There's no built-in way to do this. You'll have to write your own JsonSerializer. Something like
class ModelSerializer extends JsonSerializer<List<Model>> {
@Override
public void serialize(List<Model> value, JsonGenerator jgen,
SerializerProvider provider) throws IOException {
jgen.writeStartArray();
for (Model model : value) {
jgen.writeStartObject();
jgen.writeObjectField("model", model);
jgen.writeEndObject();
}
jgen.writeEndArray();
}
}
and then annotate the models field so that it uses it
@JsonSerialize(using = ModelSerializer.class)
private List<Model> models;
This would serialize as
{
"status": "success",
"models": [
{
"model": {
"id": 1,
"color": "red"
}
},
{
"model": {
"id": 2,
"color": "green"
}
}
]
}
If you're both serializing and deserializing this, you'll need a custom deserializer as well.
Answer from Sotirios Delimanolis on Stack OverflowThere's no built-in way to do this. You'll have to write your own JsonSerializer. Something like
class ModelSerializer extends JsonSerializer<List<Model>> {
@Override
public void serialize(List<Model> value, JsonGenerator jgen,
SerializerProvider provider) throws IOException {
jgen.writeStartArray();
for (Model model : value) {
jgen.writeStartObject();
jgen.writeObjectField("model", model);
jgen.writeEndObject();
}
jgen.writeEndArray();
}
}
and then annotate the models field so that it uses it
@JsonSerialize(using = ModelSerializer.class)
private List<Model> models;
This would serialize as
{
"status": "success",
"models": [
{
"model": {
"id": 1,
"color": "red"
}
},
{
"model": {
"id": 2,
"color": "green"
}
}
]
}
If you're both serializing and deserializing this, you'll need a custom deserializer as well.
This is an oldish question, But there is an arguably more idiomatic way of implementing this (I'm using jackson-databind:2.8.8):
Define a ModelSerializer (That extends StdSerializer as recommended by Jackson) that prints your model how you like and use the @JsonSerialize(contentUsing = ...) over your collection type:
class ModelSerializer extends StdSerializer<Model> {
public ModelSerializer(){this(null);}
public ModelSerializer(Class<Model> t){super(t);} // sets `handledType` to the provided class
@Override
public void serialize(List<Model> value, JsonGenerator jgen,
SerializerProvider provider) throws IOException,
JsonProcessingException {
jgen.writeStartObject();
jgen.writeObjectField("model", value);
jgen.writeEndObject();
}
}
Meanwhile, in another file:
class SomethingWithModels {
// ...
@JsonSerialize(contentUsing = ModelSerializer.class)
private Collection<Model> models;
// ...
}
Now you aren't bound to just Lists of models but may apply this to Collections, Sets, Native []s and even the values of Maps.
json - Java+Jackson : How to serialize a object containing array/list of other objects - Stack Overflow
java - How do I serialize a list of objects with Jackson? - Stack Overflow
java - How to serialize and deserialize a list of objects using Jackson - Stack Overflow
json - Jackson - Serialize only Ids of objects in a list attribute of a Java Pojo - Stack Overflow
I am able to achieve this by modifying the Customer class in following way.
@Data
public class Customer implements Serializable {
private long customerId;
private String name;
private String taxId;
private String phone;
private String address;
private String emailId;
private Date created;
@JsonIdentityInfo(generator= ObjectIdGenerators.PropertyGenerator.class, property="invoiceId")
@JsonIdentityReference(alwaysAsId=true)
private List<Invoice> invoices;
}
The answer is inspired from https://stackoverflow.com/a/17583175/1365340
With this I can generate Customer json with invoice Id list. The Invoice object when serialized separately gets all values from all its fields in json.
You can use @JsonIgnore for ingnoring properties in JSON response.
Or you can use transient keyword for avoiding serialization
I got it working by adding a custom serializer:
class Foo {
@JsonSerialize(using = MySerializer.class)
private List<String> fooElements;
}
public class MySerializer extends JsonSerializer<Object> {
@Override
public void serialize(Object value, JsonGenerator jgen, SerializerProvider provider)
throws IOException, JsonProcessingException {
List<String> fooList = (List<String>) value;
if (fooList.isEmpty()) {
return;
}
String fooValue = fooList.get(0);
String[] fooElements = fooValue.split(",");
jgen.writeStartArray();
for (String fooValue : fooElements) {
jgen.writeString(fooValue);
}
jgen.writeEndArray();
}
}
If you are using Jackson, then the following simple example worked for me.
Define the Foo class:
public class Foo {
private List<String> fooElements = Arrays.asList("one", "two", "three");
public Foo() {
}
public List<String> getFooElements() {
return fooElements;
}
}
Then using a standalone Java app:
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
public class JsonExample {
public static void main(String[] args) throws JsonGenerationException, JsonMappingException, IOException {
Foo foo = new Foo();
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.writeValueAsString(foo));
}
}
Output:
{"fooElements":["one","two","three"]}
First create a mapper :
import com.fasterxml.jackson.databind.ObjectMapper;// in play 2.3
ObjectMapper mapper = new ObjectMapper();
As Array:
MyClass[] myObjects = mapper.readValue(json, MyClass[].class);
As List:
List<MyClass> myObjects = mapper.readValue(jsonInput, new TypeReference<List<MyClass>>(){});
Another way to specify the List type:
List<MyClass> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class));
From Eugene Tskhovrebov
List<MyClass> myObjects = Arrays.asList(mapper.readValue(json, MyClass[].class))
This solution seems to be the best for me.