获取实现接口的的第一个泛型实例工具类

package cn.baozun.crm.base.util;

/**

 * Copyright (c) 2005-2009 springside.org.cn

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * 

 * $Id: ReflectionUtils.java,v 1.2 2009/12/02 02:09:22 kingapex Exp $

 */

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.List;

import org.apache.commons.beanutils.PropertyUtils;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.util.Assert;

/**

 * 反射的Util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,转换字符串到对象等Util函数.

 * 

 * @author calvin

 */

public class ReflectionUtils {

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

/**
* 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());
}
}

/**
* 直接调用对象方法, 无视private/protected修饰符.
*/
public static Object invokeMethod(final Object object, final String methodName, final Class<?>[] parameterTypes,
final Object[] parameters) {
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 (Exception e) {
throw convertReflectionExceptionToUnchecked(e);
}
}

/**
* 循环向上转型, 获取对象的DeclaredField.
* 
* 如向上转型到Object仍无法找到, 返回null.
*/
protected static Field getDeclaredField(final Object object, final String fieldName) {
Assert.notNull(object, "object不能为空");
Assert.hasText(fieldName, "fieldName");
for (Class<?> superClass = object.getClass(); 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;
}

/**
* 强行设置Field可访问.
*/
protected static void makeAccessible(final Field field) {
if (!Modifier.isPublic(field.getModifiers()) || !Modifier.isPublic(field.getDeclaringClass().getModifiers())) {
field.setAccessible(true);
}
}

/**
* 循环向上转型,获取对象的DeclaredMethod.
* 
* 如向上转型到Object仍无法找到, 返回null.
*/
protected static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes) {
Assert.notNull(object, "object不能为空");

for (Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass
.getSuperclass()) {
try {
return superClass.getDeclaredMethod(methodName, parameterTypes);
} catch (NoSuchMethodException e) {
// Method不在当前类定义,继续向上转型
}
}
return null;
}

/**
* 通过反射,获得Class定义中声明的父类的泛型参数的类型.
* 如无法找到, 返回Object.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);
}

/**
* 通过反射,获得定义Class时声明的父类的泛型参数的类型.
* 如无法找到, 返回Object.class.
* 
* 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
*/
@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];
}

public static Class getInterfaceClassGenricType(final Class clazz, final int index) {

Type[] genTypes = clazz.getGenericInterfaces();
if(genTypes==null || genTypes.length==0 ){
logger.warn(clazz.getSimpleName()  + "'s not impl interface ");
return Object.class;
}

if (!(genTypes[0] instanceof ParameterizedType)) {
logger.warn(clazz.getSimpleName()  + "'s superclass not ParameterizedType");
return Object.class;
}

Type[] params = ((ParameterizedType) genTypes[0]).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(通过getter函数), 组合成List.
* 
* @param collection 来源集合.
* @param propertyName 要提取的属性名.
*/
@SuppressWarnings("unchecked")
public static List convertElementPropertyToList(final Collection collection, final String propertyName) {
List list = new ArrayList();

try {
for (Object obj : collection) {
list.add(PropertyUtils.getProperty(obj, propertyName));
}
} catch (Exception e) {
throw convertReflectionExceptionToUnchecked(e);
}

return list;
}

/**
* 提取集合中的对象的属性(通过getter函数), 组合成由分割符分隔的字符串.
* 
* @param collection 来源集合.
* @param propertyName 要提取的属性名.
* @param separator 分隔符.
*/

// @SuppressWarnings("unchecked")

// public static String convertElementPropertyToString(final Collection collection, final String propertyName,

// final String separator) {

// List list = convertElementPropertyToList(collection, propertyName);

// return StringUtils.join(list, separator);

// }

/**
* 转换字符串类型到clazz的property类型的值.
* 
* @param value 待转换的字符串
* @param clazz 提供类型信息的Class
* @param propertyName 提供类型信息的Class的属性.
*/

// 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 convertReflectionExceptionToUnchecked(e);

// }

// }

/**
* 将反射时的checked exception转换为unchecked exception.
*/
public static RuntimeException convertReflectionExceptionToUnchecked(Exception e) {
if (e instanceof IllegalAccessException || e instanceof IllegalArgumentException
|| e instanceof NoSuchMethodException)
return new IllegalArgumentException("Reflection Exception.", e);
else if (e instanceof InvocationTargetException)
return new RuntimeException("Reflection Exception.", ((InvocationTargetException) e).getTargetException());
else if (e instanceof RuntimeException) {
return (RuntimeException) e;
}
return new RuntimeException("Unexpected Checked Exception.", e);
}

}