Develop Reference

Check if item in text file in JSON format Android Studio

I'm trying to check if config1 exists in a text file, I'm using Google's Gson library.
My JSON file :
{
"maps":{
"config2":{
"component1":"url1",
"component2":"url1",
"component3":"url1"
},
"config1":{
"component1":"url1",
"component2":"url1",
"component3":"url1"
}
}
}
Loading :
public void load() throws IOException {
File file = getContext().getFileStreamPath("jsonfile.txt");
FileInputStream fis = getContext().openFileInput("jsonfile.txt");
InputStreamReader isr = new InputStreamReader(fis);
BufferedReader bufferedReader = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
String line;
while ((line = bufferedReader.readLine()) != null) {
sb.append(line);
}
String json = sb.toString();
Gson gson = new Gson();
Data data = gson.fromJson(json, Data.class);
componentURL= data.getMap().get("config1").get("component1");
Saving :
Gson gson = new Gson();
webViewActivity.Data data = gson.fromJson(json, webViewActivity.Data.class);
Map<String, String> configTest = data.getMap().get("config1");
data.getMap().get("config1").put(component, itemUrl);
String json = gson.toJson(data);
String filename = "jsonfile.txt";
FileOutputStream outputStream;
try {
outputStream = openFileOutput(filename, Context.MODE_PRIVATE);
outputStream.write(json.getBytes());
outputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
Data class :
public class Data {
private Map<String, Map<String, String>> map;
public Data() {
}
public Data(Map<String, Map<String, String>> map) {
this.map = map;
}
public Map<String, Map<String, String>> getMap() {
return map;
}
public void setMap(Map<String, Map<String, String>> map) {
this.map = map;
}
}
My problem is that I need to create the file once and then check if the file exists, if it does I need to check if config1 exists if it doesn't I need to put config1 in the file.
But I can't check if config1 exists because I get :
java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.Map com.a.app.ui.app.appFragment$Data.getMap()
I check if it exists by doing :
Boolean configTest = data.getMap().containsKey("config1");
if(!configTest){}
How can I create the file and check the data without getting a NullPointerException ?

I think you should modify the way you're handling things.
First create POJO for Config1 each values as:
// file Config1.java
public class Config1
{
private String component1;
private String component2;
private String component3;
public String getComponent1 ()
{
return component1;
}
public void setComponent1 (String component1)
{
this.component1 = component1;
}
public String getComponent2 ()
{
return component2;
}
public void setComponent2 (String component2)
{
this.component2 = component2;
}
public String getComponent3 ()
{
return component3;
}
public void setComponent3 (String component3)
{
this.component3 = component3;
}
#Override
public String toString()
{
return "ClassPojo [component1 = "+component1+", component2 = "+component2+", component3 = "+component3+"]";
}
}
And then after that POJO for Config2
// file Config2.java
public class Config2
{
private String component1;
private String component2;
private String component3;
public String getComponent1 ()
{
return component1;
}
public void setComponent1 (String component1)
{
this.component1 = component1;
}
public String getComponent2 ()
{
return component2;
}
public void setComponent2 (String component2)
{
this.component2 = component2;
}
public String getComponent3 ()
{
return component3;
}
public void setComponent3 (String component3)
{
this.component3 = component3;
}
#Override
public String toString()
{
return "ClassPojo [component1 = "+component1+", component2 = "+component2+", component3 = "+component3+"]";
}
}
And then you need POJO for Maps
// file Maps.java
public class Maps
{
private Config2 config2;
private Config1 config1;
public Config2 getConfig2 ()
{
return config2;
}
public void setConfig2 (Config2 config2)
{
this.config2 = config2;
}
public Config1 getConfig1 ()
{
return config1;
}
public void setConfig1 (Config1 config1)
{
this.config1 = config1;
}
#Override
public String toString()
{
return "ClassPojo [config2 = "+config2+", config1 = "+config1+"]";
}
}
And finally the class which will wrap everything up MyJsonPojo. Though you can rename it to whatever you want.
// file MyJsonPojo.java
public class MyJsonPojo
{
private Maps maps;
public Maps getMaps ()
{
return maps;
}
public void setMaps (Maps maps)
{
this.maps = maps;
}
#Override
public String toString()
{
return "ClassPojo [maps = "+maps+"]";
}
}
Finally replace your code in the loadData() method as:
public void load() throws IOException {
File file = getContext().getFileStreamPath("jsonfile.txt");
FileInputStream fis = getContext().openFileInput("jsonfile.txt");
InputStreamReader isr = new InputStreamReader(fis);
BufferedReader bufferedReader = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
String line;
while ((line = bufferedReader.readLine()) != null) {
sb.append(line);
}
String json = sb.toString();
Gson gson = new Gson();
Data data = gson.fromJson(json, MyJsonPojo.class);
Maps maps = data.getMaps();
Config1 config1 = null;
if (maps != null) {
config1 = maps.getConfig1()
}
if (config1 != null) {
componentURL = config1.getComponent1();
}
}
For saving the values you can do this:
public void save() {
// set url here
Component1 component1 = new Component1();
component1.setComponent1(itemUrl);
// store it in maps
Maps maps = new Maps();
maps.setComponent1(component1);
// finally add it to the MyJsonPojo instance
MyJsonPojo myJsonPojo = new MyJsonPojo();
myJsonPojo.setMaps(maps);
Gson gson = new Gson();
String json = gson.toJson(maps);
String filename = "jsonfile.txt";
FileOutputStream outputStream;
try {
outputStream = openFileOutput(filename, Context.MODE_PRIVATE);
outputStream.write(json.getBytes());
outputStream.close();
} catch (Exception e) {
e.printStackTrace();
}
}
Please note that you may have to modify the save() code as per your structure because I am quite unsure about how you have handled what in the code. I have provided the basic implementation without much proof reading my code.

AsyncTask in android app for more than one REST endpoint

In Android is there a better way than using a single AsyncTask with a parameter to work out which REST endpoint to call?
e.g. I need to call:
www.test.com/api/room/id
www.test.com/api/room/id/booking
AsyncTask is designed for a single doInBackground() method that does a single thing, e.g. call:
www.test.com/api/room/id
I don't want to create multiple AsyncTasks instances, one for each REST endpoint.
The back end would use:
RoomClient = new RoomClient();
roomClient.getID()
roomClient.getBookingForRoom()
In Android it looks like I'd need
class RoomFromId extends AsyncTask
...
call www.test.com/api/room/id
class BookingForRoom extends AsyncTask
..
call www.test.com/api/room/id/booking
What I'd ideally like in the Android app is the idiom of writing a rest client that can call all REST endpoints in the background, without having to do each one in its own AsyncTask. I'd prefer to use what Android has, rather than a 3rd party library.

Create a generic Class extends from AsyncTask that return response in a generic type that extends from YourBaseModel (I called it M)
public class HttpRequest<M extends BaseModel> extends AsyncTask<Object, Integer, M> {
public enum RequestMethod {
GET("GET"), POST("POST");
private final String requestMethod;
RequestMethod(String requestMethod) {
this.requestMethod = requestMethod;
}
public String getValue() {
return requestMethod;
}
}
private Context context = null;
private String url;
private OnResponseCallback onResponseCallback;
private OnFailureCallback onFailureCallback;
private RequestMethod method;
private int statusCode;
private String message;
private Class<M> responseModel;
private Object body = null;
private String token;
private HttpRequest() {
}
#Override
protected M doInBackground(Object... voids) {
try {
HttpURLConnection connection = getHttpConnection();
connection.connect();
int statusCode = connection.getResponseCode();
if (connection.getResponseCode() / 100 != 2) {
this.statusCode = statusCode;
this.message = connection.getResponseMessage();
return JsonParser.getErrorBodyAs(responseModel, statusCode,
message);
}
InputStreamReader streamReader = new
InputStreamReader(connection.getInputStream());
return JsonParser.getErrorBodyAs(responseModel, statusCode,
convertInputStreamToString(streamReader));
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
private HttpURLConnection getHttpConnection() throws IOException {
URL url = new URL(this.url);
HttpURLConnection connection = (HttpURLConnection)
url.openConnection();
connection.setRequestMethod(method.getValue());
connection.setRequestProperty("Content-Type", "application/json");
connection.setRequestProperty("Authorization", "Bearer " + token);
connection.setReadTimeout(30000);
connection.setConnectTimeout(30000);
if (method == RequestMethod.POST) {
connection.setDoInput(true);
connection.setDoOutput(true);
if (body != null) {
OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
writer.write(new Gson().toJson(body));
writer.flush();
}
}
return connection;
}
#Override
protected void onPostExecute(M m) {
if (m == null) {
if ((message != null && !message.equals("") && statusCode != 0)) {
HttpException httpException = new HttpException(statusCode, message);
onFailureCallback.onFailure(httpException);
} else {
onFailureCallback.onFailure("unknown error");
}
} else {
onResponseCallback.onResponse(m);
}
}
public static String convertInputStreamToString(InputStreamReader inputStreamReader) throws IOException {
if (inputStreamReader == null) {
return "";
}
BufferedReader reader = new BufferedReader(inputStreamReader);
StringBuilder stringBuilder = new StringBuilder();
String inputLine;
String result;
while ((inputLine = reader.readLine()) != null) {
stringBuilder.append(inputLine);
}
reader.close();
inputStreamReader.close();
return stringBuilder.toString();
}
static public class Builder {
HttpRequest t = new HttpRequest();
public Builder setContext(Context context) {
t.context = context;
return this;
}
public Builder setUrl(String url) {
t.url = url;
return this;
}
public Builder setRequestMethod(RequestMethod method) {
t.method = method;
return this;
}
public Builder setBody(Object body) {
t.body = body;
return this;
}
public Builder setToken(String token) {
t.token = token;
return this;
}
public HttpRequest get() {
return t;
}
public HttpRequest run(Class<?> responseTypeClass,
OnResponseCallback onResponseCallback,
OnFailureCallback onFailureCallback) {
t.responseModel = responseTypeClass;
t.onResponseCallback = onResponseCallback;
t.onFailureCallback = onFailureCallback;
t.execute();
return t;
}
public Builder() {
}
}
}
You can use it like this:
HttpRequest.Builder builder = new HttpRequest.Builder();
builder.setContext(context)
.setRequestMethod(HttpRequest.RequestMethod.POST)
.setBody(body)
.setUrl("http://url")
.run(YourResponeModel.class, new OnResponseCallback() {
#Override
public void onResponse(Object response) {
},
new OnFailureCallback() {
#Override
public void onFailure(Object throwable) {
}
});

In the class you create that extends AsyncTask you can create a constructor and pass whatever you want/need.
In this case you can define a class ApiManager that extends AsyncTask and pass a constant that defines the method to call.
In that constructor you can save the variable to your ApiManager object and then check it in the doInBackground method.
So, to call the room/id you could do something like:
new ApiManager(ROOM_FROM_ID).execute(...
And to call the room/id/booking:
new ApiManager(BOOKING_FOR_ROOM).execute(...
And the ApiManager class should be something like:
class ApiManager extends AsyncTask... {
private int method;
public ApiManager(int method) {
this.method = method;
}
...
}

How do I get the parsed data using GSON

So I was following this tutorial and it has this method.
new AsyncTask<Void,Void,Void>(){
#Override
protected Void doInBackground(Void... voids) {
Reader reader=API.getData("http://beta.json-generator.com/api/json/get/DiIRBM4");
Type listType = new TypeToken<ArrayList<DoctorBean>>(){}.getType();
beanPostArrayList = new GsonBuilder().create().fromJson(reader, listType);
postList=new StringBuffer();
for(DoctorBean post: beanPostArrayList){
postList.append("\n heroName: "+post.getHeroName()+"\n realName: "+post.getRealName()+"\n\n");
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
Log.d("JSON Result ", postList.toString());
}
}.execute();
The Log Result would only show these values.
JSON Result:
heroName: null realName: null
heroName: null realName: null
heroName: null realName: null
This is my JSON data
[
{
"heroName": "Dr. Strange",
"realName": "Stephen Strange"
},
{
"heroName": "Spider-Man",
"realName": "Peter Paker"
},
{
"heroName": "Captain America",
"realName": "Stever Rogers"
}
]
This is my Data Model
import com.google.gson.annotations.SerializedName;
public class DoctorBean {
#SerializedName("heroName")
private String heroName;
#SerializedName("realName")
private String realName;
public DoctorBean(String heroName, String realName) {
this.heroName = heroName;
this.realName = realName;
}
public String getHeroName() {
return heroName;
}
public void setHeroName(String heroName) {
this.heroName = heroName;
}
public String getRealName() {
return realName;
}
public void setRealName(String realName) {
this.realName = realName;
}
}
And this is my API class
public class API {
private static Reader reader=null;
public static Reader getData(String SERVER_URL) {
try {
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(SERVER_URL);
HttpResponse response = httpClient.execute(httpPost);
StatusLine statusLine = response.getStatusLine();
if (statusLine.getStatusCode() == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
reader = new InputStreamReader(content);
} else {
// Log.e("error:", "Server responded with status code: "+ statusLine.getStatusCode());
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return reader;
}
}
I noticed that the log Result showed 3 rows, so I was thinking it was able to get the length of the array correctly. But as for the data, all was null.

As per your given tutorial,from this link response is as below:
[
{
"date":"11/8/2014",
"auther":"nirav kalola",
"description":"json object parsing using gson library is easy",
"post_name":"json object parsing"
},
{
"date":"12/8/2014",
"auther":"nirav kalola",
"description":"json array parsing using gson library",
"post_name":"json array parsing"
},
{
"date":"17/8/2014",
"auther":"nirav kalola",
"description":"store json file in assets folder and get data when required",
"post_name":"json parsing from assets folder"
}
]
So you need to try below POJO class for GSONBuilder. Replace your name with BeanPost.
import com.google.gson.annotations.SerializedName;
public class BeanPost {
#SerializedName("post_name")
private String post_name;
#SerializedName("auther")
private String auther;
#SerializedName("date")
private String date;
#SerializedName("description")
private String description;
public BeanPost(String post_name, String auther, String date, String description) {
this.post_name = post_name;
this.auther = auther;
this.date = date;
this.description = description;
}
public String getPost_name() {
return post_name;
}
public void setPost_name(String post_name) {
this.post_name = post_name;
}
public String getAuther() {
return auther;
}
public void setAuther(String auther) {
this.auther = auther;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
Try to create beanPostArrayList as above pojo class arraylist. And try your code and get appropriate fields from it.
I hope its helps you.

Try this.
Create an array from response :
DoctorBean[] doctorBeanArray = new Gson().fromJson(response, DoctorBean[].class); // Where response is your string response
Then create an ArrayList :
ArrayList<DoctorBean> doctorBeanList = new ArrayList<DoctorBean>(Arrays.asList(doctorBeanArray));

Receiving null output for tdd url test

When I run junit tests on my project I receive the following error when trying to test that my project can build a url correctly. I am not sure what I am doing wrong below is the trace of the failed test run as well as the distancematrixconnection class and test class. It is producing a blank output when trying to compile the url string.
org.junit.ComparisonFailure: expected:<[http://maps.googleapis.com/maps/api/distancematrix/xml?origins=albany&destinations=albany%20in&language=en-EN&sensor=false&language=en-EN&units=imperial]> but was:<[]>
at org.junit.Assert.assertEquals(Assert.java:115)
at org.junit.Assert.assertEquals(Assert.java:144)
at edu.bsu.cs222.gascalculator.tests.GoogleUrlTests.testAlbanyNYtoAlbanyINURL(GoogleUrlTests.java:26)
public class GoogleDistanceMatrixConnection
{
String startLocation;
String endLocation;
final String urlString = "http://maps.googleapis.com/maps/api/distancematrix/xml?origins=" + startLocation +"&destinations=" + endLocation +"&language=en-EN&sensor=false&language=en-EN&units=imperial";
private static String XMLFile;
public String makeXMLFile(String start, String end) throws IOException
{
startLocation = start;
endLocation = end;
URL url = new URL(urlString);
URLConnection connection = url.openConnection();
connection.connect();
BufferedReader reader = new BufferedReader( new InputStreamReader(
connection.getInputStream()));
for(String line = reader.readLine(); line != null; line =
reader.readLine())
{
setXMLFile(line);
}
return getXMLFile();
}
// public static void main(String[] args) throws IOException{
// GoogleDistanceMatrixConnection c = new GoogleDistanceMatrixConnection();
// }
public static String getXMLFile() {
return XMLFile;
}
public static void setXMLFile(String xMLFile) {
XMLFile = xMLFile;
}
public boolean doesPageExist() {
if(XMLFile == null)
return true;
else
return false;
}
}
public class GoogleUrlTests {
private GoogleDistanceMatrixConnection urlString = new GoogleDistanceMatrixConnection();
private String generatedUrl = "";
private String actualUrl = "";
#Test
public void testAlbanyNYtoAlbanyINURL() throws IOException {
generatedUrl = urlString.makeXMLFile("albany", "albany+in");
actualUrl = "http://maps.googleapis.com/maps/api/distancematrix/xml?origins=albany&destinations=albany%20in&language=en-EN&sensor=false&language=en-EN&units=imperial";
Assert.assertEquals(actualUrl, generatedUrl);
}
#Test
public void testLosAngelesToNewYorkURL() throws IOException {
generatedUrl = urlString.makeXMLFile("losangeles", "newyork");
actualUrl = "http://maps.googleapis.com/maps/api/distancematrix/xml?origins=losangeles&destinations=newyork&language=en-EN&sensor=false&language=en-EN&units=imperial";
Assert.assertEquals(actualUrl, generatedUrl);
}
}

Comparing your test cases and your code in makeXMLFile, I'm confused of what you are really trying to do here.
If you want to pass you tests, then I think this code will do that for you. You can use URLEncoder to properly encode your URL string.
public class GoogleDistanceMatrixConnection
{
public String makeXMLFile(String start, String end) throws IOException
{
return "http://maps.googleapis.com/maps/api/distancematrix/xml?origins=" + URLEncoder.encode(start) +"&destinations=" + URLEncoder.encode(end) +"&language=en-EN&sensor=false&language=en-EN&units=imperial";
}
}
Otherwise, you need to clarify your question.

Load very heavy stream with GSON

I'm trying to read a very heavy JSON (over than 6000 objects) and store them on a hash map to insert it into my database later.
But the problem is that I face with OOM and that's cause from my heavy JSON, however GSON library should rid me from this situation, but it is not !!!
Any ideas?
public Map<String,String> readJsonStream(InputStream in) throws IOException
{
JsonReader reader = new JsonReader(new InputStreamReader(in, "UTF-8"));
Map<String,String> contentMap = new HashMap<String,String>();
Gson mGson = new Gson();
contentMap = mGson.fromJson(reader, contentMap.getClass());
reader.close();
return contentMap;
}

From my experience, yes you can use google GSON to stream JSON data this is an example how to do it :
APIModel result = new APIModel();
try {
HttpResponse response;
HttpClient myClient = new DefaultHttpClient();
HttpPost myConnection = new HttpPost(APIParam.API_001_PRESENT(
serial_id, api_key));
try {
response = myClient.execute(myConnection);
Reader streamReader = new InputStreamReader(response
.getEntity().getContent());
JsonReader reader = new JsonReader(streamReader);
reader.beginObject();
while (reader.hasNext()) {
String name = reader.nextName();
if (name.equals("result")) {
if (reader.nextString() == "NG") {
result.setResult(Util.API_001_RESULT_NG);
break;
}
} else if (name.equals("items")) {
result = readItemsArray(reader);
} else {
reader.skipValue(); // avoid some unhandle events
}
}
reader.endObject();
reader.close();
} catch (Exception e) {
e.printStackTrace();
result.setResult(Util.API_001_RESULT_NG);
}
} catch (Exception e) {
e.printStackTrace();
result.setResult(Util.API_001_RESULT_NG);
}
readItemsArray function :
// read items array
private APIModel readItemsArray(JsonReader reader) throws IOException {
APIModel result = new APIModel();
String item_name, file_name, data;
result.setResult(Util.API_001_RESULT_OK);
reader.beginArray();
while (reader.hasNext()) {
item_name = "";
file_name = "";
data = "";
reader.beginObject();
while (reader.hasNext()) {
String name = reader.nextName();
if (name.equals("name")) {
item_name = reader.nextString();
} else if (name.equals("file")) {
file_name = reader.nextString();
} else if (name.equals("data")) {
data = reader.nextString();
} else {
reader.skipValue();
}
}
reader.endObject();
result.populateModel("null", item_name, file_name, data);
}
reader.endArray();
return result;
}
API Model Class :
public class APIModel {
private int result;
private String error_title;
private String error_message;
private ArrayList<String> type;
private ArrayList<String> item_name;
private ArrayList<String> file_name;
private ArrayList<String> data;
public APIModel() {
result = -1;
error_title = "";
error_message = "";
setType(new ArrayList<String>());
setItem_name(new ArrayList<String>());
setFile_name(new ArrayList<String>());
setData(new ArrayList<String>());
}
public void populateModel(String type, String item_name, String file_name, String data) {
this.type.add(type);
this.item_name.add(item_name);
this.file_name.add(file_name);
this.data.add(data);
}
public int getResult() {
return result;
}
public void setResult(int result) {
this.result = result;
}
public String getError_title() {
return error_title;
}
public void setError_title(String error_title) {
this.error_title = error_title;
}
public String getError_message() {
return error_message;
}
public void setError_message(String error_message) {
this.error_message = error_message;
}
public ArrayList<String> getType() {
return type;
}
public void setType(ArrayList<String> type) {
this.type = type;
}
public ArrayList<String> getItem_name() {
return item_name;
}
public void setItem_name(ArrayList<String> item_name) {
this.item_name = item_name;
}
public ArrayList<String> getFile_name() {
return file_name;
}
public void setFile_name(ArrayList<String> file_name) {
this.file_name = file_name;
}
public ArrayList<String> getData() {
return data;
}
public void setData(ArrayList<String> data) {
this.data = data;
}
}
before I use the streaming API from google GSON I also got OOM error because the JSON data I got is very big data (many images and sounds in Base64 encoding) but with GSON streaming I can overcome that error because it reads the data per token not all at once. And for Jackson JSON library I think it also have streaming API and how to use it almost same with my implementation with google GSON. I hope my answer can help you and if you have another question about my answer feel free to ask in the comment :)