连接数据库时Tomcat找不到JDBC驱动程序

Question

连接数据库时Tomcat找不到JDBC驱动程序

我已经把 mysql 驱动程序放进去了.../ROOT/WEB-INF/lib，Tomcat 8.0/lib但它没有效果。我正在使用以下类连接到数据库：

package db;

import java.sql.*;

public class ConnectToDB implements AutoCloseable {
    Connection con;

    public ConnectToDB(String server, String database, String user,
            String password) throws SQLException {
        con = DriverManager.getConnection("jdbc:mysql://" + server + "/"
                + database, user, password);
    }

    @Override
    public void close() throws SQLException {
        con.close();
    }

    public Connection getConnection() {
        return con;
    }

}

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Eclipse 项目中包含以下类：

1. src/nr3/模型

package nr3.model;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import db.ConnectToDB;
public class MusikkHandler {
    private ConnectToDB db;
    private Connection con;
    private String tableName;
    private PreparedStatement pstmtGetRows;

    public MusikkHandler(String server, String database, String user,
            String password) throws SQLException {
        db = new ConnectToDB(server, database, user, password);
        con = db.getConnection();
        tableName = "album";
    }

    public void close() throws SQLException {
        db.close();
    }

    public ArrayList<Album> getRows(String genre) throws SQLException {
        ArrayList<Album> list = new ArrayList<Album>();
        pstmtGetRows = con.prepareStatement("SELECT * FROM " + tableName
                + " WHERE SJANGER = ?");
        pstmtGetRows.setString(1, genre);
        ResultSet rs = pstmtGetRows.executeQuery();
        while (rs.next()) {
            list.add(new Album(rs.getString(1), rs.getString(2), rs.getInt(3),
                    rs.getInt(4), rs.getString(5)));
        }
        rs.close();
        pstmtGetRows.close();
        return list;
    }
}

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——

package nr3.model;

public class Album {
    private String tittel;
    private String artist;
    private int spor;
    private int utgitt;
    private String sjanger;

    public Album (String artist, String tittel, int spor, int utgitt, String sjanger){
        setArtist(artist);
        setTittel(tittel);
        setUtgitt(utgitt);
        setSpor(spor);
        setSjanger(sjanger);
    }
    public Album(){
        this(null, null, 0, 0, null);
    }
    public void setTittel(String tittel){
        this.tittel = tittel;
    }
    public void setArtist(String artist){
        this.artist = artist;
    }
    public void setSpor(int spor) {
        this.spor = spor;
    }
    public void setUtgitt(int utgitt) {
        this.utgitt = utgitt;
    }
    public void setSjanger(String sjanger) {
        this.sjanger = sjanger;
    }
    public String getTittel() {
        return tittel;
    }
    public String getArtist() {
        return artist;
    }
    public int getSpor() {
        return spor;
    }
    public int getUtgitt() {
        return utgitt;
    }
    public String getSjanger() {
        return sjanger;
    }
    public String toString(){
        return getTittel() + " (" + getArtist() + ")" + " Utgitt: " 
                                               + getUtgitt(); 
    }
}

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2. src/nr3/servlets

package nr3.servlets;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import nr3.model.Album;
import nr3.model.MusikkHandler;

public class MusikkValg extends HttpServlet {

    private static final long serialVersionUID = 428937262021570370L;

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String genre = request.getParameter("sjanger");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        MusikkHandler mh;

        out.println("<html>");
        out.println("<head>");
        out.println("<title>Musikk</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>MUSIKK-ANBEFALINGER</h1>");
        out.println("<br/>");
        out.println("<br/>");
        out.println("<h3>Da bør du kanskje forsøke en av disse:</h3>");
        out.println("<br/>");
        out.println("<br/>");
        try {
            mh = new MusikkHandler(" ", " ", " ", " ");
            for (Album a : mh.getRows(genre))
                out.println("<p>" + a + "</p>");
        } catch (SQLException e) {
            e.printStackTrace(out);
        }
        out.println("</body>");
        out.println("</html>");
    }

}

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更新：我在浏览器中有以下错误堆栈跟踪：

java.sql.SQLException: 在 db.ConnectToDB 的 java.sql.DriverManager.getConnection(Unknown Source) 的 java.sql.DriverManager.getConnection(Unknown Source) 找不到适合 jdbc:mysql://localhost/pg3100 的驱动程序。( ConnectToDB.java:10) 在 nr3.model.MusikkHandler.(MusikkHandler.java:20) 在 nr3.servlets.MusikkValg.doGet(MusikkValg.java:39) 在 javax.servlet.http.HttpServlet.service(HttpServlet.java: 618) 在 javax.servlet.http.HttpServlet.service(HttpServlet.java:725) 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) 在 org.apache.catalina.core.ApplicationFilterChain.doFilter (ApplicationFilterChain.java:206) 在 org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 在 org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) 在 org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 在 org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) 在 org.apache.catalina.core.StandardContextValve .invoke(StandardContextValve.java:106) 在 org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505) 在 org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.javaorg.142) 在apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 在 org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610) 在 org.apache.catalina.core.StandardEngineValve.Stard.invoke() java:88) 在 org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:534) 在 org.apache.coyote.http11。AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081) 在 org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658) 在 org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.Protocol$Http11ConnectionHandler.Pro(Http17)Apr2在 org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2381) 在 org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2370) 在 java.util .concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run（来源不明）process(AbstractProtocol.java:658) at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:277) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java: 2381) 在 org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2370) 在 java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 在 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)process(AbstractProtocol.java:658) at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:277) at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java: 2381) 在 org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2370) 在 java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 在 java.util.concurrent.ThreadPoolExecutor$Worker。 run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source)util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2370) 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) 在 java.lang.Thread.run（未知来源）util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2370) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache .tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 在 java.lang.Thread.run（未知来源）

Answer 1

Alf*_*avo 5

首先，您必须在开始时注册您的驱动程序，以便 DriverManager 在获得连接时可以使用它。它可能因实现而异。

DriverManager.registerDriver (new com.mysql.jdbc.Driver());

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或者

Class.forName("com.mysql.jdbc.Driver");

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然后您可以执行 a，getConnection()因为您将注册一个驱动程序以供 DriverManager 使用。

第二：/webapps/ROOT/WEB-INF/lib是一个不同的上下文，它的库将不可用于您的应用程序，除非您设置应用程序的上下文路径，如本问题所示。如果您想添加它，请先尝试放置您的 JDBC 驱动程序/webapps/<yourapp>/lib。Tomcat 库应该也能正常工作（但是当你分发你的应用程序时它并不好，可能与部署在那里的其他应用程序冲突，使用不同版本的驱动程序等）

第三：当在这里提问时，尽量将可验证的示例减少为可读的内容。有很多代码与您的问题无关。减少可以更轻松地阅读您的问题并提供帮助。

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