Can anybody tell me how to assign javascript variables to jsp request or to jsp session.
I am doing something like this
Here deletedRows is a hidden field.
var del=45;
document.getElementById("deletedRows").value=del
alert(document.getElementById("deletedRows").value);
<%String del_values = request.getParameter("deletedRows");%>
<%request.getSession().setAttribute("del_rows", del_values);%>
I don't get the value of del in my servlet.
JSP gets compiled on the server. All the client gets is the "output" of the JSP: the HTML, CSS and Javascript.
The Javascript gets executed after this. Meaning everything in the JSP has become HTML et all when the javascript executes. You way want to think this as the Java/JSP part has "completed" and now the HTML/Javascript part takes over.
Now you want to pass on some value calculated/manipulated via Javascript back to the server. (I think this is what you mean when you say "assingn javascript variables to jsp request or to jsp session"
For this you have to submit the page to the server, and these values should be part of the form that is being submitted.
You may already have these values in some HTML elements (like a <input> or <select>), if not you can create hidden elements and populate these with the values before submitting the <form>.
In the code you have provided, you are populating the hidden field correctly, but you have to retrieve the value in the servlet, not in the JSP itself. Also, make sure that the hidden field in in a <form> and that form is submitted.
Once the form is submitted (to a servlet) the values can be retrieved in the servlet via request.getParameter.
There are few other mechanisms to send a value to the server, using a URL parameter or via Asynchronous (AJAX) requests, but I am not sure whether you are looking at these also.
Any form fields, including hidden fields, that are submitted from the browser will be accessible in your JSP using request.getParameter("fieldname");. Query-string parameters may be accessed the same way.
Make sure that your form fields have a name attribute specified because it is that name (not the id attribute) that becomes the parameter name in your server-side code.
What you've already done in the little bit of code shown in your question, i.e., set the hidden form field to have the value of a JavaScript variable, should allow that value to be submitted and then accessed in the server-side code. But it's hard to see why it is not working without seeing at least some of your form HTML, particularly the definition of the hidden field. It would also help to see how that is being submitted. (I'm assuming it is being submitted: if you are trying to make all of that code run just on the server it won't work, because the JavaScript is treated as document content by the server, it isn't executed. Again, I can't really tell how you're using that code without seeing more of the surrounding JSP.)
UPDATE: I see that your code has been formatted since I started typing my answer. You aren't expecting all five lines to run on the server are you? The JavaScript code only runs on the client browser after the page is rendered. The Java code in between <% %> is executed on the server before the page gets to the browser and so can't access JavaScript at all. Anything not in the <% %> tags is simply sent to the browser as is - the servlet doesn't interact with it as such.
Related
Let's say I have an input box, on the client-side, I want to access the value of this input box and check if it exists as a record in a model. If so, I want the data to be shown. However, I want this to be done without clicking a submit button/reloading the page.
Can someone show me some sample code?
Sample code is very much frowned upon in these parts, I can give you an outline of what you could do. Use jquery to get the value of the input box, and submit this using an ajax request to some url. Map that url to a controller action that checks to see if that record exists in the db, and return some json that indicates whether it does or not. Then in your javascript, when the data is returned, you can display that to the user.
I want to create an HTML form on the Server. When the client completes the form and clicks submit, I want to be able to save HTML form and data in a single HTML file on the server.
The best suggestion I have seen is using JavaScript. Use a client side script that on click will save the document.InnerHTML to a var that can then be submitted back to the server.
Is this the best approach, or is there an easier way?
Even though I have no idea why you want to save the whole html code because I'm sure there will be parts that are the same for every user and you will be wasting memory, but ok.
So there are two ways to do this:
1. is javascript as you said
2. would be to put all the generated html code into a hidden form input (already on server side)
the first one seems more comprehensive and this is what I would do but the second one would also work for users with js disabled.
I wouldn't really recommend this way, because I'm still a huge fan of saving data in a database, but here's a general outline of what to do:
User fills out the form and submits.
Server-side code executes a method:
a. String holding the template for your HTML page with placeholders for the fields.
b. Use String.Format to put all the user input into the correct places.
c. Create a file, write the string to the file, and save.
d. Return file name to user.
HTML files are not that large, but still you risk using up your hard drive space. Also, you need write permissions which introduces security risks.
Going the database route:
1. User fills out the form and submits.
2. Server-side code saves the data to a database, and returns a link (with querystring string of ID and possibly a user id to help with security) to the user.
3. Whenever the user goes to the link, the server-side code repopulates the form with the ID passed.
I want a scenario in which I will set some value of a hidden field in a particular page.
Then that page is submitted on server (form submit). Now, i redirect on another page and there I again try to retrieve the value which I set previously. But I am not getting there the value which was set, instead i get the default value which I provided in html page itself. (Hidden field is in header page which is common for all the pages in my web app).
i tried a dummy application in which i am getting the value of hidden field even after loading/refreshing the page once i set it.
When you redirected your user to another page, it became reloaded. Unless you chose to set a value to your form (by javascript for instance), the value of the form is the default one.
The value you "set previously" wasn't definitely associated to the input because everytime you reload the page, your server will generate again the HTML and the default values and your browser will display this HTML.
This behavior is normal.
Besides, if you want to keep the values of the form while submitting it, you can use AJAX submitting.
The other answers here are factually correct (that HTML doesn't normally do what you're asking it to do), but there are a few things you can do to make it work.
First, how things usually work: In order for the second page to get the proper value of the hidden field, you would process it in the server-side component. It sounds like you are redirecting to a new page in the server-side handler. The best way to make this work is to have that server-side handler process the value and attach it to the redirect as a parameter (likely attached to the querystring). Then have some server-side code generate the second page, which would process the querystring parameter.
Here's the work-around for pure-HTML/javascript implementation:
If you can't or won't have a server-side process to generate the second page, you could pull it out of the querystring using Javascript (just search for 'getting querystring variables in javascript').
If you use javascript, it could be feasible (though probably not advisable) to have the first form go directly to the second page by setting it as the form's action with a method of 'GET'. It's definitely better to include a server-side handler though.
What your trying to do is impossible through regular HTML since HTML is stateless. What you want is to put your values in a session or in a cookie and this way you can plant it on every page that is loaded.This cannot be done by default.
You're mis-understanding how HTTP works - it is stateless.
This means that every single page you request is completely separate to previous pages. Which is the reason your hidden textbox is being set back to default.
You have to explicitly set the value server side prior to it being sent to the client.
My HTML form is clearing automatically after I click the submit button. Any idea how to stop this from happening?
Here's the opening tag for the form:
<form onsubmit="return math()">
One popular approach is to utilize a server-side language such as PHP which reads all the get values and recreates the HTML of the page using a template and substituting in variables.
<input type = "text" name = "Textbox1" id = "Textbox1" value = "{$_GET[Textbox1]}"/>
I've written it out as $_GET directly, but you'd really want to make sure the value was scrubbed so you don't get arbitrary html injection.
A little bit more complicated you could approach this purely client side and utilize javascript to parse the address bar and extract the values submitted to your page (assuming it wasn't submitted with POST as the method). Then you can dynamically repopulate the fields client side.
when you click submit the page refreshes. You'll probably need to return a page with the value of the forms set to what was in when it was submitted.
If math() returns false your data won't disappear but it won't sent data to the server either. If you want to send data to the server you could make a XMLHttpRequest.
On my page
I have one textbox and one button.
-- on the button click event. -- one function will be called.
Now,
How to get that value of textbox and store in PHP variable? This should be done in that function which we will call on button click.
You'll have to know that Javascript and PHP run on two different servers. So they can not communicate directly.
You'll basicly have two options:
POST the value
Make a form with a post action, submit the form, and you can access the value in PHP with the $_POST array
Disadvantage is that the browser leaves the page to submit the form, but it doesn't require javascript.
Use AJAX
Get the value in Javascript, make an XMLHTTPRequest to the server, and you can access the variable too via $_GET or $_POST, depending on how you sent the value.
When your page is displayed, your PHP code has already been executed.
What you want to do is to learn AJAX, i.e. JS functions that call external PHP scripts.