我这里有一个需求需要修改Person类中的一个属性上的注解的值进行修改，例如：
public class Person {
private int age;
@ApiParam(access="lala")
private String name;
//get set 方法忽略
}
将@ApiParam(access=“lala”) 修改为@ApiParam(access=“fafa”)，经过分析是可以实现的，需要用到动态代理进行操作。
具体源码如下所示：
@Target({ElementType.PARAMETER, ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
public @interface ApiParam {
String access() default "";
}
反射+动态代理代码如下：
public class TestClazz {
public static void main(String[] args) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
Person person = new Person();
Field value = person.getClass().getDeclaredField("name");
value.setAccessible(true);
//APIParam 是一个自定义的注解
ApiParam apiParam = (ApiParam) value.getAnnotation(ApiParam.class);
java.lang.reflect.InvocationHandler invocationHandler = Proxy.getInvocationHandler(apiParam);
Field memberValues = invocationHandler.getClass().getDeclaredField("memberValues");
//通过反射获取memberValues 这个属性是Map类型 存放着所有的属性。
memberValues.setAccessible(true);
Map values = (Map) memberValues.get(invocationHandler);
String val = (String) values.get("access");
System.out.println("------改之前:"+val);
values.put("access", "fafa");//修改属性
System.out.println("-----------------");
//Field value1 = person.getClass().getDeclaredField("name");
value.setAccessible(true);
ApiParam apiParam1 = (ApiParam) value.getAnnotation(ApiParam.class);
System.out.println("------改之后:"+apiParam1.access());
//动态代理的方式不会改变原先class文件的内容
}
}
补充：Java自定义注解并实现注解的伪动态参数传递
自定义注解，实现记录接口的调用日志，此注解可以实现传递伪动态参数。
一、需要引入的jar包：
org.springframework.boot spring-boot-starter-web org.springframework.boot spring-boot-starter-test org.springframework.boot spring-boot-test org.springframework.boot spring-boot-starter-aop commons-lang commons-lang 2.4 org.apache.commons commons-lang3 commons-beanutils commons-beanutils 1.8.0 commons-collections commons-collections 3.2.1 commons-logging commons-logging 1.1.1 net.sf.json-lib json-lib 2.4
二、自定义注解：
package com.example.demo.annotation;
import java.lang.annotation.*;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ApiOperationLog {
String resourceId() default "";
String operationType();
String description() default "";
}
三、定义切面：
package com.example.demo.aspect;
import com.example.demo.annotation.ApiOperationLog;
import net.sf.json.JSONObject;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;
import java.util.HashMap;
import java.util.Map;
@Aspect
@Component
public class ApiOperationAspect {
@Pointcut("@annotation ( com.example.demo.annotation.ApiOperationLog)")
public void apiLog() {
}
@AfterReturning(pointcut = "apiLog()")
public void recordLog(JoinPoint joinPoint) {
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
// 获取方法上的指定注解
ApiOperationLog annotation = signature.getMethod().getAnnotation(ApiOperationLog.class);
// 获取注解中的参数
String resourceId = getAnnotationValue(joinPoint, annotation.resourceId());
String operationType = getAnnotationValue(joinPoint, annotation.operationType());
String description = getAnnotationValue(joinPoint, annotation.description());
System.out.println("resourceId:" + resourceId);
System.out.println("operationType:" + operationType);
System.out.println("description:" + description);
// 将注解中测参数值保存到数据库，实现记录接口调用日志的功能(以下内容省略...)
}
/**
* 获取注解中传递的动态参数的参数值
*
* @param joinPoint
* @param name
* @return
*/
public String getAnnotationValue(JoinPoint joinPoint, String name) {
String paramName = name;
// 获取方法中所有的参数
Map params = getParams(joinPoint);
// 参数是否是动态的:#{paramName}
if (paramName.matches("^#\\{\\D*\\}")) {
// 获取参数名
paramName = paramName.replace("#{", "").replace("}", "");
// 是否是复杂的参数类型:对象.参数名
if (paramName.contains(".")) {
String[] split = paramName.split("\\.");
// 获取方法中对象的内容
Object object = getValue(params, split[0]);
// 转换为JsonObject
JSONObject jsonObject = JSONObject.fromObject(object);
// 获取值
Object o = jsonObject.get(split[1]);
return String.valueOf(o);
}
// 简单的动态参数直接返回
return String.valueOf(getValue(params, paramName));
}
// 非动态参数直接返回
return name;
}
/**
* 根据参数名返回对应的值
*
* @param map
* @param paramName
* @return
*/
public Object getValue(Map map, String paramName) {
for (Map.Entry entry : map.entrySet()) {
if (entry.getKey().equals(paramName)) {
return entry.getValue();
}
}
return null;
}
/**
* 获取方法的参数名和值
*
* @param joinPoint
* @return
*/
public Map getParams(JoinPoint joinPoint) {
Map params = new HashMap<>(8);
Object[] args = joinPoint.getArgs();
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
String[] names = signature.getParameterNames();
for (int i = 0; i < args.length; i++) {
params.put(names[i], args[i]);
}
return params;
}
}
四：测试前的准备内容：
// 实体类
package com.example.demo.model;
public class User {
private Long id;
private String name;
private int age;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
'}';
}
}
// controller层内容
package com.example.demo.controller;
import com.example.demo.annotation.ApiOperationLog;
import com.example.demo.model.User;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class LoginController {
@ApiOperationLog(resourceId = "#{user.id}",operationType = "SAVE",description = "测试注解传递复杂动态参数")
public void saveUser(User user,String id){
System.out.println("测试注解...");
}
@ApiOperationLog(resourceId = "#{id}",operationType = "UPDATE",description = "测试注解传递简单动态参数")
public void updateUser(User user,String id){
System.out.println("测试注解...");
}
}
五、测试类：
package com.example.demo.aspect;
import com.example.demo.DemoApplication;
import com.example.demo.controller.LoginController;
import com.example.demo.model.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes = DemoApplication.class)
public class ControllerTest {
@Autowired
private LoginController loginController;
@Test
public void test(){
User user = new User();
user.setId(1L);
user.setName("test");
user.setAge(20);
loginController.saveUser(user,"123");
loginController.updateUser(user,"666");
}
}
测试结果：
测试注解... resourceId:1 operationType:SAVE description:测试注解传递复杂动态参数 测试注解... resourceId:666 operationType:UPDATE description:测试注解传递简单动态参数
以上为个人经验，希望能给大家一个参考，也希望大家多多支持脚本之家。如有错误或未考虑完全的地方，望不吝赐教。