Spring 框架核心 AOP（LTW） 概念随笔

• 命名空间 < context:load-time-weaver/ >
• JVM参数 -javaagent:/path/to/jar/spring-agent.jar

context:load-time-weave

会把 AspectJ的LTW放到类加载器当中，所有的类都将能匹配到定义好的 Pointcut

<?xml version="1.0" encoding="UTF-8"?>
<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"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
                        http://www.springframework.org/schema/beans/spring-beans.xsd
                        http://www.springframework.org/schema/context 
                        http://www.springframework.org/schema/context/spring-context.xsd">

    <context:load-time-weaver />
    
    <bean id="processor" class="org.springbyexample.aspectjLoadTimeWeaving.Processor" />
    
</beans>
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AspectJ配置

aspectJ会自动加载 META-INF/aop.xml，有关 weaver 和 aspects 的配置示例

<!DOCTYPE aspectj PUBLIC
        "-//AspectJ//DTD//EN" "http://www.eclipse.org/aspectj/dtd/aspectj.dtd">
<aspectj>
    <weaver>
        <!-- only weave classes in this package -->
        <!-- 声明给 weaver 哪里有 weave 要处理 -->
        <include within="org.springbyexample.aspectjLoadTimeWeaving.*" />
    </weaver>
    <aspects>
        <!-- use only this aspect for weaving -->
        <!-- 这里是提议 Advice -->
        <aspect name="org.springbyexample.aspectjLoadTimeWeaving.PerformanceAdvice" />
    </aspects>
</aspectj>
             
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提议 Advice

@Aspect
public class PerformanceAdvice {

    @Pointcut("execution(public * org.springbyexample.aspectjLoadTimeWeaving..*.*(..))")
    public void aspectjLoadTimeWeavingExamples() {
    }

    @Around("aspectjLoadTimeWeavingExamples()")
    public Object profile(ProceedingJoinPoint pjp) throws Throwable {
        final Logger logger = LoggerFactory.getLogger(pjp.getSignature().getDeclaringType());

        StopWatch sw = new StopWatch(getClass().getSimpleName());

        try {
            sw.start(pjp.getSignature().getName());

            return pjp.proceed();
        } finally {
            sw.stop();

            logger.debug(sw.prettyPrint());
        }
    }

}
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