我这个使用JDOM的web应用程序为什么总是报NullPointerException error,检查了一下午也没发现问题出在了哪里（java文件编译都通过了，jdom的jar包也放到了lib文件夹下）。
哪位达人可否帮偶把错误揪出来。谢谢了。以下是几个相关有文件
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MyXml.xml（放在了和WEB-INF同级的目录下）
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<?xml version="1.0" encoding="UTF-8"?>
<书库>
<书>
<书名>Java编程入门</书名>
<作者>张三</作者>
<出版社>电子出版社</出版社>
<价格>35.0</价格>
<出版日期>2002-10-07</出版日期>
</书>
<书>
<书名>XML在Java中的应用</书名>
<作者>李四</作者>
<出版社>希望出版社</出版社>
<价格>92.0</价格>
<出版日期>2002-10-07</出版日期>
</书>
</书库>
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XmlBean.java
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package jdom.test;/**
* XMLĶдBean
*/
import java.io.*;
import java.util.*;
import org.jdom.*;
import org.jdom.output.*;
import org.jdom.input.*;
import javax.servlet.*;
import javax.servlet.http.*;public class XmlBean {
private String bookname, author, pub, price, pubdate; public String getbookname() {
return bookname;
} public String getauthor() {
return author;
} public String getpub() {
return pub;
} public String getprice() {
return price;
} public String getpubdate() {
return pubdate;
} public void setbookname(String bookname) {
this.bookname = bookname;
} public void setauthor(String author) {
this.author = author;
} public void setpub(String pub) {
this.pub = pub;
} public void setprice(String price) {
this.price = price;
} public void setpubdate(String pubdate) {
this.pubdate = pubdate;
} public XmlBean() {
} /**
* ȡXMLļϢ
*/
public Vector LoadXML(String path) throws Exception {
Vector xmlVector = null;
FileInputStream fi = null;
try {
fi = new FileInputStream(path);
xmlVector = new Vector();
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
Element book = null;
XmlBean xml = null;
for (int i = 0; i < books.size(); i++) {
xml = new XmlBean();
book = (Element) books.get(i); // õһԪ
xml.setbookname(book.getChild("").getText());
xml.setauthor(book.getChild("").getText());
xml.setpub(book.getChild("").getText());
xml.setprice(book.getChild("۸").getText());
xml.setpubdate(book.getChild("").getText());
xmlVector.add(xml);
}
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return xmlVector;
} /**
* ɾXMLļָϢ
*/
public static void DelXML(HttpServletRequest request) throws Exception {
FileInputStream fi = null;
FileOutputStream fo = null;
try {
request.setCharacterEncoding("GBK");
String path = request.getParameter("path");
int xmlid = Integer.parseInt(request.getParameter("id"));
fi = new FileInputStream(path);
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
books.remove(xmlid);// ɾָλõԪ
// String indent = " ";
// boolean newLines = true;
// XMLOutputter outp = new XMLOutputter(indent, newLines, "GBK");
Format format = Format.getPrettyFormat();
format.setIndent(" ");
format.setEncoding("utf-8");
XMLOutputter outp = new XMLOutputter(format);
fo = new FileOutputStream(path);
outp.output(doc, fo);
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
fo.close();
} catch (Exception e) {
e.printStackTrace();
}
}
} /**
* XMLļָϢ
*/
public static void AddXML(HttpServletRequest request) throws Exception {
FileInputStream fi = null;
FileOutputStream fo = null;
try {
request.setCharacterEncoding("GBK");
String path = request.getParameter("path");
fi = new FileInputStream(path);
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
String bookname = request.getParameter("bookname");
String author = request.getParameter("author");
String price = request.getParameter("price");
String pub = request.getParameter("pub");
String pubdate = request.getParameter("pubdate");
// Text newtext;
Element newbook = new Element("");
Element newname = new Element("");
newname.setText(bookname);
newbook.addContent(newname);
Element newauthor = new Element("");
newauthor.setText(author);
newbook.addContent(newauthor);
Element newpub = new Element("");
newpub.setText(pub);
newbook.addContent(newpub);
Element newprice = new Element("۸");
newprice.setText(price);
newbook.addContent(newprice);
Element newdate = new Element("");
newdate.setText(pubdate);
newbook.addContent(newdate);
books.add(newbook);// Ԫ
// String indent = " ";
// boolean newLines = true;
// XMLOutputter outp = new XMLOutputter(indent, newLines, "GBK");
Format format = Format.getPrettyFormat();
format.setIndent(" ");
format.setEncoding("utf-8");
XMLOutputter outp = new XMLOutputter(format);
fo = new FileOutputStream(path);
outp.output(doc, fo);
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
fo.close();
} catch (Exception e) {
e.printStackTrace();
}
}
} /**
* XMLļָϢ
*/
public static void EditXML(HttpServletRequest request) throws Exception {
FileInputStream fi = null;
FileOutputStream fo = null;
try {
request.setCharacterEncoding("GBK");
String path = request.getParameter("path");
int xmlid = Integer.parseInt(request.getParameter("id"));
fi = new FileInputStream(path);
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
Element book = (Element) books.get(xmlid);
String bookname = request.getParameter("bookname");
String author = request.getParameter("author");
String price = request.getParameter("price");
String pub = request.getParameter("pub");
String pubdate = request.getParameter("pubdate");
// Text newtext;
Element newname = book.getChild("");
newname.setText(bookname);// Ϊµ
Element newauthor = book.getChild("");
newauthor.setText(author);
Element newpub = book.getChild("");
newpub.setText(pub);
Element newprice = book.getChild("۸");
newprice.setText(price);
Element newdate = book.getChild("");
newdate.setText(pubdate);
// books.set(xmlid,book);//Ԫ
// String indent = " ";
// boolean newLines = true;
// XMLOutputter outp = new XMLOutputter(indent, newLines, "GBK");
Format format = Format.getPrettyFormat();
format.setIndent(" ");
format.setEncoding("utf-8");
XMLOutputter outp = new XMLOutputter(format);
fo = new FileOutputStream(path);
outp.output(doc, fo);
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
fo.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
哪位达人可否帮偶把错误揪出来。谢谢了。以下是几个相关有文件
－－－－－－－－－－－－－－－－－－－－－－－
MyXml.xml（放在了和WEB-INF同级的目录下）
－－－－－－－－－－－－－－－－－－－－－－－
<?xml version="1.0" encoding="UTF-8"?>
<书库>
<书>
<书名>Java编程入门</书名>
<作者>张三</作者>
<出版社>电子出版社</出版社>
<价格>35.0</价格>
<出版日期>2002-10-07</出版日期>
</书>
<书>
<书名>XML在Java中的应用</书名>
<作者>李四</作者>
<出版社>希望出版社</出版社>
<价格>92.0</价格>
<出版日期>2002-10-07</出版日期>
</书>
</书库>
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XmlBean.java
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package jdom.test;/**
* XMLĶдBean
*/
import java.io.*;
import java.util.*;
import org.jdom.*;
import org.jdom.output.*;
import org.jdom.input.*;
import javax.servlet.*;
import javax.servlet.http.*;public class XmlBean {
private String bookname, author, pub, price, pubdate; public String getbookname() {
return bookname;
} public String getauthor() {
return author;
} public String getpub() {
return pub;
} public String getprice() {
return price;
} public String getpubdate() {
return pubdate;
} public void setbookname(String bookname) {
this.bookname = bookname;
} public void setauthor(String author) {
this.author = author;
} public void setpub(String pub) {
this.pub = pub;
} public void setprice(String price) {
this.price = price;
} public void setpubdate(String pubdate) {
this.pubdate = pubdate;
} public XmlBean() {
} /**
* ȡXMLļϢ
*/
public Vector LoadXML(String path) throws Exception {
Vector xmlVector = null;
FileInputStream fi = null;
try {
fi = new FileInputStream(path);
xmlVector = new Vector();
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
Element book = null;
XmlBean xml = null;
for (int i = 0; i < books.size(); i++) {
xml = new XmlBean();
book = (Element) books.get(i); // õһԪ
xml.setbookname(book.getChild("").getText());
xml.setauthor(book.getChild("").getText());
xml.setpub(book.getChild("").getText());
xml.setprice(book.getChild("۸").getText());
xml.setpubdate(book.getChild("").getText());
xmlVector.add(xml);
}
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
} catch (Exception e) {
e.printStackTrace();
}
}
return xmlVector;
} /**
* ɾXMLļָϢ
*/
public static void DelXML(HttpServletRequest request) throws Exception {
FileInputStream fi = null;
FileOutputStream fo = null;
try {
request.setCharacterEncoding("GBK");
String path = request.getParameter("path");
int xmlid = Integer.parseInt(request.getParameter("id"));
fi = new FileInputStream(path);
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
books.remove(xmlid);// ɾָλõԪ
// String indent = " ";
// boolean newLines = true;
// XMLOutputter outp = new XMLOutputter(indent, newLines, "GBK");
Format format = Format.getPrettyFormat();
format.setIndent(" ");
format.setEncoding("utf-8");
XMLOutputter outp = new XMLOutputter(format);
fo = new FileOutputStream(path);
outp.output(doc, fo);
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
fo.close();
} catch (Exception e) {
e.printStackTrace();
}
}
} /**
* XMLļָϢ
*/
public static void AddXML(HttpServletRequest request) throws Exception {
FileInputStream fi = null;
FileOutputStream fo = null;
try {
request.setCharacterEncoding("GBK");
String path = request.getParameter("path");
fi = new FileInputStream(path);
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
String bookname = request.getParameter("bookname");
String author = request.getParameter("author");
String price = request.getParameter("price");
String pub = request.getParameter("pub");
String pubdate = request.getParameter("pubdate");
// Text newtext;
Element newbook = new Element("");
Element newname = new Element("");
newname.setText(bookname);
newbook.addContent(newname);
Element newauthor = new Element("");
newauthor.setText(author);
newbook.addContent(newauthor);
Element newpub = new Element("");
newpub.setText(pub);
newbook.addContent(newpub);
Element newprice = new Element("۸");
newprice.setText(price);
newbook.addContent(newprice);
Element newdate = new Element("");
newdate.setText(pubdate);
newbook.addContent(newdate);
books.add(newbook);// Ԫ
// String indent = " ";
// boolean newLines = true;
// XMLOutputter outp = new XMLOutputter(indent, newLines, "GBK");
Format format = Format.getPrettyFormat();
format.setIndent(" ");
format.setEncoding("utf-8");
XMLOutputter outp = new XMLOutputter(format);
fo = new FileOutputStream(path);
outp.output(doc, fo);
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
fo.close();
} catch (Exception e) {
e.printStackTrace();
}
}
} /**
* XMLļָϢ
*/
public static void EditXML(HttpServletRequest request) throws Exception {
FileInputStream fi = null;
FileOutputStream fo = null;
try {
request.setCharacterEncoding("GBK");
String path = request.getParameter("path");
int xmlid = Integer.parseInt(request.getParameter("id"));
fi = new FileInputStream(path);
SAXBuilder sb = new SAXBuilder();
Document doc = sb.build(fi);
Element root = doc.getRootElement(); // õԪ
List books = root.getChildren(); // õԪԪصļ
Element book = (Element) books.get(xmlid);
String bookname = request.getParameter("bookname");
String author = request.getParameter("author");
String price = request.getParameter("price");
String pub = request.getParameter("pub");
String pubdate = request.getParameter("pubdate");
// Text newtext;
Element newname = book.getChild("");
newname.setText(bookname);// Ϊµ
Element newauthor = book.getChild("");
newauthor.setText(author);
Element newpub = book.getChild("");
newpub.setText(pub);
Element newprice = book.getChild("۸");
newprice.setText(price);
Element newdate = book.getChild("");
newdate.setText(pubdate);
// books.set(xmlid,book);//Ԫ
// String indent = " ";
// boolean newLines = true;
// XMLOutputter outp = new XMLOutputter(indent, newLines, "GBK");
Format format = Format.getPrettyFormat();
format.setIndent(" ");
format.setEncoding("utf-8");
XMLOutputter outp = new XMLOutputter(format);
fo = new FileOutputStream(path);
outp.output(doc, fo);
} catch (Exception e) {
System.err.println(e + "error");
} finally {
try {
fi.close();
fo.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
test.jsp
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<%@ page language="java" import="java.util.*,jdom.test.*,org.jdom.output.*"%>
<html>
<head>
<title>读取XML文件资料</title>
</head>
<body>
<h3 align="center">JDOM操作XML文件</h3>
<p align="center">读取XML文件中的所有资料</p>
<center>
<table border="1" cellpadding="0" cellspacing="1"
style="border-collapse: collapse" width="80%" id="AutoNumber1">
<tr>
<td align="center" width="92">书名</td>
<td align="center" width="92">作者</td>
<td align="center" width="92">出版社</td>
<td align="center" width="92">价格</td>
<td align="center" width="92">出版日期</td>
<td align="center" width="94">操作</td>
</tr>
</table>
<%
String path = application.getRealPath("MyXml.xml");
XmlBean xml = new XmlBean();
Vector xmlall = xml.LoadXML(path);
for (int i = 0; i < xmlall.size(); i++) {
xml = (XmlBean) xmlall.elementAt(i);
%>
<table border="1" cellpadding="0" cellspacing="1"
style="border-collapse: collapse" width="80%" id="AutoNumber2">
<tr>
<td align="center" width="92"><%=xml.getbookname()%></td>
<td align="center" width="92"><%=xml.getauthor()%></td>
<td align="center" width="92"><%=xml.getpub()%></td>
<td align="center" width="92"><%=xml.getprice()%></td>
<td align="center" width="92"><%=xml.getpubdate()%></td>
<td align="center" width="94"><a
href="xmlaction.jsp?act=del&id=<%=i%>&path=<%=path%>">删除</a></td>
</tr>
</table>
<%}%></center>
<form method="POST" action="xmlaction.jsp">
<p align="center"><input type="radio" value="add" checked name="act">添加资料
<input type="radio" value="edit" name="act">编辑资料 序 号:<select size="1"
name="id">
<%for (int i = 0; i < xmlall.size(); i++) {%>
<option value="<%=i%>">第<%=i + 1%>条</option>
<%}%>
</select><br>
书 名:<input type="text" name="bookname" size="20"><br>
作 者:<input type="text" name="author" size="20"><br>
出版社:<input type="text" name="pub" size="20"><br>
价 格:<input type="text" name="price" size="20"><br>
日 期:<input type="text" name="pubdate" size="20"></p>
<input type="hidden" name="path" value="<%=path%>">
<p align="center"><input type="submit" value="提交" name="B1"><input
type="reset" value="重置" name="B2"></p>
</form>
</body>
</html>------------------------------------
xmlaction.jsp
---------------------------------
<%@ page contentType="text/html;charset=GBK"%>
<%@ page language="java" import="jdom.test.*"%>
<%if (request.getParameter("act") != null
&& request.getParameter("act").equals("add")) {
XmlBean.AddXML(request);
out.println("<p align='center'><br><br>添加成功<br><br><a href='test.jsp'>返回</a>");
} else if (request.getParameter("act") != null
&& request.getParameter("act").equals("del")) {
XmlBean.DelXML(request);
out.println("<p align='center'><br><br>删除成功<br><br><a href='test.jsp'>返回</a>");
} else if (request.getParameter("act") != null
&& request.getParameter("act").equals("edit")) {
XmlBean.EditXML(request);
out.println("<p align='center'><br><br>修改成功<br><br><a href='test.jsp'>返回</a>");
} else {
out.print("<p align='center'><br><br>非法操作<br><br><a href='test.jsp'>返回</a>");
}
%>-------------------------------------------