文章/答案/技术大牛

发布

社区首页 >问答首页 >java web应用程序mysql连接错误

问java web应用程序mysql连接错误
EN

Stack Overflow用户

提问于 2014-02-06 14:28:39

回答 4查看 637关注 0票数 1

我是新来的爪哇。我的Java环境是1.Windows8.2.MySQL- 5.5.27。3. Eclipse IDE for Java EE Devoper v-2。5. Apache Tomcat v-7。6. mysql-connector-java-5.1.28 bin rar 7.jdk 1.7.现在我想从jsp文件连接到mysql。我已经将mysql-connector添加到库资源中。但是我连接不上。下面给出了我的代码和错误。代码: home.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<%@ page language="java" import="java.sql.Connection"%>
<%@ page language="java" import="java.sql.PreparedStatement"%>
<%@ page language="java" import="java.sql.ResultSet"%>
<%@ page language="java" import="java.sql.SQLException"%>
<%@ page language="java" import="java.sql.DriverManager"%>
<%@ page language="java" import="java.util.*"%>
<!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=ISO-8859-1">
<title>Bengal Contact List | Home </title>
</head>
<body>
<%

Connection con = null;
try {
//Class.forName("com.mysql.jdbc.Driver");
String driver="com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost/java_contact";
String user = "root";
String password = "";
Class.forName(driver);
con = DriverManager.getConnection(url, user, password);
}
catch(ClassNotFoundException cnfe){
System.out.println(cnfe);
}
catch(SQLException ex){
System.out.println(ex);
}

// Connection con;
// con=DBConnect.GetDBConnect();
String sql="SELECT * FROM contactsinfo";
PreparedStatement ps = con.prepareStatement(sql);
ResultSet rs = ps.executeQuery(sql);

%>
<table border="1">
<tr>
<td>ID</td>
<td>Name</td>
<td>Designation</td>
</tr>
<%
  while(rs.next()){
%>
<td><%=rs.getInt("ID")%></td>
<td><%=rs.getString("Name")%></td>
<td><%=rs.getString("Designation")%></td>
<%
}
%>
</table>
 <h1>Now i am in Home Page.I want to show table information of Contact List.</h1>
</body>
</html>

错误：

type Exception report

message 

description The server encountered an internal error () that prevented it from   fulfilling this request.

exception 

org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:534)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:457)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)


root cause 

java.lang.NullPointerException
org.apache.jsp.home_jsp._jspService(home_jsp.java:96)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:391)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)


note The full stack trace of the root cause is available in the Apache Tomcat/7.0.12 logs.

请找出问题出在哪里。

java

mysql

jsp

回答 4

Stack Overflow用户

发布于 2014-02-06 14:35:17

尝试对rs.getInt("ID"), rs.getString("Name"), rs.getString("Designation")进行null检查。NullPointerException在页面中抛出了这个问题。

对con对象也使用相同的方法。

票数 0

Stack Overflow用户

发布于 2014-02-06 14:42:21

首先检查你的结果是否为空

ResultSet rs = statement.execute();
if (!rs.next()){
   //ResultSet is empty
}
else{
   <td><%=rs.getInt("ID")%></td>
   <td><%=rs.getString("Name")%></td>
   <td><%=rs.getString("Designation")%></td>
}

票数 0

Stack Overflow用户

发布于 2014-02-06 14:45:54

您必须添加数据库的端口号(3306)端口号，用户名和密码，我有附加的工作代码。检查并更新评论.....

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
    <%@ page language="java" import="java.sql.Connection"%>
    <%@ page language="java" import="java.sql.PreparedStatement"%>
    <%@ page language="java" import="java.sql.ResultSet"%>
    <%@ page language="java" import="java.sql.SQLException"%>
    <%@ page language="java" import="java.sql.DriverManager"%>
    <%@ page language="java" import="java.util.*"%>
    <!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=ISO-8859-1">
    <title>Bengal Contact List | Home </title>
    </head>
    <body>
    <%

    Connection con = null;
    try {
    //Class.forName("com.mysql.jdbc.Driver");
    String driver="com.mysql.jdbc.Driver";
    String url = "jdbc:mysql://localhost:3306/schemaname";
    String user = "username";
    String password = "password";
    Class.forName(driver);
    con = DriverManager.getConnection(url, user, password);
    }
    catch(ClassNotFoundException cnfe){
    System.out.println(cnfe);
    }
    catch(SQLException ex){
    System.out.println(ex);
    }

    // Connection con;
    // con=DBConnect.GetDBConnect();
    String sql="SELECT * FROM contactsinfo";
    PreparedStatement ps = con.prepareStatement(sql);
    ResultSet rs = ps.executeQuery(sql);

    %>
    <table border="1">
    <tr>
    <td>ID</td>
    <td>Name</td>
    <td>Designation</td>
    </tr>
    <%
      while(rs.next()){
    %>
    <td><%=rs.getInt("ID")%></td>
    <td><%=rs.getString("Name")%></td>
    <%
    }
    %>
    </table>
     <h1>Now i am in Home Page.I want to show table information of Contact List.</h1>
    </body>
    </html>

票数 0

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/21595635

复制

相似问题

问java web应用程序mysql连接错误
EN

回答 4

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问java web应用程序mysql连接错误EN

回答 4

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问java web应用程序mysql连接错误
EN