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How to conditionally exclude property from a json response

I have a class pojo used to return a response to an API call in the rest controller
EmployeeResponse response = validationService.validate(request);
return new ResponseEntity<>(response, HttpStatus.OK);
However now we want to feature flag the controller class so that if a configuration property is not set, the response will not include a property. How can we do that?
public class EmployeeResponse {
private String firstName;
private String lastName
private String address; // don't want to include this if boolean flag is not set
}
EDIT: adding the controller code here to show that an object is returned without being serialized so I don't see how to fit objectMapper into that
#RestController
public class EmployeeController {
#PostMapping(value = "/validate", produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<EmployeeResponse> get(final #RequestBody EmployeeRequest employeeRequest) {
MasterSubResponse response = validationService.validate(employeeRequest);
return new ResponseEntity<>(response, HttpStatus.OK);
}
}

You can use Jackson Filter to control the serialization process. When using JSON format, Spring Boot will use an ObjectMapper instance to serialize responses and deserialize requests. The idea is to create custom filter where you will place business logic for conditionally rendering desired field from DTO. Then you should add that filter to object mapper.
To summarize,here are the steps youn need to follow :
Anottate your DTO class with #JsonFilter("myFilter")
Create implementation class for your custom filter
Create configuration class for ObjectMapper where you will set filter created in step 1.
Create your boolean flag in application.properties file
Step 1:
import com.fasterxml.jackson.annotation.JsonFilter;
#JsonFilter("myFilter")
public class EmployeeResponse {
private String firstName;
private String lastName;
private String address;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
Step 2:
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
import com.fasterxml.jackson.databind.ser.PropertyFilter;
import com.fasterxml.jackson.databind.ser.PropertyWriter;
import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
public class CustomFilter extends SimpleBeanPropertyFilter implements PropertyFilter {
private boolean isSerializable;
#Override
public void serializeAsField
(Object pojo, JsonGenerator jgen, SerializerProvider provider, PropertyWriter writer)
throws Exception {
if (include(writer)) {
if (!writer.getName().equals("address")) {
writer.serializeAsField(pojo, jgen, provider);
return;
}
System.out.println(isSerializable);
if (isSerializable) {
writer.serializeAsField(pojo, jgen, provider);
}
} else if (!jgen.canOmitFields()) { // since 2.3
writer.serializeAsOmittedField(pojo, jgen, provider);
}
}
#Override
protected boolean include(BeanPropertyWriter writer) {
return true;
}
#Override
protected boolean include(PropertyWriter writer) {
return true;
}
public boolean isSerializable() {
return isSerializable;
}
public void setSerializable(boolean serializable) {
isSerializable = serializable;
}
}
Step 3:
import com.example.demo.filter.CustomFilter;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
#Configuration
public class ObjectMapperCofiguration {
#Value("${isSerializable}")
public boolean isSerializable;
#Configuration
public class FilterConfiguration {
public FilterConfiguration(ObjectMapper objectMapper) {
SimpleFilterProvider simpleFilterProvider = new SimpleFilterProvider().setFailOnUnknownId(true);
CustomFilter customFilter = new CustomFilter();
customFilter.setSerializable(isSerializable);
simpleFilterProvider.addFilter("myFilter", customFilter);
objectMapper.setFilterProvider(simpleFilterProvider);
}
}
}
Step 4 :
In application.properties file add following property :
isSerializable= false
Step 5:
Create Controller class to test it:
#RestController
public class RestSpringBootController {
#GetMapping(path = "/test")
public ResponseEntity<EmployeeResponse> test() throws JsonProcessingException {
EmployeeResponse employeeResponse = new EmployeeResponse();
employeeResponse.setAddress("addres");
employeeResponse.setFirstName("first");
employeeResponse.setLastName("last");
ResponseEntity<EmployeeResponse> responseEntity = ResponseEntity.ok(employeeResponse);
return responseEntity;
}
}
Finally, when you start your SpringBoot app, with boolean flag isSerializable set to false you should get following response:
If you set isSerializable flag to true and restart the app, you shoud see following response:

Create a java model from json response

I'm trying to create a java model for my json response in a melanoma detection app.
My response looks like this:
{
"success": true,
"predictions": [
{
"label": "Non-melanoma",
"probability": 0.016881238669157028
},
{
"label": "Melanoma",
"probability": 0.9831187129020691
}
]
}
I usually go with https://www.jsonschema2pojo.org/ in creating my java model from json, but this time I am getting this:
-----------------------------------com.example.Example.java-----------------------------------
package com.example;
import java.util.List;
import javax.annotation.Generated;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
#Generated("jsonschema2pojo")
public class Example {
#SerializedName("success")
#Expose
private Boolean success;
#SerializedName("predictions")
#Expose
private List<Prediction> predictions = null;
public Boolean getSuccess() {
return success;
}
public void setSuccess(Boolean success) {
this.success = success;
}
public List<Prediction> getPredictions() {
return predictions;
}
public void setPredictions(List<Prediction> predictions) {
this.predictions = predictions;
}
}
-----------------------------------com.example.Prediction.java-----------------------------------
package com.example;
import javax.annotation.Generated;
import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;
#Generated("jsonschema2pojo")
public class Prediction {
#SerializedName("label")
#Expose
private String label;
#SerializedName("probability")
#Expose
private Double probability;
public String getLabel() {
return label;
}
public void setLabel(String label) {
this.label = label;
}
public Double getProbability() {
return probability;
}
public void setProbability(Double probability) {
this.probability = probability;
}
}
which leads to different files that I don't know how to use later.
I'd like to have one response model, like response_model.java to use like this in the app:
Call<response_model> call = getResponse.uploadFile(fileToUpload, filename);
call.enqueue((Callback<response_model>)(new Callback<response_model>() {
public void onResponse(#NotNull Call call, #NotNull Response response) {
Intrinsics.checkParameterIsNotNull(call, "call");
Intrinsics.checkParameterIsNotNull(response, "response");
if (response.isSuccessful()) {
Log.v("upload", "response succ");
response_model serverResponse = (response_model) response.body();
if (serverResponse.getPredictions()!=null) {
((TextView)findViewById(R.id.output_text)).setText(serverResponse.getPredictions().toString());
} else {
loader.setVisibility(View.GONE);
Toast.makeText(getApplicationContext(), "response null",Toast.LENGTH_SHORT).show();
}
} else {
Log.v("Response 1", "wasnt successfull");
}
}
Is there a way?

Actually your java model is working just fine.
You can access each label/probability as a list element, by:
serverResponse.getPredictions().get(0).getLabel()
serverResponse.getPredictions().get(0).getProbability()
(which should give you the 1st Label-Probability element pair).
If you're always gonna have 2 elements in your response Prediction list (one for melanoma and one for non-melanoma) you can easily hard-code it with get(0) and get(1).

You can use this link to generate pojo
https://json2csharp.com/json-to-pojo
This is how your pojo will looks like in a single file
package com.test.test;
import java.util.List;
class Prediction{
public String label;
public double probability;
}
public class Test{
public boolean success;
public List<Prediction> predictions;
}

Jackson ObjectMapper readValue() unrecognized field when parsing to Object

I am creating simple rest client in Java/Spring. My request has been consumed properly by remote service and I got the response String something:
{"access_token":"d1c9ae1b-bf21-4b87-89be-262f6","token_type":"bearer","expires_in":43199,"grant_type":"client_credentials"}
The code below is the Object where I want to bind values from Json Response
package Zadanie2.Zadanie2;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
public class Token {
String access_token;
String token_type;
int expiresIn;
String grantType;
//////////////////////////////////////////////////////
public Token() {
/////////////////////////////////
}
/////////////////////////////////////////////////////
public void setAccessToken(String access_token) {
this.access_token=access_token;
}
public String getAccessToken() {
return access_token;
}
////////////////////////////////////////////////
public void setTokenType(String token_type) {
this.token_type=token_type;
}
public String getTokenType() {
return token_type;
}
//////////////////////////////////////////////////////
public void setExpiresIn(int expiresIn) {
this.expiresIn=expiresIn;
}
public int getExpiresIn() {
return expiresIn;
}
//////////////////////////////////////////////////////////
public void setGrantType(String grantType) {
this.grantType=grantType;
}
public String getGrantType() {
return grantType;
}
}
all the time I am getting "unrecognized field access_token" but when I add objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
then access_token will be null
jsonAnswer=template.postForObject(baseUriAuthorize, requestEntity, String.class);
System.out.println(jsonAnswer);
Token token=objectMapper.readValue(jsonAnswer, Token.class);
System.out.println(token.getAccessToken());
I tried with #JsonProperty annotations. I tried with changing field by for example "#JsonProperty(accessToken)" because I thought there is an issue with "_" sign in variable name. I added getters and setters. Maybe there is a problem with the version I use but I don't think so because I am using "com.fasterxml.jackson.core"

You tried with "#JsonProperty(accessToken)". But your json contains access_token. how it works?
Try with this class:
public class Token {
#JsonProperty("access_token")
String accessToken;
#JsonProperty("token_type")
String tokenType;
int expiresIn;
String grantType;
//getter setter
}

Your setters do not match with the JSON key.
To read it correctly, you should change your setters to:
setAccess_token()
setToken_type()
...
But honestly, this is so ugly.
Try following the Java bean name convention and customize the JSON key with #JsonProperty:
public class Token {
#JsonProperty("access_token")
String accessToken;
....
}

Mapping JSON into POJO using Gson

I have the following JSON to represent the server response for a salt request:
{
"USER":
{
"E_MAIL":"email",
"SALT":"salt"
},
"CODE":"010"
}
And i tried to map it with the following POJO:
public class SaltPOJO {
private String code = null;
private User user = null;
#Override
public String toString() {
return this.user.toString();
}
public String getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public class User {
private String e_mail = null;
private String salt = null;
#Override
public String toString() {
return this.e_mail + ": " + this.salt;
}
public String getE_mail() {
return e_mail;
}
public void setE_mail(String e_mail) {
this.e_mail = e_mail;
}
public String getSalt() {
return salt;
}
public void setSalt(String salt) {
this.salt = salt;
}
}
}
Now everytime i do this:
Gson gson = new Gson();
SaltPOJO saltPojo = gson.fromJson(json.toString(), SaltPOJO.class);
Log.v("Bla", saltPojo.toString());
The saltPojo.toString() is null. How can i map my JSON into POJO using Gson?
Is the order of my variables important for the Gson mapping?

Is the order of my variables important for the Gson mapping?
No, that's not the case.
How can i map my JSON into POJO using Gson?
It's Case Sensitive and the keys in JSON string should be same as variable names used in POJO class.
You can use #SerializedName annotation to use any variable name as your like.
Sample code:
class SaltPOJO {
#SerializedName("CODE")
private String code = null;
#SerializedName("USER")
private User user = null;
...
class User {
#SerializedName("E_MAIL")
private String e_mail = null;
#SerializedName("SALT")
private String salt = null;

You don't have proper mapping between your getter and setter. If you change your json to something like below, it would work:
{
"user":
{
"email":"email",
"salt":"salt"
},
"code":"010"
}
If you are getting json form third party then unfortunately, you would have to change your pojo or you could use adapter.

Generating JSON from POJO for a specific scenario

I have used Jackson and JSONObject to generate a plain JSON - things are fine here. I have a specific case where my pojo looks like below and i need the JSON is the specified format.
package test;
import javax.xml.bind.annotation.XmlRootElement;
#XmlRootElement(name = "login")
public class LoginApi implements IRestBean {
private String username;
private String password;
private String sfSessionId;
private String sfServerUrl;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getSfSessionId() {
return sfSessionId;
}
public void setSfSessionId(String sfSessionId) {
this.sfSessionId = sfSessionId;
}
public String getSfServerUrl() {
return sfServerUrl;
}
public void setSfServerUrl(String sfServerUrl) {
this.sfServerUrl = sfServerUrl;
}
}
The JSON that i am able to generate looks like this:
{
"username" : null,
"password" : null,
"sfSessionId" : null,
"sfServerUrl" : null
}
But this is not my requirement - i need the JSON in the below format so that my server accepts this as a valid JSON:
{
"#type":"login",
"username":"username#domain.com",
"password":"password",
"sfSessionId":null,
"sfServerUrl":null
}
Please help. Thanks in advance!

Add a private field to the POJO with the type.
#XmlRootElement(name = "login")
public class LoginApi implements IRestBean {
...
#XmlAttribute(name = "type")
private String getJsonType() {
return "login";
}
...
}
Note the use of XmlAttribute to automatically append an "#" to the name.

Change the IRestBean interface to include the #JsonTypeInfo annotation:
#JsonTypeInfo(use=JsonTypeInfo.Id.NAME, include=JsonTypeInfo.As.PROPERTY, property="#type")
public interface IRestBean {
...
}
Next, annotate the LoginApi class with #JsonTypeName:
#XmlRootElement(name = "login")
#JsonTypeName("login")
public class LoginApi implements IRestBean {
...
}
These are both Jackson-specific annotations.