I am trying to create a POJO for the following JSON.
{
"key1":"value1",
"key2":"value2",
"hashmap":
{
"1":"val"
"2":"val"
...
"n":"val"
}
}
Now the POJO I tried was
public class MyPOJO{
#SerializedName{"key1"}
#Expose
private String key1;
#SerializedName{"key2"}
#Expose
private String key2;
#SerializedName{"hashmap"}
#Expose
private HashMap<String,String> hMap;
}
The problem is that the hashmap is not getting serialized. It is just ignored when the class gets serialized.
This is how I use the class in Retrofit.
#POST("/endpoint/")
void foo(#Body MyPojo, Callback<Response> callback);
One suggestion I came across is to use an inner class instead of the Hashmap. But my keys are dynamic, I cannot define variables for each key. I need to get the Hashmap serialized.
http://www.jsonschema2pojo.org/ use this website to generate pojo from json
Maybe you should have a look at retrofit converters and use a converter which supports maps.
Or use a custom converter.
Related
I am currently using Jackson's XmlMapper and ObjectMapper. I want to map the string to a POJO (I think I'm using that term correctly) that has a private field with the same name as the JSON string's field. The XML string has a different name for the same field/attribute, and I want to use the JSON field name.
I also want to essentially "ignore" that field (while keeping it) and store it as something like a JsonNode, as the value of that field can be some complex, nested value without a known shape.
Example:
public static class OuterClass {
private String firstValue;
private InnerClass innerValue;
// ... getters/setters
}
public static class InnerClass {
private JsonNode data; // complex, nested, so no POJO to map to
private String otherValue;
// ... getters/setters
}
The JSON might look like this:
{
"innerValue": {
"data": {
... complex stuff
},
"otherValue": "more stuff"
},
"firstValue": "thingy"
}
The XML might look like this:
<result>
<innerValue>
<incorrectName>
... complex stuff
</incorrectName>
<otherValue>more stuff</otherValue>
</innerValue>
<firstValue>thingy</firstValue>
</result>
So the goal is to get the XML to work with that class, including both mapping incorrectName to the class' data, as well as storing the complex inner part as something like a JsonNode since I don't have a class to model it.
I have the JSON working with new ObjectMapper().readValue(jsonString, OuterClass.class), and I think the XML should work with new XmlMapper().readValue(xmlString, OuterClass.class), but I don't know where to go with annotations. I've looked at the different annotations available and I don't think I've found the right one. I've also read that I shouldn't convert XML to a JsonNode, as there can be problems with that. I don't need to convert it back to XML after, though, and can treat it as JSON once I receive the JSON/XML string. So, I'd appreciate some help, thanks!
#XmlAccessorType(XmlAccessType.PROPERTY)
public static class InnerClass {
private JsonNode data; // complex, nested, so no POJO to map to
private String otherValue;
// ... getters/setters
#XmlElement(name = "incorrectName")
protected JsonNode getData() {return data;}
}
i am trying to map certain json fields to a class instance variable.
My sample Person class looks like:
public class Person {
private String name;
private Address address;
//many more fields
//getters and setters
}
The sample Address class is:
public class Address {
private String street;
private String city;
//many more fields
// getters and setters
}
The json object to be deserialized to my Person class doesn't contain "address" field. It looks like:
{
"name":"Alexander",
"street":"abc 12",
"city":"London"
}
Is there a way to deserialize the json to the Person pojo where the Address fields are also mapped properly?
I have used a custom Address deserializer as mentioned in so many posts here. However, it's not being called as the Json object doesn't contain "address" field.
I had resolved this problem by mapping each field manually using JsonNode, however in my real project, it's not a nice solution.
Is there any work around for such problem using jackson?
Plus if this question has been asked before then apologies on my behalf as as i have intensively searched for the solution and might have not seen it yet. .
#JsonUnwrapped annotation was introduced for this problem. Model:
class Person {
private String name;
#JsonUnwrapped
private Address address;
// getters, setters, toString
}
class Address {
private String street;
private String city;
// getters, setters, toString
}
Usage:
ObjectMapper mapper = new ObjectMapper();
String json = "{\"name\":\"Alexander\",\"street\":\"abc 12\",\"city\":\"London\"}";
System.out.println(mapper.readValue(json, Person.class));
Prints:
Person{name='Alexander', address=Address{street='abc 12', city='London'}}
For more info read:
Jackson Annotation Examples
Annotation Type JsonUnwrapped
Jackson JSON - Using #JsonUnwrapped to serialize/deserialize properties as flattening data structure
I don't think you really have a deserialization problem here but rather a general Java problem: how to make sure the address field always contains a value. All you need to do is either assign address to a default value in the Person constructor, or generate and assign a default value for address in the Person.getAddress method.
I understood your problem so that it is about flat Json that has all Address fields at the same level as Person. Even if it is not exactly so this might help you. JsonDeserializer will do fine but you need to apply it to Person because it is the level where all the fields are.
So like this:
public class CustomDeserializer extends JsonDeserializer<Person> {
// need to use separate ObjectMapper to prevent recursion
// this om will not be registered with this custom deserializer
private final ObjectMapper om;
{
om = new ObjectMapper();
// this is needed because flat json contains unknown fields
// for both types.
om.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
}
#Override
public Person deserialize(JsonParser parser, DeserializationContext ctxt)
throws IOException, JsonProcessingException {
// make a string of json tree so not any particular object
String json = om.readTree(parser).toString();
// deserialize it as person (ignoring unknown fields)
Person person = om.readValue(json, Person.class);
// set address deserializing it from teh same string, same manner
person.setAddress(om.readValue(json, Address.class));
return person;
}
}
Of course this is not the only way and might not have the best performance but it is only about how you do the deserialization in your custom deserializer. If your Person & Address objects are havin like 10 fields each using this should not be a problem.
Update
I think that in your case - based on your example data - Michał Ziober's
answer might be the best but if you need any more complex handling than plain unwrapping for your data you just need to deserialize Person class somehow like I presented.
I have a class like this:
#JsonInclude(Include.NON_NULL)
#JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy.class)
public class VPC
{
#NotNull()
private String id;
#NotNull()
#DynamoDBMarshalling(marshallerClass = SubnetTypeMarshaller.class)
private Map<SubnetType, List<String>> subnetTypeToId;
}
Here, SubnetType is a enum like this:
public enum SubnetType
{
AppSubnet,
DBSubnet,
DMZSubnet;
}
Now, I want to store the above in AWS DynamoDB. For this, I need to convert enum to a string and I have written the following.
public class SubnetTypeMarshaller implements DynamoDBMarshaller<Map<SubnetType, List<String>>>
{
private Gson gson = new GsonBuilder().create();
#Override
public String marshall(final Map<SubnetType, List<String>> securityGroupTypeListMap)
{
return gson.toJson(securityGroupTypeListMap);
}
#Override
public Map<SubnetType, List<String>> unmarshall(final Class<Map<SubnetType, List<String>>> aClass,
final String s)
{
return gson.fromJson(s, aClass);
}
}
But this doesn't work. While getting values from DB, I get the following error:
java.lang.String cannot be cast to java.lang.Enum (through reference chain: java.util.ArrayList[0]->["security_group_type_to_id"])
Am I missing something in this? I searched on other posts how to convert enums to string using #SerializedName annotation. But that didn't work either. I have also tried the solution mentioned in the other post, but it doesn't work. Maybe because my enum is in itself a part of map and I can't really annotate the enum attribute inside the map.
Gson provides default serialization for enums, if you want to change it you have to build your own adapter.
Check gson docs for registerTypeAdapter.
I have a server that returns a json string:
{"pId": "ChIJ2Vn0h5wOlR4RsOSteUYYM6g"}
Now, I can use jackson to deserialize it into an object with the variable called pId, but I don't want the variable to be called pId, I would rather deserialize it to placeId.
Current object in android java:
public class Place {
private String pId;
}
What I want the object to look like:
public class Place {
private String placeId;
}
If I change the object's variable to placeId, jackson will not be able to deserialize the JSON as the property names no longer matches.
Is there a jackson annotation I can used to map the "placeId" variable in the java object to the JSON string variable "pId" returned back from the server?
Use #JsonProperty annotation:
public class Place {
#JsonProperty("pId")
private String placeId;
}
For more information you can see the related javadoc.
I'm calling a rest service that returns a json object. I'm trying to deserialize the responses to my Java Beans using Jackson and data-binding.
The example Json is something like this:
{
detail1: { property1:value1, property2:value2},
detail2: { property1:value1, property2:value2},
otherObject: {prop3:value1, prop4:[val1, val2, val3]}
}
Essentially, detail1 and detail2 are of the same structure, and thus can be represented by a single class type, whereas OtherObject is of another type.
Currently, I've set up my classes as follows (this is the structure I would prefer):
class ServiceResponse {
private Map<String, Detail> detailMap;
private OtherObject otherObject;
// getters and setters
}
class Detail {
private String property1;
private String property2;
// getters and setters
}
class OtherObject {
private String prop3;
private List<String> prop4;
// getters and setters
}
Then, just do:
String response = <call service and get json response>
ObjectMapper mapper = new ObjectMapper();
mapper.readValue(response, ServiceResponse.class)
The problem is I'm getting lost reading through the documentation about how to configure the mappings and annotations correctly to get the structure that I want. I'd like detail1, detail2 to create Detail classes, and otherObject to create an OtherObject class.
However, I also want the detail classes to be stored in a map, so that they can be easily distinguished and retrieved, and also the fact that the service in in the future will return detail3, detail4, etc. (i.e., the Map in ServiceResponse would look like
"{detail1:Detail object, detail2:Detail object, ...}).
How should these classes be annotated? Or, perhaps there's a better way to structure my classes to fit this JSON model? Appreciate any help.
Simply use #JsonAnySetter on a 2-args method in ServiceResponse, like so:
#JsonAnySetter
public void anySet(String key, Detail value) {
detailMap.put(key, value);
}
Mind you that you can only have one "property" with #JsonAnySetter as it's a fallback for unknown properties. Note that the javadocs of JsonAnySetter is incorrect, as it states that it should be applied to 1-arg methods; you can always open a minor bug in Jackson ;)