Digester如何解析xml文件

    工作原理如下: Digester底层采用SAX(Simple API for XML)析XML文件，所以很自然的，对象转换由"事件"驱动，在遍历每个节点时，检查是否有匹配模式，如果有，则执行规则定义的操作，比如创建特定的Java对象，或调用特定对象的方法等。此处的XML元素根据匹配模式(matching pattern)识别，而相关操作由规则(rule)定义。

接下来以例子说明
1.解析xml文件 view.xml

<?xml version="1.0" encoding="UTF-8" ?>
<viewcache name="test">
		<area info="area1">
			<id>1098</id>
			<parentId>1001</parentId>
			<areaType>province</areaType>
			<name>北京</name>
			<ordering>1867</ordering>
		</area>
		<area info="area2">
			<id>1099</id>
			<parentId>1098</parentId>
			<areaType>capital</areaType>
			<name>北京</name>
			<ordering>1868</ordering>
			<phoneArea>010</phoneArea>
		</area>
		<area info="area3">
			<id>4476</id>
			<parentId>1099</parentId>
			<areaType>county</areaType>	
			<name>北京市朝阳区</name>
			<ordering>1869</ordering>
			<phoneArea>010</phoneArea>
		</area>
		<area info="area4">
			<id>4477</id>
			<parentId>1099</parentId>
			<areaType>county</areaType>
			<name>北京市崇文区</name>
			<ordering>1870</ordering>
			<phoneArea>010</phoneArea>
		</area>
		<area info="area5">
			<id>4478</id>
			<parentId>1099</parentId>
			<areaType>county</areaType>
			<name>北京市大兴区</name>
			<ordering>1871</ordering>
			<phoneArea>010</phoneArea>
		</area>
</viewcache>

2.ViewCache类

import java.util.ArrayList;
import java.util.List;

public class ViewCache {
	  public String viewName;
	  public List<Area> areas = new ArrayList<Area>();
	
	public String getViewName() {
		return viewName;
	}
	public void setViewName(String viewName) {
		this.viewName = viewName;
	}
	public List<Area> getAreas() {
		return areas;
	}
	public void setAreas(List<Area> areas) {
		this.areas = areas;
	}
	  
	public void addArea(Area area){
		areas.add(area);
	}
}

3.Area类

 public class Area {
	 public String id;
	 public String parentId;
	 public String areaType;
	 public String name;
	 public String ordering;
	 public String phoneArea;
	 public String info;
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getParentId() {
		return parentId;
	}
	public void setParentId(String parentId) {
		this.parentId = parentId;
	}
	public String getAreaType() {
		return areaType;
	}
	public void setAreaType(String areaType) {
		this.areaType = areaType;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getOrdering() {
		return ordering;
	}
	public void setOrdering(String ordering) {
		this.ordering = ordering;
	}
	public String getPhoneArea() {
		return phoneArea;
	}
	public void setPhoneArea(String phoneArea) {
		this.phoneArea = phoneArea;
	}
	
	public String getInfo() {
		return info;
	}
	public void setInfo(String info) {
		this.info = info;
	}
//测试解析方法用
public String  setProperties(String id,String parentId,String areaType){
	this.id = id;
	this.parentId =parentId;
	this.areaType = areaType;
	return "id:"+id+",parentId:"+parentId+",areaType:"+areaType;
}
@Override
public String toString() {
	return "id:"+id+",parentId:"+parentId+",areaType:"+areaType+",name:"+name
			+",ordering:"+ordering+",phoneArea:"+phoneArea;
}
 
 

4.测试类

import java.io.File;
import java.io.IOException;
import java.util.List;

import org.apache.commons.digester.Digester;
import org.xml.sax.SAXException;

public class ViewMain {

	public static void main(String[] args) throws IOException, SAXException {
		// 建立一个Digester对象
		Digester digester = new Digester();
		//指定它不要用DTD验证XML文档的合法性——这是因为我们没有为XML文档定义DTD  
        digester.setValidating(false); 
		//创建一个模型对象，viewcache作为跟对象
		digester.addObjectCreate("viewcache", ViewCache.class);
		/*设置viewcache对象的属性，view.xml中的name对应ViewCache 属性 viewName；
		  如果属性多，可以调用digester.addSetProperties(pattern, attributeNames, propertyNames)方法*/
        digester.addSetProperties("viewcache","name","viewName");
        
        //创建下层节点模型对象
        digester.addObjectCreate("viewcache/area", Area.class);
        //设置属性 同上
        digester.addSetProperties("viewcache/area","info","info");
        //父节点和子节点直接的连接关系通过addSetNext方法实现。addArea为父节点类中的方法
        digester.addSetNext("viewcache/area", "addArea");
        
        /*解析子节点属性用addBeanPropertySetter方法，addBeanPropertySetter()是将子节点转换为对象的属性，
                            当对象的属性名和子节点的名字不一样时用来指定对象的属性名 */
        digester.addBeanPropertySetter("viewcache/area/id", "id");
        digester.addBeanPropertySetter("viewcache/area/parentId", "parentId");
        digester.addBeanPropertySetter("viewcache/area/areaType", "areaType");
        digester.addBeanPropertySetter("viewcache/area/name", "name");
        digester.addBeanPropertySetter("viewcache/area/ordering", "ordering");
        digester.addBeanPropertySetter("viewcache/area/phoneArea", "phoneArea");
        
        //解析节点类中的方法通过addCallMethod，如果有参数，先在改方法中设置参数个数，再用addCallParam设置参数
        digester.addCallMethod("viewcache/area", "setProperties", 3);
        digester.addCallParam("viewcache/area", 0, "id");
        digester.addCallParam("viewcache/area", 1, "parentId");
        digester.addCallParam("viewcache/area", 2, "areaType");
        
        File file = new File("D:/software/download/dubbo/sshDemo/src/com/sshdemo/executive/digister/view.xml");
        ViewCache viewCache = (ViewCache)digester.parse(file);
        
        List<Area> areas = viewCache.getAreas();
        for(Area area : areas){
        	System.out.println("area number:"+area.getInfo());
        	
        	System.out.println("area content:"+area.toString());
        	
        	System.out.println("area method:"+area.setProperties("000", "999", "county"));
        }
	}

}