java.lang.NullPointerException

請問我訪問jsp出現如下錯誤，Article article = new Article(); 是調用 article.java . 用的是 tomcat 服務器，在D:\Tomcat 5.5\work\Catalina\localhost\jspRoot\org\apache\jsp\robote 能正常生成 class 文件。 請問如何解決？



HTTP Status 500 -

--------------------------------------------------------------------------------

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: Exception in JSP: /robote/a.jsp:41

38: }else{
39: try{
40: Article article = new Article();
41: article.getAllArticle();
42: idList = article.getIdList();
43: titleList = article.getTitleList();
44: editorList = article.getEditorList();


Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:451)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


root cause

java.lang.NullPointerException
cn.robote.logic.Article.getAllArticle(Article.java:104)
org.apache.jsp.robote.a_jsp._jspService(a_jsp.java:89)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


article.java

package cn.robote.logic;

import cn.robote.bean.ConnectMySQL;
import java.sql.*;
import java.util.ArrayList;
//import cn.robote.bean.Log; //add by 1.1.0 @2009-11-06


public class Article{

// declare variable
private String id ="";
private String title = "";
private String editor = "";
private String content = "";
private ArrayList idList = new ArrayList();
private ArrayList titleList = new ArrayList();
private ArrayList editorList = new ArrayList();
private ArrayList contentList = new ArrayList();

public void setId(String id){
this.id = id;
}
public void setTitle(String title){
this.title = title;
}
public void setEditor(String editor){
this.editor = editor;
}
public void setContent(String content){
this.content = content;
}


public String getId() {
return id;
}
public String getTitle() {
return title;
}
public String getEditor() {
return editor;
}
public String getContent() {
return content;
}
public ArrayList getIdList() {
return idList;
}
public ArrayList getTitleList() {
return titleList;
}
public ArrayList getEditorList() {
return editorList;
}
public ArrayList getContentList() {
return contentList;
}

public Article(){

}

/*
get all article
*/
public void getAllArticle() throws Exception{ //get article information
// Log log = null; // add @1.0.1
ResultSet rs = null;
Connection conn = null;
Statement stmt = null;

try{
conn = ConnectMySQL.getConnection();
String sql = "SELECT id, title,editor,content FROM article ";
stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY );
rs = stmt.executeQuery(sql);


while(rs.next()){
id = rs.getString("id");
title = rs.getString("title");
editor = rs.getString("editor");
content = rs.getString("content");
// log.writeLog(1, "log:title"+title);
if(!title.equals("")){
this.idList.add(id);//get the required lot info
this.titleList.add(title);
this.editorList.add(editor);
this.contentList.add(content);
}
}
if(this.titleList.size()==0){ // no data
this.idList.add("");
this.titleList.add("");
this.editorList.add("");
this.contentList.add("");
}

}catch(Exception e){
throw e;
}finally{
conn.close();
stmt.close();
}
}