Spring入门学习(一)

Spring的主要功能是控制反转和面向切面编程,下面我们就来编写第一个spring的程序来体验一下控制反转

首先是加载配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!--
- Middle tier application context definition for the image database.
-->
<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:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">

</beans>

下面我们在程序中加载配置文件

ApplicationContext ac = new ClassPathXmlApplicationContext("spring.xml");

然后新建类

package com.service.impl;

import com.service.Service;

public class ServiceBean implements Service {

@Override
public void save(){
System.out.println("save()");
}
}

抽取出类的接口 refactor----->extract interface

然后在测试方法中控制反转

package junit.test;

import static org.junit.Assert.*;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.service.Service;

public class SpringTest {

@Test
public void test() {
ApplicationContext ac = new ClassPathXmlApplicationContext("spring.xml");
Service service = (Service)ac.getBean("service");
service.save();
}

}

下面我们来看看是怎么控制反转的吧

首先新建类来解析配置文件，然后把配置文件中的bean中的属性提取出来创建对象，通过相应的方法刚返回给页面

 package com.dom4j.test;

 import java.io.File;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Set;

 import org.dom4j.Attribute;
 import org.dom4j.Document;
 import org.dom4j.DocumentException;
 import org.dom4j.DocumentHelper;
 import org.dom4j.Element;
 import org.dom4j.io.SAXReader;

 import com.service.Service;
 import com.sun.beans.decoder.DocumentHandler;

 public class DomeStuTest {

     private Map<String,String> map = new HashMap<String,String>();
     private Map<String,Object> objMap = new HashMap<String,Object>();

     public  DomeStuTest(String xml){
         String xmlPath = getClass().getClassLoader().getResource(xml).getPath();
         Document document = null;
         SAXReader reader = new SAXReader();

         try {
             document = reader.read(new File(xmlPath));
         } catch (DocumentException e) {
             e.printStackTrace();
         }

         //获取根节点
         Element root = document.getRootElement();

         //获取根节点下的子节点
         Iterator it = root.elementIterator("bean");
         while(it.hasNext()){
             Element ele = (Element)it.next();
             Attribute attr_name  = ele.attribute("name");
             Attribute attr_class = ele.attribute("class");

             map.put(attr_name.getValue(), attr_class.getValue());
         }

         //实例化容器内的对象并存储
         Set<String> set = map.keySet();
         Iterator its = set.iterator();
         while(its.hasNext()){
             String key    = (String)its.next();
             String value  = map.get(key);
             try {
                 Class clazz = Class.forName(value);
                 Object obj = clazz.newInstance();
                 objMap.put(key, obj);
             } catch (ClassNotFoundException e) {
                 e.printStackTrace();
             } catch (InstantiationException e) {
                 e.printStackTrace();
             } catch (IllegalAccessException e) {
                 e.printStackTrace();
             }

         }

     }

     //取得对象
     public Object get(String name){
         Object obj = null;
         Set<String> set = objMap.keySet();
         Iterator it = set.iterator();
         while(it.hasNext()){
             String key = (String)it.next();
             if(key.equals(name)){
                 obj = objMap.get(key);
             }
         }
         return obj;
     }

 }

然后在页面这样就可以获得对象

package junit.test;

import org.junit.Test;

import com.dom4j.test.DomeStuTest;
import com.service.Person;
import com.service.Service;

public class SpringTest {

    @Test
    public void test() {
//        ApplicationContext ac = new ClassPathXmlApplicationContext("spring.xml");
//        Service service = (Service)ac.getBean("service");
//        service.save();

        DomeStuTest dst = new DomeStuTest("spring.xml");
        Service service = (Service)dst.get("service");
        service.save();
        Person  person  = (Person)dst.get("person");
        person.showMessage();
    }

}