我創建了一個msacess db mydb.accdb並指出odbc源代碼,並且在lserv.java文件中有以下代碼所有tomcat的必要配置都已完成,小服務程序沒有響應,所以我在init方法,其出現了以下錯誤基本的Java登錄Servlet不工作
javax.servlet.ServletException: Servlet.init() for servlet login threw exception
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:879)
org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:600)
org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1703)
java.lang.Thread.run(Thread.java:722)
root cause
java.lang.NullPointerException
lserv.init(lserv.java:23)
javax.servlet.GenericServlet.init(GenericServlet.java:212)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:879)
org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:600)
org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1703)
java.lang.Thread.run(Thread.java:722)
Java代碼
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
public class lserv extends HttpServlet
{
Connection con;
ResultSet rs;
Statement st;
PrintWriter out;
public void init()
{
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:mydb");
st=con.createStatement();
}
catch(Exception e)
{
out.println(e.getMessage());
}
}
public void doGet(HttpServletRequest req,HttpServletResponse res)
{
try
{
out=res.getWriter();
res.setContentType("text/html");
if(req.getParameter("sub").equals("value"))
{
String s1=req.getParameter("t1");
String s2=req.getParameter("t2");
rs=st.executeQuery("SELECT * FROM login WHERE uname='"+s1.trim()+"AND pass='"+s2.trim()+"';");
if(rs.next())
{
out.println("welcome");
}
else
{
out.println("sorry");
}
}
}
catch(Exception e){
out.println(e.getMessage());
}
}
}
HTML頁面代碼
加入打印錯誤<html>
<title>Login System</title>
<style type="text/css">
div.ex {
width:220px;
padding:10px;
border:5px solid gray;
margin:10px;
}
</style>
<body>
<div class="ex">
<strong>User Login</strong>
<form name=f1 method=get action="http://localhost:8080/login">
User         <input type=text name=t1><br>
Password <input type=password name=t2><br>
<input type=submit name=sub value="Login">
</div>
</body>
</html>
我有一個名爲登錄與字段uname和傳遞值的表。
有什麼問題請幫忙
我推薦做的一件事就是創建一個單獨的類,並將所有數據庫處理都放在該類中。您可以將您的servlet中的所有值傳遞給該數據庫類。另外,您需要查看JSTL(google it)usebean將值傳遞給POJO類。 – 2013-02-23 19:10:13