【spring boot】SpringBoot初学（6）– aop与自定义注解

前言

github： https://github.com/vergilyn/SpringBootDemo

一、AOP

官方demo：https://github.com/spring-projects/spring-boot/tree/master/spring-boot-samples/spring-boot-sample-aop

1.1 pom依赖

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-aop</artifactId>
</dependency>

1.2 demo

对aop的properties配置有：

#### AOP
# spring.aop.auto=true # Add @EnableAspectJAutoProxy.
# spring.aop.proxy-target-class=false # Whether subclass-based (CGLIB) proxies are to be created (true) as opposed to standard Java interface-based proxies (false).

这两个配置都允许注解配置： @EnableAspectJAutoProxy (proxyTargetClass = false,exposeProxy = false)，默认值都是false
    代码目录：

代码说明：

1. AopService：被aop增强的class。

AopAspect：aop增强的class。

AopApplication：启动、测试class。

2. 整个demo很简单，实际要用到再去细看AOP也可以。

@Component
public class AopService {
    @Value("${aop.name:Dante}")
    private String name;

    public String getMsg() {
        return "Hello, " + this.name;
    }
}

@Aspect
@Component
public class AopAspect {
    @AfterReturning("execution(* com.vergilyn.demo.springboot.aop.*Service.*(..))")
    public void afterReturning(JoinPoint joinPoint) {
        System.out.println("aop @AfterReturning: " + joinPoint);
    }
}

@SpringBootApplication
//开启aop支持; 可properties配置proxyTargetClass、exposeProxy
//@EnableAspectJAutoProxy //(proxyTargetClass = true,exposeProxy = false)
public class AopApplication implements CommandLineRunner {
    @Autowired
    private AopService aopService;

    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(AopApplication.class);
        app.setAdditionalProfiles("aop");
        app.run(args);
    }

    @Override
    public void run(String... args) {
        System.out.println(this.aopService.getMsg());
    }
}

aop.name=vergilyn

#### AOP
# spring.aop.auto=true # Add @EnableAspectJAutoProxy.
# spring.aop.proxy-target-class=false # Whether subclass-based (CGLIB) proxies are to be created (true) as opposed to standard Java interface-based proxies (false).

application-aop.properties

console输出结果：

aop @AfterReturning: execution(String com.vergilyn.demo.springboot.aop.AopService.getMsg())
Hello, vergilyn

二、自定义注解

其实我本来是要做的是：自定义注解注入Logger，所以才顺道写了一下AOP的demo。

需求：

1. 通过注解，注入Logger（org.apache.log4j.Logger）。

说明：

之前注入日志都是在每个类中写代码，ex:

public class XXclass{
  private Logger log = Logger.getLogger(XXclass.class);
}

现在想通过自定义注解注入，ex:

public class XXclass{
  private Logger log1 = Logger.getLogger(XXclass.class);

  @Log //自定义注解
  private Logger log2;
}

其中log2的效果与log1一样。

实现：

1. 可以通过aop注入。

2. 可以通过实现org.springframework.beans.factory.config.BeanPostProcessor注入;

（其实是一样的，了解spring的就知道Bean的注入都会通过BeanPostProcessor）

代码demo:

注解Log的定义

@Retention(RUNTIME)
@Target(FIELD)
@Documented
@Inherited
public @interface Log {

}

注解的实现

@Component
@Aspect
public class LogInjector implements BeanPostProcessor {

    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
        return bean;
    }

    public Object postProcessBeforeInitialization(final Object bean,String beanName) throws BeansException {
        ReflectionUtils.doWithFields(bean.getClass(), new FieldCallback() {
            public void doWith(Field field) throws IllegalArgumentException,
                    IllegalAccessException {
                // System.out.println("Logger Inject into :" + bean.getClass());
                // make the field accessible if defined private
                ReflectionUtils.makeAccessible(field);
                if (field.getAnnotation(Log.class) != null) {
                    Logger log = Logger.getLogger(bean.getClass());
                    field.set(bean, log);
                }
            }
        });
        return bean;
    }
}

启动、测试类

@SpringBootApplication
public class AnnotationApplication implements CommandLineRunner{
    @Log
    private Logger log;

    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(AnnotationApplication.class);
        app.setAdditionalProfiles("log");
        app.run(args);
    }

    @Override
    public void run(String... args) throws Exception {
        System.out.println("log : " + log);
        log.info("log 注解注入成功. log：" + log);
    }
}

输出结果：

log : org.apache.log4j.Logger@24d31b86
2017-03-19 19:44:34.576  INFO 7688 --- [  restartedMain] ication$$EnhancerBySpringCGLIB$$52ae5e8e : log 注解注入成功. log：org.apache.log4j.Logger@24d31b86

三、扩展：spring boot之@Import、@ImportResource

缘由：由于我代码的目录结构是，一个project中根据package不同（因为spring boot默认扫描启动类所在的包，及其子包），测试spring boot的各种功能。

比如图中的*Application.class都是spring boot的启动类。然而我想把前面写的Log注解用在所有的*Application对应的项目中。

这就迁出一个问题：*Application.class只扫描所在的package及其sub-packages。从目录结构可以看到，Log并不能被别的*Application.class扫描到。

所以，要怎么解决呢?

这就需要spring boot提供的注解：@Import、@ImportResource。ex:

@SpringBootApplication
@EnableScheduling //通过@EnableScheduling注解开启对计划任务的支持
//@ImportResource(locations = "ConfigXML/annotation-scan.xml" )
@Import(value = LogInjector.class)
public class TimmerApplication {
	public static void main(String[] args) {
		SpringApplication.run(TimmerApplication.class, args);
	}
}

对于@ImportResource需要通过xml注入bean（就是普通的spring），annotation-scan.xml：

<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:jee="http://www.springframework.org/schema/jee"
	xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:tx="http://www.springframework.org/schema/tx"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.1.xsd
        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.1.xsd
         http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd">

	<!-- 扫描公共组件 -->
	<context:component-scan base-package="com.vergilyn.demo.annotation" />

</beans>