菜鸟提问：不能连接到MYSQL，代码如下：

Question

org.apache.jasper.JasperException
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:254)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:575)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:498)
at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:822)
at org.apache.jsp.index_jsp._jspService(index_jsp.java:53)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2422)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:163)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:199)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:828)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:700)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:584)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:534)
root cause java.lang.NullPointerException
at com.bwm.database.Dbssort.Select(Dbssort.java:110)
at com.bwm.database.DbBasetableFactory.ListSsort(DbBasetableFactory.java:138)
at com.bwm.BasetableFactoryProxy.ListSsort(BasetableFactoryProxy.java:134)
at org.apache.jsp.top_jsp._jspService(top_jsp.java:59)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:575)
at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:498)
at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:822)
at org.apache.jsp.index_jsp._jspService(index_jsp.java:53)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2422)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:163)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:199)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:828)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:700)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:584)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:534)

Answer 1

package com.bwm.core;import java.sql.Connection;
import java.sql.SQLException;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;public class Database {
    private static Connection con;
    private static String proxool = "org.logicalcobwebs.proxool.ProxoolDriver";
    private static String poolname = "proxool.mingri";
    public Database() {
    }    public static Connection getConnection() {
        try {
            Class.forName(proxool);
            con = DriverManager.getConnection(poolname);
        } catch (ClassNotFoundException e) {
            System.out.println(e.getMessage());
        } catch (SQLException e) {
            System.out.println(e.getMessage());
        }
        if (con == null) {
            System.out.println("没有获取到数据库连接");
        }
        return con;
    }    public static int getRow(String sql) {
        int i = 0;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            ps = con.prepareStatement("SELECT COUNT(*) FROM " + sql,
                                      ResultSet.TYPE_SCROLL_INSENSITIVE,
                                      ResultSet.CONCUR_READ_ONLY);
            rs = ps.executeQuery();
            if (rs.next()) {
                i = rs.getInt(1);
            }
        } catch (SQLException e) {
            System.out.println(e.getMessage());
            i = 0;
        } finally {
            System.out.println("SELECT COUNT(*) FROM " + sql);
            try {
                rs.close();
            } catch (SQLException e) {}
            try {
                ps.close();
            } catch (SQLException e) {}
            return i;
        }
    }
    public static boolean Delete(String sql) {
        boolean b = false;
        Connection con = null;
        PreparedStatement ps = null;
        try {
            con = Database.getConnection();
            ps = con.prepareStatement(sql);
            if (ps.executeUpdate() > 0) {
                b = true;
            } else {
                b = false;
            }
        } catch (SQLException e) {
            b = false;
            e.printStackTrace();
        } finally {
            System.out.println(ps + " Database.Delete() "+sql);
            try {
                if (ps != null) {
                    ps.close();
                }
            } catch (SQLException e) {
                ps = null;
            }
            try {
                if (con != null) {
                    con.close();
                }
            } catch (SQLException e) {
                con = null;
            }
        }
        return b;
    }
}
用的是MYSQL。

Answer 2

package com.webwork.javabean.dao;import java.sql.*;/**
 * 数据源
 */
public class DateSource {
 public static Connection getconn() throws ClassNotFoundException, SQLException
     {
      Connection conn=null;  //MYSQL数据库
 String url="jdbc:mysql://localhost:3306/mydata";  Class.forName("org.gjt.mm.mysql.Driver");  conn=DriverManager.getConnection(url, "root", "123456");   return conn;
    
 }
}