Seasar2框架：AOP

Seasar2是由日本人开发的一个框架。它通过自己定义的规约，很大程度上地减少了设定代码。但是由于这个原因，导致了框架学习初期会有比较大的跨越。

AOP例子：

Greeting.java

 package examples.di;

 public interface Greeting {

     String greet();
 }

GreetingImpl.java

 package examples.di.impl;

 import examples.di.Greeting;

 public class GreetingImpl implements Greeting {

     public String greet() {
         return "Hello World!";
     }
 }

GreetingClient.java

 package examples.di;

 public interface GreetingClient {

     void execute();
 }

GreetingClientImpl.java

 package examples.di.impl;

 import examples.di.Greeting;
 import examples.di.GreetingClient;

 public class GreetingClientImpl implements GreetingClient {

     private Greeting greeting;

     public void setGreeting(Greeting greeting) {
         this.greeting = greeting;
     }

     public void execute() {
         System.out.println(greeting.greet());
     }
 }

GreetingMain3.dicon

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE components PUBLIC
     "-//SEASAR//DTD S2Container 2.3//EN"
     "http://www.seasar.org/dtd/components23.dtd">
 <components>
     <include path="aop.dicon"/>
     <component name="greeting"
         class="examples.di.impl.GreetingImpl">
         <aspect>aop.traceInterceptor</aspect>
     </component>
     <component name="greetingClient"
         class="examples.di.impl.GreetingClientImpl">
         <property name="greeting">greeting</property>
         <aspect>aop.traceInterceptor</aspect>
     </component>
 </components>

GreetingMain3.java

 package examples.di.main;

 import org.seasar.framework.container.S2Container;
 import org.seasar.framework.container.factory.S2ContainerFactory;

 import examples.di.GreetingClient;

 public class GreetingMain3 {

     private static final String PATH =
         "examples/di/dicon/GreetingMain3.dicon";

     public static void main(String[] args) {
         S2Container container =
             S2ContainerFactory.create(PATH);
         GreetingClient greetingClient = (GreetingClient)
             container.getComponent("greetingClient");
         greetingClient.execute();
     }
 }

　　除了官网上的这些文件，还需要

aop.dicon

<?xml version="1.0" encoding="Shift_JIS"?>
<!DOCTYPE components PUBLIC "-//SEASAR//DTD S2Container//EN"
"http://www.seasar.org/dtd/components.dtd">
<components namespace="aop">
    <component name="traceInterceptor"
        class="org.seasar.framework.aop.interceptors.TraceInterceptor"/>
    <component name="traceThrowsInterceptor"
        class="org.seasar.framework.aop.interceptors.TraceThrowsInterceptor"/>
</components>

log4j.properties

log4j.category.org.seasar=DEBUG, C
log4j.additivity.org.seasar=false

log4j.appender.C=org.apache.log4j.ConsoleAppender
log4j.appender.C.Target=System.out
log4j.appender.C.ImmediateFlush=true
log4j.appender.C.layout=org.apache.log4j.PatternLayout
log4j.appender.C.layout.ConversionPattern=%-5p %d [%t] %m%n

这里，aop.dicon中的“org.seasar.framework.aop.interceptors.TraceInterceptor”默认的切面输出是“方法函数”和“返回值”。

注意：log4j的配置要使用debug。

输出：

DEBUG 2014-02-20 11:23:10,957 [main] BEGIN examples.di.main.GreetingClientImpl#execute()
DEBUG 2014-02-20 11:23:10,957 [main] BEGIN examples.di.main.GreetingImpl#greet()
DEBUG 2014-02-20 11:23:10,957 [main] END examples.di.main.GreetingImpl#greet() : Hello World!
Hello World!
DEBUG 2014-02-20 11:23:10,957 [main] END examples.di.main.GreetingClientImpl#execute() : nul