关于 MySql JDBC 在netbeans中连接不上的问题

[超gogo]

 Connection con;
            Statement sql = null;
            ResultSet rs = null;
            try {
                Class.forName("com.mysql.jdbc.Driver");
            } catch (ClassNotFoundException e) {
                out.print(e);
            }
            try {
                String url="jdbc:mysql://localhost:3306/ChatDB";
                con = DriverManager.getConnection(url,
                        "wtc", " 9999999");
            } catch (SQLException e) {
                out.print(e);
            }
            sql = con.createStatement();

错误为
G:\programming\Netbeans\WebApplication1\build\generated\src\org\apache\jsp\index_jsp.java:84: 可能尚未初始化变量 con
sql = con.createStatement();

应该是上面的con没有得到连接上的值 请大家帮帮忙 谢谢！！！！

[超gogo]

下面是服务器日志

An error occurred at line: 39 in the jsp file: /index.jsp
The local variable con may not have been initialized
36: {
37: out.print(e);
38: }
39: sql=con.createStatement();
40: //rs=sql.executeQuery()
41: %>
42: </body>


Stacktrace:
at org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:92)
at org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:330)
at org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:423)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:317)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:295)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:282)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:586)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)
2009-11-9 22:18:29 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet jsp threw exception
org.apache.jasper.JasperException: Unable to compile class for JSP:

[jackHanQi]

你是在jsp页面上连接数据库的啊？给的部分代码貌似没问题。
把整个页面粘出来看一下

[zl3450341]

Connection con=null;


再试试

[zl3450341]

package com.car.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DBCon {
	public static String driver="oracle.jdbc.driver.OracleDriver";
	public static String url="jdbc:oracle:thin:@127.0.0.1:1521:orcl";
	public static String user="scott";
	public static String pwd="tiger";
	
	public static Connection getConnection(){
		try {
			Class.forName(driver);
			Connection con=DriverManager.getConnection(url, user, pwd);
			System.out.println("OK");
			return con;
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}
	
	public static void close(Connection con,Statement stm,ResultSet rs){
		if(con!=null){
			try {
				con.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		if(stm!=null){
			try {
				stm.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		if(rs!=null){
			try {
				rs.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
	
	public static void main(String[] args) {
		DBCon.getConnection();
	}
}

给你个例子
不过是在MyEclipse里面写的

[超gogo]

改成null也是不行的 编译的时候错误会消失，但是运行的时候总是错误HTTP500
HTTP Status 500 -

--------------------------------------------------------------------------------

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:522)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)


root cause

java.lang.NullPointerException
org.apache.jsp.index_jsp._jspService(index_jsp.java:85)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)

仍然是没有获得 空指针错误

[sangshusen_1988]

看看后台，如果数据库连接获取失败，后台肯定会拉出错误信息的

[超gogo]

继续啊 谢谢

[超gogo]

如何看啊？我初学 不明白啊

[超gogo]

出现空指针的错误 我觉得肯定就是没有连上MySql tomcat应该没有问题，我用的是netbeans原带的
tomcat 执行非数据库操作的JSP文件都是可以执行的。

请各位说一下MySql失败的原因啊？
谢谢