JDBC:MySql连接在Ajax请求-Java中不起作用

我在主方法和其他方法中都有完全相同的函数，JDBC连接工作正常。如果调用另一个函数，它将抛出错误java.sql.SQLException:找不到适合jdbc的驱动程序：mysql://localhost:3306/wine：

我已经在库[Netbeans]中包含了MySql驱动程序

处理请求方法：

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    String process = (String) request.getParameter("process");
    String name = (String) request.getParameter("process");
    String phone=(String) request.getParameter("phone");
    String email = (String) request.getParameter("email");
    String pwd = (String) request.getParameter("pwd");
    PrintWriter out = response.getWriter();
    out.println("Hello");
   signup(out,process,name,email,phone,pwd);

}

private static int signup(PrintWriter out,String process,String name,String email,String phone,String pwd){
    Connection con = null;
    PreparedStatement stmt = null;
    ResultSet rs = null;
    try {
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wine", "root", "");


        out.println("Process Not Found");
        if (process == "signup") {

            String query = "INSERT INTO user(name,phone,email,password,role) VALUES(?,?,?,?,1)";
            stmt = con.prepareStatement(query);
            stmt.setString(1, name);
            stmt.setString(2, phone);
            stmt.setString(3, email);
            stmt.setString(4, pwd);

            stmt.execute();

        } else {
            out.println("Process Not Found");
        }
    } catch (SQLException e) {
        // do something appropriate with the exception, *at least*:

        out.println(e);
        e.printStackTrace();
        return 0;
    }
    return 1;
}

public static void main(String[] args) {

    Connection con = null;
    PreparedStatement stmt = null;
    ResultSet rs = null;
    String process = "signup";
    String name = "Test";
    String phone="45885";
    String email = "Test@gmail.com";
    String pwd = "dkjsdh";

    try {
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wine", "root", "");



        if (process == "signup") {

            String query = "INSERT INTO user(name,phone,email,password,role,status) VALUES(?,?,?,?,1,1)";
            stmt = con.prepareStatement(query);
            stmt.setString(1, name);
            stmt.setString(2, phone);
            stmt.setString(3, email);
            stmt.setString(4, pwd);

            stmt.execute();

        } else {
            System.out.println("Process Not Found");
        }
    } catch (SQLException e) {
        // do something appropriate with the exception, *at least*:

        System.out.println(e);
        e.printStackTrace();
    }
}

注册方法：

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    String process = (String) request.getParameter("process");
    String name = (String) request.getParameter("process");
    String phone=(String) request.getParameter("phone");
    String email = (String) request.getParameter("email");
    String pwd = (String) request.getParameter("pwd");
    PrintWriter out = response.getWriter();
    out.println("Hello");
   signup(out,process,name,email,phone,pwd);

}

private static int signup(PrintWriter out,String process,String name,String email,String phone,String pwd){
    Connection con = null;
    PreparedStatement stmt = null;
    ResultSet rs = null;
    try {
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wine", "root", "");


        out.println("Process Not Found");
        if (process == "signup") {

            String query = "INSERT INTO user(name,phone,email,password,role) VALUES(?,?,?,?,1)";
            stmt = con.prepareStatement(query);
            stmt.setString(1, name);
            stmt.setString(2, phone);
            stmt.setString(3, email);
            stmt.setString(4, pwd);

            stmt.execute();

        } else {
            out.println("Process Not Found");
        }
    } catch (SQLException e) {
        // do something appropriate with the exception, *at least*:

        out.println(e);
        e.printStackTrace();
        return 0;
    }
    return 1;
}

public static void main(String[] args) {

    Connection con = null;
    PreparedStatement stmt = null;
    ResultSet rs = null;
    String process = "signup";
    String name = "Test";
    String phone="45885";
    String email = "Test@gmail.com";
    String pwd = "dkjsdh";

    try {
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wine", "root", "");



        if (process == "signup") {

            String query = "INSERT INTO user(name,phone,email,password,role,status) VALUES(?,?,?,?,1,1)";
            stmt = con.prepareStatement(query);
            stmt.setString(1, name);
            stmt.setString(2, phone);
            stmt.setString(3, email);
            stmt.setString(4, pwd);

            stmt.execute();

        } else {
            System.out.println("Process Not Found");
        }
    } catch (SQLException e) {
        // do something appropriate with the exception, *at least*:

        System.out.println(e);
        e.printStackTrace();
    }
}

主要方法：

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    String process = (String) request.getParameter("process");
    String name = (String) request.getParameter("process");
    String phone=(String) request.getParameter("phone");
    String email = (String) request.getParameter("email");
    String pwd = (String) request.getParameter("pwd");
    PrintWriter out = response.getWriter();
    out.println("Hello");
   signup(out,process,name,email,phone,pwd);

}

private static int signup(PrintWriter out,String process,String name,String email,String phone,String pwd){
    Connection con = null;
    PreparedStatement stmt = null;
    ResultSet rs = null;
    try {
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wine", "root", "");


        out.println("Process Not Found");
        if (process == "signup") {

            String query = "INSERT INTO user(name,phone,email,password,role) VALUES(?,?,?,?,1)";
            stmt = con.prepareStatement(query);
            stmt.setString(1, name);
            stmt.setString(2, phone);
            stmt.setString(3, email);
            stmt.setString(4, pwd);

            stmt.execute();

        } else {
            out.println("Process Not Found");
        }
    } catch (SQLException e) {
        // do something appropriate with the exception, *at least*:

        out.println(e);
        e.printStackTrace();
        return 0;
    }
    return 1;
}

public static void main(String[] args) {

    Connection con = null;
    PreparedStatement stmt = null;
    ResultSet rs = null;
    String process = "signup";
    String name = "Test";
    String phone="45885";
    String email = "Test@gmail.com";
    String pwd = "dkjsdh";

    try {
        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/wine", "root", "");



        if (process == "signup") {

            String query = "INSERT INTO user(name,phone,email,password,role,status) VALUES(?,?,?,?,1,1)";
            stmt = con.prepareStatement(query);
            stmt.setString(1, name);
            stmt.setString(2, phone);
            stmt.setString(3, email);
            stmt.setString(4, pwd);

            stmt.execute();

        } else {
            System.out.println("Process Not Found");
        }
    } catch (SQLException e) {
        // do something appropriate with the exception, *at least*:

        System.out.println(e);
        e.printStackTrace();
    }
}

---

有两个选项可以尝试：

Class.forName("com.mysql.jdbc.Driver").newInstance() //older bug

及

在评论中，当我打算粘贴第二个bug解决方案时，我粘贴了旧的bug解决方案

---

无论哪种方式，我都很高兴它适合您

这行“Class.forName（“com.mysql.jdbc.Driver”）.newInstance（）；”怎么样？你试过以防万一吗？请看。修复后，让我们知道还有什么问题。@efekActive

newInstance（）

完全没有必要（除非您使用的连接器/J在+/-15年前有一个bug）。我指的是没有newInstance（）的类.forName（…）。SorryIt从main开始工作，因为驱动程序位于初始类路径上，当驱动程序是web应用程序部署的一部分（而不是在tomcat lib文件夹中）时，

DriverManager将自动检测并加载该驱动程序，然后自动加载驱动程序不起作用，因为类加载器层次结构限制了驱动程序的可见性，因此
DriverManager
无法自动加载它。也就是说：在web应用程序中，通常不使用
DriverManager
创建连接，而是使用
DataSource
（通常使用连接池）。