I have a DTO where Spring Boot tries to deserialize the request body, but, in this case, I need to deserialize a JSON array object as a String.
This is the JSON Request:
{
"metadata": [{
"example": 1
}]
}
This is my dto:
#Data
#Builder
#NoArgsConstructor
#AllArgsConstructor
#ToString
public class someDto implements Serializable {
#JsonDeserialize(using = MetadataDeserializer.class)
#JsonProperty("metadata")
#JsonbProperty("metadata")
private String metadata;
}
I try to deserialize with this deserializer, but, It didn't work:
public class MetadataDeserializer extends StdDeserializer<String> {
public MetadataDeserializer() {
super(String.class);
}
#Override
public String deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
return jsonParser.getValueAsString();
}
}
I need to catch some similar like this:
"metadata": "[{ "example": 1 }]"
This deserializer is start when receiving the payload with #RequestBody.
I resolved that problem with this deserializer:
public class MetadataDeserializer extends StdDeserializer<String> {
public MetadataDeserializer() {
super(String.class);
}
#Override
public String deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
return jsonParser.readValueAsTree().toString();
}
}
Related
The issue is i'm getting this error.
I have to simulate rest service call because it's being developed now by another team.
com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of com.egencia.service.invoiceaggregator.cache.SaleListDTO out of START_ARRAY token
Here is my jackson mapper bean
Jackson2ObjectMapperBuilder
.json()
.featuresToEnable(DeserializationFeature.UNWRAP_ROOT_VALUE, DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT) .serializationInclusion(JsonInclude.Include.NON_NULL)
.serializationInclusion(JsonInclude.Include.NON_EMPTY)
.failOnUnknownProperties(false)
.build();
#JsonRootName("list")
public class SaleListDTO {
private SaleDTO[] list;
public SaleDTO[] getList() {
return list;
}
public void setList(SaleDTO[] list) {
this.list = list;
}
}
Here is the JsON file
{"list": [
{
"id": 111111,
"currency": "EUR",
"country": "ITA",
"name": "Italy",
"code": "IT"
},...
]}
I have tested so many combinations but in vain. please help
Remove #JsonRootName("list").
Here is the working example :
#Getter
#Setter
#Data
#AllArgsConstructor
#NoArgsConstructor
#ToString
public class SaleListDTO {
#JsonProperty("list")
private SaleDTO[] list;
}
#Getter
#Setter
#Data
#AllArgsConstructor
#NoArgsConstructor
#ToString
public class SaleDTO {
private int id;
private String currency;
private String country;
private String name;
private String code;
}
Test Method:
#Test
public void testConversion() throws JsonParseException, JsonMappingException, IOException{
ObjectMapper mapper=new ObjectMapper();
SaleListDTO dto=mapper.readValue(new File(PATH), SaleListDTO.class);
System.out.println(dto.toString());
}
Response :
SaleListDTO(list=[SaleDTO(id=111111, currency=EUR, country=ITA, name=Italy, code=IT), SaleDTO(id=22222, currency=IN, country=INDIA, name=CHENNAI, code=IT)])
In my Application i have something like this.
public class Question{}
public class MCQ extends Question{}
public class TrueAndFalse Question{}
public class Match Question{}
and in my RestController i have a service that adds question.
#RequestMapping(value = "/game/question/add", method = RequestMethod.POST)
public Question addQuuestion(#RequestParam("gameId") long id, #RequestBody Question question)
But i get an error when i try to call this service as i send json file with different structures one for MCQ, TrueAndFalse and Match.
so is it possible to deserialize the received json to Question abstract class.
And thanks in advance.
You can create a custom deserializer which will create Question instances based on json payload properties.
For example if the Question class looks like this:
public class Question {
private final String name;
#JsonCreator
Question(#JsonProperty("name") String name) {
this.name = name;
}
public String getName() {
return name;
}
}
And sub-class TrueAndFalse:
public class TrueAndFalse extends Question {
private final String description;
#JsonCreator
TrueAndFalse(#JsonProperty("name") String name,
#JsonProperty("description") String description) {
super(name);
this.description = description;
}
public String getDescription() {
return description;
}
}
Then you can create a deserializer, which will create an instance of TrueAndFale sub-class by checking if it has description property:
public class QuestionDeserializer extends JsonDeserializer<Question> {
#Override
public Question deserialize(JsonParser p, DeserializationContext ctx) throws IOException {
ObjectCodec codec = p.getCodec();
JsonNode tree = codec.readTree(p);
if (tree.has("description")) {
return codec.treeToValue(tree, TrueAndFalse.class);
}
// Other types...
throw new UnsupportedOperationException("Cannot deserialize to a known type");
}
}
And afterwards, make sure to register it on the object mapper:
#Configuration
public class ObjectMapperConfiguration {
#Bean
public ObjectMapper objectMapper() {
SimpleModule module = new SimpleModule();
module.addDeserializer(Question.class, new QuestionDeserializer());
return new ObjectMapper().registerModules(module);
}
}
I have following Incoming json, which I deserialize to Model.java and then copy that java object to ModelView.java. I wan't to convert date from String to milliseconds and send the Outgoing json as response.
How do I go for it ?
I've specific reason to copy the value from Model.java to ModelView.java using object mapper. So please don't suggest to modify that part. I'm looking to do this via annotation. I'm pretty sure that it can be done, but don't know how.
The json provided here is a simplistic one. I have a large json in actual scenario.
Incoming json
{
"date":"2016-03-31"
}
Outgoing Json
{
"date":236484625196
}
My Controller Class
#Controller
public class SomeController extends BaseController {
#Autowired
private SomeService someService;
#RequestMapping(method = RequestMethod.GET, produces = "application/json")
public #ResponseBody
ResponseEntity<RestResponse> getDetails(HttpServletRequest request, HttpServletResponse response) {
Model model = someService.getData();
ModelView modelView = ModelView.valueOf(model);
return getSuccessResponse(modelView);
}
}
Model.java
#JsonInclude(Include.NON_NULL)
#JsonIgnoreProperties(ignoreUnknown = true)
public class Model implements Serializable {
private String date;
//normal getters and setters
}
ModelView.java
#JsonInclude(Include.NON_NULL)
#JsonIgnoreProperties(ignoreUnknown = true)
public class ModelView implements Serializable {
private Long date;
//normal getters and setters
public static ModelView valueOf(Model model){
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");
ObjectMapper mapper = new ObjectMapper();
ModelView modelView = mapper.convertValue(model, ModelView.class);
try {
modelView.setDate(sdf.parse(model.getDate()).getTime());
} catch (ParseException e) {
IntLogger.error("logging error here");
}
return modelView;
}
}
I'm open to change the variable name from "date" to something else in ModelView.java but the outgoing json should remain same.
Jackson has some build in date formatting, for example, you can set the DateFormatter on the object mapper, but i believe this only works if the serialization and deserialization format is the same.
A simpler approach to date serialization and deserialization, if you want serialization and deserialization to be different format, is to use #JsonSerialize and #JsonDeserialize annotations on your Model.class directly (this could obsolete the need for ModelView if your only purpose was to convert the date).
You can create two classes for serialization and deserialization:
public class JsonDateDeserializer extends JsonDeserializer<Date> {
#Override
public Date deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {
final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
String dateString = jsonParser.getText();
try {
return dateFormat.parse(dateString);
}
catch (ParseException e) {
throw new RuntimeException(e);
}
}
}
Then for the serialization to your Outgoing json:
public class JsonDateSerializer extends JsonSerializer<Date> {
#Override
public void serialize(Date date, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, JsonProcessingException {
jsonGenerator.writeString(Long.toString(date.getTime()));
}
}
Now, you an just annotate your Model.java:
#JsonInclude(Include.NON_NULL)
#JsonIgnoreProperties(ignoreUnknown = true)
public class Model implements Serializable {
#JsonSerialize(using = JsonDateSerializer.class)
#JsonDeserialize(using = JsonDateDeserializer.class)
private String date;
//normal getters and setters
}
Ok, so first off here's the JSON that's returning from my web service. I'm trying to deserialize it into pojos after an asynchronous query in a ResponseHandler in my Android ContentProvider.
{"exampleList" : [{
"locationId" : "00001" ,
"owners" : [
{
"paidID" : { "$oid" : "50a9c951300493f64fbffdb6"} ,
"userID" : { "$oid" : "50a9c951300493f64fbffdb6"}
} ,
{
"paidID" : { "$oid" : "50a9c951300493f64fbffdb7"} ,
"userID" : { "$oid" : "50a9c951300493f64fbffdb7"}
}
]
}]}
At first, I was confused about the problem I was seeing, since I use the same Jackson-annotated beans for my web service as I do in my Android app--but then I realized that the owners object was never getting sent in the sample JSON to my web service (it skips the POJOs on my web service and gets added into the documents in mongoDB through atomic updates from the DAO).
So OK. Up to now, Jackson wasn't having to handle the owners object, and now that it is it is choking on it, namely:
JsonMappingException: Can not deserialize instance of java.lang.String out of
START_OBJECT token at [char position where you can find "userID" and "paidID"]
through reference chain [path to my Jackson bean which contains the owners class]
My Jackson bean has a wrapper, which is what that "exampleList" is all about:
public class Examples extends HashMap<String, ArrayList<Example>> {
}
And then the actual Example class:
#JsonIgnoreProperties(ignoreUnknown = true)
public class Example implements Comparable<Example> {
#ObjectId #Id
private String id;
#JsonProperty(Constants.Example.location)
private String location;
#JsonProperty(Constants.Example.OWNERS)
private List<Owners> owners;
public int compareTo(Example _o) {
return getId().compareTo(_o.getId());
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public List<Example.Owners> getOwners() {
return owners;
}
public void setOwners(List<Example.Owners> owners) {
this.owners = owners;
}
public Example() {
}
#JsonCreator
public Example(#Id #ObjectId String id) {
this.id = id;
}
#JsonIgnoreProperties(ignoreUnknown = true)
public static class Owners implements Comparable<Owners> {
#JsonProperty(Constants.Example.USERID)
private String userID;
#JsonProperty(Constants.Example.PAIDID)
private String paidID;
public Owners() {
}
public int compareTo(Owners _o) {
return getUserID().compareTo(_o.getUserID());
}
#ObjectId
public String getUserID() {
return userID;
}
#ObjectId
public void setUserID(String userID) {
this.userID = userID;
}
#ObjectId
public String getPaidID() {
return paidID;
}
#ObjectId
public void setPaidID(String paidID) {
this.paidID = paidID;
}
}
}
And finally, the code in the ResponseHandler where this is all failing (the 2nd line produces the JsonMappingException):
objectMapper = MongoJacksonMapperModule.configure(objectMapper);
mExamples = objectMapper.readValue(jsonParser, Examples.class);
I have a feeling the issue is that Jackson still doesn't know how to map those $oid, which are the mongoDB ObjectIds. The MongoJacksonMapper library is supposed to help that by providing the #ObjectId annotation and a way to configure the ObjectMapper to use that library, but it still isn't working. For some reason, it's still looking for the userID or paidID as a String, not an ObjectId. Any ideas?
Another alternative is
com.fasterxml.jackson.databind.ser.std.ToStringSerializer.
#Id
#JsonSerialize(using = ToStringSerializer.class)
private final ObjectId id;
This will result in:
{
"id": "5489f420c8306b6ac8d33897"
}
For future users: Use a custom jackson deserializer to convert $oid back to ObjectId.
public class ObjectIdDeserializer extends JsonDeserializer<ObjectId> {
#Override
public ObjectId deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
JsonNode oid = ((JsonNode)p.readValueAsTree()).get("$oid");
return new ObjectId(oid.asText());
}
}
How to use:
ObjectMapper mapper = new ObjectMapper();
SimpleModule mod = new SimpleModule("ObjectId", new Version(1, 0, 0, null, null, null));
mod.addDeserializer(ObjectId.class, new ObjectIdDeserializer());
mapper.registerModule(mod);
YourClass obj = mapper.readValue("{your json with $oid}", YourClass.class);
My code had at least two problems that were pretty tough to track down answers to online, so I'll make sure to link here. Basically, child classes need a constructor in the parent class that calls Jackson's readValue() to map the child. As far as mongoDB $oid's go, you should create a separate MongoId class to represent these mongo objects, and follow a similar pattern as with the child class to map the data when it comes in for deserialization. Here's a blog post I found that describes this well and provides some examples.
Jackson does not know how to serialize an ObjectId. I tweaked Arny's code to serialize any ObjectId and provide this working example:
public class SerialiserTest {
private ObjectMapper mapper = new ObjectMapper();
public static class T {
private ObjectId objectId;
public ObjectId getObjectId() {
return objectId;
}
public void setObjectId(ObjectId objectId) {
this.objectId = objectId;
}
}
#Test
public final void serDeser() throws IOException {
T t = new T();
t.setObjectId(new ObjectId());
List<T> ls = Collections.singletonList(t);
String json = mapper.writeValueAsString(ls);
System.out.println(json);
SimpleModule mod = new SimpleModule("ObjectId", new Version(1, 0, 0, null, null, null));
mod.addDeserializer(ObjectId.class, new ObjectIdDeserializer());
mapper.registerModule(mod);
JavaType type = mapper.getTypeFactory().
constructCollectionType(List.class, T.class);
List<?> l = mapper.readValue(json, type);
System.out.println(l);
}
}
public class ObjectIdDeserializer extends JsonDeserializer<ObjectId> {
#Override
public ObjectId deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
JsonNode n = (JsonNode)p.readValueAsTree();
return new ObjectId(n.get("timestamp").asInt(), n.get("machineIdentifier").asInt(), (short) n.get("processIdentifier").asInt(), n.get("counter").asInt());
}
}
There's an even easier way documented here which was a lifesaver for me. Now you can use the ObjectId in Java but when you go to/from JSON it'll be a String.
public class ObjectIdJsonSerializer extends JsonSerializer<ObjectId> {
#Override
public void serialize(ObjectId o, JsonGenerator j, SerializerProvider s) throws IOException, JsonProcessingException {
if(o == null) {
j.writeNull();
} else {
j.writeString(o.toString());
}
}
}
And then in your beans:
#JsonSerialize(using=ObjectIdJsonSerializer.class)
private ObjectId id;
I did it like this:
#Configuration
public class SpringWebFluxConfig {
#Bean
#Primary
ObjectMapper objectMapper() {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.serializerByType(ObjectId.class, new ToStringSerializer());
builder.deserializerByType(ObjectId.class, new JsonDeserializer() {
#Override
public Object deserialize(JsonParser p, DeserializationContext ctxt)
throws IOException {
Map oid = p.readValueAs(Map.class);
return new ObjectId(
(Integer) oid.get("timestamp"),
(Integer) oid.get("machineIdentifier"),
((Integer) oid.get("processIdentifier")).shortValue(),
(Integer) oid.get("counter"));
}
});
return builder.build();
}
}
I have a java object as given below. How to serialize/deserialize with Jackson json?
public class Employee {
private String name;
List<Employee> friends;
}
The JSON:
{"friends":[{"name":"abc"}],[{{"name":"pqr"}}]}
My Implementation class:
public class EmployeeImpl implements Employee, Serializable {
private String name;
private List<Employee> friends;
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public List<Employee> getFriends() { return friends; }
public void setFriends(List<Employee> friends) { this.friends = friends; }
}
Test Class:
public class Test {
public static void main(String[] args) throws Exception {
String json = "{\"name\":\"gangi\", \"friends\":[{\"name\":\"abc\"},{\"name\":\"pqr\"}]}";
Employee employee = deserializeJson(json, new TypeReference<EmployeeImpl>(){});
}
public static <T> T deserializeJson(String jsonData, TypeReference<T> typeRef) throws Exception {
ObjectMapper mapper = new ObjectMapper();
return mapper.<T>readValue(jsonData, typeRef);
}
}
Exception stacktrace...
Exception in thread "main" org.codehaus.jackson.map.JsonMappingException:
Can not construct instance of Employee,
problem: abstract types can only be instantiated with additional type information at
[Source: java.io.StringReader#68da4b71; line: 1, column: 29]
(through reference chain: EmployeeImpl["friends"]) at
org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:163)
Add following annotation to your Employee interface
`#JsonDeserialize(as=EmployeeImpl.class)`
Your json format is incorrect. See [http://www.json.org/] on how to define array/lists in json. Example for json building [http://java.dzone.com/tips/json-processing-using-jackson]