我正在尝试使用下面的jsp代码插入查询
<%@ page import="java.sql.*, javax.servlet.http.*" language="java"
contentType="text/html; charset=windows-1256" pageEncoding="windows-1256" %>
<%!public static Connection connect ()
{
try
{
Class.forName("com.mysql.jdbc.Driver").newInstance();
return DriverManager.getConnection("jdbc:mysql://localhost/test","root","dhawanbhai1");
}
catch (Exception e)
{
//throw new Error(e);
return null;
}
}
public static boolean close(Connection c)
{
try
{
c.close();
return true;
}
catch (Exception e)
{
return false;
}
}
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org
/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1256">
<title>Login Page</title>
</head>
<body>
<form action="">
Please enter your username
<input type="text" name="un"/>
<br>
Please enter your password
<input type="password" name="pw"/>
<input type="submit" value="submit">
</form>
</body>
</html>
<%
Connection c = connect();
String user=request.getParameter("un");
String pass=request.getParameter("pw");
PreparedStatement pst=c.prepareStatement("insert into userpass (id,password)
values (?,?)");
pst.setString(1, user);
pst.setString(2, pass);
int val=pst.executeUpdate();
if(val>0)
System.out.println("Inserted record");
%>
但得到
org.apache.jasper.JasperException: An exception occurred processing JSP page
/LoginPage.jsp at line 68
65: pst.setString(2, pass);
66:
67:
68: int val=pst.executeUpdate();
69:
70: if(val>0)
71: System.out.println("Inserted record");
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455) 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:728) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
root cause
javax.servlet.ServletException:
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column
'id' cannot be null
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:912)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:841)
org.apache.jsp.LoginPage_jsp._jspService(LoginPage_jsp.java:147)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
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:728)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
最佳答案
在堆栈跟踪中，它表明列“id”不能为空。所以问题可能是 request.getParameter("un"); 为 null。检查您是否传递了“un”参数，并且在两个地方都有正确的名称“un”。
将代码的底部部分更改为如下所示:
<%
String user=request.getParameter("un");
String pass=request.getParameter("pw");
if (user != null && pass != null) {
Connection c = connect();
PreparedStatement pst=c.prepareStatement("insert into userpass (id,password) values (?,?)");
pst.setString(1, user);
pst.setString(2, pass);
int val=pst.executeUpdate();
if(val>0)
System.out.println("Inserted record");
}
%>
当您第一次加载页面时，“un”和“pw”不会被设置，因此它不应该调用插入方法。这会在尝试插入之前检查参数是否已设置。
关于java - 无法使用jsp插入数据库，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20440112/