Question

任何人都可以帮我这个吗？第一个if语句完全正常但第二个如果永远不是真的这意味着无论什么时候我打印'不'它都很好但是什么时候打印'确定'它不起作用，显然如果我使用第一个，如果那么它也不起作用

<script type="text/javascript">
    function signupfunction(){
        var name = document.getElementById('signupname').value;
        var email = document.getElementById('signupemail').value;
        var password = document.getElementById('signuppassword').value; 
        $.ajax({
            url : "AdminSignup?name=" + name + "&email=" + email + 
"&password=" + password + "",
            type : "GET",
            async : true,
            success : function(data) {
                if(data == 'not'){
                    alert("Email already exists");
                } 
                if(data == 'ok'){
                    alert('hello');
                }
            }
        });
    }
</script>

这是我的servlet的doGet（）函数

protected void doGet(HttpServletRequest request, HttpServletResponse 
    response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = 
                DriverManager.getConnection("jdbc:mysql://localhost/amazon? 
                user=root&password=test123");
            PreparedStatement statement = con.prepareStatement("select * from 
                sellers where email=?");
            statement.setString(1, request.getParameter("email"));
            ResultSet rs = statement.executeQuery();
            if(rs.next()) {
                response.getWriter().print("not");
            } else {
                PreparedStatement statement1 = con.prepareStatement("insert 
                    into sellers(email,password,name) values(?,?,?)");
                statement1.setString(1, request.getParameter("email"));
                statement1.setString(2, request.getParameter("password"));
                statement1.setString(3, request.getParameter("name"));
                statement1.executeUpdate();
                session.setAttribute("sessionAdminEmail", 
                    request.getParameter("email"));
                session.setAttribute("sessionAdminName", 
                    request.getParameter("name"));
                response.getWriter().print("ok");
            }
        } catch (Exception e) {

          }
    }

Answer 1

你正在混淆

response.getWriter().print("ok"); //this will not send your value to ajax

使用：

response.getWriter().write("inserted new user");   //this will

您的Servlet：

protected void doGet(HttpServletRequest request, HttpServletResponse 
        response) throws ServletException, IOException {
            HttpSession session = request.getSession();
            response.setContentType("text/plain");  // Set content type of the response so that jQuery knows what it can expect.
            response.setCharacterEncoding("UTF-8"); // You want world domination, huh?
 try {


        Class.forName("com.mysql.jdbc.Driver");
        Connection con = DriverManager.getConnection("jdbc:mysql://localhost/amazon?user=root&password=test123");

        PreparedStatement statement = con.prepareStatement("select * from sellers where email=?");
        statement.setString(1, request.getParameter("email"));
        ResultSet rs = statement.executeQuery();

        if(rs.next()) {
            //if the email exists in sellers, then this will always evaluate to true...
            //response.getWriter().print("not"); //print will not send your value back to ajax..
            response.getWriter().write("email exists");       // Write response body.
        } else {
            PreparedStatement statement1 = con.prepareStatement("insert into sellers(email,password,name) values(?,?,?)");
            statement1.setString(1, request.getParameter("email"));
            statement1.setString(2, request.getParameter("password"));
            statement1.setString(3, request.getParameter("name"));
            statement1.executeUpdate();
            session.setAttribute("sessionAdminEmail", request.getParameter("email"));
            session.setAttribute("sessionAdminName", request.getParameter("name"));
            //response.getWriter().print("ok"); print will not send your value back to ajax
            response.getWriter().write("inserted new user");       // Write response body.
        }
    } catch (Exception e) {

      }
}

另外值得一提的是==与===不同。在这种情况下使用===，它是您正在寻找的比较运算符。查看this以获取有关差异的说明

<script type="text/javascript">
    function signupfunction(){
        var name = document.getElementById('signupname').value;
        var email = document.getElementById('signupemail').value;
        var password = document.getElementById('signuppassword').value; 
        $.ajax({
            url : "AdminSignup?name=" + name + "&email=" + email + 
"&password=" + password + "",
            type : "GET",
            async : true,
            success : function(data) {
                if(data === 'email exists'){
                    alert("Email already exists");
                } 
                if(data === 'inserted new user'){
                    alert('new user');
                }
            }
        });
    }
</script>

同时查看这个答案，它给出了如何将Ajax与Servlet一起使用的一个很好的解释。（比你目前正在做的方式容易得多）

How to use Servlets and Ajax?

我无法比较来自servlet的ajax请求返回的字符串

1 个答案: