Question

我已将mysql驱动程序放在.../ROOT/WEB-INF/lib和Tomcat 8.0/lib中，但它没有效果。我正在使用以下类连接到DB：

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;
    }

}

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;
    }
}

-

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(); 
    }
}

2。 SRC / NR3 / servlet的

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>");
    }

}

更新：我在浏览器中遇到以下错误堆栈跟踪：

java.sql.SQLException：找不到合适的驱动程序 jdbc：mysql：// localhost / pg3100 at java.sql.DriverManager.getConnection（未知来源）at java.sql.DriverManager.getConnection（未知来源）at db.ConnectToDB。（ConnectToDB.java:10）at nr3.model.MusikkHandler。（MusikkHandler.java:20）at nr3.servlets.MusikkValg.doGet（MusikkValg.java:39）at at javax.servlet.http.HttpServlet.service（HttpServlet.java:618）at at javax.servlet.http.HttpServlet.service（HttpServlet.java:725）at at 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.java:142）在 org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:79）在 org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:610）在 org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.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.process（Http11AprProtocol.java:277）在 org.apache.tomcat.util.net.AprEndpoint $ SocketProcessor.doRun（AprEndpoint.java:2381）在 org.apache.tomcat.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）在 org.apache.tomcat.util.threads.TaskThread $ WrappingRunnable.run（TaskThread.java:61）在java.lang.Thread.run（未知来源）

Answer 1

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。关于实施的It might vary。

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

或

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

然后您可以执行getConnection()，因为您已经注册了DriverManager使用的驱动程序。

第二：/webapps/ROOT/WEB-INF/lib是一个不同的上下文，除非您要设置应用as shown in this question的上下文路径，否则它的库将无法用于您的应用。如果您想添加它，请先尝试将JDBC驱动程序放在/webapps/<yourapp>/lib上。 Tomcat lib也应该可以工作（但是当你分发应用程序时，它可能会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：在这里提问时，尽量将可验证的例子减少到可读的范围。有很多代码与您的问题无关。减少使您更容易阅读问题并提供帮助。

连接到数据库

1 个答案: