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How to deserialize complex JSON to java object

I need to deserialize JSON to java class.
I have JSON like the following:
{
"data": {
"text": "John"
},
"fields":[
{
"id": "testId",
"name": "fieldName",
"options": {
"color": "#000000",
"required": true
}
},
{
"id": "testId",
"name": "fieldName1",
"options": {
"color": "#000000",
"required": false
}
}
]
}
and I need to deserialize this JSON (only "fields" section) to java class like the following:
public class Field {
public final String id;
public final String name;
public final String color;
public final boolean required;
}
and I need to get something like the following:
// The key is the id from field object (it can be the same in the multiple objects.)
Map<String, List<Field>> fields = objectMapper.readValue(json, Map<String, List<Field>>);
How can I do it using Jackson?

As long as jackson doesn't support #JsonWrapped, you have to use the following work around.
First you need to create a custom class which contains the fields:
public class Fields {
public List<Field> fields;
}
Depending on your ObjectMapper configuration you have to add #JsonIgnoreProperties(ignoreUnknown = true) to the Fields class, to ignore any other properties.
Next is that you have to define the nested Options class which is solely used temporarily:
public class Options {
public String color;
public boolean required;
}
And at last add this constructor to your Field class:
#JsonCreator
public Field(#JsonProperty("id") String id, #JsonProperty("name") String name, #JsonProperty("options") Options options){
this.id = id;
this.name = name;
this.color = options.color;
this.required = options.required;
}
The #JsonCreator annotation indicates to jackson that this constructor needs to be used for the deserialization. Also the #JsonProperty annotations are required as arguments to constructors and methods are not preserved in the bytecode
Then you can deserialize your json just like this:
List<Field> fields = objectMapper.readValue(json, Fields.class).fields;

convert List<Object> to List<HashMap<String,Double>> for a json array

I have a Json as shown below:-
{
"componentModelData": {
"modelNumber": "ABC",
"modelName": "",
"modelDescription": "",
"modelVendor": null,
"componentName": "HELO"
},
"revisionData": {
"revisionName": "rev12",
"revisionComment": "Comment",
"modifiedBy": "2323553"
},
"configData": [{"nodes":2085,"FxPOS-SX":16.5051,"FxPOS-SY":11.0479,"FxPOS-SZ":115.3421,"FxPOS-SXY":-13.8094,"FxPOS-SYZ":36.0105
},{"nodes":2085,"FxPOS-SX":16.5051,"FxPOS-SY":11.0479,"FxPOS-SZ":115.3421,"FxPOS-SXY":-13.8094,"FxPOS-SYZ":36.0105}]
}
DataMapping.java
#Getter
#Setter
#JsonSerialize
#NoArgsConstructor
#AllArgsConstructor
public class DataMapping implements Serializable {
/**
*
*/
private static final long serialVersionUID = -2635323042843403966L;
#JsonProperty("componentModelData")
#Valid
public ComponentModelDTO componentModelDTO;
#JsonProperty("revisionData")
#Valid
public RevisionDTO revisionDTO;
#JsonProperty("configData")
private List<Object> configData;
}
I want to convert the configData list to List<HashMap<String,Double>> list where String is the keys like 'nodes,FxPOS-SX,FxPOS-SY' and value is their respective values.
Can anyone please help me how can i achieve this?

Just replace List<Object> with List<Map<String,Double>>. Jackson will do the hard work for you:
#JsonProperty("configData")
private List<Map<String, Double>> configData;

spring restTemplate dynamic mapping

I am using spring restTemplate to map a response to a POJO.
The response of the rest api is like this:
"attributes": {
"name": {
"type": "String",
"value": ["John Doe"]
},
"permanentResidence": {
"type": "Boolean",
"value": [true]
},
"assignments": {
"type": "Grid",
"value": [{
"id": "AIS002",
"startDate": "12012016",
"endDate": "23112016"
},{
"id": "AIS097",
"startDate": "12042017",
"endDate": "23092017"
}]
}
}
in the parent class, I have:
public class Users {
private Map<String, Attribute> attributes;
}
If all the values of were String type, then I could have done like:
public class Attribute {
private String type;
private String[] value;
}
But the values are of different types. So I thought of doing the following:
public class Attribute {
private String type;
private Object[] value;
}
The above should work, but at every step I have to find out what is the type of Object.
So, my question is can I have something like this:
public class Attribute {
#JsonProperty("type")
private String type;
#JsonProperty("value")
private String[] stringValues;
#JsonProperty("value")
private Boolean[] booleanValues;
#JsonProperty("value")
private Assignments[] assignmentValues; // for Grid type
}
But it is not working and throwing errors: Conflicting setter definitions for property "value"
What is the recommended way of handling this scenario?

I would recommend Jackson facilities for handling polymorphism here:
#JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "type")
#JsonSubTypes({
#JsonSubTypes.Type(value = BooleanAttribute.class, name = "Boolean"),
#JsonSubTypes.Type(value = StringAttribute.class, name = "String")
})
class Attribute {
private String type;
}
class BooleanAttribute extends Attribute {
private Boolean[] value;
}
class StringAttribute extends Attribute {
private String[] value;
}
JsonTypeInfo tells Jackson that this is a base class and the type will be determined by a JSON field named "type"
JsonSubTypes maps subtypes of Attribute to values of "type" in JSON.
If you add an appropriate subtype for Assignments and getters/setters Jackson will be able to parse your JSON.

How do I parse a JSON array into different objects using Jackson on Android?

I'm trying to parse JSON like the following into object using Jackson on Android (Note: I'm not in control of the JSON format - the format comes from Yammer)
"references": [
{
"type": "user",
"id": 12345678,
"name": "Wex"
},
{
"type": "message",
"id": 12345679,
"body":
{
"plain":"A short message"
}
},
{
"type": "thread",
"id": 12345670,
"thread_starter_id": 428181699
}
]
The problem is that each entry in references is a different type of object with different properties. As a start I've got:
public static class Reference
{
public String type;
public String id;
}
I'd rather avoid putting all potential properties in one object like:
public static class Reference
{
public static class Body
{
public String plain;
}
public String type;
public String id;
public String name;
public Body body;
public String thread_starter_id;
}
And want to use separate classes that are created dependant on the type value like:
public static class ReferenceUser extends Reference
{
public String name;
}
public static class ReferenceMessage extends Reference
{
public static class Body
{
public String plain;
}
public Body body;
}
public static class ReferenceThread extends Reference
{
public String thread_starter_id;
}
So... what's the best way of getting Jackson to parse the JSON like that?
I'm currently parsing it quite simply like this:
ObjectMapper mapper = new ObjectMapper();
Reference[] references = mapper.readValue(json, Reference[].class);

you can do something like this with Jackson:
#JsonTypeInfo(
use = JsonTypeInfo.Id.NAME,
include = JsonTypeInfo.As.PROPERTY,
property = "type")
#JsonSubTypes({
#JsonSubTypes.Type(name = "user", value = ReferenceUser.class),
#JsonSubTypes.Type(name = "message", value = ReferenceMessage.class),
#JsonSubTypes.Type(name = "thread", value = ReferenceThread.class)
})
public class Reference {
int id;
String name;
}
This way you will generate subclasses.
John

How to map JSON data into any Object in JAVA?

I would like to map from JSON-Response into my Java Object using Jersey. I have this such Json response:
{
"act": "add",
"col": "student",
"data": [
{
"firstName": "alex",
"lastName": "homer",
"age": "18",
"roomNo": "1301"
},
{
"firstName": "alex",
"lastName": "homer",
"age": "18",
"roomNo": "1301"
}
]
}
And this is my bean that I'd like to map the Json-response into:
#XmlRootElement(name = "request")
#XmlAccessorType(XmlAccessType.FIELD)
public class RequestAction implements RequestOperations {
#XmlElement(required = true, name = "act")
private String action;
#XmlElement(required = true, name = "col")
private String collectionName;
#XmlElement(required = false, name = "oid")
private String objectId;
#XmlElement(name = "data")
private List<Object> data;
public RequestAction() {
}
//getters setters
}
So, my problem is how to map data under "data": {[....]}?
Because it also can be identified with any Object.
For this example, the object is Customer. How about if object is Student, Animal, or anything else? If possible, I dont need create that object (I means Customer, and others).
Do you have any idea or suggestion?

Consider use of Gson library: https://code.google.com/p/google-gson/
I didn't have a problem with lists there.

if your bean property name are the same as your JSON's, you can use json-lib.
For maven project, just put
<dependency>
<groupId>net.sf.json-lib</groupId>
<artifactId>json-lib</artifactId>
<version>2.4</version>
<classifier>jdk15</classifier>
</dependency>
into the pom.xml.
JSONObject jsonObject = (JSONObject) JSONSerializer.toJSON(YOUR JSON STRING);
RequestAction re = (RequestAction) JSONObject.toBean(jsonObject,RequestAction.class);