CODEWITHSUNDEEP
jsonjacksonjson-deserialization
Crazyk
Crazyk

Reputation: 23

How to deserialize JSON to complex POJO<> with List of Generic Objects

I use jackson-databind 2.8.0 I have object with Generic Data

public class JsonItem<T> implements Serializable {

    private static final long serialVersionUID = -8435937749132073097L;

    @JsonProperty(required = true)
    private boolean success;

    @JsonProperty(required = false)
    private T data;

    @JsonProperty(required = false)
    private Map<String, String> errors = new HashMap<>();

    JsonItem() {
    }

    public boolean getSuccess() {
        return success;
    }

    public void setSuccess(boolean success) {
        this.success = success;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }

    public Map<String, String> getErrors() {
        return errors;
    }

    public void setErrors(Map<String, String> errors) {
        this.errors = errors;
    }
  }

and have Object 

@JsonInclude(JsonInclude.Include.NON_EMPTY)
public class DepositInfoDto implements Serializable {

    private static final long serialVersionUID = -4123441934244992311L;

    @NotNull
    @JsonProperty(required = true)
    private String productName;

    @NotNull
    @JsonProperty(required = true)
    private String contractName;

    @NotNull
    @JsonProperty(required = true)
    private List<ContractDto> contracts;

    @NotNull
    @JsonProperty(required = true)
    private StatusDto status;
//...getters and setters
}

I recevied object like JsonItem<List<DepositInfoDto>>.

I try to create universal method to deserealize 

 public <T> List<T> getObjects(){
       ObjectMapper mapper = new ObjectMapper();
       List<T> myObjects = mapper.readValue(jsonInput, new TypeReference<JsonItem<List<T>>(){});
    return myObjects;
    }

Not work because T cast to Object in runtime

  public List<DepositInfoDto> getObjects(){
       ObjectMapper mapper = new ObjectMapper();
       List<DepositInfoDto> myObjects = mapper.readValue(jsonInput, new TypeReference<JsonItem<List<DepositInfoDto >>(){});
    return myObjects;
    }

work but i want universal method because i have DepositInfoDto, CardinfoDto, ContractDto etc.

I see method 

public List<T> getObjects(Class<T> clazz){
       ObjectMapper mapper = new ObjectMapper();
       List<T> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, clazz));
    return myObjects;
    }

but didn't work because i have JsonItem with data List<T>

How can i resolve this problem? Maybe mapper.getTypeFactory() have complex method like mapper.getTypeFactory().constructType(JsonItem.class, List.class,DepositInfoDto.class)

EDIT

In my case 

ObjectMapper mapper = new ObjectMapper();
                    try {
                        JsonItem<T> item  = mapper.readValue(objectWrapper.get(0), mapper.getTypeFactory().constructParametricType(
                                JsonItem.class, mapper.getTypeFactory().constructCollectionType(List.class, resourceClass)));
                        return item.getData();
                    } catch (IOException e) {
                        LOG.error("Can't deserialize JSON to class: "+ resourceClass +". Error: " + e);
                        Thread.currentThread().interrupt();
                    }

Upvotes: 1

Views: 2043

Answers (1)

Wilson
Wilson

Reputation: 11619

You can use TypeFactory#constructParametricType to create a JavaType for JsonItem<T> and then use TypeFactory#constructCollectionType to create CollectionType for List<JsonItem<T>>. Following is the example:

public <T> List<JsonItem<T>> getObjects(String jsonInput, Class<T> clazz) {

    ObjectMapper mapper = new ObjectMapper();
    return mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(
           List.class, mapper.getTypeFactory().constructParametricType(JsonItem.class, clazz)));
}

Upvotes: 2

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