用代码学习Spring：IoC、AOP

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;
    }
}

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