package online;
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;public class LoginCheck extends HttpServlet
{
private Connection conn=null;
private ResultSet rs =null;
private Statement stmt=null; public void init() throws ServletException
{
try
{
String host = "localhost";
String db = "db2";
String use = "root";
String pass = "password";
String url = "jdbc:mysql://"+host+":3306/"+db+"?user="+use+"&password="+pass+"&useUnicode=true&characterEncoding=gb2312" ;
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
conn=DriverManager.getConnection(url);
}
catch(Exception e)
{
System.out.println("error:"+e.getMessage());
} } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
PrintWriter out = response.getWriter();
String userid = request.getParameter("id");
String userpwd = request.getParameter("password");
try
{
stmt=conn.createStatement();
rs=stmt.executeQuery("select * from member where id='"+userid+"'");
if(rs.next()){
String pwd=rs.getString("passwd").trim();
if(!pwd.equals(userpwd)){
out.println("<script>alert('密码错误');document.location='javascript:history.go(-1);'</script>");
}
else{
out.println("<script>alert('登陆成功');document.location='global_login.jsp'</script>");
}
}
else{
out.println("<script>alert('用户名不存在');document.location='javascript:history.go(-1);'</script>");
}
}
catch(SQLException e)
{
out.println(e.getMessage());
} finally
{
try
{
rs.close();
stmt.close();
conn.close();
}
catch(SQLException e) {
out.println(e.getMessage());
}
}
}
}
-------------------------------错误提示!-----------------------------java.lang.NullPointerException
at blog.LoginCheck.doPost(LoginCheck.java:76)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:763)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:286)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:205)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:177)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:156)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:203)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:637)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:488)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:568)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:631)
at java.lang.Thread.run(Unknown Source)
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;public class LoginCheck extends HttpServlet
{
private Connection conn=null;
private ResultSet rs =null;
private Statement stmt=null; public void init() throws ServletException
{
try
{
String host = "localhost";
String db = "db2";
String use = "root";
String pass = "password";
String url = "jdbc:mysql://"+host+":3306/"+db+"?user="+use+"&password="+pass+"&useUnicode=true&characterEncoding=gb2312" ;
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
conn=DriverManager.getConnection(url);
}
catch(Exception e)
{
System.out.println("error:"+e.getMessage());
} } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
PrintWriter out = response.getWriter();
String userid = request.getParameter("id");
String userpwd = request.getParameter("password");
try
{
stmt=conn.createStatement();
rs=stmt.executeQuery("select * from member where id='"+userid+"'");
if(rs.next()){
String pwd=rs.getString("passwd").trim();
if(!pwd.equals(userpwd)){
out.println("<script>alert('密码错误');document.location='javascript:history.go(-1);'</script>");
}
else{
out.println("<script>alert('登陆成功');document.location='global_login.jsp'</script>");
}
}
else{
out.println("<script>alert('用户名不存在');document.location='javascript:history.go(-1);'</script>");
}
}
catch(SQLException e)
{
out.println(e.getMessage());
} finally
{
try
{
rs.close();
stmt.close();
conn.close();
}
catch(SQLException e) {
out.println(e.getMessage());
}
}
}
}
-------------------------------错误提示!-----------------------------java.lang.NullPointerException
at blog.LoginCheck.doPost(LoginCheck.java:76)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:763)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:286)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:205)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:177)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:149)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:156)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:151)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:562)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:974)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:203)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:637)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:488)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:568)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:631)
at java.lang.Thread.run(Unknown Source)
也可以使用log4j来弄
你贴出的代码只有74行,并且package为online, 似乎与运行时提示的blog.LoginCheck不一致
但是 编译器 报了这样的错误提示:
------------------------------------------------------------------------------
LoginCheck.java:58: cannot resolve symbol
symbol : variable session
location: class online.LoginCheck
session.setAttribute("id",userid);-----------------------------------------------------------------------------'登陆成功'的上面加了 那个代码
HttpSession session = request.getSession();
我想在 servlet 中访问 javabean 里的数据!怎么做好呢?如:
javabean 里写 用 jdbc 连接 数据库的代码!
在 servlet 里写sql 程序 但是先 import javabean的 数据!
data = bean.getData(); // your bean's method答案似乎太简单了,可能没有弄懂你的问题?
但出现了错误提示!LoginCheck.java:3: package bean does not exist
import bean.DataDo;这是什么意思呢?
2. 不行的话,从简单的做起: 把 DataDo.java 拷贝到你的 servlet 目录下(应该是online吧),把DataDo.java中的package改成online, 这样在servlet中就不要引用了,可以去掉import xx.DataDo;
LoginCheck.java:3: package bean does not exist说明是在编译LoginCheck.java 第3行的时候出现错误。不是吗?我也很迷惑啊?!
这样问太麻烦了!直接跟你问的话 快一些! 可以吗?