I ultimately want to create inverted indexes using my JSON dataset. I know how to parse through one JSON object but how can I iterate through many? Here is what I have working:
File1:
{
"doc_id": "2324jos",
"screen_name": "twitter_user101",
"tweet_text": "Its a beautiful day to be productive",
"hashtags": "[]",
"links": "[]",
"place_type": "city",
"place_name": "Evergreen Park",
"created_at": "2019-02-08 22:24:03"
}
My code:
public class ParseJson {
public static void main(String[] args) throws Exception {
// this is the key object to convert JSON to Java
Tweet tweet;
ObjectMapper mapper = new ObjectMapper();
try {
File json = new File("test.json");
tweet = mapper.readValue(json, Tweet.class);
System.out.println("Java object created from JSON String :");
System.out.println(tweet);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
public class Tweet {
public String doc_id;
public String screen_name;
public String tweet_text;
public String hashtags;
public String links;
public String place_type;
public String place_name;
public String created_at;
public Tweet() {
}
public Tweet(String doc_id, String screen_name, String tweet_text, String hashtags, String links, String place_type, String place_name, String created_at) {
this.doc_id = doc_id;
this.screen_name = screen_name;
this.tweet_text = tweet_text;
this.hashtags = hashtags;
this.links = links;
this.place_name = place_name;
this.place_type = place_type;
this.created_at = created_at;
}
#Override
public String toString() {
return doc_id + screen_name + tweet_text;
}
}
Now, I want to iterate through this JSON file which has 2 JSON objects in an array:
File2:
[
{
"doc_id": "2324jos",
"screen_name": "b'LIBBYRULZ'",
"tweet_text": "#ABC ya'll be lying",
"hashtags": "[]",
"links": "[]",
"place_type": "city",
"place_name": "Evergreen Park",
"created_at": "2019-02-08 22:24:03"
},
{
"doc_id": "8982hol",
"screen_name": "b'eddylee_1'",
"tweet_text": "Hungry for money",
"hashtags": "[]",
"links": "[]",
"place_type": "city",
"place_name": "Manhattan",
"created_at": "2/7/2019 17:01"
}
]
How can I adjust my above code using Jackson to do so where the doc_id is the unique key? I want to be able to return all the data in each JSON object for each doc_id.
To parse an array of JSON objects using Jackson:
Tweet[] tweets = mapper.readValue(json, Tweet[].class);
should do the trick. See below:
public class ParseJson {
public static void main(String[] args) throws Exception {
Tweet[] tweets;
ObjectMapper mapper = new ObjectMapper();
try {
File json = new File("test.json");
tweets = mapper.readValue(json, Tweet[].class);
System.out.println("Java object created from JSON String :");
Arrays.asList(tweets).forEach(System.out::println); // Prints each element in the array
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
You could try to put it in a list so you can iterate on it:
List<Tweet> data = mapper.readValue(json, new TypeReference<List<Tweet>>(){});
I would suggest using the TypeFactory to create a CollectionType and use it to parse the JSON as List<Tweet>.
CollectionType tweetListType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, Tweet.class);
List<Tweet> tweets = mapper.readValue(json, tweetListType);
tweets.forEach(System.out::println);
Here is the complete example you shared:
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.type.CollectionType;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class ParseJson {
public static void main(String[] args) {
// this is the key object to convert JSON to Java
ObjectMapper mapper = new ObjectMapper();
try {
File json = new File("test.json");
CollectionType tweetListType = mapper.getTypeFactory().constructCollectionType(ArrayList.class, Tweet.class);
List<Tweet> tweets = mapper.readValue(json, tweetListType);
System.out.println("Java objects created from JSON String:");
tweets.forEach(System.out::println);
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
Related
Hi i am getting Json Response Body from a get request in REST request.
{
"outputData": {
"data": {
"leaveList": [
{
"leaveTypeID": 1,
"leaveBalance": 2
},
{
"leaveTypeID": 2,
"leaveBalance": 9
}
]
}
}
}
I want to get leaveBalance of leaveType 2.
Index of the leaveTypeID keep changing.
Thanks
You can do it by iterating through leaveList JsonArray.
Response response = given()
.when()
.get("URL")
.then()
.extract()
.response();
int leaveTypeId = 2; // You can change this get the required leaveBalance
int leaveBalance = 0;
JSONObject responseObject = new org.json.JSONObject(response.body().asString());
JSONObject object1 = responseObject.getJSONObject("outputData");
JSONObject dataObject = object1.getJSONObject("data");
JSONArray jsonArray = dataObject.getJSONArray("leaveList");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
if (jsonObject.get("leaveTypeID").equals(leaveTypeId)) {
leaveBalance = Integer.parseInt(jsonObject.get("leaveBalance").toString());
}
}
System.out.println("leaveBalance = " + leaveBalance);
This will print;
leaveBalance = 9
You can assign values dynamically to leaveTypeId and get the leaveBalance you want.
You can use jackson-databind library for converting json string to object. I used maven package manager to add into my project.
I suggest the following solution to provide a well structure in your project. In my solution I used classes to keep json values. You can use Json To Pojo to generate objects from json string.
The output : 9
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.List;
public class RestAssuredDemo {
public static void main(String[] args) {
String json = """
{
"outputData": {
"data": {
"leaveList": [
{
"leaveTypeID": 1,
"leaveBalance": 2
},
{
"leaveTypeID": 2,
"leaveBalance": 9
}
]
}
}
}
""";
ObjectMapper om = new ObjectMapper();
Root root = null;
try {
root = om.readValue(json, new TypeReference<Root>() {});
for (LeaveList leave: root.outputData.data.leaveList) {
if(leave.leaveTypeID == 2) {
System.out.println(leave.leaveBalance);
}
}
} catch (JsonProcessingException e) {
e.printStackTrace();
}
}
public static class LeaveList{
public int leaveTypeID;
public int leaveBalance;
}
public static class Data{
public List<LeaveList> leaveList;
}
public static class OutputData{
public Data data;
}
public static class Root{
public OutputData outputData;
}
}
GroovyPath = "outputData.data.leaveList.find{it.leaveTypeID==2}.leaveBalance"
String leaveBalance = response.extract().jsonPath().getString("outputData.data.leaveList.find{it.leaveTypeID==2}.leaveBalance");
it will provide you the leave balance of where leaveTypeID is 2 index of this object can be anywhere this will work.
I try to generate csv file from json type data. These are my json test data.
{
"realtime_start":"2020-09-25",
"realtime_end":"2020-09-25",,
"units": "Percent",
"seriess": [
{
"name": "James",
"age": 29,
"house": "CA"
},
{
"name": "Jina",
"age": 39,
"house": "MA",
"notes": "Million tonne punch"
},
}
The problem is json array type "seriess" does not contain "notes" node in all every nodes.
I made the below java codes to change this json data to csv file with header columns
JSONObject json = getJsonFileFromURL(...)
JSONArray docsArray = json.getJSONArray("seriess");
docsArray.put(json.get("realtime_start"));
docsArray.put(json.get("realtime_end"));
docsArray.put(json.get("units"));
JsonNode jsonTree = new ObjectMapper().readTree(docsArray.toString());
Builder csvSchemaBuilder = CsvSchema.builder();
for(JsonNode node : jsonTree) {
node.fieldNames().forEachRemaining(fieldName -> {csvSchemaBuilder.addColumn(fieldName);} );
}
CsvSchema csvSchema = csvSchemaBuilder.build().withHeader();
CsvMapper csvMapper = new CsvMapper();
csvMapper.writerFor(JsonNode.class).with(csvSchema).writeValue(new File("test.csv"), jsonTree);
But the incorrect results are shown like below,
realtime_start,realtime_end,units,names,age,house,realtime_start,realtime_end,units,names,age,house,notes, realtime_start,.....
The generated header columns does not contain distinct values. The header columns are added in duplicate. How can I generate the distinct header like below
realtime_start,realtime_end,units,names,age,house, notes
Any idea?
Update Part
I try to extract data from the FRED (FEDERAL RESERVE BANK OF ST. LOUIS). FRED provide simple and convenient Python api like below,
from fredapi import Fred
import pandas as pd
fred = Fred(api_key='abcdefghijklmnopqrstuvwxyz0123456789')
data_unemploy = fred.search('Unemployment Rate in California')
data_unemploy.to_csv("test_unemploy.csv")
But the java apis are deprecated, so I have to develop simple Java api which convert json values to csv file. I found the below Java codes with googling
JSONObject json = getJsonFileFromURL("https://api.stlouisfed.org/fred/series/search?search_text=Unemployment+Rate+in+California&api_key=abcdefghijklmnopqrstuvwxyz0123456789&file_type=json");
JSONArray docsArray = json.getJSONArray("seriess");
docsArray.put(json.get("realtime_start"));
docsArray.put(json.get("realtime_end"));
JsonNode jsonTree = new ObjectMapper().readTree(docsArray.toString());
JsonNode firstObject = jsonTree.elements().next(); // I am struggling with this line
firstObject.fieldNames().forEachRemaining(fieldName -> {csvSchemaBuilder.addColumn(fieldName);} );
CsvSchema csvSchema = csvSchemaBuilder.build().withHeader();
CsvMapper csvMapper = new CsvMapper();
csvMapper.writerFor(JsonNode.class).with(csvSchema).writeValue(new File("test.csv"), jsonTree);
To extract columns from json data JsonNode firstObject = jsonTree.elements().next(); return the first json node. But this line does not return notes column. because the first line does not contain the notes key value.
So I change this code line to following lines
for(JsonNode node : jsonTree) {
node.fieldNames().forEachRemaining(fieldName -> {
csvSchemaBuilder.addColumn(fieldName);
} );
}
But these lines throws the results which I do not expect. The repeated duplicated columns like below
realtime_start,realtime_end,units,names,age,house,realtime_start,realtime_end,units,names,age,house,notes, realtime_start,.....
I am totally stuck with this part.
Most probably it is easiest to write a bin type class like below :
public class CsvVo {
private String realtime_start;
private String realtime_end;
private String units;
private String name;
private String age;
private String house;
private String notes;
public void setRealtime_start(String realtime_start) {
this.realtime_start = realtime_start;
}
//Other getters and Setters
Then you can Write :
public class ConvertJsonToCSVTest {
public static void main(String[] args) throws JSONException {
String jsonArrayString = "{\n" +
"\t\"realtime_start\": \"2020-09-25\",\n" +
"\t\"realtime_end\": \"2020-09-25\",\n" +
"\t\"units\": \"Percent\",\n" +
"\t\"seriess\": [{\n" +
"\t\t\t\"name\": \"James\",\n" +
"\t\t\t\"age\": 29,\n" +
"\t\t\t\"house\": \"CA\"\n" +
"\t\t},\n" +
"\t\t{\n" +
"\t\t\t\"name\": \"Jina\",\n" +
"\t\t\t\"age\": 39,\n" +
"\t\t\t\"house\": \"MA\",\n" +
"\t\t\t\"notes\": \"Million tonne punch\"\n" +
"\t\t}\n" +
"\t]\n" +
"}";
JSONObject inJson;
List<CsvVo> list = new ArrayList<>();
inJson = new JSONObject(jsonArrayString);
JSONArray inJsonSeries = inJson.getJSONArray("seriess");
for (int i = 0, size = inJsonSeries.length(); i < size; i++){
CsvVo line = new CsvVo();
line.setRealtime_start(inJson.get("realtime_start").toString());
line.setRealtime_end(inJson.get("realtime_end").toString());
line.setUnits(inJson.get("units").toString());
JSONObject o = (JSONObject)inJsonSeries.get(i);
line.setName(o.get("name").toString());
line.setAge(o.get("age").toString());
line.setHouse(o.get("house").toString());
try {
line.setNotes(o.get("notes").toString());
}catch (JSONException e){
line.setNotes("");
}
list.add(line);
}
String[] cols = {"realtime_start", "realtime_end", "units", "name", "age", "house", "notes"};
CsvUtils.csvWriterUtil(CsvVo.class, list, "in/EmpDetails.csv", cols);
}
}
csvWriterUtil is like below :
public static <T> void csvWriterUtil(Class<T> beanClass, List<T> data, String outputFile, String[] columnMapping){
try{
Writer writer = new BufferedWriter(new FileWriter(outputFile));
ColumnPositionMappingStrategy<T> strategy = new ColumnPositionMappingStrategy<>();
strategy.setType(beanClass);
strategy.setColumnMapping(columnMapping);
StatefulBeanToCsv<T> statefulBeanToCsv =new StatefulBeanToCsvBuilder<T>(writer)
.withMappingStrategy(strategy)
.build();
writer.write(String.join(",",columnMapping)+"\n");
statefulBeanToCsv.write(data);
writer.close();
} catch (IOException e) {
e.printStackTrace();
} catch (CsvRequiredFieldEmptyException e) {
e.printStackTrace();
} catch (CsvDataTypeMismatchException e) {
e.printStackTrace();
}
}
Full example is available in GitRepo
You can do it with a library Apache Commons IO
pom.xml
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.6</version>
</dependency>
ConvertJsonToCSVTest.java
import java.io.File;
import org.apache.commons.io.FileUtils;
import org.json.*;
public class ConvertJsonToCSVTest {
public static void main(String[] args) throws JSONException {
String jsonArrayString = "{\"fileName\": [{\"first name\": \"Adam\",\"last name\": \"Smith\",\"location\": \"London\"}]}";
JSONObject output;
try {
output = new JSONObject(jsonArrayString);
JSONArray docs = output.getJSONArray("fileName");
File file = new File("EmpDetails.csv");
String csv = CDL.toString(docs);
FileUtils.writeStringToFile(file, csv);
System.out.println("Data has been Sucessfully Writeen to "+ file);
System.out.println(csv);
}
catch(Exception e) {
e.printStackTrace();
}
}
}
Output
Data has been Sucessfully Writeen to EmpDetails.csv
last name,first name,location
Smith,Adam,London
I have the following json
"notes": {"note": [
{
"content": "Having wisdom teeth removed.",
"from": "employee"
},
{
"content": "Get well soon",
"from": "manager"
}
]},
the issue is that the value coud also be
"notes": "",
or
"notes": {"note": {
"content": "This is a test note.",
"from": "employee"
}},
and storing it in these
public class Notes
{
#SerializedName ("note")
public List<Note> note;
}
public class Note
{
#SerializedName ("content")
public String content;
#SerializedName ("from")
public String from;
}
I believe I solved the issue of not being an array but being an single object by doing this
public class Json {
private static Gson gson;
private static class MyNoteClassTypeAdapter implements JsonDeserializer<List<RequestsDTO.Note>> {
public List<RequestsDTO.Note> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext ctx) {
List<RequestsDTO.Note> vals = new ArrayList<RequestsDTO.Note>();
if (json.isJsonArray()) {
for (JsonElement e : json.getAsJsonArray()) {
vals.add((RequestsDTO.Note) ctx.deserialize(e, RequestsDTO.Note.class));
}
} else if (json.isJsonObject()) {
vals.add((RequestsDTO.Note) ctx.deserialize(json,RequestsDTO.Note.class));
} else {
throw new RuntimeException("Unexpected JSON type: " + json.getClass());
}
return vals;
}
}
public static Gson getGson()
{
if (gson == null)
{
Type ListType = new TypeToken<List<RequestsDTO.Note>>() {}.getType();
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(DateTime.class, new DateTimeSerializer());
builder.registerTypeAdapter(ListType, new MyNoteClassTypeAdapter());
gson = builder.create();
}
return gson;
}
}
And now I am stuck on when the whole thing just comes back as a string....
Refer the code snippet below to deserialize your json using Gson library without exceptions.
String jsonStr = "your json string ";
Gson gson = new Gson();
JsonObject jsonObj = gson.fromJson (jsonStr, JsonElement.class).getAsJsonObject();
JsonElement elem = jsonObj.get("note");
if(elem.isJsonArray()) { //**Array**
List<Note> notelist = gson.fromJson(elem.toString(), new TypeToken<List<Note>>(){}.getType());
} else if(elem.isJsonObject()) { //**Object**
Note note = gson.fromJson(elem.toString(), Note.class);
} else { //**String**
String note = elem.toString();
}
The idea is try to get "note" field (from "notes" JSONObject) as JSONArray first and if it throws exception that will mean that there is no "note" JSONArray into "notes" JSONObject and that will mean that "note" is JSONObject. The same way we can figure out situation when note field is String.
try {
//String jsonString="{\"notes\": {\"note\": [{\"content\": \"Having wisdom teeth removed.\",\"from\": \"employee\" }, {\"content\": \"Get well soon\", \"from\": \"manager\"} ] }}";
//String jsonString="{\"notes\": { \"note\": {\"content\": \"This is a test note.\",\"from\": \"employee\"}}}";
String jsonString="{\"notes\": { \"note\": \"\"}}";
JSONObject jsonObject=new JSONObject(jsonString);
JSONObject jsonObjectNotes=jsonObject.getJSONObject("notes");
try{
JSONArray jsonArrayNote=jsonObjectNotes.getJSONArray("note");
for (int i = 0; i < jsonArrayNote.length(); i++) {
JSONObject jsonObject2= jsonArrayNote.getJSONObject(i);
String stringContent=jsonObject2.getString( "content");
String stringFrom= jsonObject2.getString( "from");
Log.e(getClass().getName(), "content="+stringContent +"; from="+stringFrom);
}
}
catch(JSONException e){
//that means that jsonObjectNotes has no jsonArray with name "notes" and "notes" is jsonObject
try{
JSONObject jsonObject3=jsonObjectNotes.getJSONObject("note");
String stringContent=(String) jsonObject3.get( "content");
String stringFrom=(String) jsonObject3.get( "from");
Log.e(getClass().getName(), "content="+stringContent +"; from="+stringFrom);
}
catch(JSONException ex){
//that means that jsonObjectNotes has no jsonObject with name "notes" and "notes" is empty String
String stringNote=jsonObjectNotes.getString("note") ;
Log.e(getClass().getName(), "note is string ="+ stringNote);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
In my example code another get operations can also throw jsonExceptions but I think you get the idea.
Have a look at Genson library http://code.google.com/p/genson/.
If your classes are inner classes make them static.
The following code should solve your problem.
Genson genson = new Genson.Builder().withDeserializerFactory(new NotesDeserializerFactory()).create();
Notes notes = genson.deserialize(in, Notes.class);
// Define a factory so you can delegate the deserialization to existing mechanisms for lists and beans
class NotesDeserializerFactory implements Factory<Deserializer<Notes>> {
#Override
public Deserializer<Notes> create(Type type, Genson genson) {
Converter<List<Note>> noteListConverter = genson.provideConverter(new GenericType<List<Note>>() {}.getType());
Converter<Note> noteConverter = genson.provideConverter(Note.class);
return new NotesDeserializer(noteListConverter, noteConverter);
}
}
// define an implementation for you Notes class so you can handle the different cases
class NotesDeserializer implements Deserializer<Notes> {
private final Converter<List<Note>> noteListConverter;
private final Converter<Note> noteConverter;
public NotesDeserializer(Converter<List<Note>> noteListConverter,
Converter<Note> noteConverter) {
this.noteListConverter = noteListConverter;
this.noteConverter = noteConverter;
}
#Override
public Notes deserialize(ObjectReader reader, Context ctx) throws TransformationException,
IOException {
Notes notes = new Notes();
if (reader.getValueType() == ValueType.ARRAY) notes.note = noteListConverter.deserialize(reader, ctx);
else if (reader.getValueType() == ValueType.OBJECT) notes.note = Arrays.asList(noteConverter.deserialize(reader, ctx));
else { // it is a litteral (string, numeric, boolean, null)
notes.note = new ArrayList<Note>();
}
return notes;
}
}
I'm trying to read JSON file in Java (I'm starting with JSON).
The JSON file:
[
{
"idProducto":1,
"Nombre":"Coca Cola",
"Precio":0.9,
"Cantidad":19
},
{
"idProducto":2,
"Nombre":"Coca Cola Zero",
"Precio":0.6,
"Cantidad":19
},
[....]
]
I tried the following:
ArrayList<Dispensador> Productos = new ArrayList<Dispensador>();
FileReader reader = new FileReader(new File("productos.json"));
JSONParser jsonParser = new JSONParser();
JSONArray jsonArray = (JSONArray) jsonParser.parse(reader);
JSONObject object = (JSONObject) jsonArray.get(0);
Long idProducto = (Long) object.get("idProducto");
JSONArray nombres = object.getJSONArray("idProducto");
Iterator i = jsonArray.iterator();
while (i.hasNext()) {
String nombre = (String) object.get("Nombre");
Double precio = (Double) object.get("Precio");
BigDecimal precioB = new BigDecimal(precio);
Long cantidad = (Long) object.get("Cantidad");
int cantidadB = toIntExact(cantidad);
System.out.println(nombre);
Productos.add(new Dispensador(nombre, precioB, cantidadB));
}
But enters into loop. Also I tried with a for loop, but no luck.
Thanks!
You can use gson library
You can use Maven or jar file: http://mvnrepository.com/artifact/com.google.code.gson/gson
package com.test;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
public class AppJsonTest {
public static void main(String[] args) {
List<DataObject> objList = new ArrayList<DataObject>();
objList.add(new DataObject(1, "Coca Cola", 0.9, 19));
objList.add(new DataObject(2, "Coca Cola Zero", 0.6, 19));
// Convert the object to a JSON string
String json = new Gson().toJson(objList);
System.out.println(json);
// Now convert the JSON string back to your java object
Type type = new TypeToken<List<DataObject>>() {
}.getType();
List<DataObject> inpList = new Gson().fromJson(json, type);
for (int i = 0; i < inpList.size(); i++) {
DataObject x = inpList.get(i);
System.out.println(x.toString());
}
}
}
class DataObject {
int idProducto;
String Nombre;
Double Precio;
int Cantidad;
public DataObject(int idProducto, String nombre, Double precio, int cantidad) {
this.idProducto = idProducto;
Nombre = nombre;
Precio = precio;
Cantidad = cantidad;
}
public int getIdProducto() {
return idProducto;
}
public void setIdProducto(int idProducto) {
this.idProducto = idProducto;
}
public String getNombre() {
return Nombre;
}
public void setNombre(String nombre) {
Nombre = nombre;
}
public Double getPrecio() {
return Precio;
}
public void setPrecio(Double precio) {
Precio = precio;
}
public int getCantidad() {
return Cantidad;
}
public void setCantidad(int cantidad) {
Cantidad = cantidad;
}
#Override
public String toString() {
return "DataObject [idProducto=" + idProducto + ", Nombre=" + Nombre + ", Precio=" + Precio + ", Cantidad=" + Cantidad + "]";
}
}
Use gson library to read and write json:
try {
JsonReader reader = new JsonReader(new FileReader("json_file_path.json"));
reader.beginArray();
while (reader.hasNext()) {
reader.beginObject();
while (reader.hasNext()) {
String name = reader.nextName();
if (name.equals("idProducto")) {
System.out.println(reader.nextInt());
} else if (name.equals("Nombre")) {
System.out.println(reader.nextString());
} else if (name.equals("Precio")) {
System.out.println(reader.nextDouble());
} else if (name.equals("Cantidad")) {
System.out.println(reader.nextInt());
} else {
reader.skipValue();
}
}
reader.endObject();
}
reader.endArray();
reader.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
download http://www.java2s.com/Code/JarDownload/gson/gson-2.2.2.jar.zip
You are testing whether the iterator has a next element with i.hasNext(). But you don't consume (or retrieve) this next element by i.next() which is typically in the first statement of the looped block. Therefore i.hasNext() will return true forever.
EDIT: You probably want to set object to i.next() because in your code snippet it always remains at the 0's element you assigned before the loop.
There are many open source libraries, present to parse json to object or just to read and write json values. If you want to read and write json then you can use org.json library.
Use org.json library to parse it and create JsonObject :-
JSONObject jsonObj = new JSONObject(<jsonStr>);
Now, use this object to get your values :-
String id = jsonObj.getString("pageInfo");
You can see complete example here :-
How to parse Json in java
If you want to parse your json to particular POJO and then use that pojo to get values, then use jackson-databind library, this will parse your json to POJO class :-
ObjectMapper mapper = new ObjectMapper();
book = mapper.readValue(json, Book.class);
You can see complete example here, How to parse json in java
I have the following json
"notes": {"note": [
{
"content": "Having wisdom teeth removed.",
"from": "employee"
},
{
"content": "Get well soon",
"from": "manager"
}
]},
the issue is that the value coud also be
"notes": "",
or
"notes": {"note": {
"content": "This is a test note.",
"from": "employee"
}},
and storing it in these
public class Notes
{
#SerializedName ("note")
public List<Note> note;
}
public class Note
{
#SerializedName ("content")
public String content;
#SerializedName ("from")
public String from;
}
I believe I solved the issue of not being an array but being an single object by doing this
public class Json {
private static Gson gson;
private static class MyNoteClassTypeAdapter implements JsonDeserializer<List<RequestsDTO.Note>> {
public List<RequestsDTO.Note> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext ctx) {
List<RequestsDTO.Note> vals = new ArrayList<RequestsDTO.Note>();
if (json.isJsonArray()) {
for (JsonElement e : json.getAsJsonArray()) {
vals.add((RequestsDTO.Note) ctx.deserialize(e, RequestsDTO.Note.class));
}
} else if (json.isJsonObject()) {
vals.add((RequestsDTO.Note) ctx.deserialize(json,RequestsDTO.Note.class));
} else {
throw new RuntimeException("Unexpected JSON type: " + json.getClass());
}
return vals;
}
}
public static Gson getGson()
{
if (gson == null)
{
Type ListType = new TypeToken<List<RequestsDTO.Note>>() {}.getType();
GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(DateTime.class, new DateTimeSerializer());
builder.registerTypeAdapter(ListType, new MyNoteClassTypeAdapter());
gson = builder.create();
}
return gson;
}
}
And now I am stuck on when the whole thing just comes back as a string....
Refer the code snippet below to deserialize your json using Gson library without exceptions.
String jsonStr = "your json string ";
Gson gson = new Gson();
JsonObject jsonObj = gson.fromJson (jsonStr, JsonElement.class).getAsJsonObject();
JsonElement elem = jsonObj.get("note");
if(elem.isJsonArray()) { //**Array**
List<Note> notelist = gson.fromJson(elem.toString(), new TypeToken<List<Note>>(){}.getType());
} else if(elem.isJsonObject()) { //**Object**
Note note = gson.fromJson(elem.toString(), Note.class);
} else { //**String**
String note = elem.toString();
}
The idea is try to get "note" field (from "notes" JSONObject) as JSONArray first and if it throws exception that will mean that there is no "note" JSONArray into "notes" JSONObject and that will mean that "note" is JSONObject. The same way we can figure out situation when note field is String.
try {
//String jsonString="{\"notes\": {\"note\": [{\"content\": \"Having wisdom teeth removed.\",\"from\": \"employee\" }, {\"content\": \"Get well soon\", \"from\": \"manager\"} ] }}";
//String jsonString="{\"notes\": { \"note\": {\"content\": \"This is a test note.\",\"from\": \"employee\"}}}";
String jsonString="{\"notes\": { \"note\": \"\"}}";
JSONObject jsonObject=new JSONObject(jsonString);
JSONObject jsonObjectNotes=jsonObject.getJSONObject("notes");
try{
JSONArray jsonArrayNote=jsonObjectNotes.getJSONArray("note");
for (int i = 0; i < jsonArrayNote.length(); i++) {
JSONObject jsonObject2= jsonArrayNote.getJSONObject(i);
String stringContent=jsonObject2.getString( "content");
String stringFrom= jsonObject2.getString( "from");
Log.e(getClass().getName(), "content="+stringContent +"; from="+stringFrom);
}
}
catch(JSONException e){
//that means that jsonObjectNotes has no jsonArray with name "notes" and "notes" is jsonObject
try{
JSONObject jsonObject3=jsonObjectNotes.getJSONObject("note");
String stringContent=(String) jsonObject3.get( "content");
String stringFrom=(String) jsonObject3.get( "from");
Log.e(getClass().getName(), "content="+stringContent +"; from="+stringFrom);
}
catch(JSONException ex){
//that means that jsonObjectNotes has no jsonObject with name "notes" and "notes" is empty String
String stringNote=jsonObjectNotes.getString("note") ;
Log.e(getClass().getName(), "note is string ="+ stringNote);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
In my example code another get operations can also throw jsonExceptions but I think you get the idea.
Have a look at Genson library http://code.google.com/p/genson/.
If your classes are inner classes make them static.
The following code should solve your problem.
Genson genson = new Genson.Builder().withDeserializerFactory(new NotesDeserializerFactory()).create();
Notes notes = genson.deserialize(in, Notes.class);
// Define a factory so you can delegate the deserialization to existing mechanisms for lists and beans
class NotesDeserializerFactory implements Factory<Deserializer<Notes>> {
#Override
public Deserializer<Notes> create(Type type, Genson genson) {
Converter<List<Note>> noteListConverter = genson.provideConverter(new GenericType<List<Note>>() {}.getType());
Converter<Note> noteConverter = genson.provideConverter(Note.class);
return new NotesDeserializer(noteListConverter, noteConverter);
}
}
// define an implementation for you Notes class so you can handle the different cases
class NotesDeserializer implements Deserializer<Notes> {
private final Converter<List<Note>> noteListConverter;
private final Converter<Note> noteConverter;
public NotesDeserializer(Converter<List<Note>> noteListConverter,
Converter<Note> noteConverter) {
this.noteListConverter = noteListConverter;
this.noteConverter = noteConverter;
}
#Override
public Notes deserialize(ObjectReader reader, Context ctx) throws TransformationException,
IOException {
Notes notes = new Notes();
if (reader.getValueType() == ValueType.ARRAY) notes.note = noteListConverter.deserialize(reader, ctx);
else if (reader.getValueType() == ValueType.OBJECT) notes.note = Arrays.asList(noteConverter.deserialize(reader, ctx));
else { // it is a litteral (string, numeric, boolean, null)
notes.note = new ArrayList<Note>();
}
return notes;
}
}