This question is about a proper architecture using JSP as a controller for ExtJS.
I am fairly new to server side development but I am pretty familiar with ExtJS 4 and getting better with Java and SQL daily.
I am trying to create a JSP controller to write the data from stores in ExtJS. I have MSSQL database and Tomcat running on the server.
I successfully created a JSP (sqlData.jsp) that reads from the database and returns JSON data. I pass a query name to this JSP, it then looks up what the query is from a "query" table (columns: [query_id],[query_name],[query]). It then runs the query and returns the data in a JSON format - this is working fine to get data into ExtJS from a database.
To use this backend set-up I usually configure the store like this:
var store = Ext.create('Ext.data.Store', {
model: 'aModel',
proxy: {
type: 'ajax',
url: 'sqlData.jsp?queryName=aQueryName',
reader: 'json'
},
autoLoad: true
});
Somehow, I need this sqlData.jsp to also handle a store.save() call from the ExtJS framework. Which means the JSP needs to receive a POST request and then do an update based on a pile of JSON data (ExtJS sends read request as GET and write methods like store.save() are POST).
My plan was to add something in the Java to recognize whether it is a POST or GET request. Then, if it is a POST request, I would send it to a different Java method in the JSP to parse the JSON and write it to the database.
Of course I would have to change my "query" table to have another column for update/insert statements linked to the same queryName (i.e.: [query_id],[query_name],[select_query],[update_query]).
Does this backend implementation make any sense?
Anyone else use JSP and ExtJS to achieve this smoother?
I noticed that there is an api config option I can set in my proxy to specify different URLs for the different operations (READ, WRITE, DELETE, etc). Should I make a separate JSP and direct all write requests using this config instead?
Would it be wiser to add a writer: 'json' config on the proxy so that it parses before POSTING? I figured I would have to parse it in the JSP either way so I didn't think I should.
Any pointers will be much appreciated.
since your backend is Java, I would really recommend using Spring 3.0 MVC to code your backend.
JSP is not a good option for the stuff you are doing because:
the functions you write in there are not unit testable.
the functions you write in there are not reusable.
the code you write in JSP are functional in nature, not object oriented, you can't inject the services you need into your JSP.
Spring 3.0 MVC has really good synergy with ExtJS 4, namely the RESTful URL's and content negotiation.
This example shows how to integrate the two things together. http://java.dzone.com/articles/extjs-4-file-upload-spring-mvc
I would skip jsp and just go directly to servlets. i.e. implement the logic in the servlets for both returning json, and handling things like POST, PUT, etc.....
jsps are meant to be views. But in your case, your view layer is its own application running in the client. You only need the data.
The Servlet API puts allows you to handle requests, get the http method, and stream data to the response.
My advice is go with an MVC server side framework. My favorite is Grails which lets you work with JSON objects directly for both input and output. Its also super simple to with grails to read and write data to the database.
Related
Basically I am hosting a database on server side using spring boot. And I wanted to write custom query from client side which is developed in angular and call a function from server side for giving me the needed results.
The function for server side will look like this:
List<rows> func(String customQuery){
//fetch rows from table using this custom query and return those rows
//which I can use in client side.
}
Below are examples of customQuery which I need to send from client side:
select * from table;
select * from table where id>10;
select * from table where id>20 and id<30;
So far I searched in Internet I could not find any solution. Please help.
Sending SQL directly from the client would be a complete security failure, because a malicious user could easily figure out how it works and send a delete from table to kill your entire app.
Much worse, they might even be able to run create user ... to give themselves complete access to your entire database, get sensitive information, install malware, etc.
Instead you'll want to create a REST service in your application with methods such as
GET /table
GET /table?minId=10
GET /table?minId=20&maxId=30
Return as application/json or a similar data format and only return the information your angular app really needs.
Angular would then be responsible for selectively updating the display with your data.
Edit:
This is a guide I have found for creating a basic web app based on Spring Boot and Angular. Might be a good starting point for you:
https://www.baeldung.com/spring-boot-angular-web
The best way is to send only the parameters (minID and maxID in your case) from the client-side and then build the query dynamically on server-side using Spring JPA Specifications.
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).
yesterday i started brainstorm for a project of mine and I'm not sure if its the correct approach.
On my website I'm having an (kind of an order form) which sends a post to a target URL, which works with a simple curl php script. The target is an external service (where I have no access no rights, nothing). I only know that I will get a POST with further processed data back from the service, which I have to save into my DB.
in steps:
Users fills out the (order) form and posts data to an external url on my website.
data gets externally handled and after finishing that resents a post.
read incoming post data.
save data into DB.
Success page on my website.
My thoughts were to handle the incoming data with a servlet (spring maven project) but I'm not sure if this is a correct approach. Is there a better why to do this. Or is the first step with the php scripts wrong. thx for any help.
A simplest workflow could be
1. Forward the initial (Order form with values) request to a servlet
2. Invoke a post request using java to an external url inside this servlet (Using Apache http client, or libraries such as HTMLUnit)
3. Once you get the incoming response in your servlet, you can update your database.
If you are using spring, the controller could forward initial request to a business class which will handle this post processing and delegate the database update to respective DAO.
There are a number of suitable ways to handle this, and the decision is largely a matter of preference and what you're familiar with. Spring can handle this sort of job quite well.
Note: Maven is a build system for Java and some other JVM languages. I recommend using it, but it's not part of Spring; what you're probably looking for is Spring MVC.
Am developing an app using SpringMVC. In that app, I have a list of crud screens(almost 20 screens).
Now, I designed my controller in the following pattern of request mapping
create
show
update
delete
Here , the problem is, I would like to expose this URL as both REST Service as Well as Normal Spring controller(directs to a new page after CRUD operations).
ie. When I use the application, it should do the CRUD operation and redirect to specific pages(Accordingly)
When I call as a rest service (using REST Clients). I should get the JSON data
Is it possible??
I would cleanly separate your AJAX/JSON calls from your page navigation. In other words, assign responsibility for the page navigation to one controller (or leverage an SPA routing mechanism on the client side), and the data access to another "service" controller. You then have a reusable and testable service and an independent navigation flow (which could evolve, change technologies etc).
As far as know, I don't think so. But one way will be like, each time your controller will produce JSON response. But for web application you need to add extra call for each request which will load desired page and then call your CRUD methods on load of your page and parse the JSON response to fill the data.
I think what you are looking for is content negotiation. Google recommends this article: http://blog.springsource.org/2013/05/11/content-negotiation-using-spring-mvc/
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.