package org.sl.xml;

import java.io.File;
import java.io.FileInputStream;
import java.net.URL;
import java.util.List;

import org.apache.log4j.Logger;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;

/**
 * 以xpath方式读取xml
 * @author Shanl
 *
 */
public class XPathHelper {
    private File file = null;
    private boolean cache = false;
    
    private static Logger logger = Logger.getLogger(XPathHelper.class);
    
    /**
     * 构造器<br>
     * 相当于XPathHelper(res, true);
     * @param res 资源名
     */
    public XPathHelper(String res){
        this(res, true);
    }
    
    /**
     * 构造器<br>
     * 注:这个方法会在系统中查找与res匹配的资源,如果找不到则抛出RunntimeException
     * @param res 资源名
     * @param cahce 是否缓存XML
     */
    public XPathHelper(String res, boolean cache){
        this.cache = cache;
        URL url = ClassLoader.getSystemResource(res);
        
        if(null == url){
            throw new RuntimeException(res + " not found.");
        }
        
        String protocol = url.getProtocol();            
        String path = url.toString();
        path = path.replaceFirst(protocol + ":/", "");
        file = new File(path);
        
        if(!file.exists()){
            throw new RuntimeException(res + " not found.");
        }
    }
    
    /**
     * 返回xpath所表示的结点数
     * @param xpath
     * @return
     */
    public int countNode(String xpath){        
        Document fileDocument = readDocument();
        
        if(!findXPath(xpath)){
            return 0;
        }
        
        List es = fileDocument.selectNodes(xpath);
        
        if(null == es){
            return 0;
        }else{
            return es.size();
        }
    }
    
    /**
     * 以xpath方式得到结果的文本
     * @param xpath
     * @return
     */
    public String getText(String xpath){
        String text = "";
        Document fileDocument = readDocument();
        
        if(!findXPath(xpath)){
            return "";
        }
        
        Node node = fileDocument.selectSingleNode(xpath);
        
        text = node.getText();
        return text;
    }    
    
    /**
     * 以xpath方式得到结点某属性的值
     * @param xpath
     * @param attrName
     * @return
     */
    public String getAttribute(String xpath, String attrName){
        String attr = "";
        Document fileDocument = readDocument();
        
        if(!findXPath(xpath)){
            return "";
        }
        
        List es = fileDocument.selectNodes(xpath);
        attr = ((Element)es.get(0)).attributeValue(attrName);
        
        return attr;
    }
    
    /**
     * 查找xpath是否存在
     * @param xpath
     * @return 存在返回true,否则返回false;
     */
    public boolean findXPath(