我這里有一個需求需要修改Person類中的一個屬性上的注解的值進行修改，例如：
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public class Person { private int age; @ApiParam(access="lala") private String name; //get set 方法忽略 } |
將@ApiParam(access=“lala”) 修改為@ApiParam(access=“fafa”)，經過分析是可以實現的，需要用到動態代理進行操作。
具體源碼如下所示：
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@Target({ElementType.PARAMETER, ElementType.METHOD, ElementType.FIELD})@Retention(RetentionPolicy.RUNTIME)public @interface ApiParam { String access() default "";} |
反射+動態代理代碼如下：
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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 是一個自定義的注解 ApiParam apiParam = (ApiParam) value.getAnnotation(ApiParam.class); java.lang.reflect.InvocationHandler invocationHandler = Proxy.getInvocationHandler(apiParam); Field memberValues = invocationHandler.getClass().getDeclaredField("memberValues"); //通過反射獲取memberValues 這個屬性是Map類型 存放著所有的屬性。 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");//修改屬性 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()); //動態代理的方式不會改變原先class文件的內容 }} |
補充：Java自定義注解并實現注解的偽動態參數傳遞
自定義注解，實現記錄接口的調用日志，此注解可以實現傳遞偽動態參數。
一、需要引入的jar包：
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<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、自定義注解：
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package com.example.demo.annotation; import java.lang.annotation.*; @Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface ApiOperationLog { String resourceId() default ""; String operationType(); String description() default "";} |
三、定義切面：
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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@Componentpublic 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(); // 獲取方法上的指定注解 ApiOperationLog annotation = signature.getMethod().getAnnotation(ApiOperationLog.class); // 獲取注解中的參數 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); // 將注解中測參數值保存到數據庫，實現記錄接口調用日志的功能(以下內容省略...) } /** * 獲取注解中傳遞的動態參數的參數值 * * @param joinPoint * @param name * @return */ public String getAnnotationValue(JoinPoint joinPoint, String name) { String paramName = name; // 獲取方法中所有的參數 Map<String, Object> params = getParams(joinPoint); // 參數是否是動態的:#{paramName} if (paramName.matches("^#\\{\\D*\\}")) { // 獲取參數名 paramName = paramName.replace("#{", "").replace("}", ""); // 是否是復雜的參數類型:對象.參數名 if (paramName.contains(".")) { String[] split = paramName.split("\\."); // 獲取方法中對象的內容 Object object = getValue(params, split[0]); // 轉換為JsonObject JSONObject jsonObject = JSONObject.fromObject(object); // 獲取值 Object o = jsonObject.get(split[1]); return String.valueOf(o); } // 簡單的動態參數直接返回 return String.valueOf(getValue(params, paramName)); } // 非動態參數直接返回 return name; } /** * 根據參數名返回對應的值 * * @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; } /** * 獲取方法的參數名和值 * * @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[i], args[i]); } return params; } } |
四：測試前的準備內容：
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// 實體類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層內容package com.example.demo.controller; import com.example.demo.annotation.ApiOperationLog;import com.example.demo.model.User;import org.springframework.web.bind.annotation.RestController; @RestControllerpublic class LoginController { @ApiOperationLog(resourceId = "#{user.id}",operationType = "SAVE",description = "測試注解傳遞復雜動態參數") public void saveUser(User user,String id){ System.out.println("測試注解..."); } @ApiOperationLog(resourceId = "#{id}",operationType = "UPDATE",description = "測試注解傳遞簡單動態參數") public void updateUser(User user,String id){ System.out.println("測試注解..."); } } |
五、測試類：
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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"); }} |
測試結果：
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測試注解...resourceId:1operationType:SAVEdescription:測試注解傳遞復雜動態參數測試注解...resourceId:666operationType:UPDATEdescription:測試注解傳遞簡單動態參數 |
以上為個人經驗，希望能給大家一個參考，也希望大家多多支持服務器之家。如有錯誤或未考慮完全的地方，望不吝賜教。
原文鏈接：https://blog.csdn.net/ltllml44/article/details/84305262
