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I am new to jsp and servlet. My scenario is as follows
I have a jsp page which have a form in it. with two fields. The code snipet of the jsp page is as follows.
MyFirstJSP.jsp file
<body>
<h1> This is my first jsp and servlet project</h1>
<%
//System.out.println(request.getAttribute("fname"));
if(request.getAttribute("fname")!=null){
System.out.println(request.getAttribute("fname"));
}else{
System.out.println("No request ");
}
%>
<form action="MyFirstServlet" method="get">
First Name<input type="text" name="fname" value= ${fname}><br>
Last Name<input type="text" name="lname" value= ${lname}>
<input type="submit" value="Send">
</form>
</body>
When I submit this form the MyFirstServlet is called which checks the first name entered by user. If the first name is equals to "abc" then servlet sets the attribute to request object and send redirect it to the callsing jsp page i.e. above page. Which will get the value from request object and fill it in to respective field of form. I have Java Expression language too for same effect.
Here is my code snipet of the MyFirstServlet.java servlet file
/**
* Servlet implementation class MyFirstServlet
*/
public class MyFirstServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public MyFirstServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub
String firstname=request.getParameter("fname");
if(firstname.equalsIgnoreCase("abc")){
System.out.println("Setting attributes");
request.setAttribute("fname",firstname);
request.setAttribute("lname",request.getParameter("lname"));
response.sendRedirect("MyFirstJSP.jsp");
}else{
System.out.Println("No problem");
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
PrintWriter p=response.getWriter();
p.println("Success!");
doGet(request,response);
}
}
But when I execute the code the servlet redirects to the jsp page but not fills the form fields with the respective values. As to find the cause I have added the if-else-block to know the cause and I get to know that the request objects attribute is not available here.
If I use the request dispatcher in this case then the values are gets available and the form is gets filled with the values but the url in the address bar does not chage and always shows the url to the servlet.
So My query is
**1)Why the request object is not available to jsp page using sendRedirect.
2)Is thre any other way to show my form in jsp page prefilled with the values entered by user if the servlet sendredirects to the calling jsp so that user need not to reenter the data in to form.**
Please guide me friends in this problem Thank You!
335
The getAttribute() method of the Element interface returns the value of a specified attribute on the element. If the given attribute does not exist, the value returned will either be null or "" (the empty string); see Non-existing attributes for details.
1) First create data at the server side and pass it to a JSP. Here a list of student objects in a servlet will be created and pass it to a JSP using setAttribute(). 2) Next, the JSP will retrieve the sent data using getAttribute(). 3) Finally, the JSP will display the data retrieved, in a tabular form.
sendRedirect() accepts the respective URL to which the request is to be redirected. Can redirect the request to another resource like Servlet, HTML page, or JSP page that are inside or outside the server. It works on the HTTP response object and always sends a new request for the object.
An attribute in servlet is an object that can be set, get or removed from one of the following scopes: request scope. session scope. application scope.
You need to forward to the jsp page on server side, as a redirect is a client side action (check out the location header 1) the request attributes get lost.
replace
response.sendRedirect("MyFirstJSP.jsp");
with
request.getRequestDispatcher("MyFirstJSP.jsp").forward(request, response);
Edit: sorry, I skipped this part
If I use the request dispatcher in this case then the values are gets available and the form is gets filled with the values but the url in the address bar does not chage and always shows the url to the servlet.
nevertheless, you cannot pass request attributes to your jsp when redirecting (as i've already mentioned above it's a clientside action)
I'd suggest doing the following:
In both, doGet and doPost, use forward to render the *.jsp page.
GET /MyFirstServlet -> forward to MyFirstJSP.jsp
POST /MyFirstServlet -> forward to MyFirstJSP.jsp
this is the most commonly used and clean approach.
EDIT 2: Simple Example
SimpleFormServlet.java
public class SimpleFormServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private static final String VIEW_NAME = "/WEB-INF/jsp/simpleForm.jsp";
private static final String MODEL_NAME = "form";
public SimpleFormServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setAttribute(MODEL_NAME, new SimpleForm());
request.getRequestDispatcher(VIEW_NAME).forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
final SimpleForm form = map(request);
if(form.getfName().equalsIgnoreCase("abc")){
request.setAttribute(MODEL_NAME, form);
// put additional attributes on the request
// e.g. validation errors,...
request.getRequestDispatcher(VIEW_NAME).forward(request, response);
}else{
System.out.println("No problem");
response.sendRedirect("/SuccessServlet");
}
}
private SimpleForm map(final HttpServletRequest request) {
SimpleForm form = new SimpleForm();
form.setfName(request.getParameter("fName"));
form.setlName(request.getParameter("lName"));
return form;
}
public static class SimpleForm implements Serializable {
private static final long serialVersionUID = -2756917543012439177L;
private String fName;
private String lName;
public String getfName() {
return fName;
}
public void setfName(String fName) {
this.fName = fName;
}
public String getlName() {
return lName;
}
public void setlName(String lName) {
this.lName = lName;
}
}
}
/WEB-INF/jsp/simpleForm.jsp
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
</head>
<body>
<form method="POST">
First Name<input type="text" name="fName" value="${form.fName}"><br>
Last Name<input type="text" name="lName" value="${form.lName}">
<input type="submit" value="Send">
</form>
</body>
</html>
I know it's too late to answer but this would be helpful to someone. redirect is a client side action so that we can't getAttribute values but we can solve it by using URL Rewriting concept.
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub
String firstname=request.getParameter("fname");
if(firstname.equalsIgnoreCase("abc")){
//System.out.println("Setting attributes");
response.sendRedirect("MyFirstJSP.jsp?fname="+firstname+"&lname="+request.getParameter("lname")+"");
}
else{
System.out.Println("No problem");
}
}
then use request.getParameter() to extract values as string in MyFirstJSP.jsp.
27
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