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【Java】 Java反射工具类
作者:磊.Y / 发布于2011/10/26/ 863
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.
<div>package reflection;</div>
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;</div>
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;</div>
<div>/**
* 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 lei
*/
public class ReflectionUtils {</div>
<div>private static Logger logger = LoggerFactory.getLogger(ReflectionUtils.class);</div>
<div>private ReflectionUtils() {
}
<div>/**
 * 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);</div>
if (field == null)
throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");</div>
<div>makeAccessible(field);</div>
<div>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;
}
<div>/**
 * 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);</div>
if (field == null)
throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");</div>
<div>makeAccessible(field);</div>
<div>try {
field.set(object, value);
} catch (IllegalAccessException e) {
logger.error("不可能抛出的异常:{}", e.getMessage());
}
}
<div>/**
 * 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);
}
<div>/**
 * 循环向上转型,获取类的DeclaredField.
 */
@SuppressWarnings("unchecked")
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;
}
<div>/**
 * 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);
}
}
<div>/**
 * 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
 */
@SuppressWarnings("unchecked")
public static Class getSuperClassGenricType(final Class clazz) {
return getSuperClassGenricType(clazz, 0);
}
<div>/**
 * 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
 */</div>
<div>@SuppressWarnings("unchecked")
public static Class getSuperClassGenricType(final Class clazz, final int index) {</div>
<div>Type genType = clazz.getGenericSuperclass();</div>
if (!(genType instanceof ParameterizedType)) {
logger.warn(clazz.getSimpleName() + "'s superclass not ParameterizedType");
return Object.class;
}
<div>Type[] params = ((ParameterizedType) genType).getActualTypeArguments();</div>
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];
}
<div>/**
 * 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 {</div>
<div>List list = new ArrayList();</div>
<div>for (Object obj : collection) {
list.add(PropertyUtils.getProperty(obj, propertyName));
}
<div>return list;
}
<div>/**
 * 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.
 */
@SuppressWarnings("unchecked")
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);
}
}
</div>
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