Question

I’m trying to implement JSON array iterator with Jackson SAX parser (please, don’t ask why).
My app should work with huge files (up to 5 MiB), and that’s a problem.

That’s how I initialize JsonParser and call iterator creation.
I create InputStream initialized with JSON placed in \raw folder.

    private JsonArrayIterator getIterator(String needle) throws IOException
    {
        InputStream inputStream = getApplicationContext().getResources().openRawResource(R.raw.products);
        inputStream.mark(-1);

        try {
        JsonParser jsonParser = createJsonParser(inputStream);

        // Some unrelated code

        return new JsonArrayIterator(jsonParser);
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        inputStream.close();
    }

        return null;
    }

And here is my iterator class.

    private Object parseNextObject() throws IOException {
        // I'm not using ObjectMapper because of reasons
        HashMap nextObject = new HashMap();

        int objectsCount = 1;

        while (objectsCount > 0) {
            JsonToken currentToken = currentParser.nextValue();

            if(currentToken == JsonToken.START_OBJECT) {
                ++objectsCount;
            }
            else if(currentToken == JsonToken.END_OBJECT) {
                --objectsCount;
            }
            else if(currentToken == JsonToken.START_ARRAY) {
                String currentName = currentParser.getCurrentName();
                ArrayList list = new ArrayList(100);
                JsonArrayIterator it = new JsonArrayIterator(currentParser);

                while (it.hasNext()) {
                    list.add(it.next());
                }

                nextObject.put(currentName, list);
            }
            else {
                // Here exception is throwed
                nextObject.put(currentParser.getCurrentName(), currentParser.getText());
            }
        }

        currentParser.nextToken();  // Skip END_OBJECT
        return nextObject;
    }

It seem to work perfe… OH, WAIT.

I have 3 sections (named arrays) in some huge file.
It successfully parses first (a tiny one, under 1000 bytes). But I can’t parse next.

Next array has nested array with simple objects (like this):

    {
        "properties":[
            {
                "id":"1",
                "title":"\u0426\u0432\u0435\u0442",
                "values":[
                    {
                        "id":"1_2",
                        "title":"\u0427\u0435\u0440\u043d\u044b\u0439"
                    },
                    {
                        "id":"1_5005",
                        "title":"\u0417\u0435\u043b\u0435\u043d\u044b\u0439"
                    },
                    {
                        "id":"1_5006",
                        "title":"\u0421\u0435\u0440\u044b\u0439"
                    }
                ]
            }
        ]
    }

For one object in values I call nextObject.put. currentParser.getCurrentName() is runs successfully and returns correct string, but currentParser.getText() fails. It’s not a JSON problem: it perfectly being mapped on iOS. It’s not an object or iterator creation problem: I can delete that where parser throws exception, but it will fail in the same place.

Here is stack trace:

    05-15 21:57:28.617: ERROR/AndroidRuntime(14758): FATAL EXCEPTION: main
    java.lang.NullPointerException: asset
    at android.content.res.AssetManager.readAsset(Native Method)
    at android.content.res.AssetManager.access$700(AssetManager.java:36)
    at android.content.res.AssetManager$AssetInputStream.read(AssetManager.java:576)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.loadMore(UTF8StreamJsonParser.java:174)
    at com.fasterxml.jackson.core.base.ParserBase.loadMoreGuaranteed(ParserBase.java:425)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._finishString2(UTF8StreamJsonParser.java:1930)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser._finishString(UTF8StreamJsonParser.java:1911)
    at com.fasterxml.jackson.core.json.UTF8StreamJsonParser.getText(UTF8StreamJsonParser.java:276)
    at ru.studiomobile.JsonArrayIterator.parseNextObject(JsonArrayIterator.java:57)
    at ru.studiomobile.JsonArrayIterator.next(JsonArrayIterator.java:73)
    at ru.studiomobile.JsonArrayIterator.parseNextObject(JsonArrayIterator.java:47)
    at ru.studiomobile.JsonArrayIterator.next(JsonArrayIterator.java:73)
    at ru.studiomobile.MainActivity$2.onClick(MainActivity.java:81)
    at android.view.View.performClick(View.java:3127)
    at android.view.View$PerformClick.run(View.java:12025)
    at android.os.Handler.handleCallback(Handler.java:587)
    at android.os.Handler.dispatchMessage(Handler.java:92)
    at android.os.Looper.loop(Looper.java:132)
    at android.app.ActivityThread.main(ActivityThread.java:4126)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:491)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
    at dalvik.system.NativeStart.main(Native Method)

I noticed that there are something called Utf8StreamJsonParser. It has a field named _inputEnd equal 4000 (why 4000?). When other field, _inputPtr, become bigger it throw an exception. How do I can handle it? I tried to use BufferedInputStream with predefined block size instead of InputStream but it had no effect.

Update

Info about some lines

    47: list.add(it.next());  
    73: return parseNextObject();  
    75: e.printStackTrace();

Nothing special.

Answer 1

It was an obvious problem: I forgot that I close stream after creating parser…