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servlet is not connecting to mysql database

 原文  2015-05-04 12:18:36  6   5    java/ mysql/ servlets

Question

I'm getting a error when trying to connect to a mysql database. I have an DatabaseAccess.java: 

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

@SuppressWarnings("serial")
public class DatabaseAccess extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    // Set response content type
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    String title = "Database Result";
    String docType = "<!doctype html public \"-//w3c//dtd html 4.0 "
            + "transitional//en\">\n";
    out.println(docType + "<html>\n" + "<head><title>" + title
            + "</title></head>\n" + "<body bgcolor=\"#f0f0f0\">\n"
            + "<h1 align=\"center\">" + title + "</h1>\n");
    try {
        Class.forName("com.mysql.jdbc.Driver").newInstance();
        Connection conn = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/test", "root", "root");
        PreparedStatement stmt = conn
                .prepareStatement("select name, pass, mail, phone from user");
        ResultSet rs = stmt.executeQuery();
        while (rs.next()) {
            String name = rs.getString("name");
            String pass = rs.getString("pass");
            String mail = rs.getString("mail");
            String phone = rs.getString("phone");

            out.println("ID: " + name + "<br>");
            out.println(", Age: " + pass + "<br>");
            out.println(", First: " + mail + "<br>");
            out.println(", Last: " + phone + "<br>");
        }
        out.println("</body></html>");

        rs.close();
        stmt.close();
        conn.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}
}

When I run the servlet class, it works partially and it is giving me these errors: 

    SEVERE: Exception creating UserDatabase MBeans for UserDatabase
javax.management.MalformedObjectNameException: Invalid character ',' in key part of property
    at javax.management.ObjectName.construct(Unknown Source)
    at javax.management.ObjectName.<init>(Unknown Source)
    at org.apache.catalina.mbeans.MBeanUtils.createObjectName(MBeanUtils.java:868)
    at org.apache.catalina.mbeans.MBeanUtils.createMBean(MBeanUtils.java:377)
    at org.apache.catalina.mbeans.GlobalResourcesLifecycleListener.createMBeans(GlobalResourcesLifecycleListener.java:192)
    at org.apache.catalina.mbeans.GlobalResourcesLifecycleListener.createMBeans(GlobalResourcesLifecycleListener.java:148)
    at org.apache.catalina.mbeans.GlobalResourcesLifecycleListener.createMBeans(GlobalResourcesLifecycleListener.java:110)
    at org.apache.catalina.mbeans.GlobalResourcesLifecycleListener.lifecycleEvent(GlobalResourcesLifecycleListener.java:82)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
    at org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:402)
    at org.apache.catalina.util.LifecycleBase.setState(LifecycleBase.java:347)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:689)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:321)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:455)

May 04, 2015 5:43:57 PM org.apache.catalina.core.StandardService startInternal
INFO: Starting service Catalina
May 04, 2015 5:43:57 PM org.apache.catalina.core.StandardEngine startInternal
INFO: Starting Servlet Engine: Apache Tomcat/7.0.59
May 04, 2015 5:43:58 PM org.apache.catalina.util.SessionIdGeneratorBase createSecureRandom
INFO: Creation of SecureRandom instance for session ID generation using [SHA1PRNG] took [218] milliseconds.
May 04, 2015 5:43:59 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["http-bio-8080"]
May 04, 2015 5:43:59 PM org.apache.coyote.AbstractProtocol start
INFO: Starting ProtocolHandler ["ajp-bio-8009"]
May 04, 2015 5:43:59 PM org.apache.catalina.startup.Catalina start
INFO: Server startup in 2026 ms
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at DatabaseAccess.doGet(DatabaseAccess.java:25)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1074)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

I have added the mysql connector mysql-connector-java-5.1.35.jar also to Build path. How can resolve these errors

5 answers

solution1
 2 ACCPTED  2015-05-04 12:33:34

在WEB-INF / lib文件夹下添加mysql-connector-java-5.1.35.jar jar，以便由tomcat加载

solution2
 0  2015-05-04 12:21:10

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

Means that you are not including the respective driver jar into your war or classpath . Try including the Jar file to fix this.

solution3
 0  2015-05-04 12:21:10

You miss the Mysql driver class in your classpath: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver download and add it to your classpath.

Buildpath is not the classpath !!

solution4
 0  

Your error is 

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

Add the MySQL JAR to your classpath. How is can be done depends on your servlet container. Read the documentation.

solution5
 0  2015-05-04 12:26:42

Well there is Driver Missing.

Here download jar and put in Lib folder.

jar Connector

and Run again Problem will be solved.

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