利用JDOM解析xml文件

利用JDOM解析xml文件

JDOM是一个开源项目，它基于树型结构，利用纯JAVA的技术对XML文档实现解析、生成、序列化以及多种操作。JDOM直接为JAVA编程服务。它利用更为强有力的JAVA语言的诸多特性（方法重载、集合概念以及映射），把SAX和DOM的功能有效地结合起来。

JDOM的官方地址：http://www.jdom.org/

参考：马士兵 设计模式 工厂模式

1.首先新建一个接口和2个类，为后续做准备

[Moveable.java]

package com.njupt.zhb.test;


public interface Moveable {
  void run();
}

[Plane.java]

package com.njupt.zhb.test;

public class Plane implements Moveable {

  @Override
  public void run() {
    // TODO Auto-generated method stub
    System.out.println("飞机在翱翔.....");
  }

}

[Train.java]

package com.njupt.zhb.test;


public class Train implements Moveable{

  @Override
  public void run() {
    System.out.println("火车在飞奔....");
  }
  
}

2.新建一个接口，主程序可以调用getBean方法，获得相应的对象。

package com.njupt.zhb.test;

public interface BeanFactory {
  Object getBean(String id);
}

3.需要解析的xml文件如下：

<?xml version="1.0" encoding="UTF-8"?>
<beans>
  <bean 
      id="train"
      class="com.njupt.zhb.test.Train">
  </bean>
  <bean
      id="plane"
      class="com.njupt.zhb.test.Plane">
  </bean>
</beans>

4.解析文件的主类，实现了BeanFactory接口。

package com.njupt.zhb.test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
import org.jdom.xpath.XPath;

public class ClassPathXmlApplicationContext implements BeanFactory {
  private Map<String, Object> mapContainer = new HashMap<String, Object>();//用于存放解析出来的id和对象
  public ClassPathXmlApplicationContext(String fileName) throws Exception {
    SAXBuilder sb = new SAXBuilder();
    Document doc = sb.build(this.getClass().getClassLoader()
        .getResourceAsStream(fileName));
    Element root = doc.getRootElement();
    List list = XPath.selectNodes(root, "/beans/bean");//获得此节点下的所有值
    System.out.println(list.size());
    for (int i = 0; i < list.size(); i++) {
      Element bean = (Element) list.get(i);
      String id = bean.getAttributeValue("id");//获得id对应的值
      String clazz = bean.getAttributeValue("class");//获得class对应的值
      Object o = Class.forName(clazz).newInstance();//Java反射机制，根据类名生成对象
      mapContainer.put(id, o);//保存到map中
      System.out.println(id + " " + clazz);
    }
  }

  @Override
  public Object getBean(String id) {
    return mapContainer.get(id);
  }

}

5.主程序TestMain调用。

package com.njupt.zhb.test;


public class TestMain {
  public static void main(String[] args) throws Exception {
    BeanFactory f = new ClassPathXmlApplicationContext(
        "com/njupt/zhb/test/sample.xml");
    Object obj1 = f.getBean("train");//获得标签为train的对象
    Moveable m1 = (Moveable)obj1;//接口调用子类
    m1.run();
    // //----------------------
    Object obj2 = f.getBean("plane");
    Moveable m2 = (Moveable) obj2;
    m2.run();
    
  }
}

实验结果：

2
train com.njupt.zhb.test.Train
plane com.njupt.zhb.test.Plane
火车在飞奔....
飞机在翱翔.....