將MySQL JDBC驅動程序導入動態Web項目

Question

我在連接到基於Web（而非本地）的MySQL數據庫時遇到問題。 我不斷收到錯誤消息：在控制台中找不到適用於jdbc：mysql：// host：port / database的合適驅動程序 （我當然使用的是實際的主機）。 該網頁僅顯示“空”。

我是Java的新手，因此一直以這篇文章作為參考來開始使用。 我在Eclipse中創建了一個動態Web項目，並在WebContent> WEB-INF> LIB下添加了JDBC連接器JAR文件。 我完全迷失了為什么這繼續給我一個錯誤。

我正在Tomcat 7中使用Eclipse IDE。

在過去的幾個小時里，我一直在谷歌搜索，沒有運氣...請幫助！ 這是我正在使用的代碼：

Connect.java

package dbObjects;

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

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;

public class Connect {
    protected Connection getConnection() throws SQLException {
        String url = "jdbc:mysql://host:port/database";
        String username = "username";
        String password = "password";

        Connection conn = (Connection) DriverManager.getConnection(url, username, password);
        return conn;
    }

    protected ResultSet getResultSet(String sql) throws SQLException {
        Connection conn = getConnection();
        Statement st = (Statement) conn.createStatement();
        return st.executeQuery(sql);
    }
}

Employees.java

package dbObjects;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Date;

public class Employees extends Connect {
    private String login;
    private String workgroup;
    private String csm;

    public Employees(String login, String workgroup, String csm) {
        super();
        this.login = login;
        this.workgroup = workgroup;
        this.csm = csm;
    }

    public Employees(String login) throws SQLException {
        super();
        this.login = login;
        setUserById(login);
    }

    private void setUserById(String login) throws SQLException {
        ResultSet resultSet = getResultSet("SELECT * FROM employeeData LIMIT 5");
        while(resultSet.next()) {
            System.out.println(resultSet.getString("login"));
            workgroup = resultSet.getString("workgroup");
            csm = resultSet.getString("csm");
        }
    }

    @Override
    public String toString() {
        return workgroup;
    }

}

我正在嘗試運行的servlet

package servlets;

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

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

import dbObjects.Employees;

/**
 * Servlet implementation class HomeServlet
 */
@WebServlet(description = "Home page shown to user", urlPatterns = { "/HomeServlet" })
public class HomeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public HomeServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        Employees user = null;
        try {
            user = new Employees(null);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        PrintWriter pw = response.getWriter();
        pw.println(user);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

我還創建了一個簡單的連接測試類，該類正在運行並且沒有返回任何合適的驅動程序錯誤。

import java.sql.DriverManager;
import java.sql.SQLException;

import com.mysql.jdbc.Connection;

public class connTest {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String url = "jdbc:mysql://host:port/database";
    String username = "username";
    String password = "password";

        System.out.println("Connecting database...");

        try (Connection connection = (Connection) DriverManager.getConnection(url, username, password)) {
            System.out.println("Database connected!");
        } catch (SQLException e) {
            throw new IllegalStateException("Cannot connect the database!", e);
        }
    }

}

Answer 1

問題出在Connect.java類中。 我添加了以下代碼行DriverManager.registerDriver(new com.mysql.jdbc.Driver ()); 就在Connection conn = (Connection) DriverManager.getConnection(url, username, password);

現在正在工作！