getResourceAsStream()读取取资源文件的探讨

首先是this.getClass().getClassLoader().getResourceAsStream（）的问题。

1. java.lang.NoClassDefFoundError: org/jaxen/JaxenException
 at org.dom4j.DocumentFactory.createXPath(DocumentFactory.java:230)
 at org.dom4j.tree.AbstractNode.createXPath(AbstractNode.java:207)
 at org.dom4j.tree.AbstractNode.selectNodes(AbstractNode.java:164)
 at com.classLoader.resource.BinaryServiceManager.initialMapping(BinaryServiceManager.java:39)
 at com.classLoader.resource.BinaryServiceManager.refresh(BinaryServiceManager.java:68)
 at com.classLoader.resource.BinaryServiceServlet.doGet(BinaryServiceServlet.java:10)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
 at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
 at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
 at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
 at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
 at java.lang.Thread.run(Thread.java:595)
原因： 没有导入jaxen包，一般情况下，dom4j-1.6.1.jar和jaxen-1.1.1.jar要同时使用，后者是前者的基础包。

2， 源代码：

package com.classLoader.resource;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.util.HashMap;
import java.util.List;

import org.dom4j.Document;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;

public class BinaryServiceManager {
 
 private HashMap<String, String> binaryMap = null;
 
 private static BinaryServiceManager instance = null;
 
 private BinaryServiceManager() {}
 
 public static BinaryServiceManager getInstance() {
  if (instance == null) {
   instance = new BinaryServiceManager();
  }
  return instance;
 }
 
 private void initialMapping() {
  HashMap<String, String> tempBinaryMap = new HashMap<String, String>();
  Document doc = null;
  try {
   SAXReader reader = new SAXReader();
   doc = reader.read(this.getClass().getClassLoader().getResourceAsStream("BinaryServiceMapping.xml"));
   System.out.println(this.getClass().getClassLoader().getResourceAsStream("BinaryServiceMapping.xml"));
   List binaryServiceList = doc.selectNodes("/binaryServiceMapping/binaryService");
   Node binaryServiceInfo = null;
   for (int i = 0; i < binaryServiceList.size(); i++) {
    binaryServiceInfo = (Node) binaryServiceList.get(i);
    String shortCode = binaryServiceInfo.selectSingleNode("./shortCode").getText();
    List serviceList = binaryServiceInfo.selectNodes("./services/service");
    List carrierList = binaryServiceInfo.selectNodes("./carriers/carrier");
    for (int j = 0; j < serviceList.size(); j++) {
     Node serviceInfo = (Node) serviceList.get(j);
     String serviceId = serviceInfo.selectSingleNode("./serviceId").getText();
     String serviceName = serviceInfo.selectSingleNode("./serviceName").getText();
     for (int k = 0; k < carrierList.size(); k++) {
      Node accountInfo = (Node) carrierList.get(k);
      String carrierId = accountInfo.selectSingleNode("./carrierId").getText();
      String carrierName = accountInfo.selectSingleNode("./carrierName").getText();
      String key = shortCode + "::" + serviceId + "::" + carrierId;
      System.out.println("shortCode=" + shortCode + " serviceId=" + serviceId + " carrierId=" + carrierId);
      System.out.println("key=" + key);
      tempBinaryMap.put(key, shortCode);
     }     
    }
   }
   binaryMap = tempBinaryMap;
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
 
 public void refresh() {
  initialMapping();  
 }
}
当刷新xml文件时，总是刷新失败，即使把classes下面的xml文件删除，  this.getClass().getClassLoader().getResourceAsStream（）仍能读取到数据，并且数据和服务启动时读取到的数据完全一样，查看了源代码，发现this.getClass().getClassLoader().getResourceAsStream（）首先从java虚拟机中查找文件，如果找不到，再按文件路径查找，找到后放到虚拟机中，也就是说第一次读取的时候已经把文件放到Java虚拟机中了，所以再读取的时候，直接从虚拟机中读取，所以，不能刷新成功。 修改代码 doc = reader.read(this.getClass().getClassLoader， 修改代码如下，

InputStream input = null;
   String path = this.getClass().getClassLoader().getResource(File.separator).getPath();
   input = new FileInputStream(new File(path + File.separator + "BinaryServiceMapping.xml"));
   doc = reader.read(input);

此时报了一个错误，

java.io.FileNotFoundException: F:\program%20files\tomcat-5.5.23\webapps\Agaro_4_0_Problem\WEB-INF\classes\BinaryServiceMapping.xml (系统找不到指定的路径。)
 at java.io.FileInputStream.open(Native Method)
 at java.io.FileInputStream.<init>(FileInputStream.java:106)
 at com.classLoader.resource.BinaryServiceManager.initialMapping(BinaryServiceManager.java:35)
 at com.classLoader.resource.BinaryServiceManager.refresh(BinaryServiceManager.java:68)
 at com.classLoader.resource.BinaryServiceServlet.doGet(BinaryServiceServlet.java:10)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
 at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
 at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
 at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
 at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
 at java.lang.Thread.run(Thread.java:595)

发现这样的写法系统不认空格键，也就是说文件夹的命名不能有空格键，把有空格的文件名的空格去掉，则能成功刷新xml文件。