I'm trying to do a single page application using servlets and jsp pages.
For the moment I have the first page, which is simple to do: a servlet that forwards to the corresponding jsp.
How should the implementation look when navigating to the second page?
I guess it should be an ajax call, the servlet would populate the necessary data, but how to display the second page jsp?
JSP is a server side ui technology. A Servlet listens to specific urls and redirects to JSPs pages. The JSP is compiled to a class (another servlet in fact), invoked (data will be added and inline scripts will run) and the output, whith is HTML, is send to the client (browser). To get to a different page its neccessary to query the server (servlet) for another url, resulting in another html page.
To create an SPA you need a client side technology like JavaScript. Your query the server for a single html page. The page, made of HTML and JavaScript, for example, (could even be the output of a single JSP, dont get confused) is send to the client (browser) and the JS is run. This is nomaly backed up by a framework like AngularJS, EmberJS or Backbone. Once the page is set up, the links within the page are anchors (http://example.com/#/mySecondPage), so clicking them will invoke the framework again (Ajax, querying the server for new data), but will stay on the same page. Some contents of the page might then be replaced by new content.
If it is a true SPA then you would just have a single JSP and handle all your functionality (after your initial page load) using Ajax.
Have you looked at using a client-side framework such as Angular to help you with this?
Depending on how rich your SPA is, you could either use the same servlet or multiple servlets to serve each page.
Unless you are doing this for a course or tutorial and have some constraints on how to achieve it, you will very probably save yourself a lot of time if you couple something like Angular with a server-side framework like Spring instead of coding servlets. As a suggestion have a look at Spring with Angular.
In SPA the browser only loads the document once (or a few, once per sub-application), and further communication to the server is done usually via AJAX or Websockets.
I recommend you to model your application as a thin server architecture, that is, a client application running in the browser (HTML, CSS, Javascript) consuming a web service API provided by the server.
The following are some points worth knowing;
Client-side:
Only presentation logic
Represent state by URL hash. This enables bookmarking, hyperlinking and browsing history. Your client app should listen to changes in the URL hash and act in consequence. This technique is called "routing" and it is implemented by all Javascript frameworks.
Client application is packaged server-side such it can be downloaded in a single request (in .html, .jsp, servlet, .jsp + multiple .jspf, ...)
Consumes services provided by the server via AJAX or Websockets
Server:
Offers client application to download
Provides a clean, stateless API to be consumed by the client application, better returning JSON (data) than HTML (presentation logic) (Why is it a bad practice to return generated HTML instead of JSON? Or is it?)
Use a REST or JSON-RPC frameworks to create the API. There is a lot of debate on what to choose (see here or here). In my opinion the only advantage of REST over RPC is that since REST has become a "de facto" standard its interoperability is higher, so my recommendation for SPA applications is using JSON-RPC, because your code is the only client of the API.
There are lots of alternatives for both client and server frameworks.
Javascript: AngularJS, EmberJS or Backbone,...
REST: Spring, Jersey, Restlet,..
JSON-RPC: https://en.wikipedia.org/wiki/JSON-RPC#Implementations
Regarding JSON-RPC, you might want to take a look to Brutusin-RPC, a JEE microframework I have created :)
If you are using an Ajax request, then you need to tell the browser that redirect to the second page. Example:
response.sendRedirect("second_page.jsp");
In your servlet, you need to differentiate a request to the first page, from a request that need to be redirected to the second page. You can use parameters, or session values, for example.
if (request.getParameter("page2") != null) {
response.sendRedirect("second_page.jsp");
} else {
.... // include here the normal logic of your Servlet for page 1
}
Then, you can invoke your servlet with or wihout the parameter page2, to go to page 1 (without parameter), or page 2 (with parameter).
Related
I am developing an application in which i am using angularjs at client side and java,spring at server side,all communication is in the form of JSON.
The problem i am getting is about security.
I have multiple roles, user can have and based on these roles,tabs on UI are visible or not.
If i use JSP then it is easy to use taglib for this problem because jsp is compiled at server and returned html will not have html section for hidden tabs and there is no way by which end-user can see these tabs or their URL part.
But how to solve this problem in angular based application because whatever code i write in angular file,user can change it by firebug etc. and can see the tabs and their URLs.
example : i have following in my html :
Users
I want to hide this thing completely if user is not having required role.
One solution can be writing some directive but user can edit the script of this directive and can see this thing in html.
You need to do 2 things :
Implements an angular Service, giving your client side the authorization (obtained by REST)
Then, on the server side :
you need to protect ALL RESOURCES (html, angular controllers, angular services, rest resources) depending on the user's rights.
May you can protect only Rest Resources if Client side's ones are not critical (I don't mind if my user get my html).
This way, the user won't see the tabs he is not supposed to, but more important, he can't bypass your security in order to show it.
By protecting HTML, I mean that for the tab XX I use ng-include="'tabXX.html'", and I protect this html with Spring Security the same way I protect RestResources.
I'm developing a web app using JSTL and Javascript in Eclipse Juno. I've been reading questions like How to set the JSTL variable value in javascript? and my code works good even if I have error in eclipse:
But... Is it a good practice to use JSTL and Javascript like this?
Does it cause a low performance in the time of rendering the webpage?
Can this be done in other way?
Is it a good practice to use JSTL and Javascript like this?
It is not bad practice or good practice. The bad practice would be using JSTL to control the flow of JavaScript, which is plain wrong because JSTL runs on server side and JavaScript on client side.
Does it cause a low performance in the time of rendering the webpage?
JSTL will only help to generate the HTML for the current view. JavaScript is not involved in the HTML generation at server side but at client side unless you work with nodejs or similar technologies.
Can this be done in other way?
This depends on what you're doing. Common way to access to data when accessing to a web page:
Application Server (AS) receives a GET request on http://www.foo.com/bar
AS pre process the GET request (load data from database or another data source, pre calculations, etc)
AS creates the response for the GET request (apply the data to generate the HTML)
AS sends the response to the client.
The browser client renders the HTML.
Another way to do it:
Application Server (AS) receives a GET request on http://www.foo.com/bar
AS creates the response for the GET request (generate the HTML which contains JavaScript functions to load the data in the onload event).
AS sends the response to the client.
The browser client renders the HTML.
The onload event fires and load data in the onload event through RESTful services. This way, the data interaction is handled in client side only, but the data comes from server side.
These are two very simple alternatives to handle the same problem. Which one to choose and work with will depend entirely on your design, there's no definitive answer.
Is there any way to redirect to a page/template using webcenter sites tags? or we need to depend on standard j2ee respnose.sendRedirect() method??
If you're using a JSP wrapper, then you can't really do this since JSPs start sending the response headers too early. You'll have to render an HTML page with the meta redirect tag.
If your wrapper is XML or Groovy, then you can do this using WebCenter Sites APIs. There's a Groovy example here.
Redirecting a request is a tricky part in oracle webcenter sites. The response.sendRedirect code doesn’t work in sites JSP. Because the response headers are committed early in the page evolution, so we can not set the return status code in jsp in sites.
We can control this at client side immediately after loading the webpage. In javascript we can set the condition to forward to the respective page/url. Return the below javascript code as the response from the sites’s jsp page. Here is the best solution to achieve this task.
http://devble.com/forward-and-redirect-request-in-webcenter-sites/
Is it possible to embed html with java
test.html
<input id="buttonId" type="button" class="button-click"
value="" onClick="checkSucess(2)" onload="counts(count)">
test.js
checkSucess = function(firstVal) {
// Jquery Ajax with url,params and response
doPost('test.java',
'first=' + firstVal,
function(response) {
});
test.java
Here get the 'first' value from ajax request, and further processing.
I believe you're looking for JavaServer Pages (.jsp), a starting point for implementing server-side logic using Java. (You can GET/POST to a jsp.)
Reference
JSP + Ajax Example
JavaServer Pages Technology
JSP Tutorial
Well, Java on the server side doesn't work quite like PHP. i.e. you can't simply drop your java files in your htdocs directory and trigger it by filename directly. Firstly you'll need an app server like tomcat or jetty (instead of just a webserver like apache httpd). Secondly, you'll need to create a Servlet (simplest case) and write your java code there and trigger it using the server request url. Google "servlets" and you should be able to pick it from there..
No, you can't do like that, you have to use AJAX request to interact with java from your html or javascript. For that you have to use servlet and pass the servlet URL to doPost function.
doPost('url to servlet',
'first=' + firstVal,
function(response) {
});
Since this is your first java project, you should do some reading to come up to speed with java. Here are some good tutorials:
Core Servlets, Intermediate Servlets
Apache Tomcat 6 - Apache is a nice tool for learning servlets; it is easy to install and run.
Core Servlets; Advanced Servlets - This may be more than you need.
Applets are Java, and the only (usual) way for Java in the browser.
You can communicate with Applets from Javascript/JQuery code. Applets have ending .class (.java is source code, you can't communicate with it).
In the case you want to communicate with serverside Java, you need servlets there. Then send requests to the url of the servlets.
No. Besides using Java Applets - which are actually just plugins - there is no way to embed Java into HTML.
That being said, It is possible to generate HTML using Java Server Pages.
It is also possible to use an HTML page in conjunction with JavaScript to interact with Java via subsequent HTTP Requests made using AJAX. These requests are initiated on the client browser, and received and fulfilled by a server capable of executing Java Server Pages (JPS).
Example:
An HTML page is loadad with some JavaScript that requests some url upon completion of DOM loading.
The request is received by some server which then responds to the request.
The client browser receives the response and provides it to JavaScript to be dealt with.
JavaScript reads the response, and uses it in some way (like "refreshing" some information on the page).
I need to get userPrincipal inside a piece of Javascript code. My app currently uses Dojo on the client side and servlets on the server side. I am not using JSF, nor JSP (and if possible I would try to avoid using it only for this purpose), nor JQuery (I would avoid mixing JQuery with Dojo).
I have read this interesting post Mixing JSF EL in a JavaScript file . Following the idea #1, I have written a Bean but I am not sure on how to embed the call to the Bean in my (quite long) js file.
If you don't use JSF or JSP or anything similar, just bare servlets, I recommend creating a servlet which takes the userPrincipal name from the HttpServletRequest (or any other place) and returns it in JSON format. Then you can do an AJAX call to the servlet and find out what you need. I don't know Dojo too well, but I believe you can insert this AJAX call in your event chains pretty easily.
I don't recommend mixing managed beans with plain-old servlets.
If AJAX is not an option for you because of its asynchronous nature, you cand create a servlet that serves text/javascript content which offers the principal's name in the form of javascript code and then add a script tag to your page.