I have this method:
public static Object parseStringToObject(String json) {
String Object = json;
Gson gson = new Gson();
Object objects = gson.fromJson(object, Object.class);
parseConfigFromObjectToString(object);
return objects;
}
And I want to parse a JSON with:
public static void addObject(String IP, Object addObject) {
try {
String json = sendPostRequest("http://" + IP + ":3000/config/add_Object", ConfigJSONParser.parseConfigFromObjectToString(addObject));
addObject = ConfigJSONParser.parseStringToObject(json);
} catch (Exception ex) {
ex.printStackTrace();
}
}
But I get an error message:
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException:
Expected BEGIN_OBJECT but was STRING at line 1 column 1
Even without seeing your JSON string you can tell from the error message that it is not the correct structure to be parsed into an instance of your class.
Gson is expecting your JSON string to begin with an object opening brace. e.g.
{
But the string you have passed to it starts with an open quotes
"
Invalid JSON from the server should always be an expected use case. A million things can go wrong during transmission. Gson is a bit tricky, because its error output will give you one problem, and the actual exception you catch will be of a different type.
With all that in mind, the proper fix on the client side is
try
{
gson.fromJSON(ad, Ad.class);
//...
}
catch (IllegalStateException | JsonSyntaxException exception)
{
//...
If you want to know why the JSON you received from the server is wrong, you can look inside your catch block at the exception. But even if it is your problem, it's not the client's responsibility to fix JSON it is receiving from the internet.
Either way, it is the client's responsibility to decide what to do when it gets bad JSON. Two possibilities are rejecting the JSON and doing nothing, and trying again.
If you are going to try again, I highly recommend setting a flag inside the try / catch block and then responding to that flag outside the try / catch block. Nested try / catch is likely how Gson got us into this mess with our stack trace and exceptions not matching up.
In other words, even though I'll admit it doesn't look very elegant, I would recommend
boolean failed = false;
try
{
gson.fromJSON(ad, Ad.class);
//...
}
catch (IllegalStateException | JsonSyntaxException exception)
{
failed = true;
//...
}
if (failed)
{
//...
I had a similar problem recently and found an interesting solution. Basically I needed to deserialize following nested JSON String into my POJO:
"{\"restaurant\":{\"id\":\"abc-012\",\"name\":\"good restaurant\",\"foodType\":\"American\",\"phoneNumber\":\"123-456-7890\",\"currency\":\"USD\",\"website\":\"website.com\",\"location\":{\"address\":{\"street\":\" Good Street\",\"city\":\"Good City\",\"state\":\"CA\",\"country\":\"USA\",\"postalCode\":\"12345\"},\"coordinates\":{\"latitude\":\"00.7904692\",\"longitude\":\"-000.4047208\"}},\"restaurantUser\":{\"firstName\":\"test\",\"lastName\":\"test\",\"email\":\"test#test.com\",\"title\":\"server\",\"phone\":\"0000000000\"}}}"
I ended up using regex to remove the open quotes from beginning and the end of JSON and then used apache.commons unescapeJava() method to unescape it. Basically passed the unclean JSON into following method to get back a cleansed one:
private String removeQuotesAndUnescape(String uncleanJson) {
String noQuotes = uncleanJson.replaceAll("^\"|\"$", "");
return StringEscapeUtils.unescapeJava(noQuotes);
}
then used Google GSON to parse it into my own Object:
MyObject myObject = new.Gson().fromJson(this.removeQuotesAndUnescape(uncleanJson));
In Retrofit2, When you want to send your parameters in raw you must use Scalars.
first add this in your gradle:
compile 'com.squareup.retrofit2:retrofit:2.3.0'
compile 'com.squareup.retrofit2:converter-gson:2.3.0'
compile 'com.squareup.retrofit2:converter-scalars:2.3.0'
public interface ApiInterface {
String URL_BASE = "http://10.157.102.22/rest/";
#Headers("Content-Type: application/json")
#POST("login")
Call<User> getUser(#Body String body);
}
my SampleActivity :
public class SampleActivity extends AppCompatActivity implements Callback<User> {
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sample);
Retrofit retrofit = new Retrofit.Builder()
.baseUrl(ApiInterface.URL_BASE)
.addConverterFactory(ScalarsConverterFactory.create())
.addConverterFactory(GsonConverterFactory.create())
.build();
ApiInterface apiInterface = retrofit.create(ApiInterface.class);
// prepare call in Retrofit 2.0
try {
JSONObject paramObject = new JSONObject();
paramObject.put("email", "sample#gmail.com");
paramObject.put("pass", "4384984938943");
Call<User> userCall = apiInterface.getUser(paramObject.toString());
userCall.enqueue(this);
} catch (JSONException e) {
e.printStackTrace();
}
}
#Override
public void onResponse(Call<User> call, Response<User> response) {
}
#Override
public void onFailure(Call<User> call, Throwable t) {
}
}
Reference: [How to POST raw whole JSON in the body of a Retrofit request?
I have come to share an solution. The error happened to me after forcing the notbook to hang up. possible solution clean preject.
Maybe your JSON Object is right,but the response that you received is not your valid data.Just like when you connect the invalid WiFi,you may received a strange response < html>.....< /html> that GSON can not parse.
you may need to do some try..catch.. for this strange response to avoid crash.
Make sure you have DESERIALIZED objects like DATE/DATETIME etc. If you are directly sending JSON without deserializing it then it can cause this problem.
In my situation, I have a "model", consist of several String parameters, with the exception of one: it is byte array byte[].
Some code snippet:
String response = args[0].toString();
Gson gson = new Gson();
BaseModel responseModel = gson.fromJson(response, BaseModel.class);
The last line above is when the
java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column
is triggered. Searching through the SO, I realised I need to have some form of Adapter to convert my BaseModel to and fro a JsonObject. Having mixed of String and byte[] in a model does complicate thing. Apparently, Gson don't really like the situation.
I end up making an Adapter to ensure byte[] is converted to Base64 format. Here is my Adapter class:
public class ByteArrayToBase64Adapter implements JsonSerializer<byte[]>, JsonDeserializer<byte[]> {
#Override
public byte[] deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
return Base64.decode(json.getAsString(), Base64.NO_WRAP);
}
#Override
public JsonElement serialize(byte[] src, Type typeOfSrc, JsonSerializationContext context) {
return new JsonPrimitive(Base64.encodeToString(src, Base64.NO_WRAP));
}
}
To convert JSONObject to model, I used the following:
Gson customGson = new GsonBuilder().registerTypeHierarchyAdapter(byte[].class, new ByteArrayToBase64Adapter()).create();
BaseModel responseModel = customGson.fromJson(response, BaseModel.class);
Similarly, to convert the model to JSONObject, I used the following:
Gson customGson = new GsonBuilder().registerTypeHierarchyAdapter(byte[].class, new ByteArrayToBase64Adapter()).create();
String responseJSon = customGson.toJson(response);
What the code is doing is basically to push the intended class/object (in this case, byte[] class) through the Adapter whenever it is encountered during the convertion to/fro JSONObject.
Don't use jsonObject.toString on a JSON object.
In my case, I am Returning JSON Object as
{"data":"","message":"Attendance Saved
Successfully..!!!","status":"success"}
Resolved by changing it as
{"data":{},"message":"Attendance Saved
Successfully..!!!","status":"success"}
Here data is a sub JsonObject and it should starts from { not ""
Don't forget to convert your object into Json first using Gson()
val fromUserJson = Gson().toJson(notificationRequest.fromUser)
Then you can easily convert it back into an object using this awesome library
val fromUser = Gson().fromJson(fromUserJson, User::class.java)
if your json format and variables are okay then check your database queries...even if data is saved in db correctly the actual problem might be in there...recheck your queries and try again.. Hope it helps
I had a case where I read from a handwritten json file. The json is perfect. However, this error occurred. So I write from a java object to json file, then read from that json file. things are fine. I could not see any difference between the handwritten json and the one from java object. Tried beyondCompare it sees no difference.
I finally noticed the two file sizes are slightly different, and I used winHex tool and detected extra stuff.
So the solution for my situation is, make copy of the good json file, paste content into it and use.
In my case, my custom http-client didn't support the gzip encoding. I was sending the "Accept-Encoding: gzip" header, and so the response was sent back as a gzip string and couldn't be decoded.
The solution was to not send that header.
I was making a POST request with some parameters using Retrofit in Android
WHAT I FACED:
The error I was getting in Android Studio logcat:
java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING
at line 2 column 1 path $
[but it was working fine with VOLLY library]
when I googled it...
you know[ Obviously json is expecting a OBJECT but...]
BUT when I changed my service to return a simple string [ like print_r("don't lose hope") ] or
Noting at all
It was getting printed fine in Postman
but in Android studio logcat, it was still SAME ERROR [
java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING
at line 2 column 1 path $
]
Hold up now, I am sending a simple message or not sending anything in response and still studio is
telling me "...Expected BEGIN_OBJECT but was STRING..."
SOMETHING IS WRONG
On 4th day:
I finally stopped for looking "QUICK SOLUTIONS" and REALLY READ some stack overflow questions
and articles carefully.
WHAT I GOT:
Logging interceptor
It will show you whatever data comes from your server[even eco messages] which are not shown in
Andorid studios logcat,
that way you can FIND THE PROBLEM.
What I found is I was sending data with #Body like-
#Headers("Content-Type: application/json")
#POST("CreateNewPost")
Call<Resp> createNewPost(#Body ParaModel paraModel);
but no parameter was reaching to server, everything was null [I found using Logging interceptor]
then I simply searched an article "how to make POST request using Retrofit"
here's one
SOLUTION:
from here I changed my method to:
#POST("CreateNewPost")
#FormUrlEncoded
Call<Resp> createNewPost(
#Field("user_id") Integer user_id,
#Field("user_name") String user_name,
#Field("description") String description,
#Field("tags") String tags);
and everything was fine.
CONCLUSION:
I don't understand why Retrofit gave this error
java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING
at line 2 column 1 path $
it doesn't make any sense at all.
So ALWAYS DEBUG in detail then find WHERE THINGS ARE LEAKING and then FIX.
This error solved for by replacing .toString method to .string on the response
toString => string (add in try{...code..}catche(IOException e))
below code is working for me
try {
MainModelResponse model;
Gson gson = new GsonBuilder().create();
if (response.code() == ConstantValues.SUCCESS_OK) {
model = gson.fromJson(response.body().string(), MainModelResponse.class);
} else {
model = gson.fromJson(response.errorBody().string(), MainModelResponse.class);
}
moduleData.postValue(model);
}catch (IllegalStateException | JsonSyntaxException | IOException exception){
exception.printStackTrace();
}
}
use a string begin & end with {}.
such as
final String jsStr = "{\"metric\":\"opentsdb_metric\",\"tags\":{\"testtag\":\"sunbotest\"},\"aggregateTags\":[],\"dps\":{\"1483399261\":18}}";
DataPoint dataPoint = new Gson().fromJson(jsStr, DataPoint.class);
this works for me.
In my case the object was all fine even the Json Validator was giving it a valid resposne but I was using Interface like this
#POST(NetworkConstants.REGISTER_USER)
Call<UserResponse> registerUser(
#Query("name") String name,
#Query("email") String email,
#Query("password") String password,
#Query("created_date") Long creationDate
);
Then I changed the code to
#FormUrlEncoded
#POST(NetworkConstants.REGISTER_USER)
Call<UserResponse> registerUser(
#Field("name") String name,
#Field("email") String email,
#Field("password") String password,
#Field("created_date") Long creationDate
);
And everything was resolved.
my problem not related to my codes
after copy some files from an other project got this issue
in the stack pointed to Gson library
in android studio 4.2.1 this problem not solved when I try file-> invalidate and restart
and
after restart in first time build got same error but in second build this problem solved
I don't understand why this happened
I was using an old version of retrofit library. So what I had to do was to change my code from this after upgrading it to com.squareup.retrofit2:retrofit:2.9.0:
#POST(AppConstants.UPLOAD_TRANSACTION_DETAIL)
fun postPremiumAppTransactionDetail(
#Query("name") planName:String,
#Query("amount") amount:String,
#Query("user_id") userId: String,
#Query("sub_id") planId: String,
#Query("folder") description:String,
#Query("payment_type") paymentType:String):
Call<TransactionResponseModel>
To this:
#FormUrlEncoded
#POST(AppConstants.UPLOAD_TRANSACTION_DETAIL)
fun postPremiumAppTransactionDetail(
#Field("name") planName:String,
#Field("amount") amount:String,
#Field("user_id") userId: String,
#Field("sub_id") planId: String,
#Field("folder") description:String,
#Field("payment_type") paymentType:String):
Call<TransactionResponseModel>
For me it turned out that I was trying to deserialize to an object that used java.time.ZonedDateTime for one of the properties. It worked as soon as I changed it to a java.util.Date instead.
I'm using Jackson with DataBind library to parse json and map it java object. I'm also using Gson on other project where perf is less required.
On 17 Feb, LoganSquare library is first released, promising 4-10 time faster parsing as Gson.
What advantages as LoganSquare than Gson/Jackson didn't have ?
Pros and cons ?
Do you have benchmarks in production application ?
Is is stable enough for a production app?
I understand it can be a primarly opinion base question, so be as technic and specific as possible and base your answer on real data.
Well to be clear if you are releasing your app to devices with ART you will have a huge speed advantage trough parsing.
so i will explain my experience with logansquare so far.
pros :
Easy to use: with Gson you have to use Type for parsing json array to a object list, in loganSquare it is so easy as LoganSquare.parseList()
Faster : in any device (test it yourself) it is slightly faster.
FasterER: in ART devices its speed gap is really giant see their benchmark
RetroFit friendly: yeah it plays well with retrofit.
cons :
NO REALM DB : I could't make it run with Realm db so far(I didnt tried hard yet)
Custom Type Adapter :Couldn't find a type adapter or something similar so far but I am not sure.
see their benchmark here
and here is my poor benchmark results(it is not a proper benchmark but it is something):
Emulator nexus 5, with DalvikVM,4.2 jellybean
Benchmarks
Parsed model
import com.bluelinelabs.logansquare.annotation.JsonField;
import com.bluelinelabs.logansquare.annotation.JsonObject;
import com.google.gson.annotations.SerializedName;
/**
* Created by Ercan on 6/26/2015.
*/
#JsonObject(serializeNullCollectionElements = true ,serializeNullObjects = true)
public class Village {
#SerializedName("IdVillage")
#JsonField(name ="IdVillage")
String tbsVillageId;
#SerializedName("TBS_VillageId")
#JsonField(name ="TBS_VillageId")
String townRefId;
#SerializedName("VillageName")
#JsonField(name ="VillageName")
String villageName;
#SerializedName("Status")
#JsonField(name ="Status")
String status;
#SerializedName("DateInserted")
#JsonField(name ="DateInserted")
String dateInserted;
#SerializedName("DateLastModified")
#JsonField(name ="DateLastModified")
String datelastModified;
public String getTbsVillageId() {
return tbsVillageId;
}
public void setTbsVillageId(String tbsVillageId) {
this.tbsVillageId = tbsVillageId;
}
public String getTownRefId() {
return townRefId;
}
public void setTownRefId(String townRefId) {
this.townRefId = townRefId;
}
public String getVillageName() {
return villageName;
}
public void setVillageName(String villageName) {
this.villageName = villageName;
}
public String getStatus() {
return status;
}
public void setStatus(String status) {
this.status = status;
}
public String getDateInserted() {
return dateInserted;
}
public void setDateInserted(String dateInserted) {
this.dateInserted = dateInserted;
}
public String getDatelastModified() {
return datelastModified;
}
public void setDatelastModified(String datelastModified) {
this.datelastModified = datelastModified;
}
}
I have run LoganSquare Benchmark project on my Nexus 5 device with Android 6.0.1 and here is the result:
Also, after a short time spend with the lib, here are my pros and cons:
Pros
is really fast in both parsing and serialization
small library size
handy methods for lists parsing and serialization
useful converters
compile-time errors instead of run-time only
Cons
not much of a documentation, also not many questions & answers on
StackOverflow :)
not many types supported
only String keys supported in Map collections
I wrote an example project to see how LoganSquare works and also a blog post, so take a look there for more information.
response.body() it is string json response
// MovieData it is a model Class
MovieData movieData=LoganSquare.parse(response.body(),MovieData.class);
Log.d("onResponse: ",movieData.getTitle());
The library is not updated since 4+ years.
It was working mostly fine till now but according to my knowledge it will stop working after gradle 5.
I am sending string messages from a .NET application via Bluetooth to an Android Java Application.
Using Newtonsoft JSON.NET I serialize my messages in JSON and send them as-is to the Android application that attempts to convert them back with Gson.
This is my Message class:
public final class Message {
private final String content;
private final String address;
private final long timeStamp;
private boolean isRead;
private boolean isSent;
public Message(final String content, final String address, final long timeStamp,
final boolean isSent, final boolean isRead) {
this.content = content;
this.address = address;
this.timeStamp = timeStamp;
this.isSent = isSent;
this.isRead = isRead;
}
public final String getContent() {
return this.content;
}
public final String getAddress() {
return this.address;
}
public final boolean isRead() {
return this.isRead;
}
public final boolean isSent() {
return this.isSent;
}
public final long getTimeStamp() {
return this.timeStamp;
}
}
As you can see, nothing to fancy here. The .NET version of this class is rather similar, where instead of getters, there are properties in pascal case per as C# coding conventions.
I managed to solve the case-sensitiveness of Gson via
GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE);
Now my problem is straigforward : the following line will fail and throw a com.google.gson.JsonSyntaxException: java.io.EOFException whenever I send a message containing "non-english" letters.
final Message msg = gson.fromJson(message, Message.class);
where message is a non-null not-empty String
Exemple : la vie est très belle (life is very beautiful)
The "intruder" here is the french accent è.
So here is the logcat of the stacktrace :
om.google.gson.JsonSyntaxException: java.io.EOFException: End of input at line 1 column 94
at com.google.gson.Gson.fromJson(Gson.java:820)
at com.google.gson.Gson.fromJson(Gson.java:775)
at com.google.gson.Gson.fromJson(Gson.java:724)
at com.google.gson.Gson.fromJson(Gson.java:696)
at mackosoft.almightymessage.MainActivity$10.onNewMessageArrived(MainActivity.java:257)
at mackosoft.almightymessage.bluetooth.module.events.BluetoothEventManager.notifyNewMessageArrived(BluetoothEventManager.java:77)
at mackosoft.almightymessage.bluetooth.module.BluetoothManager$2.run(BluetoothManager.java:180)
at java.lang.Thread.run(Thread.java:818)
Caused by: java.io.EOFException: End of input at line 1 column 94
at com.google.gson.stream.JsonReader.nextNonWhitespace(JsonReader.java:1414)
at com.google.gson.stream.JsonReader.doPeek(JsonReader.java:486)
at com.google.gson.stream.JsonReader.hasNext(JsonReader.java:418)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:190)
at com.google.gson.Gson.fromJson(Gson.java:810)
at com.google.gson.Gson.fromJson(Gson.java:775)
at com.google.gson.Gson.fromJson(Gson.java:724)
at com.google.gson.Gson.fromJson(Gson.java:696)
at mackosoft.almightymessage.MainActivity$10.onNewMessageArrived(MainActivity.java:257)
at mackosoft.almightymessage.bluetooth.module.events.BluetoothEventManager.notifyNewMessageArrived(BluetoothEventManager.java:77)
at mackosoft.almightymessage.bluetooth.module.BluetoothManager$2.run(BluetoothManager.java:180)
at java.lang.Thread.run(Thread.java:818)
Note: I made sure all data transfered over Bluetooth back & forth between my .NET app and Android app is encoded in UTF-8.
Note bis : I tested multiple text messages. All of them worked except for the one with foreign letters !
I found the solution.
When looking at the JSON received by the Android application via the debugger on Android Studio, I could not see something wrong : all letters were correct, not strange or missing characters.
So I manually copied the JSON and created a quick Java Application with Gson to see if it would fail with the same kind of JSON content.
Guess what ? It worked ! So I thought, knowing that Java strings are by default always encoded in UTF-8, perhaps the JSON I actually send from the .NET application via Bluetooth is not ?
My .NET Windows Store App uses a DataWriter to write data over an OutputStream.
I was using DataWriter.WriteString(string json). I changed it for DataWriter.WriteBytes(System.Text.Encoding.UTF8.GetBytes(string json)) and it worked !
So that's it, problem solved !
It is strange that DataWriter.WriteString does not tell wich encoding it uses and if I can change it. The document only states : Writes a string value to the output stream.
I am new to android developing, my website returns posts with following format in json:
post= {
'artist':'xxxx',
'title':'xxxx',
'text':'xxxx',
'url':'http://xxxx'
}
I know something about receiving a file from the net and saving it to a SD card, but I want to do it on fly, parse it and show in on some text view, can you please give me some simple code for this?
I tried searching but I can't find a good tutorial for this, so this is the last place I'm coming to solve my problem.
A good framework for parsing XML is Google's GSON.
Basically you could deserialize your XML as follows (import statements left out):
public class Post {
private String artist, title, text, url;
public Post() {} // No args constructor.
}
public class Main {
public static void main(String[] args) {
Gson gson = new Gson();
String jsonString = readFromNetwork(); // Read JSON from network...
Post post = gson.fromJson(jsonString, Post.class);
// Use post instance populated with your JSON data.
}
}
Read more in GSON's user guide.