How do I make use of an already existing, external servlet? - java

We have a form with 2 input fields.
These allow a user to type in destinations to plan a flight.
We want to use an external servlet that allows us to use autocompletion on the fields
(e.g. type "LO" and it gets the matches for that - London Heathrow would be at the top)
The servlet can be found at a URL like this: http://www.companyname.com/servlet/ac.json?n=12&q=LO
with "n" being the amount of results it should return, and "q" being the query.
How do I call that servlet from my HTML form, everytime the input field changes?
The servlet is on a different domain than my page, and I have absolutely no other access than calling it with the URL I posted.
The response from the servlet will always be a JSON string like this:
[{"type":"airport","city":"Cape Town","airport":"International","iata":"CPT","country":"South Africa","locationId":"airport_CPT"},
{"type":"city","city":"Chicago, IL","airport":"All Airports","iata":"CHI","country":"United States","locationId":"US_city_CHI"},
{"type":"airport","city":"Victoria","airport":"CA","iata":"YYJ","country":"Canada","locationId":"airport_YYJ"}]

How do I call that servlet from my HTML form, everytime the input field changes?
I strongly belive ,you need AJAX for this.If you use a normal servlet and use a form to submit each time the page will reload.
And coming to same servlet part,
You can specify the method names in AJAX request

You can try with JSP page in place of Servlet. You can call it very easily and it will complete your purpose also. Otherwise AJAX is best for this type of problem.

Related

How to change the url after forwarding a servlet to jsp page?

I have a search.jsp page that has some html content and a form. When the form is submitted, there is a servlet handle the form data and forward the results to the search.jsp page. However, the url in the browser after processing the form is changed to the servlet name:
http://localhost:8080/MyProject/SearchServlet
not the search.jsp page:
http://localhost:8080/MyProject/Search.jsp
How I can change the url to the search.jsp? In other words, I just want to refresh the search.jsp page to display the results in the same page. How I can do that?
You cannot do that by forwarding the request: you need to "tell" the browser to generate a new http request by using the response.sendRedirect() method.
Now the question is why do you want the url bar to display the name of the Jsp?
Hiding the real destination path is a desired feature when forwarding requests: users do not need to know the server side redirects (that's how they are also called) happening in your web app.
Think about it: to carry out its tasks a servlet potentially can forward the request a number of times before getting to the final destination: you don't want the url bar to change each and every single time.
Give a fancier name to your servlet like: "Search" rather than "SearchServlet" so that users will know they are on the search page of your web application and not in the "SearchServlet" page.
In addition to that, if you visit any professional website, you will hardly ever see the .jsp or .html or .php extension on the address bar. While that is not a requirement or specification and you are free to do so, I believe the first approach is best practice (it looks even better to me honestly). There is even a folder WEB-INF whose purpose is to hide your .jsp pages from direct access via url bar.
What I like doing is having a servlet as the landing-welcome page of the web app, that will be responsible to forward and redirect requests based on the user input and the inner working of the application.
Now back to your final request (pun intended)
"In other words, I just want to refresh the search.jsp page to display the results in the same page. How I can do that?"
What I would do is:
redirect the user to the "Search" servlet from the welcome/home servlet.
In the doGet method of the Search servlet I would forward the request to the search.jsp page (you could set attributes before forwarding if you need to).
In the search.jsp I would set the action attribute of the form to "Search" (the name of the servlet) and the method to POST.
In the doPost method of the Search servlet you would implement whatever logic you wish to implement and finally forward the request to the search.jsp
After hitting the search button (and even after the submit button is clicked) what the user will see on the address bar is simply
http://localhost:8080/MyProject/Search
Hope that makes sense.
Are you using the same search.jsp for searching and well as showing the result? It is possible to use the same jsp to perform both the functions but it's easier and desirable to make another jsp which will only show the results.
If you are not able to see the results on search.jsp then make sure that you are setting the proper response in the Servlet class before forwarding it to the jsp and also whether you are reading the response sent by the Servlet class properly in the jsp.
If you want, the page to not refresh at all, then go for AJAX.

Sending info from Servlet to JSP

What I want to do:
I have a form with a lot of fields(nick, email, name, surname, etc.) but the user has to fill Nick and Email first in order to be able to fill the other fields(this is because we want to check that the nick and mail aren't in use by another client before he can introduce the rest of his information(name, surname, etc.)).
So, the user introduces Nick and Email and then he must press a button named "Validate", if the values are available(successful validation) then the rest of the fields are enabled and the user can continue filling the form, otherwise the fields stay disabled and an error is showed to the user.
The form will be located in a JSP, it will be submitted to a Servlet, once in the servlet I must validate the information that is in the form(i have a .JAR file included in this servlet, the validation consists in calling a function from that library, the function returns a boolean) and then I must return back to the same JSP the boolean that will represent the result of the validate function.
Now in the JSP I must enable(or not, depending on the value of the boolean) the rest of the TextFields.
I'm not sure if this is right but i was trying to submit with the button and at the same time run a javascript(onclick) that will use this boolean value that the servlet sends back to the JSP after making the validation. The javascript consists on an IF sentence that evaluates the boolean and if it's true then it enables all the fields on the JSP.
Problems so far:
I was able to send the Nick and Email from the JSP to the Servlet and to make the validation of the values, now i have the boolean but i have no idea on how to send it from the Servlet to the same JSP and use it in the onclick event of the same button I used to submit the info. I don't even know if it's possible to do this...
I'd be grateful if someone could give me a hand with this, i'm newbie in Java programming so i would appreciate simple explanations if possible.
Also, if there is a better way of doing what i want please share it, and if there are any doubts ask and i will try to explain it better.
There is no need for JavaScript at all.
In your servlet you can store the validation result into the request context:
req.setAttribute('checkResult', checkResult);
where req is of type HttpServletRequest and checkResult is a Boolean.
Then you can forward to your JSP:
RequestDispatcher dispatcher = req.getRequestDispatcher("/your.jsp");
dispatcher.forward(req, resp);
In your JSP you can set your form elements as read only depending on the attribute checkResult which you have put into the request context:
<textarea name="text" cols="50" rows="10"
<%= request.getAttribute("checkResult") != null && request.getAttribute("checkResult") ? "" : "readonly" %>
>...</textarea>
So if the check is not valid then the <textarea> element will contain the readonly attribute. Otherwise readonly is not present.
As Roy mentioned AJAX is best suited for your problem. You can use DWR! , it makes normal java classes available as AJAX services, just call the method on them and get the result. So easy.
I think AJAX is more suitable for your application, which will not require to submit the whole form and you can send back the validation flag as plain responseText or well-formatted responseXML. Also you can use a lot of good javascript library such as jQuery that helps you send an AJAX request quickly and simply.

Pass parameters from one jsp to another using post method

I want to pass parameters from one jsp to another.
I have tried using the post method, <jsp:forward/>, but it doesn't work.
I have created a <form> in html (parameters passed using POST), which is submitted to a servlet which processes the request and forwards it to another servlet that displays a page.
From this servlet i have created links to another jsp, passing through the parameters as GETs in the URL. However, I actually want to pass the parameters to another jsp using POST, and then pass it on to another jsp.
What solutions do you have or this problem?
Check out the Request Dispatcher. You need to forward the request to the landing JSP.
http://docs.oracle.com/javaee/6/api/javax/servlet/RequestDispatcher.html
Sounds like you are creating a multipage form that gathers information from the user across several distinct pages. In that case one option is to use hidden fields on a form to store the previous values. This of course means that as the pages progress the amount of data passing back and forth from client to server increases.
You may consider a server side approach by storing the interim values in a database for instance, then only passing a token back to the client. When the next JSP page is submitted, use the token to look up the values in the database.
JSP has built-in request object.when one jsp redirect to another jsp with some parameter, you can get parameter value using this request object.
<%
String param1 = request.getParameter("parameter_name");
%>
you can find example here -
http://www.roseindia.net/jsp/RequestObjectInJSP.shtml
Why don't you call a page on the click of a submit button by creating
an url in the below format (in javascript):- var
url="your_page_name.jsp?value1="+encodeURIComponent(document.getElementById("your_text_field_or_any_other_field_id"));
and then call the page by using your url
document.your_form_name.action=url;
document.your_form_name.submit();
and then use request.getParameter() method either in servlet
or in the jsp that u'v metioned in the url (servlet or the jsp u'll be
calling thorugh u'r jsp).

jsp to servlet communication with parameters from URL, not a form

I'm using netbeans to create a web application that allows a cell phone user to scan a QR code and retrieve a journal's previous/next title information. The take home point is that there's no form that the user will input data into. The QR code will contain the search string at the end of the URL and I want the search to start on page load and output a page with the search results. For now (due to simplicity), my model is simply parsing an XML file of a small sample of MARC records. Oh, to top it off...I'm brand new to programming in java and using netbeans. I have no clue about what javabeans are, or any of the more advance techniques. So, with that background explanation here's my question.
I have created a java class (main method) that parses my xml and retrieves the results correctly. I have an index.jsp with my html in it. Within the index.jsp, I have no problem using get to get the title information from my URL. But I have no clue how I would get those parameters to a servlet that contains my java code. If I manage to get the search string to the servlet, then I have no idea how to send that data back to the index.jsp to display in the browser.
So far every example I've seen has assumed you're getting form data, but I need parameters found, processed and returned on page load...IOW, with no user input.
Thanks for any advice.
Ceci
Just put the necessary preprocessing code in doGet() method of the servlet:
String foo = request.getParameter("foo");
// ...
request.getRequestDispatcher("/WEB-INF/page.jsp").forward(request, response);
And call the URL of the servlet instead of the JSP one e.g. http://example.com/page?foo=bar instead of http://example.com/page.jsp?foo=bar in combination with a servlet mapping on an URL pattern of /page/*.
You can get the url parameter in servlet using request.getParameter("paramName");
and you can pass the attribute to page from servlet using forwarding request from servlet to jsp.
See Also
Servlet wiki page
Bear in mind that your JSP page will compile internally to a servlet. So you can retrieve the string and print it back in the same JSP. For instance assuming you get the string in a parameter called param you would have something like this in your JSP:
<%
String param = request.getParameter( "param" );
out.println( "String passed in was " + param );
%>
One last thing, you mentioned the main method -- that only gets executed for stand alone applications -- whereas you're talking web/JSP :O

why use<bean:include instead of <jsp:include in struts?

why use<bean:include instead of <jsp:include in struts?
from the documentation for bean:include
Perform an internal dispatch to the specified application component (or external URL) and make the response data from that request available as a bean of type String. This tag has a function similar to that of the standard jsp:include tag, except that the response data is stored in a page scope attribute instead of being written to the output stream. If the current request is part of a session, the generated request for the include will also include the session identifier (and thus be part of the same session).
first hit on google
bean:include works almost like jsp:include except that the result is stored in the page scope. This means that your code on the current page can access the results and manipulate it. See this page.

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