I wanted to know, how I could pass a dynamic value from one JSP to another.
For example, I want to know what I need to call to pass the value of name parameter to JSP2, when I clicked on the link in JSP1. I have tried following, but it's not working.
in JPS1:
<a href="JPS2.jsp" name="<%= packets.getString("BatchNo")%>">
in JPS2:
<% String UN = request.getParameter("name");%>
If you want to pass the value of packets.getString("BatchNo") from first.jsp to second.jsp, you can do that as below.
first.jsp :
LINK
second.jsp :
<% String un = request.getParameter("name");%>
I'm doing a project using jsp pages and servlets.
In my servlet I need to identify which jsp page is doing the request.
How can I do this?
The simplest way to identify the form from which the request come from would be to add a hidden field containing a form identifier. But this is a very uncommon requirement: if you post to same URL, it normally means that the origine of the post does not matter. If it matters (why?), the difference should be in posted data (hence the proposal of a hidden field), or you should post to different URLs. Servlet are not so expensive that you need to limit their number.
I have found a solution.
I set a name to the submit button.
<input type="submit" name="button" value="button1">
and then in the servlet I check with
String r = request.getParameter("button");
Doing that I know from where the request came from
For your servlet, i suppose you are using doGet/doPost to handle request and return response, then in your request from jsp, you can always add a hidden input field to let your servlet know which jsp you come from as follow:
In your jsp:
add a new hidden input textfield:
<input type="hidden" name="jspname" value="jspname" />
In your Servlet:
use getparameter method for doPost or getQueryString() for doGet:
in doPost:
String jspname = request.getParameter("jspname");
By making use of the jspname String, you can easily find out which jsp it is using.
Using hidden input is solution in other answers. But you can do that without hidden input.
String referer = new URI(request.getHeader("referer")).getPath();
referer String gives you full URI. Additionally for getting jsp page name you can use java code.
String[] uriNames = referer.split("/");
String jspPageName = uriNames[uriNames.length-1];
Also with regex you can get jsp page name.
Pattern pattern = Pattern.compile("(\\w+)(\\.)(jsp)");
Matcher matcher = pattern.matcher(mydata);
String jspPageName = "";
while(matcher.find()) {
jspPageName = matcher.group();
}
I have a line of code like this in the jsp:
<button name="CurrentDelete" value="${ra_split}" type="submit">Delete</button>
And in my Controller I use:
#RequestParam String CurrentDelete
I am trying to pass the value of ${ra_split} into the Controller when I hit the Delete button, but all I am getting is the value of the text 'Delete' instead. Why is that?
Here's the explanation
If you use the element in an HTML form, Internet Explorer, prior version 8, will submit the text between the and tags, while the other browsers will submit the content of the value attribute.
By returning to this issue after a few days I figured out a solution.
Just use:
<input type="hidden" value="${ra_split}" name="CurrentDelete">
<input type="submit" value="Delete" />
instead of:
<button name="CurrentDelete" value="${ra_split}" type="submit">Delete</button>
Then the problem will be solved and the String CurrentDelete will contain the value ${ra_split} instead of the text 'Delete'.
Extra information I have got when trying to solve the problem:
The button tag:
<button name="CurrentDelete" value="${ra_split}" type="submit">Delete</button>
Will always pass the value between the button tags to the Controller (in this case the text 'Delete') instead of passing the value="${ra_split}".
Either using
HttpServletRequest req
in the Controller and then do:
String CurrentDelete = req.getParameter("CurrentDelete");
or using
#RequestParam String CurrentDelete
in the Controller,
would both get the same result.
Consider this form:
<form action="http://www.blabla.com?a=1&b=2" method="GET">
<input type="hidden" name="c" value="3" />
</form>
When submitting this GET form, the parameters a and b are disappearing.
Is there a reason for that?
Is there a way of avoiding this behaviour?
Isn't that what hidden parameters are for to start with...?
<form action="http://www.example.com" method="GET">
<input type="hidden" name="a" value="1" />
<input type="hidden" name="b" value="2" />
<input type="hidden" name="c" value="3" />
<input type="submit" />
</form>
I wouldn't count on any browser retaining any existing query string in the action URL.
As the specifications (RFC1866, page 46; HTML 4.x section 17.13.3) state:
If the method is "get" and the action is an HTTP URI, the user agent takes the value of action, appends a `?' to it, then appends the form data set, encoded using the "application/x-www-form-urlencoded" content type.
Maybe one could percent-encode the action-URL to embed the question mark and the parameters, and then cross one's fingers to hope all browsers would leave that URL as it (and validate that the server understands it too). But I'd never rely on that.
By the way: it's not different for non-hidden form fields. For POST the action URL could hold a query string though.
In HTML5, this is per-spec behaviour.
See Association of controls and forms - Form submission algorithm.
Look at "4.10.22.3 Form submission algorithm", step 17. In the case of a GET form to an http/s URI with a query string:
Let destination be a new URL that is equal to the action except that
its <query> component is replaced by query (adding a U+003F QUESTION
MARK character (?) if appropriate).
So, your browser will trash the existing "?..." part of your URI and replace it with a new one based on your form.
In HTML 4.01, the spec produces invalid URIs - most browsers didn't actually do this though...
See Forms - Processing form data, step four - the URI will have a ? appended, even if it already contains one.
What you can do is using a simple foreach on the table containing the GET information. For example in PHP :
foreach ($_GET as $key => $value) {
$key = htmlspecialchars($key);
$value = htmlspecialchars($value);
echo "<input type='hidden' name='$key' value='$value'/>";
}
As the GET values are coming from the user, we should escape them before printing on screen.
You should include the two items (a and b) as hidden input elements as well as C.
I had a very similar problem where for the form action, I had something like:
<form action="http://www.example.com/?q=content/something" method="GET">
<input type="submit" value="Go away..." />
</form>
The button would get the user to the site, but the query info disappeared so the user landed on the home page rather than the desired content page. The solution in my case was to find out how to code the URL without the query that would get the user to the desired page. In this case my target was a Drupal site, so as it turned out /content/something also worked. I also could have used a node number (i.e. /node/123).
If you need workaround, as this form can be placed in 3rd party systems, you can use Apache mod_rewrite like this:
RewriteRule ^dummy.link$ index.php?a=1&b=2 [QSA,L]
then your new form will look like this:
<form ... action="http:/www.blabla.com/dummy.link" method="GET">
<input type="hidden" name="c" value="3" />
</form>
and Apache will append 3rd parameter to query
When the original query has array, for php:
foreach (explode("\n", http_build_query($query, '', "\n")) as $keyValue) {
[$key, $value] = explode('=', $keyValue, 2);
$key = htmlspecialchars(urldecode($key), ENT_COMPAT | ENT_HTML5);
$value = htmlspecialchars(urldecode($value), ENT_COMPAT | ENT_HTML5);
echo '<input type="hidden" name="' . $key . '" value="' . $value . '"' . "/>\n";
}
To answer your first question yes the browser does that and the reason is
that the browser does not care about existing parameters in the action URL
so it removes them completely
and to prevent this from happening use this JavaScript function that I wrote
using jQuery in:
function addQueryStringAsHidden(form){
if (form.attr("action") === undefined){
throw "form does not have action attribute"
}
let url = form.attr("action");
if (url.includes("?") === false) return false;
let index = url.indexOf("?");
let action = url.slice(0, index)
let params = url.slice(index);
url = new URLSearchParams(params);
for (param of url.keys()){
let paramValue = url.get(param);
let attrObject = {"type":"hidden", "name":param, "value":paramValue};
let hidden = $("<input>").attr(attrObject);
form.append(hidden);
}
form.attr("action", action)
}
My observation
when method is GET and form is submitted, hidden input element was sent as query parmater. Old params in action url were wiped out. So basically in this case, form data is replacing query string in action url
When method is POST, and form is submitted, Query parameters in action url were intact (req.query) and input element data was sent as form data (req.body)
So short story long, if you want to pass query params as well as form data, use method attribute as "POST"
This is in response to the above post by Efx:
If the URL already contains the var you want to change, then it is added yet again as a hidden field.
Here is a modification of that code as to prevent duplicating vars in the URL:
foreach ($_GET as $key => $value) {
if ($key != "my_key") {
echo("<input type='hidden' name='$key' value='$value'/>");
}
}
Your construction is illegal. You cannot include parameters in the action value of a form. What happens if you try this is going to depend on quirks of the browser. I wouldn't be surprised if it worked with one browser and not another. Even if it appeared to work, I would not rely on it, because the next version of the browser might change the behavior.
"But lets say I have parameters in query string and in hidden inputs, what can I do?" What you can do is fix the error. Not to be snide, but this is a little like asking, "But lets say my URL uses percent signs instead of slashes, what can I do?" The only possible answer is, you can fix the URL.
I usually write something like this:
foreach($_GET as $key=>$content){
echo "<input type='hidden' name='$key' value='$content'/>";
}
This is working, but don't forget to sanitize your inputs against XSS attacks!
<form ... action="http:/www.blabla.com?a=1&b=2" method ="POST">
<input type="hidden" name="c" value="3" />
</form>
change the request method to' POST' instead of 'GET'.
how to get button id from jsp to servlet instead of getting the button value
<input id="${section.id}" type="submit" name="submit" value="Edit">
how to get that id in servlet?
You can't that id is for client side use only. You will need to set the name or value to match the id of the element.
Alternatively as a workaround you could create a hidden input field that contains the id value by adding something like this to your JSP:
<input type="hidden" name="submit_id" value="${section.id}" />
This will then be available in the servlet upon form submit under the submit_id parameter.
String submitId = (String)request.getParameter("submit_id");
The only way you would be able to do that is by intercepting the form submit using javascript and setting the id as an extra post/get parameter.
the only way is make a javascript function that change your button value for the id , but i dont know why you want to do that, you could use a hidden input to send the data in the form
<input type="hidden" name="id" value="the_id_number" />
You cannot get any button id value to servlet. When a request from browser is submitted, all the input fields(input tag) will be transferred to server.The value of each input attribute can be accessed using the name of that field.All other fields like id, class etc are used for css and JavaScript functionalists.You should not design to pass the button id to server side.Think of other methods like hidden input fields