Reputation: 67
I would like to generate JSON String from Java object
public class Resource {
String name;
List<Item> items;
public String resourceAsJson(Resource resource) throws JsonProcessingException {
ObjectMapper objectMapper = new ObjectMapper();
return objectMapper.writeValueAsString(resource);
}
Where Item
public class Item {
Map<String, String> systemFields;
Map<String, String> dataFields;
}
The form of the JSON String at this moment is
{
"name": "Person",
"items": [
{
"systemFields": {
"systemField1": "xxx",
"systemField2": "xxx",
"systemField3": "x"
},
"dataFields": {
"dataField1": "xxx",
"dataField2": "xxx",
"dataField3": "x"
}
}
]
}
What I try to obtain is the different form of JSON (ommiting the Item and have "system fields" "data fields" in one Json table)
{
"Person":[
{
"systemField1": "xxx",
"systemField2": "xxx",
"systemField3": "Warsaw",
"dataField1": "xxx",
"dataField2": "xxx",
"dataField3": "xxx"
}
]
}
Is there a way to do this with Jackson without changing the model?
Upvotes: 2
Views: 700
Reputation: 38645
In cases like this where default representation of POJO
is not what you want you need to implement custom serialisers. In your case they could look like below:
class ResourceJsonSerializer extends JsonSerializer<Resource> {
@Override
public void serialize(Resource value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
gen.writeStartObject();
gen.writeFieldName(value.getName());
gen.writeObject(value.getItems());
gen.writeEndObject();
}
}
class ItemJsonSerializer extends JsonSerializer<Item> {
@Override
public void serialize(Item value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
gen.writeStartObject();
writeMap(value.getSystemFields(), gen);
writeMap(value.getDataFields(), gen);
gen.writeEndObject();
}
private void writeMap(Map<String, String> map, JsonGenerator gen) throws IOException {
if (map != null) {
for (Map.Entry<String, String> entry : map.entrySet()) {
gen.writeStringField(entry.getKey(), entry.getValue());
}
}
}
}
You can register them using com.fasterxml.jackson.databind.annotation.JsonSerialize
annotation:
@JsonSerialize(using = ResourceJsonSerializer.class)
class Resource {
and:
@JsonSerialize(using = ItemJsonSerializer.class)
class Item {
Upvotes: 1