Java servlet not redirecting properly

Question

I have two pages jsp pages First one is AppLogin.jsp and other one is Login.jsp

I want that when i click on Submit button of AppLogin.jsp page, i want redirect to Login.jsp page with password value and check this value on page load of Login.jsp page.

For this i did following code but the below code did not work.

I don't want to use Session and append value on url.

AppLogin.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>App Login</title>
</head>
<body>
    <form action="loginServlet" method="post">
        <table>
            <tr>
                <td>Application Name</td>
                <td><input type="text" value="" name="txtApplication" /></td>
            </tr>
            <tr>
                <td>Username</td>
                <td><input type="text" value="" name="txtUsername" /></td>
            </tr>
            <tr>
                <td>Password</td>
                <td><input type="text" value="" name="txtPassword" /></td>
            </tr>
            <tr align="center">
                <td colspan="2"><input type="submit" value="Submit" /></td>
            </tr>
        </table>
    </form>
</body>
</html>

public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest req, HttpServletResponse res)
            throws ServletException, ClientProtocolException {
        try {
            String password = req.getParameter("txtPassword");
            req.setAttribute("crendential",password);
            RequestDispatcher rd = req.getRequestDispatcher("Login.jsp");
            rd.forward(req,res);
        }

        catch (Exception e) {
            System.out.println("LoginServletException>>>>>>>>>>" + e);
        }
    }
}

Login.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login</title>
</head>
<body>
    <form action="saveServlet" method="post">
        <table>
            <tr>
                <td>Application :</td>
                <td><input type="text" value="" name="txtApplication" /></td>
            </tr>
            <tr>
                <td>Username :</td>
                <td><input type="text" value="" name="txtUsername" /></td>
            </tr>
            <tr>
                <td>Password :</td>
                <td><input type="text" value="" name="txtPassword" /></td>
            </tr>
            <tr align="center">
                <td colspan="2"><input type="submit" value="Submit" /></td>
            </tr>
        </table>
    </form>
</body>
</html>

public class SaveServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest req, HttpServletResponse res)
            throws ServletException {
        try {
            String crendential = (String) req.getAttribute("crendential");
            System.out.println("crendential>>>>>>>>>>" + crendential);
        }

        catch (Exception e) {
            System.out.println("LoginServletException>>>>>>>>>>" + e);
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        String crendential = (String) req.getAttribute("crendential");
        System.out.println("crendential>>>>>>>>>>" + crendential);
    }
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
    <display-name>xyz</display-name>
    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>xyz.io.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/loginServlet</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>save</servlet-name>
        <servlet-class>xyz.io.SaveServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>save</servlet-name>
        <url-pattern>/Login.jsp</url-pattern>
    </servlet-mapping>

    <welcome-file-list>
        <welcome-file>AppLogin.jsp</welcome-file>
    </welcome-file-list>
</web-app>

I am using Java with Eclipse Mars.

Did you try to store value in HttpSession and use response.sendRedirect in doGet() ? — Alekhya Vemavarapu, Jun 24 '16 at 11:36
What is not working? Where is the redirect? I can see only a forward. — tak3shi, Jun 24 '16 at 11:47
@tak3sh my url is change to /Login.jsp, but it showing me blank. — user3441151, Jun 24 '16 at 11:55
If you get a blank screen, have you checked your logfile for exceptions? — tak3shi, Jun 24 '16 at 11:57
Obviously it will show blank page because you have not written anything in `SaveServlet` look in console in eclipse is there anything printing there? — Naman, Jun 24 '16 at 12:14
@Naman I have to redirect to Login.jsp when i click on Submit button of AppLogin.jsp page with password value. — user3441151, Jun 24 '16 at 12:16
Change web.xml to `save/saveServlet` then it will redirect to `Login.jsp` — Naman, Jun 24 '16 at 12:34
@Naman when i change my code it redirect me to "Login.jsp" properly but my url show change to "/loginServlet" and my doGet method of Login.jsp not call. — user3441151, Jun 24 '16 at 12:44
Have a look at http://stackoverflow.com/questions/2047122/requestdispatcher-forward-vs-httpservletresponse-sendredirect , this will solve why url show /loginservlet — Naman, Jun 24 '16 at 12:49
@Naman I already read this, so can we have any other option to achieve this? — user3441151, Jun 24 '16 at 12:56

Joop Eggen · Answer 1 · 2016-06-24T12:27:39.197

Login.jsp has a request attribute "credentials." To pass this value to the saveServlet there would be two possibilities:

Store the credentials instead as session attribute
Pass the credentials on in Login.jsp, say as hidden form input field.
```
<input type="hidden" name="credentials" value="${credentials}">
```

Correction:

I did miss the somewhat hard to digest web.xml with its servlet mappings.

In general how it often is done

A servlet mapping:

xyz.io.DisplayLoginServlet /login

xyz.io.ProcessLoginServlet /authorize
DisplayLoginServlet

doGet prepares the form data (request attributes) forwards to some displayLogin.jsp

doPost validates the form, possibly redisplays the form with error messages (doGet) otherwise when successfully done, set session attributes and redirect to the home page.
displayLogin.jsp

(posts to the same servlet)

And so on.

The mapped servlet URLs do not relate to JSPs. The servlet is the entry point, the controller. It prepares the data model, puts them in the request attributes, and forwards to some JSP, the view. The servlet can on successfull login use an other JSP for instance.

Here we redirect after a successfull post. That is the brower is told to get the redirected page as answer. The effect is that the user cannot reload the page and effectively re-post the HTML form.

I think making a clean distinction will already help.

user3441151 has already mentioned in `web.xml`, pattern `/Login.jsp` is being forwarded to `SaveServlet`. — Naman, Jun 24 '16 at 11:44
@JoopEggen my url is change to /Login.jsp, but it showing me blank. — user3441151, Jun 24 '16 at 11:54
@user3441151 rather than trying to explain the knot in the control flow, I tried to add a how-to, — Joop Eggen, Jun 24 '16 at 12:31

Java servlet not redirecting properly

1 Answers1