Java HTTP状态500错误。日食+；Tomcat+；MS SQL 2005_Java_Sql Server 2005_Jsp

Java HTTP状态500错误。日食+；Tomcat+；MS SQL 2005

java sql-server-2005 jsp

Java HTTP状态500错误。日食+；Tomcat+；MS SQL 2005,java,sql-server-2005,jsp,Java,Sql Server 2005,Jsp,我正在尝试这段代码，以便了解如何将MS SQL 2005连接到Eclipse和Tomcat 7作为我的服务器。我刚刚开始制作java web应用程序，请耐心听我说。在下面的错误中，如何跟踪错误的原因？该项目有2个jsp和3个类文件index.jsp，result.jsp，SQLConnection.java，Items.java和ItemController.java java.lang.NullPointerException connection.SQLConnection.execSele

我正在尝试这段代码，以便了解如何将MS SQL 2005连接到Eclipse和Tomcat 7作为我的服务器。我刚刚开始制作java web应用程序，请耐心听我说。在下面的错误中，如何跟踪错误的原因？该项目有2个jsp和3个类文件

index.jsp

，

result.jsp

，

SQLConnection.java

，

Items.java

和

ItemController.java

java.lang.NullPointerException
connection.SQLConnection.execSelectQuery(SQLConnection.java:35)

错误如下所示，

type Exception report

message 

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

exception 

org.apache.jasper.JasperException: java.lang.NullPointerException
      org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)


root cause 

java.lang.NullPointerException
connection.SQLConnection.execSelectQuery(SQLConnection.java:35)
model.Item.lastItems(Item.java:10)
org.apache.jsp.index_jsp._jspService(index_jsp.java:83)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

SQLConnection.java和index.jsp的代码如下：

SQLConnection.java

    package connection;
    import java.sql.*;
    public class SQLConnection {
    protected Connection con=null;
    protected ResultSet rs=null;

    public SQLConnection(String address)
    {
        try
    {
    String conString = "jdbc:sqlserver://localhost:1433;databaseName=Chingdb;    integratedSecurity=true;";
con = DriverManager.getConnection(conString);
}catch(SQLException sqlError){
//ERROR MANAGEMENT HERE
}
}
public boolean execQuery(String sql)
{
boolean result = false;
try
{
Statement stmt = con.createStatement();
stmt.execute(sql);
result = true;
}catch(SQLException sqlError){
//ERROR MANAGEMENT HERE
result = false;
}
return result;
}
public void execSelectQuery(String sql)
{
try
{
Statement stmt = con.createStatement();
this.rs = stmt.executeQuery(sql);
}catch(SQLException sqlError){
//ERROR MANAGEMENT HERE
}
}
public void disconnect()
{
try
{
con.close();
}catch(SQLException sqlError){
//ERROR MANAGEMENT HERE
}

}
}

index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org    /TR/html4/loose.dtd">
<%@page import="model.Item"%><html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Todo-List App</title>
</head>
<body>
<h2>Add a new item</h2>
<form action="addItem" method="post">
<table>
<tr>
<td><input type="text" value="I have to..." onClick="this.value('')" name="todo"/></td>
<td><input type="submit" value="Send" name="send"/> </td>
</tr>
</table>
</form>
<h2>Todo-List</h2>
<%
Item item = new Item();
String[] lastest = item.lastItems();
for(int i=0;i<lastest.length;i++)
{%>
<%=lastest[i] %> <br>
<%}item.disconnect();
%>
</body>
</html>


待办事项列表应用程序
添加新项目
待办事项清单
错误堆栈跟踪表明您在SQLConnection.java
的execSelectQuery
方法中获得了NullPointerException
，并且当您从Item.java
调用此方法时，获得了此异常
java.lang.NullPointerException
connection.SQLConnection.execSelectQuery(SQLConnection.java:35)

在model.Item.lastItems（Item.java:10）
中的Item.java处放置一个调试点，然后
语句stmt=con.createStatement（）
我怀疑您的连接可能为空。
在此处添加一些相关代码：）谢谢您的回复。我已经在我的问题上添加了SQLConnection.java和index.jsp的代码。希望你能帮助我^_^@Ching29：试着调试代码，检查你的连接是否为空