HTTP Status 500 -
type Exception report
message
description The server encountered an internal error that prevented it from fulfilling this request.
exception
java.lang.NullPointerException
org.cai.servlet.LoginServlet.doPost(LoginServlet.java:69)
javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.39 logs.
LoginServlet.java
package org.cai.servlet ;
import java.sql.* ;
import java.io.* ;
import javax.servlet.http.* ;
import javax.servlet.* ;
public class LoginServlet extends HttpServlet implements Servlet{
public LoginServlet(){
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
}
// protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
// System.out.println("-------------------------") ;
// doPost(request, response) ;
// }
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
response.setContentType("text/html;charset=gb2312") ;
request.setCharacterEncoding("gb2312") ;
String result = "" ;
//获取用户名
String username = request.getParameter("username") ;
String psw = request.getParameter("password") ;
if ((username == "") || (username==null) || (username.length() > 20 )){
try{
result = "请输入用户名(不能超过20个字符)!" ;
request.setAttribute("message" ,result) ;
response.sendRedirect("login.jsp") ;
}catch(Exception e){
e.printStackTrace() ;
}
}
if ((psw == "") || (psw==null) || (psw.length() > 20 )){
try{
result = "请输入密码(不能超过20个字符)!" ;
request.setAttribute("message" ,result) ;
response.sendRedirect("login.jsp") ;
}catch(Exception e){
e.printStackTrace() ;
}
}
//登记JDBC驱动程序
try{
Class.forName("org.gjt.mm.mysql.Driver") ;
}catch(ClassNotFoundException e){
e.printStackTrace() ;
System.out.println("Class Not Found Exception . ") ;
}
//连接URL
String url ="jdbc:mysql://localhost:3306/learnJSP" ;
Connection conn = null ;
Statement stmt = null ;
ResultSet rs = null ;
try{
conn = DriverManager.getConnection(url, "root", "520") ;
stmt = conn.createStatement() ;
//SQL语句
String sql ="select * from userInfo where username='"+username+"' and userpsw= '"+psw+"'" ;
rs = stmt.executeQuery(sql) ;//返回查询结果
}catch(SQLException e){
e.printStackTrace() ;
}
HttpSession session = request.getSession() ;
session.setAttribute("username", username) ;
//System.out.println("+++++++++++++++++++++++"+ username) ;
try{
if (rs.next()){ //如果记录集非空，表明有匹配的用户名和密码，登陆成功
// 登录成功后将username设置为session变量的username
// 这样在后面就可以通过 session.getAttribute("username") 来获取用户名，
// 同时这样还可以作为用户登录与否的判断依据
session.setAttribute("age",rs.getString("age")) ;
session.setAttribute("sex",rs.getString("sex")) ;
session.setAttribute("weight",rs.getString("weight")) ;
response.sendRedirect("success.jsp") ;
}else{
session.setAttribute("message", "用户名或密码不匹配。");
response.sendRedirect("fail.jsp") ;
}
}catch(SQLException e){
e.printStackTrace() ;
}
}
private static final long serialVersionUID = 1L;
}
