java web项目本地运行正常发布到阿里云服务器上之后出错
<%@ page language="java" import="java.util.*,db.DBLink,java.sql.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<%
DBLink db=new DBLink("my_test_db");
Connection con=db.getDefaultCon();
Statement sta=con.createStatement();
ResultSet rs=sta.executeQuery("select * from users");
if(rs.next()){
out.print(rs.getString(1)+" "+rs.getString(2));
}
%>
</body>
</html>
//数据库连接
DBLink.java
package db;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class DBLink {
Connection con;
Statement sta;
ResultSet rs;
PreparedStatement psta;
ResultSetMetaData rsm;
//119.23.240.242
private String user = null, pwd = null, dataBaseName = "my_test_db", id = "localhost", port = "3306";
public DBLink(String dataBaseName) {
this.user = "root";
this.pwd = "abc";
this.dataBaseName = dataBaseName;
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (Exception e) {
}
}
public Connection getDefaultCon() {
String uri = "jdbc:mysql://localhost:3306/" + dataBaseName+"?useUnicode=true&characterEncoding=utf-8&useSSL=false";
setUser("root");
setPwd("lfy");
try {
con = DriverManager.getConnection(uri, "root", "abc");
return con;
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
}
java web在本地可以正常运行
但是发布到阿里云服务器上就不能运行
错误信息:
HTTP Status 500 - An exception occurred processing JSP page /index.jsp at line 27
type Exception report
message An exception occurred processing JSP page /index.jsp at line 27
description The server encountered an internal error that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: An exception occurred processing JSP page /index.jsp at line 27
24: <%
25: DBLink db=new DBLink("my_test_db");
26: Connection con=db.getDefaultCon();
27: Statement sta=con.createStatement();
28: ResultSet rs=sta.executeQuery("select * from users");
29: if(rs.next()){
30: out.print(rs.getString(1)+" "+rs.getString(2));
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:567)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:469)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause
java.lang.NullPointerException
org.apache.jsp.index_jsp._jspService(index_jsp.java:126)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:431)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.0.18 logs.
org.apache.jasper.JasperException: An exception occurred processing JSP page /index.jsp at line 27
java.lang.NullPointerException
27: Statement sta=con.createStatement();
报错为27这一行，空指针异常
26:Connection con=db.getDefaultCon();
这一行的con，返回值为null，到27行，null.createStatement();当然是不行的，所以报了空指针异常。
问题出在：数据库建立连接失败
你的阿里云服务器是不是也是linux服务器？如果是，有可能是db路径出问题了。我之前遇到过类似问题，项目同样是在本地windows运行没问题，但到liunx服务器上就出问题了。原因是一个配置文件因为路径差异没找到。
你这个是数据库访问问题吧，我之前也出现这个问题