Spring 下基于自定义注解拦截方法调用

1org.springframework:spring-context:4.3.11.RELEASE:runtime
2org.aspectj:aspectjweaver:1.8.9:runtime
3javax.inject:javax.inject:1:runtime
4junit:junit:4.12:test
5org.springframework:spring-test:4.3.11.RELEASE:runtime

1@Target(ElementType.METHOD)
2@Retention(RetentionPolicy.RUNTIME)
3public @interface LogStartTime {
4}

 1@Named   //它也必须是一个 Spring bean，它要能被 Spring 扫描到
 2@Aspect  //说明这是一个切面定义类
 3public class MethodStartAspect {
 4
 5    private static ThreadLocal<Long> startTime = new ThreadLocal<>();
 6
 7    @Pointcut("@annotation(cc.unmi.aspects.LogStartTime)") //切面表达式, 从织入效率上还应该加上像 execution 限制
 8    private void logStartTime() {  //切面签名，凡是被 LogStartTime 注解的方法都是 logStartTime() 切面
 9
10    }
11
12    @Before("logStartTime()")  //进入切面 logStartTime() 之前把当前系统时间存入 startTime, 以备后用
13    public void setStartTimeInThreadLocal() {
14        startTime.set(System.currentTimeMillis());
15        System.out.println("saved method start time in threadLocal");
16    }
17
18    public static Long getStartTime() {
19        return startTime.get();
20    }
21
22    public static void clearStartTime() {
23        startTime.set(null);
24    }
25}

1@Configuration
2@EnableAspectJAutoProxy //在原生 Spring 中这个是必须的，在 Spring Boot 中默认是被启用了的
3@ComponentScan(basePackages = "cc.unmi") //注意这个要兼顾到 @AspectJ 注释的类
4public class AppConfig {
5
6}

 1@Named
 2public class UserService {
 3
 4    @LogStartTime  //因为有了这个注解，在方法中便随时能拿到进入该方法的时间，在 ThreadLocal 中
 5    public String fetchUserById(int userId) {
 6        try {
 7            Thread.sleep(2000);
 8        } catch (InterruptedException e) {
 9            e.printStackTrace();
10        }
11
12        System.out.println("start time: " + MethodStartAspect.getStartTime() + ", execution time: " +
13            (System.currentTimeMillis() - MethodStartAspect.getStartTime()));
14
15        return "nameOf" + userId;
16    }
17}

1public class HelloAop {
2
3    public static void main(String[] args) {
4        ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
5
6        UserService userService = context.getBean(UserService.class);
7        System.out.println(userService.fetchUserById(234));
8    }
9}

 1@ContextConfiguration(classes = AppConfig.class)
 2@RunWith(SpringJUnit4ClassRunner.class)
 3public class HelloAopTest {
 4
 5    @Inject
 6    private UserService userService;
 7
 8    @Before
 9    public void setup() {
10        MethodStartAspect.clearStartTime();
11    }
12
13    @Test
14    public void testSettingMethodStartTimeInThreadLocal() {
15        userService.fetchUserById(9999);
16
17        assertThat(MethodStartAspect.getStartTime(), notNullValue());
18    }
19}

1@Target(ElementType.METHOD)
2@Retention(RetentionPolicy.RUNTIME)
3public @interface LogStartTime {
4    String value() default "";
5}

 1@Named
 2@Aspect
 3public class MethodStartAspect {
 4
 5    @Pointcut("execution(* cc.unmi..*(..)) && @annotation(logStartTime)")
 6    private void logStartTimePointcut(LogStartTime logStartTime) {
 7
 8    }
 9
10    @Before("logStartTimePointcut(logStartTime)")
11    public void setStartTimeInThreadLocal(LogStartTime logStartTime) {
12        System.out.println(logStartTime.value());
13    }
14}