LogFrm.htm: <h3 align="center">用户登录 </h3>
<hr />
<form method="post" action="Login.jsp">
用户名称
<input name="name" type="text" value="" />
<br /> <br /> 用户密码
<input name="password" type="text" value="" />
<br /> <input type="submit" name="Submit" value="登录" /> </form> Login.jsp:
<%@page contentType="text/html;charset=gbk" import="java.sql.*" %>
<%!
public String login(String name,String password)
{
Connection con = null;
PreparedStatement sql = null;
ResultSet re = null;
String result = null;
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con = DriverManager.getConnection("jdbc:odbc:Access");
sql = con.prepareStatement("select * from JSP where 账号 = '" + name + "'");
re = sql.executeQuery();
if(!re.next())
{
result = "无此账号!";
}
else
if(!re.getString(2).equals(password))
{
result = "密码错误!";
}
else
{
result = "登陆成功!";
}
con.close();
}
catch(Exception e)
{
out.print(e);
}
return result ;
}
%>
<%
String name = request.getParameter("name");
String password = request.getParameter("password");
if(name == null || password == null)
response.sendRedirect("LogFrm.htm");
String str = login(name,password);
if(str.equals("登陆成功!"))
response.sendRedirect("LoginSuccess.jsp");
%>
<html>
<head>
<title>用户登录</title>
</head>
<body>
<center><br><a href="LogFrm.htm">重新登录</a></center>
</body>
</html>
登录成功后的界面还没有写,先不管,为什么输入用户名称和用户密码后跳转到Login.jsp页面的时候会有空指针异常?
错误如下:
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: 2 in the jsp file: /Login/Login.jsp
Generated servlet error:
out cannot be resolved
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: 2 in the jsp file: /Login/Login.jsp
Generated servlet error:
out cannot be resolved
org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:84)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:328)
org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:414)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:297)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:276)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:264)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:563)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:303)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.
<hr />
<form method="post" action="Login.jsp">
用户名称
<input name="name" type="text" value="" />
<br /> <br /> 用户密码
<input name="password" type="text" value="" />
<br /> <input type="submit" name="Submit" value="登录" /> </form> Login.jsp:
<%@page contentType="text/html;charset=gbk" import="java.sql.*" %>
<%!
public String login(String name,String password)
{
Connection con = null;
PreparedStatement sql = null;
ResultSet re = null;
String result = null;
try
{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con = DriverManager.getConnection("jdbc:odbc:Access");
sql = con.prepareStatement("select * from JSP where 账号 = '" + name + "'");
re = sql.executeQuery();
if(!re.next())
{
result = "无此账号!";
}
else
if(!re.getString(2).equals(password))
{
result = "密码错误!";
}
else
{
result = "登陆成功!";
}
con.close();
}
catch(Exception e)
{
out.print(e);
}
return result ;
}
%>
<%
String name = request.getParameter("name");
String password = request.getParameter("password");
if(name == null || password == null)
response.sendRedirect("LogFrm.htm");
String str = login(name,password);
if(str.equals("登陆成功!"))
response.sendRedirect("LoginSuccess.jsp");
%>
<html>
<head>
<title>用户登录</title>
</head>
<body>
<center><br><a href="LogFrm.htm">重新登录</a></center>
</body>
</html>
登录成功后的界面还没有写,先不管,为什么输入用户名称和用户密码后跳转到Login.jsp页面的时候会有空指针异常?
错误如下:
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: 2 in the jsp file: /Login/Login.jsp
Generated servlet error:
out cannot be resolved
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: 2 in the jsp file: /Login/Login.jsp
Generated servlet error:
out cannot be resolved
org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:84)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:328)
org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:414)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:297)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:276)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:264)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:563)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:303)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.17 logs.
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String password = request.getParameter("password");
放在逻辑代码上面 Java一般都是从上到下 从内到外执行,你在下面获取name当然得不到值,而且是空指针异常