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Recommended way / order to read data from a webservice, parse that data and insert it in a SQLite db

由 此生再无相见时 提交于 2019-11-26 02:20:31
mmlooloo

I decided to come to you because you're the experts

first i am not expert and also i am not knowledgeable you can find more expert people than me but this is my opinion hope to give you some help.

first of all forget to use AsyncTask to download because it must be used for short background jobs not like yours i think the amount of file you want to download is pretty large.(i think so)

check downloadmanager of google to see how it works it may help you.

http://developer.android.com/reference/android/app/DownloadManager.html

http://blog.vogella.com/2011/06/14/android-downloadmanager-example/

if you want to use service use unbound service because you do not want the service to be destroyed by android or user when the user close the apps do you? i think you want to get your data any way.

in order to be efficient i recommend these steps:

a. Read a restful service to retrieve the Customers Data

b. when you get Customer data do :

  • create another service or thread to Read a restful service to retrieve the Articles Data

  • Parse the response to Json Objects on your old service or thread

now you have 2 services or threads that run concurrently so follow the steps that obvious insert parse and so, on each service or thread.

why do not i combine a and d? because i think user do not like to wait much time behind download progress bar.

in order to insert your data to database use transaction and i recommend you use:

http://greendao-orm.com/

it is more efficient ORM than others for database and you get free from db implementation.

If the activity that started the service is explicitly cancelled or is hidden by another activity, the service has to have a way to let the user know that the process has finished. How could I implement that?

use notification:

http://developer.android.com/training/notify-user/build-notification.html

http://www.tutorialspoint.com/android/android_notifications.htm

http://www.vogella.com/tutorials/AndroidNotifications/article.html

While all this long processing is taking place in the background I'll have to show some sort of indicator (a ProgressDialog) This is the reason I opted for using a Bound Service`

how can I update the UI from an Unbound Service?`

Use a LocalBroadCastManager, or in general BroadCastReciever

Android update activity UI from service

In J2ME I've done something similar, and when I put something like the 6 steps I mentioned above all of them are executed sequentially, that is , one after the other. Is it the same in Android?

this is depends on your steps, if you follow my idea you run concurrently and if you run your idea you will run sequentially.

Good Luck.

I did something like yours.

In first step I get data from webservice in HTTP GET of POST method using AsyncTask like this: 

public class GetService extends AsyncTask<String, String, String> {

private String mRestUrl;
private ServiceCallback mCallback;
private final HttpClient Client = new DefaultHttpClient();
private String Content;
private String url;
private String Error;
private ProgressDialog barProgressDialog;
private ProgressDialog Dialog;

public GetService(String restUrl, ServiceCallback callback) {
    this.mRestUrl = restUrl;
    this.mCallback = callback;
    this.url = restUrl;
    Dialog = new ProgressDialog(AppContext.CurrentContext);
}

@Override
protected void onPreExecute() {
    super.onPreExecute();
}

@Override
protected String doInBackground(String... urls) {

    Content = null;

    BufferedReader reader = null;

    try {

        StringBuilder builder = new StringBuilder();

        HttpClient client = new DefaultHttpClient();

        HttpGet get = new HttpGet(this.url);

        HttpResponse response = client.execute(get);
        int status = response.getStatusLine().getStatusCode();

        if (status == 200) // sucess
        {
            HttpEntity e = response.getEntity();
            // String data = EntityUtils.toString(e);
            InputStream content = e.getContent();
            reader = new BufferedReader(new InputStreamReader(content));

            String line;
            while ((line = reader.readLine()) != null) {
                builder.append(line);
            }

            Content = builder.toString();
        } else if (status == 401) {
            return "-Auth Failed Error Code 400";
        } else {
            return "-Error Code: " + status;
        }

    } catch (Exception ex) {
        Error = ex.getMessage();
    } finally {
        Dialog.dismiss();
        try {
            reader.close();
        }

        catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    return Content;

}

@Override
protected void onPostExecute(String result) {
    try {
        GetService.this.get(20000, TimeUnit.MILLISECONDS);
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (ExecutionException e) {
        e.printStackTrace();
    } catch (TimeoutException e) {
        e.printStackTrace();
    }
    mCallback.onTaskComplete(result);
    super.onPostExecute(result);
}
}

and my callback class is:
public abstract class ServiceCallback{

public abstract void onTaskComplete(String result);
}

I call AsyncTask in my code everywhere I want to get data from webservice: 

 new GetService(url, new ServiceCallback() {
                public void onTaskComplete(String response) {
                       // Parse Response of WebService
                }
            }).execute();

In second step I Parse response of WebService in onTaskComplete method using json helper Libraries like Gson or Jackson. for example in jackson: 

List<YourClass> data = new ObjectMapper()
                .readValue(
                        response,
                        new TypeReference<List<YourClass>>() {
                        });

At the end I store Data in Database. for connecting to DB I Prefer to use GreenDao as my ORM. In this way storin data in DB can be done in one line code like this: 

//after converting json to object
YourORMDaoClass.insertOrReplaceInTx(data);

To Use GreenDao ORM this link is very helpful;

Do you think the order in which I'm executing all the 6 steps of the process described is correct / efficient? If you had to make some changes, what would you change?

It depends. If this data is related and cannot exists without each other then you should change the order like this:

a. Read a restful service to retrieve the Customers Data
b. Parse the response to Json Objects
d. Read a restful service to retrieve the Articles Data
e. Parse the response to Json Objects
c. Insert those customers to the Customers Table
f. Insert those articles to the Articles Table

Steps c and f should be combined in transaction.

Otherwise, the order does not matter. If data is not related then separating these processes and running them in sequence might be a good idea.

If the activity that started the service is explicitly cancelled or is hidden by another activity, the service has to have a way to let the user know that the process has finished. How could I implement that?

I suggest to start with implementation of the IntentService class. It handles for you background thread and works like a queue of events where single Intent delivers a data to process.

Actually you could implement one of the patterns presented by Google on one of their IO conferences. I have implemented an option A shown on the video. It works for me really well. The trick is that using ContentProvider from the background automatically updates UI which listen for changes thanks to CursorAdapter.

To update UI progress you can use LocalBroadcastManager or event bus libraries e.g. Otto.

You can also extend your tables and store status and progress, updating tables would automatically update UI as well, just keep in mind that these updates should be rare e.g. control in the service background how often table progress is updated calculating the progress first and checking with service local variable if it's changed.

In case your app is in the background, post status notification. User should be able to navigate back to your app clicking on the notification.

Is it possible/ recommended to write to the SQLite DB within the service? Is it the same as when I do so within an activity?

You can do it within the Service. Actually, if you follow the pattern I have mentioned above, you would do it in the Processor tier on the background service thread.

In J2ME I've done something similar, and when I put something like the 6 steps I mentioned above all of them are executed sequentially, that is , one after the other. Is it the same in Android?

It's completely up to you how communication with the server will work. If you decide to use IntentService class then it will work in a sequence which is not a bad idea on Android. On the other hand you may extend Service class directly and implement own thread executor with a thread pool. You can also have dedicated IntentService classes for unrelated operations.

I also recommend to read lessons:

If you don't want to play directly with HTTP connection implementation then consider using Retrofit or Volley

If you just need JSON parsers then these 2 are the best:

标签
android
android-service
android-sqlite
android-webservice
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