requestDispatcher.forward（）在servlet通过Ajax POST调用时不转发

Question

我有一个登录页面，通过firebase对用户进行身份验证，并将请求发送到servlet。当我使用正确的身份验证点击submit按钮时，firebase身份验证工作，servlet被调用，但在浏览器中我看到一个错误。

首先，这是我的javascript代码

function toggleSignIn() {
    if (firebase.auth().currentUser) {
        alert('existing user');
        firebase.auth().signOut();
    } else {
        var email = document.getElementById('email').value;
        var password = document.getElementById('password').value;

        if (email.length < 4) {
            alert('Please enter an email address.');
            return;
        }

        if (password.length < 4) {
            alert('Please enter a password.');
            return;
        }

        firebase.auth().signInWithEmailAndPassword(email, password).then(function (firebaseUser) {
            var email = firebase.auth().currentUser.email;
            const options = {
                method: 'POST',
                url: 'LoginValidator',
                headers: {
                    "Content-Type": "application/x-www-form-urlencoded"
                },
                body: `email=${email}`
            }
            url = 'LoginValidator'
            fetch(url, options)
                .then(response = > response.json())
                .then(data = > console.log(data))
                .catch(e = > console.error(e))
        }).catch(function (error) {
            var errorCode = error.code;
            var errorMessage = error.message;
            if (errorCode === 'auth/wrong-password') {
                alert('Wrong password.');
            } else {
                alert(errorMessage);
            }
            console.log(error);
            document.getElementById('quickstart-sign-in').disabled = false;
        });
    }
    document.getElementById('quickstart-sign-in').disabled = true;
}

HTML

<div id="login-box" class="col-md-12">

    <div class="form-group">
        <input type="text" name="email" id="email" class="form-control login-input" placeholder="username">
    </div>
    <div class="form-group">
        <input class="form-control login-input" type="password" placeholder="Password" id="password" name="password">
        <i id="open" class="fa fa-eye fa-2x"></i>
        <i id="closed" class="fa fa-eye-slash fa-2x"></i>
    </div>
    <div class="form-group">
        <input type="submit" id="quickstart-sign-in" name="quickstart-sign-in"
               class="form-control btn btn-info btn-md login-bt" value="Login" onclick="toggleSignIn()">
    </div>
    <div class="form-group text-center forgot">
        <a href="#">Forgot username</a> / <a href="#">password?</a>
    </div>

</div>

public class LoginValidator extends HttpServlet {

    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");

        String email = request.getParameter("email");
        System.out.println("Printing email: "+email);

        try {

            System.out.println("inside try");

            User user = new User();
            UserRight userRight = new UserRight();

            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.registerTypeAdapter(Date.class, new DateTypeDeserializer());
            Gson gson = gsonBuilder.create();

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(BaseURLs.BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create(gson))
                    .build();

            //Get user
            RestEndPointsInterface endPoint = retrofit.create(RestEndPointsInterface.class);
            Call<User> call = endPoint.getUserByEmail(email);
            user = call.execute().body();

            System.out.println(user.getName());

            //Get user rights
            Call<UserRight> userRightCall = endPoint.getUserRightByID(user.getUserRights().getIduserRight());
            userRight = userRightCall.execute().body();

            System.out.println(userRight.getUserRight());

            if(userRight.getUserRight().equals("admin"))
            {
                response.getWriter().write("{url:LoadSellPendingApprovals}");
            }
            else
            {
                response.getWriter().write("{url:index.html}");
            }


        } catch (Exception e) {
            e.printStackTrace();
        } 
    }

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

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

    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

code>LogInvalidator调用LoadSellPendingApprovals，下面是它的代码

public class LoadSellPendingApprovals extends HttpServlet {


    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");

        List<ProductSellAdvertisement> categoryList = new ArrayList<ProductSellAdvertisement>();

        try {

            System.out.println("INSIDE LoadSellPendingApprovals");

            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.registerTypeAdapter(Date.class, new DateTypeDeserializer());
            Gson gson = gsonBuilder.create();

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(BaseURLs.BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create(gson))
                    .build();

            RestEndPointsInterface endPoint = retrofit.create(RestEndPointsInterface.class);
            Call<List<ProductSellAdvertisement>> call = endPoint.getAllPendingApprovals();
            categoryList = call.execute().body();

            for (int i = 0; i < categoryList.size(); i++) {
                System.out.println(categoryList.get(i).getProduct().getProductName());
            }

        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        finally {
            RequestDispatcher requestDispatcher = request.getRequestDispatcher("/WEB-INF/jsp/product-sell-pending-approvals.jsp");
            request.setAttribute("approvalList", categoryList);
            requestDispatcher.forward(request, response);
        }
    }


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

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


    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

这就是我得到的错误

SyntaxError: Unexpected token < in JSON at position 0
    at (index):71

在我的javascript代码中指向的行是-。然后(response=>response.json())

>

用户输入凭据

使用FireBasejavascript API

验证凭据

如果凭据正确，则将它们发送到loginvalidatorservlet，它将在其中进一步检查用户的真实性。

然后LogInvalidator将请求发送到LoadSellPendingApprovals，在那里它将执行以下代码

RequestDispatcher RequestDispatcher=request.getRequestDispatcher（“/web-inf/jsp/product-sell-pending-approvals.jsp”）；Request.SetAttribute（“ApprovalList”,categoryList）；RequestDispatcher.Forward（请求、响应）；

除了我得到的错误之外，我也从未被转发到JSP页面。如何修复此问题？

我来自java和移动背景，对Javascript技术没有太多的线索。因此，感谢详细明确的答复。

Answer 1

您的错误表明结果“body”不包含JSON，而是包含HTML：

JSON中位置0处的意外标记<

JSON将如下所示：

{ key: value }

<html>....</html>

其中一个原因可能是您发送的请求被重定向到登录页面，因此您得到的是HTML而不是预期的JSON。或者您会得到一个错误页面,试图将其传递给JSON解析器。

不幸的是，只有这么一点信息很难判断。您应该调试您的代码并检查您得到的响应。