,不经过getter函数.
     */
    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("不可能抛出的异常{}", e.getMessage());
        }
        return result;
    }

    /**
     * 直接设置对象属性值,无视private/protected修饰符,不经过setter函数.
     */
    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("不可能抛出的异常:{}", e.getMessage());
        }
    }

    /**
     * 循环向上转型,获取对象的DeclaredField.
     */
    protected static Field getDeclaredField(final Object object, final String fieldName) {
        Assert.notNull(object, "object不能为空");
        return getDeclaredField(object.getClass(), fieldName);
    }

    /**
     * 循环向上转型,获取类的DeclaredField.
     */
	protected static Field getDeclaredField(final Class clazz, final String fieldName) {
        Assert.notNull(clazz, "clazz不能为空");
        Assert.hasText(fieldName, "fieldName");
        for (Class superClass = clazz; superClass != Object.class; superClass = superClass.getSuperclass()) {
            try {
                return superClass.getDeclaredField(fieldName);
            } catch (NoSuchFieldException e) {
                // Field不在当前类定义,继续向上转型
            }
        }
        return null;
    }

    /**
     * 强制转换fileld可访问.
     */
    protected static void makeAccessible(final Field field) {
        if (!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers())) {
            field.setAccessible(true);
        }
    }

    /**
     * 通过反射,获得定义Class时声明的父类的泛型参数的类型. 如public UserDao extends HibernateDao<User>
     *
     * @param clazz The class to introspect
     * @return the first generic declaration, or Object.class if cannot be
     * determined
     */
    public static Class getSuperClassGenricType(final Class clazz) {
        return getSuperClassGenricType(clazz, 0);
    }

    /**
     * 通过反射,获得定义Class时声明的父类的泛型参数的类型. 如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
     */

    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];
    }

    /**
     * 提取集合中的对象的属性,组合成List.
     *
     * @param collection     来源集合.
     * @param propertityName 要提取的属性名.
     */
    @SuppressWarnings("unchecked")
    public static List fetchElementPropertyToList(final Collection collection, final String propertyName) throws Exception {

        List list = new ArrayList();

        for (Object obj : collection) {
            list.add(PropertyUtils.getProperty(obj, propertyName));
        }

        return list;
    }

    /**
     * 提取集合中的对象的属性,组合成由分割符分隔的字符串.
     *
     * @param collection     来源集合.
     * @param propertityName 要提取的属性名.
     * @param separator      分隔符.
     */
    public static String fetchElementPropertyToString(final Collection collection, final String propertyName, final String separator) throws Exception {
        List list = fetchElementPropertyToList(collection, propertyName);
        return StringUtils.join(list.toArray(), separator);
    }
}