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Java 反射工具类 ReflectionUtils



import lombok.extern.slf4j.Slf4j;

import java.lang.reflect.*;

/**
* 反射的 Utils 函数集合
* 提供访问私有变量, 获取泛型类型 Class, 提取集合中元素属性等 Utils 函数
*/
@Slf4j
public class ReflectionUtils {


/**
* 直接读取对象的属性值, 忽略 private/protected 修饰符, 也不经过 getter
*
* @param object
* @param fieldName
* @return
*/
public static Object getFieldValue(Object object, 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) {
log.error("getFieldValue:", e);
}

return result;
}

/**
* 直接设置对象属性值, 忽略 private/protected 修饰符, 也不经过 setter
*
* @param object
* @param fieldName
* @param value
*/
public static void setFieldValue(Object object, String fieldName, 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) {
log.error("setFieldValue:", e);
}
}


/**
* 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 EmployeeDao extends BaseDao<Employee, String>
*
* @param clazz
* @param index
* @return
*/
@SuppressWarnings("unchecked")
public static Class getSuperClassGenricType(Class clazz, int index) {
Type genType = clazz.getGenericSuperclass();

if (!(genType instanceof ParameterizedType)) {
return Object.class;
}

Type[] params = ((ParameterizedType) genType).getActualTypeArguments();

if (index >= params.length || index < 0) {
return Object.class;
}

if (!(params[index] instanceof Class)) {
return Object.class;
}

return (Class) params[index];
}

/**
* 通过反射, 获得 Class 定义中声明的父类的泛型参数类型
* 如: public EmployeeDao extends BaseDao<Employee, String>
*
* @param <T>
* @param clazz
* @return
*/
@SuppressWarnings("unchecked")
public static <T> Class<T> getSuperGenericType(Class clazz) {
return getSuperClassGenricType(clazz, 0);
}

/**
* 循环向上转型, 获取对象的 DeclaredMethod
*
* @param object
* @param methodName
* @param parameterTypes
* @return
*/
public static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes) {

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;
}

/**
* 使 filed 变为可访问
*
* @param field
*/
public static void makeAccessible(Field field) {
if (!Modifier.isPublic(field.getModifiers())) {
field.setAccessible(true);
}
}

/**
* 循环向上转型, 获取对象的 DeclaredField
*
* @param object
* @param filedName
* @return
*/
public static Field getDeclaredField(Object object, String filedName) {

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

/**
* 直接调用对象方法, 而忽略修饰符(private, protected)
*
* @param object
* @param methodName
* @param parameterTypes
* @param parameters
* @return
* @throws InvocationTargetException
* @throws IllegalArgumentException
*/
public static Object invokeMethod(Object object, String methodName, Class<?>[] parameterTypes,
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) {
log.error("invokeMethod:", e);
}

return null;
}
}

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