This is a dropdownlist in which multiple values can be selected -- http://paste.ubuntu.com/7845559/
A loop has been used to create the options in the list accessing values from database.
This is the javascript function I am trying to use to read the multiple datas selected in the list -- http://paste.ubuntu.com/7845571/
I am not sure if the variable str in the javascript function is storing the values from dropdownlist. My questions are--
How can I assign the javascript variable str to java string variable ?
After doing 1 how can I send the java variable to a servlet ? I need to send this information to servlet to update infos in database.
If this approach is wrong which one is a better way to access datas from the list and send them to servlet ? A simple code snippet will be very helpful.
You are mixing up client-side and server-side code. A JSP is can be thought of as 2 programs intermingled. The program which runs on the server (anything that is inside scriptlets <% or output by custom tags) and the program which is executed by the user's browser when they receive the response.
Things the Server-side code can do:
Access the database
Create Java variables (which are stored as request or session attributes)
Interact with other Java objects
Output HTML and in-line JavaScript
Things the Client-side code can do:
Create and manipulate JavaScript variables
Dynamically edit the HTML DOM
Submit Forms
Things the Client-side code can't do:
Access the database
Create Java variables
Interact with other Java objects
Therefore, your Server-side code should output the HTML code for a Form, and this Form can be filled out by the user, submitted and the data will be sent back to a Servlet on the server which can access the database, make the changes and generate more HTML to send back to the user (eg validation error or thank-you page).
Please see this question (although it is PHP, the ideas are the same):
What is the difference between client-side and server-side programming?
Related
i have created dynamic rows(textboxes) in jsp by using javascript. After giving the values to those fields how can i retrieve the values into my result jsp page.
You might be overlooking on something. What is the exact requirement?
I doubt that is even possible because
JavaScript executes on the client side after JSP page is already compiled and sent to the browser as response.
While creating your rows in js assign a unique name to each cell (something like 'text_[i]_[j]' if you are using two loops the outer running on i and the inner running on j)
Submit the page
Use request.getParameter("text_[i]_[j]") to retrieve the value.
I have a form on my jsp with fields - Name, IP, username, token.
It is mapped to a table with same column names. I have created a Bean class too.
Now, I am not sure what is an ideal way to send all the parameters from jsp to the java code.
I know few options like -
Create input with type hidden and then set its value in the jsp.
<input type="hidden" id="name" name="name"/>
and then retrieve its value in the code using request.getParameter("name")
Somehow I dont feel this is an ideal way.
Create a JSON with all the values of the input boxes and set the json file as one input and read it on the java code using org.json;
Which one of the two is the better way to do it? Is there any simpler, effective and much better way?
Everything which is built using HTTP methods must send values to the server in one of three places:
Parameters in the url itself (GET requests)
Content in the body of the request (POST requests)
Key-value pairs in the header of the request (HTTP method agnostic)
Any mechanism you use to send a value back to the server (excluding web sockets), no matter what the framework, will use one of these mechanisms underneath.
That being said, use whatever best meets the requirements of your application:
Form-based, GET requests:
are simple to understand
don't require much overhead either on the front-end or back-end
are easy to test (just access the url using the appropriate query string)
Form-based, POST requests:
are also simple to understand
also don't require much overhead either on the front-end or back-end
are not as easy to test (you can't just access the url using the appropriate query string)
Ajax-y, JSON body, POST requests:
are the new hotness
require a bit more front-end work (creating the request in JS and sending it)
don't require the browser to make a full-page request/response
I am working on JSP-servlet application and now I am programming a page which edit information about registrars.
The senario is that there's an ArrayList I send form servlet to JSP page when I load the page. The ArrayList contains information about groups the registrar belongs, the ArrayList is resulted after making multiple SQL statements. When user try to edit some fields and make one required field empty and submit the form, the servlet makes validation and return error to edit page.
The problem I face is that all the groups I sent in the first time fly in the sky. So I have to make connection to DB again and make multiple queries to get the groups again and send it back to JSP page.
Is there's another simple way to make arrayList stable in JSP page ?
EDIT
Here's the code which I make the scope of the ArrayList in the session.
<c:set var="userGroups" value="${userGroups}" scope="session"></c:set>
Either store it in the session or just live with it. I really don't see any issues with that. If the concrete problem is that you have to copypaste the same code again or that the whole code is ugly to have in a Servlet class, then just refactor/hide that into an useable DAO class which you import/call/reuse in the Servlet the usual Java way.
Update: as per your update, this doesn't make sense. You just need to change your servlet code from
request.setAttribute("userGroups", userGroups);
to
request.getSession().setAttribute("userGroups", userGroups);
You don't need <c:set> for this.
Using Java (.jsp or whatever) is there a way where I can send a request for this page:
http://www.mystore.com/store/shelf.jsp?category=mens#page=2
and have the Java code parse the URL and see the #page=2 and respond accordingly?
Basically, I'm looking for the Java code that allows me to access the characters following the hash tag.
The reason I'm doing this is that I want to load subsequent pages via AJAX (on my shelf) and then allow the user to copy and paste the URL and send it to a friend. Without the ability of Java being able to read the characters following the hash tag I'm uncertain as to how I would manipulate the URL with Javascript in a way that the server would be able to also read without causing the page to re-load.
I'm having trouble even figuring out how to access/see the entire URL (http://www.mystore.com/store/shelf.jsp?category=mens#page=2) from within my Java code...
You can't.
The fragment identifier is only used client side, so it isn't sent to the server.
You have to parse it out with JavaScript, and then run your Ajax routines.
If you are loading entire pages (and just leaving some navigation and branding behind) then it almost certainly isn't worth using Ajax for this in the first place. Regular links work better.
Why can't you use a URL like this:
http://www.mystore.com/store/shelf.jsp?category=mens&page=2
If you want the data to be stored in the url, it's gotta be in the query string.
I am interested in creating a simple web application that will take in user input, convert it to an XML file and send the file to a database.
Coding wise I feel I am okay, it is just the general setup and what implementation to use I am a bit unsure of.
At the moment I have a JSP page containing a form, the user fills out the form and on submit a POST method is sent to a servlet, in the servlet doPost() method the servlet is instantiating a java object and passing it the user inputted data. The java object then writes that data to an XML file and sends it to the database via REST.
All I would be interested to know is if this the standard/optimal way of creating such a web application.
Any and all feedback is appreciated.
Thanks
For a "simple webapplication" this high level approach looks fine in general. However, if you want more critical feedback, you'd need to give more details about the low-level approach. It may for example happen that it isn't memory efficient and thus may break when the webapp is been used by over 10 users concurrently, just to give an example.
I only question the choice for the GET method. You'd normally only use it to retrieve data (SELECT), not to create/alter data (INSERT/UPDATE/DELETE). For that you'd normally use POST, so that no one can execute it "accidently" by just clicking a (bookmarked) link. Changing GET to POST isn't that hard, add method="post" to the <form> element and rename doGet() to doPost().