绝代码农 发表于 2021-8-16 18:46:40

如何动态修改JavaBean中注解的参数值

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<String, Object> values = (Map<String, Object>) 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:


<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
</dependency>
<!-- test -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-test</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<!-- json -->
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.4</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
</dependency>
<dependency>
<groupId>commons-beanutils</groupId>
<artifactId>commons-beanutils</artifactId>
<version>1.8.0</version>
</dependency>
<dependency>
<groupId>commons-collections</groupId>
<artifactId>commons-collections</artifactId>
<version>3.2.1</version>
</dependency>
<dependency>
<groupId>commons-logging</groupId>
<artifactId>commons-logging</artifactId>
<version>1.1.1</version>
</dependency>
<dependency>
<groupId>net.sf.json-lib</groupId>
<artifactId>json-lib</artifactId>
<version>2.4</version>
</dependency>
</dependencies>
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<String, Object> 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);
    // 转换为JsonObject
    JSONObject jsonObject = JSONObject.fromObject(object);
    // 获取值
    Object o = jsonObject.get(split);
    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<String, Object> map, String paramName) {
for (Map.Entry<String, Object> 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<String, Object> getParams(JoinPoint joinPoint) {
Map<String, Object> 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, args);
}
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CodeAE代码之家
。如有错误或未考虑完全的地方,望不吝赐教。
原文链接:https://blog.csdn.net/ltllml44/article/details/84305262

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