Question

我在使用注册servlet向mySQL表中添加行时遇到问题。话虽这么说，servlet可以看到用户是否已经在我的表中，并将相应地重定向（所以我知道我的连接在那里）。我还测试了我的查询字符串，看起来是正确的。我不确定我做错了什么，或者我怎么能确切地看到我的mySQL服务器看到的消息/它如何响应注册请求。

嗯，这是我的代码：

index.jsp

                    <div id="loginDiv">

                <form action="LoginHandler" method="post" id="1">
                Login Here! -->
                    Username: <input type="text" name="username" required="required"> </input>
                    Password: <input type="password" name="password" required="required"> </input>
                <input type="submit" value="Login"> </input> 
                </form>
                </div>

                <div id="registerDiv">
                <form action="RegistrationHandler" method="post" id="2">
                Register Here! -->
                    Username: <input type="text" name="username" required="required"> </input>
                    Password: <input type="password" name="password" required="required"> </input>
                <input type="submit" value="Register"> </input>
                </form>
                </div>

loginHandler.java：

public class RegistrationHandler extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    //get username & pass from jsp login
        String userName = request.getParameter("username");
        String passWord = request.getParameter("password");
    //pass username & pass to mysql query
    Connection conn = null;
    String url = "jdbc:mysql://localhost:8888/";
    String dataBase = "usersdb";
    String driver = "com.mysql.jdbc.Driver";
    String dBUserName = "admin";
    String dBPassword = "xxxx";
    RequestDispatcher rd = null;

    try{

        Class.forName(driver).newInstance();
        conn = (Connection) DriverManager.getConnection(url+dataBase,dBUserName,dBPassword);
        String strQuery = "select * from playerinfo where usrname='" + userName + "'" + ";" ;
        Statement st = (Statement) conn.createStatement();
        ResultSet rs = st.executeQuery(strQuery);

        if(rs.next())
        //username already exists
        {
        request.setAttribute("userName", userName);
        RequestDispatcher requestDispatcher = request
            .getRequestDispatcher("/registrationError.jsp");
        requestDispatcher.forward(request,response);
        }

        else
        //create new user in database
        {
        String createUserQuery = "insert into playerinfo values ('" + userName + "','" + passWord + "'," + 100 + "," + 100 + "," + 100 + "," + "NULL" + "," + "NULL" + ") ;" ;
        Statement create = (Statement) conn.createStatement();
        rs = st.executeQuery(createUserQuery);

        RequestDispatcher requestDispatcher = request
            .getRequestDispatcher("/userHome.jsp");
        requestDispatcher.forward(request,response);
        }
    //close connection
    rs.close();
    st.close();
    }
    catch (ClassNotFoundException | InstantiationException | IllegalAccessException | SQLException e){
    }
}

}

rs.next（）条件函数将正常工作，即如果我的数据库中已存在用户名，则它将正确地重定向到错误页面。

但是，如果它们不在表格中，那么它就不会添加它们，或者重定向到正确的页面。

所以我认为我不正确地告诉mySQL将新用户添加到我的表中。它是否正确？如果是的话，我哪里出错？

谢谢！

修改：

这些是我对我的servlet所做的更改，但仍无法让它运行起来：（

public class RegistrationHandler extends HttpServlet {

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    //get username & pass from jsp login
        String userName = request.getParameter("username");
        String passWord = request.getParameter("password");
    //pass username & pass to mysql query
    Connection conn = null;
    Connection conn2 = null;
    String url = "jdbc:mysql://localhost:8888/";
    String dataBase = "usersdb";
    String driver = "com.mysql.jdbc.Driver";
    String dBUserName = "admin";
    String dBPassword = "xxxx";
    RequestDispatcher rd = null;

    try{

        Class.forName(driver).newInstance();
        conn = (Connection) DriverManager.getConnection(url+dataBase,dBUserName,dBPassword);
        String strQuery = "select * from playerinfo where usrname='" + userName + "'"  ;
        Statement st = (Statement) conn.createStatement();
        ResultSet rs = st.executeQuery(strQuery);

        if(rs.next())
        //username already exists
        {
        request.setAttribute("userName", userName);
        RequestDispatcher requestDispatcher = request
            .getRequestDispatcher("/registrationError.jsp");
        requestDispatcher.forward(request,response);
        }

        else
        //create new user in database
        {
        register(userName, passWord);

        RequestDispatcher requestDispatcher = request
            .getRequestDispatcher("/userHome.jsp");
        requestDispatcher.forward(request,response);
        }
    //close connection
    rs.close();
    st.close();
    }
    catch (ClassNotFoundException | InstantiationException | IllegalAccessException | SQLException e){
    }



        }
private static void register(String username, String password){
    Connection conn = null;
    String url = "jdbc:mysql://localhost:8888/";
    String dataBase = "usersdb";
    String driver = "com.mysql.jdbc.Driver";
    String dBUserName = "admin";
    String dBPassword = "xxxx";

    try{

        Class.forName(driver).newInstance();
        conn = (Connection) DriverManager.getConnection(url+dataBase,dBUserName,dBPassword);
        String strQuery = "insert into playerinfo values ('" + username + "','" + password + "'," + 100 + "," + 100 + "," + 100 + "," + "NULL" + "," + "NULL" + ") " ;
        Statement st = (Statement) conn.createStatement();
        st.executeQuery(strQuery);

    }
    catch(ClassNotFoundException | InstantiationException | IllegalAccessException | SQLException e){

    }
  }
}

为什么我无法成功查询mysql以将新用户添加到表中的任何提示或线索？

Answer 1

在else块中，您实际上想要将用户添加到数据库，您仍然在调用第一个语句。不是你新创建的那个。这可能是造成问题的原因。

话虽这么说，您可能还想查看Hibernate框架。它可以让你自己完成所有这些工作，而不是只编写Java而不是实际的SQL。我发现让生活变得更轻松。

使用MySQL登录/注册Servlet

1 个答案: