Develop Reference

Why org.json.JSONObject excludes POJO fields start with x while converting to JSON object?

Diferent results occur when mapping an object containing a field starting with "x" to org.json.JSONObject and com.fasterxml.jackson.core.ObjectMapper:
JSONObject
{"one":"One"}
ObjectMapper
{"one":"One","xOne":"xOne"}
Why does the JSONObject not include the "xOne" field?
public class Test {
private String one;
private String xOne;
public String getOne() {
return one;
}
public void setOne(String one) {
this.one = one;
}
public String getxOne() {
return xOne;
}
public void setxOne(String xOne) {
this.xOne = xOne;
}
#Override
public String toString() {
return "Test [one=" + one + ", xOne=" + xOne + "]";
}
}
public class PojoToJson {
public static void main(String[] args) throws JsonGenerationException, JsonMappingException, IOException {
Test test = new Test();
test.setOne("One");
test.setxOne("xOne");
JSONObject json = new JSONObject(test);
System.out.println("JSONObject o/p: " + json);
ObjectMapper mapper = new ObjectMapper();
String mapperString = mapper.writeValueAsString(test);
System.out.println("ObjectMapper o/p: " + mapperString);
}
}
Here is my output difference using JSONObject and ObjectMapper:

According to the Jackson reference documentation:
In absence of a registered custom strategy, the default Java property
naming strategy is used, which leaves field names as is, and removes
set/get/is prefix from methods (as well as lower-cases initial
sequence of capitalized characters).
As I understand it, this means that Jackson will understand that getxOne() actually correspond to xOne property.
org.json.JSONObject may have a different naming strategy (which I was not able to find anywhere) and hence the reason for getxOne() to work with Jackson's ObjectMapper but not with org.json.JSONObject.

JSON to Java object with Random Key

I am trying to convert following JSON to Java object and ending up with UnrecognizedPropertyException.
{
"5214": [{
"name": "sdsds",
"age": "25",
"address": null
},
{
"name": "sdfds",
"age": "26",
"address": null
}]
}
Here "5214" is the random key that I get. I can covert it by modifying JSON little bit. But I want to know whether any possible way to convert the mentioned JSON. I even tried with following snippet taking some reference.
public class SampleTest {
private Map<String, List<EmployeeDetails>> employeeDetails = new HashMap<String, List<EmployeeDetails>>();
public Map<String, List<EmployeeDetails>> getEmployeeDetails() {
return employeeDetails;
}
public void setEmployeeDetails(Map<String, List<EmployeeDetails>> employeeDetails) {
this.employeeDetails = employeeDetails;
}
}
public class EmployeeDetails {
private String name;
private String age;
private String address;
//Getters and Setters
}
Can someone guide me on this?

Use Type Reference (Import Jackson Package for Java)
TypeReference<Map<String, List<EmployeeDetails>>> typeReference = new TypeReference<Map<String, List<EmployeeDetails>>>()
{
};
Map<String, List<EmployeeDetails>> employeeDetails = new ObjectMapper().readValue(jsonString, typeReference);

Check something from that
Maybe:
public class Data {
// String contain the Key, for example: 5214
Map<String, List<EmployeeDetails>> employeeDetails =
new HashMap<String,List<EmployeeDetails>>();
public Data() {
}
#JsonAnyGetter
public Map<String, List<EmployeeDetails>> getEmployeeDetails() {
return employeeDetails;
}
}

I would use custom deserializer with few helper classes. To make the code (matter of opinion I guess) clearer, create the list object:
#SuppressWarnings("serial")
#Getter #Setter
public class EmployeeDetailsList extends ArrayList<EmployeeDetails> {
// this will hold the arbitrary name of list. like 5214
private String name;
}
Then this list seems to be inside an object, say Wrapper:
#Getter
#RequiredArgsConstructor
#JsonDeserialize(using = WrapperDeserializer.class)
public class Wrapper {
private final EmployeeDetailsList employeeDetailsList;
}
So there is annotation #JsonDeserializer that handles deserializing Wrapper. It is not possible to directly deserialize unknown field names to some defined type so we need to use mechanism like this custom deserializer that inspects what is inside Wrapper and determines what to deserialize and how.
And here is how the deserializer works:
public class WrapperDeserializer extends JsonDeserializer<Wrapper> {
private final ObjectMapper om = new ObjectMapper();
#Override
public Wrapper deserialize(JsonParser p, DeserializationContext ctxt)
throws IOException, JsonProcessingException {
TreeNode node = p.readValueAsTree();
// This is the place for caution. You should somehow know what is the correct node
// Here I happily assume there is just the one and first
String fName = node.fieldNames().next();
EmployeeDetailsList edl = om.readValue(node.get(fName).toString(),
EmployeeDetailsList.class);
edl.setName(fName);
return new Wrapper(edl);
}
}
Please check it carefully it is not perfect in sense finding alwasy the correct node and maybe the instantiation can be done in other ways better. But it shoudl give you a hunch how it could be done.

JSON field - Parse String to Int

Have a relatively simple (I think) issue, but being a novice to JSON cannot seem to find a neat solution.
I have an Entity object with Id field as type Integer. However, the incoming Json data to be mapped has the id as a string.
With this a straightforward map does not seem to be possible. Is there a way to change the string data in the JSON to an integer, before mapping?
Example Json data
{"Id": "021", "userAge": 99}
Example Entity
#Entity
public class User{
#id
int userId;
int userAge;
}
Many Thanks.

You don't need to.
Jackson is smart enough to convert a JSON string to a numerical value if the target field is numerical.
It's not obvious what the leading 0 is meant to represent, but Jackson will simply ignore it.
Also, if your field name is different in Java, you'll need #JsonProperty("theJsonName").
public class Jackson {
public static void main(String[] args) throws Exception {
String json = "{\"userId\": \"021\", \"userAge\": 99}";
ObjectMapper mapper = new ObjectMapper();
User user = mapper.readValue(json, User.class);
System.out.println(user.userId);
}
}
class User {
int userId;
int userAge;
public void setUserId(int userId) {
this.userId = userId;
}
public void setUserAge(int userAge) {
this.userAge = userAge;
}
}
prints
21

You can write a custom jackson deserializer to cope with this behaviour. There's an good blog post on this topic here.
public class ItemDeserializer extends JsonDeserializer<Item> {
#Override
public Item deserialize(JsonParser jp, DeserializationContext ctxt)
throws IOException, JsonProcessingException {
JsonNode node = jp.getCodec().readTree(jp);
int id = Integer.parseInt(node.get("userId").asText());
int userAge = (Integer) ((IntNode) node.get("userAge")).numberValue();
return new Item(id, userAge);
}
}

Json Data assign to java class

I'm having problem to assign json data into java class.Please do help anyone,
My java class is like,
public class ListofGridRecords<T> {
public int Totalrecords;
public List<T> GridRecords;//using TraderTransaction class.
}
and TraderTransaction class is,
public class TraderTransaction {
public Date AddedTime;
public String TransactId;
public TransactStatus Status;
public String OtherPartyAccountNo;
public Double AmountPaid;
public Double AmountRecieved;
public Double ClosingBalance;
public TransactionTypes TransType;
public String Narration;
public TraderTransaction() {
super();
}
}
and my json conversion function look like,
JsonObject returndata = JsonObject.parse(responseString);
String operationresult = returndata.get("OperationResult").toString();
if (Result.values()[Integer.parseInt(operationresult)] == Result.Success) {
Gson gson = new Gson();
#SuppressWarnings("unchecked")
ListofGridRecords<TraderTransaction> traderlist =
gson.fromJson(returndata.get("ResultData").toString(), ListofGridRecords.class);
Log.i("LIST DATA:", "" + traderlist);
for (TraderTransaction trader: traderlist.GridRecords) {
HashMap<String, String> map = new HashMap<String, String>();
map.put(TRANS_FIRST_COLUMN, currentformatter.format(trader.AddedTime));
map.put(TRANS_SECOND_COLUMN, trader.TransactId);
map.put(TRANS_THIRD_COLUMN, trader.OtherPartyAccountNo);
map.put(TRANS_FOURTH_COLUMN, trader.AmountPaid.toString());
map.put(TRANS_FIFTH_COLUMN, trader.AmountRecieved.toString());
map.put(TRANS_SIXTH_COLUMN, OpenOrClosed.values()[Integer.parseInt(trader.TransType.toString())].toString());
list.add(map);
}
}
I'm getting conversion error at for (TraderTransaction trader : traderlist.GridRecords).
My Json data look like,
{
"Messages":"RESULTS_RETRIEVAL_SUCCESSFULL",
"OperationResult":0,
"ResultData":{
"GridRecords":[
{
"AddedBy":"Distributor-9787457361-Rathinavel",
"AddedTime":"2013-04-12T16:26:24.0140117",
"AmountPaid":0.0,
"AmountRecieved":10000.0,
"ClosingBalance":10000.0,
"Narration":null,
"OtherPartyAccountNo":"0102849015327675",
"Status":2,
"TransType":2,
"TransactId":"TDRF483679051236"
},
{
"AddedBy":"Distributor-9787457361-Rathinavel",
"AddedTime":"2013-04-12T16:20:54.8681857",
"AmountPaid":0.0,
"AmountRecieved":0.0,
"ClosingBalance":0.0,
"Narration":null,
"OtherPartyAccountNo":"0102849015327675",
"Status":0,
"TransType":2,
"TransactId":"TDRF706925413802"
}
],
"Totalrecords":2
},
"UpdateAvailable":"0"
}

In order to parse your JSON, I'd use a slightly different strategy. As you seem to be interested in parsing only the "ResultData", I'd create classes to wrap the response, very similar to those you have already created, namely:
public class Response {
#SerializedName("ResultData")
public ResultData resultData;
}
and,
public class ResultData {
#SerializedName("GridRecords")
public List<GridRecord> gridRecords;
#SerializedName("Totalrecords")
public int totalrecords;
}
and,
public class GridRecord {
#SerializedName("AddedTime")
public String addedTime;
#SerializedName("TransactId")
public String transactId;
//other fields...
}
and other classes if necessary...
Then, in order to parse your JSON reponse, you just have to do:
Gson gson = new Gson();
Response data = gson.fromJson(responseString, Response.class);
and you'll be able to access any field, for example:
data.resultData.gridRecords.transactId;
Note 1: If you are interested in more fields of the JSON response, you just have to add more fields to your wrap classes, according to the JSON response...
Note 2: I've changed the type of addedTime to String, instead of Date because it throws an exception for unparseable date. Anyway I usually leave the types in the Response objects as simple String and then in the class from where I retrieve the response, I do the correct formatting while creating my objects, for example, when you put the values in your Map...
Note 3: The use of the annotation #SerializedName is interesting to separate the name of a field in the JSON response and in your app, in order to follow Java naming conventions, which your attributes are not following...
Note 4: You shouldn't use public attributes in your classes. It's more recommendable to use private/protected attributes and their correspondent getters and setters...

How can I include raw JSON in an object using Jackson?

I am trying to include raw JSON inside a Java object when the object is (de)serialized using Jackson. In order to test this functionality, I wrote the following test:
public static class Pojo {
public String foo;
#JsonRawValue
public String bar;
}
#Test
public void test() throws JsonGenerationException, JsonMappingException, IOException {
String foo = "one";
String bar = "{\"A\":false}";
Pojo pojo = new Pojo();
pojo.foo = foo;
pojo.bar = bar;
String json = "{\"foo\":\"" + foo + "\",\"bar\":" + bar + "}";
ObjectMapper objectMapper = new ObjectMapper();
String output = objectMapper.writeValueAsString(pojo);
System.out.println(output);
assertEquals(json, output);
Pojo deserialized = objectMapper.readValue(output, Pojo.class);
assertEquals(foo, deserialized.foo);
assertEquals(bar, deserialized.bar);
}
The code outputs the following line:
{"foo":"one","bar":{"A":false}}
The JSON is exactly how I want things to look. Unfortunately, the code fails with an exception when attempting to read the JSON back in to the object. Here is the exception:
org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token
at [Source: java.io.StringReader#d70d7a; line: 1, column: 13] (through reference chain: com.tnal.prism.cobalt.gather.testing.Pojo["bar"])
Why does Jackson function just fine in one direction but fail when going the other direction? It seems like it should be able to take its own output as input again. I know what I'm trying to do is unorthodox (the general advice is to create an inner object for bar that has a property named A), but I don't want to interact with this JSON at all. My code is acting as a pass-through for this code -- I want to take in this JSON and send it back out again without touching a thing, because when the JSON changes I don't want my code to need modifications.
Thanks for the advice.
EDIT: Made Pojo a static class, which was causing a different error.

#JsonRawValue is intended for serialization-side only, since the reverse direction is a bit trickier to handle. In effect it was added to allow injecting pre-encoded content.
I guess it would be possible to add support for reverse, although that would be quite awkward: content will have to be parsed, and then re-written back to "raw" form, which may or may not be the same (since character quoting may differ).
This for general case. But perhaps it would make sense for some subset of problems.
But I think a work-around for your specific case would be to specify type as 'java.lang.Object', since this should work ok: for serialization, String will be output as is, and for deserialization, it will be deserialized as a Map. Actually you might want to have separate getter/setter if so; getter would return String for serialization (and needs #JsonRawValue); and setter would take either Map or Object. You could re-encode it to a String if that makes sense.

Following #StaxMan answer, I've made the following works like a charm:
public class Pojo {
Object json;
#JsonRawValue
public String getJson() {
// default raw value: null or "[]"
return json == null ? null : json.toString();
}
public void setJson(JsonNode node) {
this.json = node;
}
}
And, to be faithful to the initial question, here is the working test:
public class PojoTest {
ObjectMapper mapper = new ObjectMapper();
#Test
public void test() throws IOException {
Pojo pojo = new Pojo("{\"foo\":18}");
String output = mapper.writeValueAsString(pojo);
assertThat(output).isEqualTo("{\"json\":{\"foo\":18}}");
Pojo deserialized = mapper.readValue(output, Pojo.class);
assertThat(deserialized.json.toString()).isEqualTo("{\"foo\":18}");
// deserialized.json == {"foo":18}
}
}

I was able to do this with a custom deserializer (cut and pasted from here)
package etc;
import java.io.IOException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.TreeNode;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
/**
* Keeps json value as json, does not try to deserialize it
* #author roytruelove
*
*/
public class KeepAsJsonDeserializer extends JsonDeserializer<String> {
#Override
public String deserialize(JsonParser jp, DeserializationContext ctxt)
throws IOException {
TreeNode tree = jp.getCodec().readTree(jp);
return tree.toString();
}
}
Use it by annotating the desired member like this:
#JsonDeserialize(using = KeepAsJsonDeserializer.class)
private String value;

#JsonSetter may help. See my sample ('data' is supposed to contain unparsed JSON):
class Purchase
{
String data;
#JsonProperty("signature")
String signature;
#JsonSetter("data")
void setData(JsonNode data)
{
this.data = data.toString();
}
}

This is a problem with your inner classes. The Pojo class is a non-static inner class of your test class, and Jackson cannot instantiate that class. So it can serialize, but not deserialize.
Redefine your class like this:
public static class Pojo {
public String foo;
#JsonRawValue
public String bar;
}
Note the addition of static

Adding to Roy Truelove's great answer, this is how to inject the custom deserialiser in response to appearance of #JsonRawValue:
import com.fasterxml.jackson.databind.Module;
#Component
public class ModuleImpl extends Module {
#Override
public void setupModule(SetupContext context) {
context.addBeanDeserializerModifier(new BeanDeserializerModifierImpl());
}
}
import java.util.Iterator;
import com.fasterxml.jackson.annotation.JsonRawValue;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.deser.BeanDeserializerBuilder;
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier;
import com.fasterxml.jackson.databind.deser.SettableBeanProperty;
public class BeanDeserializerModifierImpl extends BeanDeserializerModifier {
#Override
public BeanDeserializerBuilder updateBuilder(DeserializationConfig config, BeanDescription beanDesc, BeanDeserializerBuilder builder) {
Iterator<SettableBeanProperty> it = builder.getProperties();
while (it.hasNext()) {
SettableBeanProperty p = it.next();
if (p.getAnnotation(JsonRawValue.class) != null) {
builder.addOrReplaceProperty(p.withValueDeserializer(KeepAsJsonDeserialzier.INSTANCE), true);
}
}
return builder;
}
}

This easy solution worked for me:
public class MyObject {
private Object rawJsonValue;
public Object getRawJsonValue() {
return rawJsonValue;
}
public void setRawJsonValue(Object rawJsonValue) {
this.rawJsonValue = rawJsonValue;
}
}
So I was able to store raw value of JSON in rawJsonValue variable and then it was no problem to deserialize it (as object) with other fields back to JSON and send via my REST. Using #JsonRawValue didnt helped me because stored JSON was deserialized as String, not as object, and that was not what I wanted.

This even works in a JPA entity:
private String json;
#JsonRawValue
public String getJson() {
return json;
}
public void setJson(final String json) {
this.json = json;
}
#JsonProperty(value = "json")
public void setJsonRaw(JsonNode jsonNode) {
// this leads to non-standard json, see discussion:
// setJson(jsonNode.toString());
StringWriter stringWriter = new StringWriter();
ObjectMapper objectMapper = new ObjectMapper();
JsonGenerator generator =
new JsonFactory(objectMapper).createGenerator(stringWriter);
generator.writeTree(n);
setJson(stringWriter.toString());
}
Ideally the ObjectMapper and even JsonFactory are from the context and are configured so as to handle your JSON correctly (standard or with non-standard values like 'Infinity' floats for example).

Here is a full working example of how to use Jackson modules to make #JsonRawValue work both ways (serialization and deserialization):
public class JsonRawValueDeserializerModule extends SimpleModule {
public JsonRawValueDeserializerModule() {
setDeserializerModifier(new JsonRawValueDeserializerModifier());
}
private static class JsonRawValueDeserializerModifier extends BeanDeserializerModifier {
#Override
public BeanDeserializerBuilder updateBuilder(DeserializationConfig config, BeanDescription beanDesc, BeanDeserializerBuilder builder) {
builder.getProperties().forEachRemaining(property -> {
if (property.getAnnotation(JsonRawValue.class) != null) {
builder.addOrReplaceProperty(property.withValueDeserializer(JsonRawValueDeserializer.INSTANCE), true);
}
});
return builder;
}
}
private static class JsonRawValueDeserializer extends JsonDeserializer<String> {
private static final JsonDeserializer<String> INSTANCE = new JsonRawValueDeserializer();
#Override
public String deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
return p.readValueAsTree().toString();
}
}
}
Then you can register the module after creating the ObjectMapper:
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JsonRawValueDeserializerModule());
String json = "{\"foo\":\"one\",\"bar\":{\"A\":false}}";
Pojo deserialized = objectMapper.readValue(json, Pojo.class);

I had the exact same issue.
I found the solution in this post :
Parse JSON tree to plain class using Jackson or its alternatives
Check out the last answer.
By defining a custom setter for the property that takes a JsonNode as parameter and calls the toString method on the jsonNode to set the String property, it all works out.

Using an object works fine both ways... This method has a bit of overhead deserializing the raw value in two times.
ObjectMapper mapper = new ObjectMapper();
RawJsonValue value = new RawJsonValue();
value.setRawValue(new RawHello(){{this.data = "universe...";}});
String json = mapper.writeValueAsString(value);
System.out.println(json);
RawJsonValue result = mapper.readValue(json, RawJsonValue.class);
json = mapper.writeValueAsString(result.getRawValue());
System.out.println(json);
RawHello hello = mapper.readValue(json, RawHello.class);
System.out.println(hello.data);
RawHello.java
public class RawHello {
public String data;
}
RawJsonValue.java
public class RawJsonValue {
private Object rawValue;
public Object getRawValue() {
return rawValue;
}
public void setRawValue(Object value) {
this.rawValue = value;
}
}

I had a similar problem, but using a list with a lot of JSON itens (List<String>).
public class Errors {
private Integer status;
private List<String> jsons;
}
I managed the serialization using the #JsonRawValue annotation. But for deserialization I had to create a custom deserializer based on Roy's suggestion.
public class Errors {
private Integer status;
#JsonRawValue
#JsonDeserialize(using = JsonListPassThroughDeserialzier.class)
private List<String> jsons;
}
Below you can see my "List" deserializer.
public class JsonListPassThroughDeserializer extends JsonDeserializer<List<String>> {
#Override
public List<String> deserialize(JsonParser jp, DeserializationContext cxt) throws IOException, JsonProcessingException {
if (jp.getCurrentToken() == JsonToken.START_ARRAY) {
final List<String> list = new ArrayList<>();
while (jp.nextToken() != JsonToken.END_ARRAY) {
list.add(jp.getCodec().readTree(jp).toString());
}
return list;
}
throw cxt.instantiationException(List.class, "Expected Json list");
}
}