用代码学习Spring：IoC、AOP(上)

1 从http://www.springframework.org下载Spring

2 用eclipse新建Java项目

3 建立我们的业务方法接口

public interface BusinessObject {

    public void doSomething();

    public void doAnotherThing();

}

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;public interface BusinessObject {

    public void doSomething();

    public void doAnotherThing();

}

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

4 实现业务方法，注意这是的setWords使用了依赖注入，所谓依赖注入就是把配置文件中的字符串什么的在程序运行时“自动”放到我们的程序中来。如果不是这样，我们就只能在代码中固化这些东西，从而违背了面向对象的依赖倒置原则，还有一种满足依赖倒置的方法，即依赖查询，这就是所谓的factory模式，即在代码中请求某种抽象的东西，然后根据配置得到它，但这种办法向对于依赖注入多了对环境的依赖，且代码冗余，EJB的JNDI查询就属于这种。另外我们的Spring配置文件是以bean为核心的，就是我们写的一个类，在XML中描述它的名称、位置和涵盖的内容、关系。

public class BusinessObjectImpl implements BusinessObject {

    private String words;

    public void setWords(String words){

        this.words = words;

    }

    public void doSomething() {

        Log log = LogFactory.getLog(this.getClass());

        log.info(words);

    }

    public void doAnotherThing() {

        Log log = LogFactory.getLog(this.getClass());

        log.info("Another thing");

    }

}public class BusinessObjectImpl implements BusinessObject {

    private String words;

    public void setWords(String words){

        this.words = words;

    }

    public void doSomething() {

        Log log = LogFactory.getLog(this.getClass());

        log.info(words);

    }

    public void doAnotherThing() {

        Log log = LogFactory.getLog(this.getClass());

        log.info("Another thing");

    }

}

5 建立一个运行方法类，从配置文件spring-beans.xml中读入bo这个类的定义，然后实例化一个对象

import org.springframework.beans.factory.xml.XmlBeanFactory;

import org.springframework.core.io.ClassPathResource;

public class Main {

    public static void main(String[] args){

        XmlBeanFactory xbf = new XmlBeanFactory(new ClassPathResource("spring-beans.xml"));

        BusinessObject bo = (BusinessObject)xbf.getBean("bo");

        bo.doSomething();

        bo.doAnotherThing();

    }

}import org.springframework.beans.factory.xml.XmlBeanFactory;

import org.springframework.core.io.ClassPathResource;

public class Main {

    public static void main(String[] args){

        XmlBeanFactory xbf = new XmlBeanFactory(new ClassPathResource("spring-beans.xml"));

        BusinessObject bo = (BusinessObject)xbf.getBean("bo");

        bo.doSomething();

        bo.doAnotherThing();

    }

}

6 建立一个拦截器类invoke是MethodInterceptor必须实现的方法，表示拦截时的动作，大家仔细体会代码中的含义

import org.aopalliance.intercept.MethodInterceptor;

import org.aopalliance.intercept.MethodInvocation;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

public class MyInterceptor implements MethodInterceptor {

    private String before, after;

    public void setAfter(String after) {

        this.after = after;

    }

    public void setBefore(String before) {

        this.before = before;

    }

    public Object invoke(MethodInvocation invocation) throws Throwable {

        Log log = LogFactory.getLog(this.getClass());

        log.info(before);

        Object rval = invocation.proceed();

        log.info(after);

        return rval;

    }

}import org.aopalliance.intercept.MethodInterceptor;

import org.aopalliance.intercept.MethodInvocation;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

public class MyInterceptor implements MethodInterceptor {

    private String before, after;

    public void setAfter(String after) {

        this.after = after;

    }

    public void setBefore(String before) {

        this.before = before;

    }

    public Object invoke(MethodInvocation invocation) throws Throwable {

        Log log = LogFactory.getLog(this.getClass());

        log.info(before);

        Object rval = invocation.proceed();

        log.info(after);

        return rval;

    }

}