I have implemented a REST api using Wildfly 8.1. The endpoint is something like:
/rest/v1/users
In my implementation for every request I read users from the db and give back a json representation of the collection.
The strange think is that if I call the api I don't get a unique result for the collection (i.e., for each request it randomly provides one betweenn the older values and new values). This goes on until I restart the server.
The db interface is correct, so my guess is that Wildfly is caching the previous data, is it possible and why does it provides different results for different calls?
Related
I am looking for a REST API to do following
Search based on parameters sent, if results found, return the results.
If no results found, create a record based on search parameters sent.
Can this be accomplished by creating one single API or 2 separate APIs are required?
I would expect this to be handled by a single request to a single resource.
Which HTTP method to use
This depends on the semantics of what is going on - we care about what the messages mean, rather than how the message handlers are implemented.
The key idea is the uniform interface constraint it REST; because we have a common understanding of what HTTP methods mean, general purpose connectors in the HTTP application can do useful work (for example, returning cached responses to a request without forwarding them to the origin server).
Thus, when trying to choose which HTTP method is appropriate, we can consider the implications the choice has on general purpose components (like web caches, browsers, crawlers, and so on).
GET announces that the meaning of the request is effectively read only; because of this, general purpose components know that they can dispatch this request at any time (for instance, a user agent might dispatch a GET request before the user decides to follow the link, to make the experience faster).
That's fine when you intend the request to provide the client with a copy of your search results, and the fact that you might end up making changes to server local state is just an implementation detail.
On the other hand, if the client is trying to edit the results of a particular search (but sometimes the server doesn't need to change anything), then GET isn't appropriate, and you should use POST.
A way to think about the difference is to consider what action you want to be taken when an intermediate cache holds a response from an earlier copy of "the same" request. If you want the cache to reuse the response, GET is the best; on the other hand, if you want the cache to throw away the old response (and possibly store the new one), then you should be using POST.
We are having java application which consumes salesforce partner.wsdl. We login to salesforce instance, then we get metadata for all the objects and we cache it. As salesforce objects become more we are seeing more time in getting metadata and cache it for first call.
What is the best way we can reduce this time, even if more objects are introduced in salesforce?
Is there any soap api call I can make to get metadata only for the object and its dependencies?
do we need to use only describeSobject to get these information.?
Cache the SF responses, flush the cache once a day, not with every request?
Look into REST API, either as complete replacement or just to take advantage of the "if-modified-since". This header works also per object.
Experiment with queries on EntityDefinition table to learn names of only the objects you're interested with (you probably don't care about apex classes, custom settings, *share and *history tables..). For example https://stackoverflow.com/a/64276053/313628
Then yes - describe just them, using REST or SOAP's describeSobject. If you have many objects - the network roundtrips might be an issue, you'd need to debug the app to see where it spends most time. Combat it by requesting up to 100 objects at a time, maybe issuing multiple requests (async processing? threads?) and combining results later.
Does it have to be partner WSDL? You could "preload" objects in your app using enterprise wsdl and combine some techniques listed above.
I have a Web Service and sqlite database. In this, web service will be used to store data inside database. Now I want to include sync functionality as - Whenever application starts at that time the database will start to load its table's data through web service.
Now after some time when I update my my web service the database will be updated accordingly. My question is that what are the best practices that I must follow for this update. Should I clear whole DB and start adding all rows again(I know this will take a lot time) but If not this then how do my database will add only particular data from the web service?
Thank you.
What I suggest you is:
store all your webservice content into db first when the app starts.
display your content on the screen from db only.
again when you need to refresh or recall your data just update the database.
Thus, you will always find all your fresh data into database.
Downloading and updating the entire server data will prove expensive. It will use more bandwidth and prove costly to your customer. Rather than pushing the entire load (even for minor update), send a delta. I will suggest you to maintain version information.
When application downloads the data from web service for a said version and store it successfully in the database, set the current updated version as well in the DB.
When app starts the next time, make a light weight header request to get just the version info from the server. The server should respond to this header request with the latest data version number.
Check the version from WS with the current application data version stored in the DB. If the server has an updated version, start the sync.
The version change information should be delta i.e.
For new version, server should send only the information that is changed since the version available with the device.
You server should have capability to calculate the delta between two versions.
Delta information will typically have sections like, new data, updated data, deleted data etc.
Based on this, the iOS app will make the necessary CRUD(Create, Read, Update and Delete) operations on the DB data.
Once the iOS app updates itself, then you can update the DB version to the latest received version from server. Until then let it remain dirty for proper error handling.
Hope that helps.
I would recommend you use RestKit's superb Core Data support.
By using RKEntityMapping you can map your remote objects from JSON or XML directly to Core Data entities in your database.
RestKit will automatically maintain the database for you, inserting and updating entries as appropriate from your web service. (In my experience, I've found deleting objects requires a tiny bit of extra work depending on how RESTful your web service is).
RestKit definitely does have a learning curve attached, but it's well worth it: having deployed it a couple of times now, is definitely a much better solution than manually writing your own SQLite/Web Service syncing code.
First you need to set all webservice content into your SQLITE.and what you want to display get that data from SQLITE.and perform opertaion into that sqlite table and when once all this done you need to changes made are saved it into webservice.
Follow this way.
I am very new to backbone.js (and MVC with javascript), and while reading several resources about backbone.js to adopt it in my project, I now have a question: how can I detect when multiple users(browsers) attempt to update? (and prevent it?)
My project is a tool for editing surveys/polls for users who want to create and distribute their own surveys. So far, my web app maintains a list of edit-commands fired by browser, sends it to the server, and the server does batch update.
What I did was, each survey maintains a version number and browser must request update with that version number, and if the request's version number does not match with the one in the server, the request fails and the user must reload his page (you know, implementing concurrent editing is not easy for everyone). Of course, when the browser's update was successful, it gets new version number from the server as ajax response, and one browser can request update to server only when its past update request is done.
Now, I am interested in RESTful APIs and MV* patterns, but having a hard time to solve this issue. What is the best / common approach for this?
There is a common trick instead of using versions, use TIMESTAMPS in your DB and then try to UPDATE WHERE timestamp = model.timestamp. If it returns zero result count - use appropriate HTTP 409 (conflict) response and ask the user to update the page in save() error callback. You can even use the local storage to merge changes, and compare the non-equivalent side by side.
I have a question regarding this topic.Like for Client Server Applications
1) is it necessary to load database directly into the Application.
Suppose if I have a DB in the back end and My application has to connect to that DB and display the results on the View for this do I need to Add DB into the Application directly.
2) can we access any DB or a File on the Remote server and show the required results.( with out adding that particular DB or A File into the application directly). How can we do this.
I saw a similar question in stackoverflow one answer was to use a PList, I am new to this.I am browsing the net but not able to get clear results. I lost many of my interviews because of this question.
Thanks,
1) is it necessary to load database
directly into the Application.
Suppose if I have a DB in the back end
and My application has to connect to
that DB and display the results on the
View for this do I need to Add DB into
the Application directly.
I'm not sure I understand this question. No, you don't need to load a database directly into a client in a client-server architecture. Normally, when I think of a design where a server has a database, I imagine there's some kind of way for the client to query the server for information. Perhaps it's making HTTP requests, which the server parses into a query, runs the query, and then returns the results (perhaps in XML form?).
2) can we access any DB or a File on
the Remote server and show the
required results.( with out adding
that particular DB or A File into the
application directly). How can we do
this.
Are you asking if it's possible, in general, to access a server database from a client? Yes, of course. (See above, re: HTTP Requests).
Any arbitrary file? That depends on how the server is set up. Again, HTTP is one protocol works that way; if you send an HTTP query like "GET someimage.png HTTP/1.0", the server could just be grabbing the whole file someimage.png and sending it back in the response. (Technically, it's not necessarily snarfing a whole file -- it could be creating that PNG dynamically since there's nothing in the HTTP protocol that says it must be sending an existing file -- but that's outside the scope of your question.)
I lost many of my interviews because
of this question.
Not to sound too snarky, but interviews are often won and lost not because you don't know the answer, but when you can't communicate effectively. You haven't phrased your question(s) here particularly well.