java.sql.SQLException:找不到适用于jdbc:mysql://localhost:3306/db的驱动程序 [英] java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/db

问题描述

页面始终转发到"custLogin"，但数据正确.

the page always forward to "custLogin" but the data is correct.

以下代码:

班级登录:

private CustomerDB db;

public void init() {
    String dbUrl = "jdbc:mysql://localhost:3306/fyp";
    String dbUser = "root";
    String dbPassword = "";
    db = new CustomerDB(dbUrl, dbUser, dbPassword);
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doPost(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String action = request.getParameter("action");

    if (!isAuthenticated(request) && !("authenticate".equals(action))) {
        doLogin(request, response);
        return;
    }
    if ("authenticate".equals(action)) {
        doAuthenticate(request, response);
    } else if ("logout".equals(action)) {
        doLogout(request, response);
    } else {
        response.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED);
    }
}

private void doAuthenticate(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
    String username = request.getParameter("custID");
    String password = request.getParameter("custPW");
    String targetURL;
    init();
    boolean isValid = db.isValidUser("chan123", "123456");

    if (isValid) {
        targetURL = "/index.jsp";
    } else {
        targetURL = "/custLogin.jsp";
    }
    RequestDispatcher rd;
    rd = getServletContext().getRequestDispatcher("/" + targetURL);
    rd.forward(request, response);
}

public boolean isAuthenticated(HttpServletRequest request) {
    boolean result = false;
    HttpSession session = request.getSession();
    if (session.getAttribute("userInfo") != null) {
        result = true;
    }
    return result;
}

private void doLogin(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
    String targetURL = "login.jsp";
    RequestDispatcher rd;
    rd = getServletContext().getRequestDispatcher("/" + targetURL);
    rd.forward(request, response);
}

private void doLogout(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
    HttpSession session = request.getSession(false);
    if (session != null) {
        session.removeAttribute("userInfo");
        session.invalidate();
    }
    doLogin(request, response);
}

chan123是custID. custPW是123456.

chan123 is the custID. 123456 is the custPW.

Class CustomerDB:

Class CustomerDB:

private String dbUrl;
private String dbUser;
private String dbPassword;

public CustomerDB() {
}

public CustomerDB(String dburl, String dbUser, String dbPassword) {
    this.dbUrl = dbUrl;
    this.dbUser = dbUser;
    this.dbPassword = dbPassword;
}

public Connection getConnection() throws SQLException, IOException {
    System.setProperty("jdbc.drivers", "com.mysql.jdbc.Driver");
    Connection conn = (Connection) DriverManager.getConnection("jdbc:mysql://localhost:3306/fyp", "root", "");
    return conn;
}

public boolean isValidUser(String custID, String custPW) {
    boolean isValid = false;
    Connection cnnct = null;
    PreparedStatement pStmnt = null;

    try {
        cnnct = getConnection();
        String preQueryStatement = "SELECT * FROM customer WHERE custID=? and custPW=?";
        pStmnt = cnnct.prepareStatement(preQueryStatement);
        pStmnt.setString(1, custID);
        pStmnt.setString(2, custPW);
        ResultSet rs = null;
        rs = pStmnt.executeQuery();
        if (rs.next()) {
            isValid = true;
        }
        pStmnt.close();
        cnnct.close();
    } catch (SQLException ex) {
        while (ex != null) {
            ex.printStackTrace();
            ex = ex.getNextException();
        }
    } catch (IOException ex) {
        ex.printStackTrace();
    }
    return isValid;
}

我创建测试Java.它可以加载正确的结果.

I create the test java. It can load the correct result.

public static void main(String[] arg) {
    String dbUrl = "jdbc:mysql://localhost:3306/fyp";
    String dbUser = "root";
    String dbPassword = "";
    CustomerDB db = new CustomerDB(dbUrl, dbUser,dbPassword);
    boolean n = db.isValidUser("chan123", "123456");
    if (n) {
        System.out.println("TTTTTT");
    }else 
        System.out.println("f");
}

}

显示"TTTTTT".

it shows "TTTTTT".

但是该页面前进至"custLogin". 输出:

But the page forward to "custLogin". the output:

SEVERE:   java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/fyp
    at java.sql.DriverManager.getConnection(DriverManager.java:596)
    at java.sql.DriverManager.getConnection(DriverManager.java:215)
    at fyp.db.CustomerDB.getConnection(CustomerDB.java:29)
    at fyp.db.CustomerDB.isValidUser(CustomerDB.java:39)
    at fyp.servlet.Login.doAuthenticate(Login.java:52)
    at fyp.servlet.Login.doPost(Login.java:39)
...

请帮助我解决此问题. 谢谢！

Please help me solve this problem. Thank you!

推荐答案

您无需使用

You don't need to use Class.forName("com.mysql.jdbc.Driver"); from the DriverManager Javadoc Applications no longer need to explictly load JDBC drivers using Class.forName(). Existing programs which currently load JDBC drivers using Class.forName() will continue to work without modification.

您需要添加mysql连接器/j jar文件(例如，一个可用的此处)添加到您的服务器类路径.

You need to add the mysql connector/j jar file (for example, the one available here) to your server classpath.

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