SpringMVC中的自定义注解-2-阿里云开发者社区

自定义注解

如何使用自定义注解？

案例1:获取类与方法上的注解值

MyAnnotation1

package com.liao.annotation;
import java.lang.annotation.*;
/**
 * MyAnnotation1注解可以用在类、接口、属性、方法上
 * 注解运行期也保留
 * 不可继承
 */
@Target({ElementType.TYPE, ElementType.FIELD,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MyAnnotation1 {
    String name();
}

MyAnnotation2

package com.liao.annotation;
import com.liao.model.TranscationModel;
import java.lang.annotation.*;
/**
 *  MyAnnotation2注解可以用在方法上
 *  注解运行期也保留
 *  不可继承
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface MyAnnotation2 {
    TranscationModel model() default TranscationModel.ReadWrite;
}

MyAnnotation3

package com.liao.annotation;
import com.l.model.TranscationModel;
import java.lang.annotation.*;
/**
 * MyAnnotation3注解可以用在方法上
 * 注解运行期也保留
 * 可继承
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface MyAnnotation3 {
    TranscationModel[] models() default TranscationModel.ReadWrite;
}

Demo1测试类 : 获取类与方法上的注解值

package com.liao.annotation.demo;
import com.liao.annotation.MyAnnotation1;
import com.liao.annotation.MyAnnotation2;
import com.liao.annotation.MyAnnotation3;
import com.liao.model.TranscationModel;
/**
 * 获取类与方法上的注解值
 */
@MyAnnotation1(name = "abc")
public class Demo1 {
    @MyAnnotation1(name = "xyz")
    private Integer age;
    @MyAnnotation2(model = TranscationModel.Read)
    public void list() {
        System.out.println("list");
    }
    @MyAnnotation3(models = {TranscationModel.Read, TranscationModel.Write})
    public void edit() {
        System.out.println("edit");
    }
}

案例二:获取类属性上的注解属性值

TestAnnotation

package com.liao.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
//@Retention(RetentionPolicy.SOURCE)
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface TestAnnotation {
    String value() default "默认value值";
    String what() default "这里是默认的what属性对应的值";
}

测试类

package com.liao.annotation.demo2;
import com.liao.annotation.TestAnnotation;
/**
 * 获取类属性上的注解属性值
 */
public class Demo2 {
    @TestAnnotation(value = "这就是value对应的值_msg1", what = "这就是what对应的值_msg1")
    private static String msg1;
    @TestAnnotation("这就是value对应的值1")
    private static String msg2;
    @TestAnnotation(value = "这就是value对应的值2")
    private static String msg3;
    @TestAnnotation(what = "这就是what对应的值")
    private static String msg4;
}

测试

package com.liao.annotation.demo2;
import com.liao.annotation.TestAnnotation;
import org.junit.Test;
public class Demo2Test {
    @Test
    public void test1() throws Exception {
        TestAnnotation msg1 = Demo2.class.getDeclaredField("msg1").getAnnotation(TestAnnotation.class);
        System.out.println(msg1.value());
        System.out.println(msg1.what());
    }
    @Test
    public void test2() throws Exception{
        TestAnnotation msg2 = Demo2.class.getDeclaredField("msg2").getAnnotation(TestAnnotation.class);
        System.out.println(msg2.value());
        System.out.println(msg2.what());
    }
    @Test
    public void test3() throws Exception{
        TestAnnotation msg3 = Demo2.class.getDeclaredField("msg3").getAnnotation(TestAnnotation.class);
        System.out.println(msg3.value());
        System.out.println(msg3.what());
    }
    @Test
    public void test4() throws Exception{
        TestAnnotation msg4 = Demo2.class.getDeclaredField("msg4").getAnnotation(TestAnnotation.class);
        System.out.println(msg4.value());
        System.out.println(msg4.what());
    }
}

示例三：获取参数修饰注解对应的属性值

IsNotNull自定义注解

package com.liao.annotation;
import java.lang.annotation.*;
/**
 * 非空注解：使用在方法的参数上，false表示此参数可以为空，true不能为空
 */
@Documented
@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
public @interface IsNotNull {
    boolean value() default false;
}

测试：

package com.liao.annotation.demo3;
import com.liao.annotation.IsNotNull;
/**
 * 获取参数修饰注解对应的属性值
 */
public class Demo3 {
    public void hello1(@IsNotNull(true) String name) {
        System.out.println("hello:" + name);
    }
    public void hello2(@IsNotNull String name) {
        System.out.println("hello:" + name);
    }
}

package com.liao.annotation.demo3;
import com.liao.annotation.IsNotNull;
import org.junit.Test;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;
public class Demo3Test {
    @Test
    public void hello1() throws Exception {
        Demo3 demo3 = new Demo3();
        for (Parameter parameter : demo3.getClass().getMethod("hello1", String.class).getParameters()) {
            IsNotNull annotation = parameter.getAnnotation(IsNotNull.class);
            if(annotation != null){
                System.out.println(annotation.value());//true
            }
        }
    }
    @Test
    public void hello2() throws Exception {
        Demo3 demo3 = new Demo3();
        for (Parameter parameter : demo3.getClass().getMethod("hello2", String.class).getParameters()) {
            IsNotNull annotation = parameter.getAnnotation(IsNotNull.class);
            if(annotation != null){
                System.out.println(annotation.value());//false
            }
        }
    }
    @Test
    public void hello3() throws Exception {
//        模拟浏览器传递到后台的参数 解读@requestParam
        String name = "zs";
        Demo3 demo3 = new Demo3();
        Method method = demo3.getClass().getMethod("hello1", String.class);
        for (Parameter parameter : method.getParameters()) {
            IsNotNull annotation = parameter.getAnnotation(IsNotNull.class);
            if(annotation != null){
                System.out.println(annotation.value());//true
                if (annotation.value() && !"".equals(name)){
                    method.invoke(demo3,name);
                }
            }
        }
    }
}

Aop自定义注解的应用

MyLog自定义注解类

package com.liao.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyLog {
    String desc();
}

MyLogAspect切面类

package com.liao.aspect;
import com.liao.annotation.MyLog;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
@Component
@Aspect
public class MyLogAspect {
    private static final Logger logger = LoggerFactory.getLogger(MyLogAspect.class);
    /**
     * 只要用到了com.javaxl.p2.annotation.springAop.MyLog这个注解的，就是目标类
     */
    @Pointcut("@annotation(com.liao.annotation.MyLog)")
    private void MyValid() {
    }
    @Before("MyValid()")
    public void before(JoinPoint joinPoint) {
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        logger.debug("[" + signature.getName() + " : start.....]");
        System.out.println("[" + signature.getName() + " : start.....]");
        MyLog myLog = signature.getMethod().getAnnotation(MyLog.class);
        logger.debug("【目标对象方法被调用时候产生的日志，记录到日志表中】："+myLog.desc());
        System.out.println("【目标对象方法被调用时候产生的日志，记录到日志表中】：" + myLog.desc());
    }
}

controller层

package com.liao.web;
import com.liao.annotation.aop.MyLog;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
public class LogController {
    @RequestMapping("/mylog")
    @MyLog(desc = "这是结合spring aop知识，讲解自定义注解应用的一个案例")
    public void testLogAspect(){
        System.out.println("记录日志。。。");
    }
}

SpringMVC中的自定义注解-2

自定义注解

如何使用自定义注解？

案例1:获取类与方法上的注解值

案例二:获取类属性上的注解属性值

示例三：获取参数修饰注解对应的属性值

Aop自定义注解的应用

MyLog自定义注解类

MyLogAspect切面类

controller层

热门文章

最新文章

相关电子书