Jackson ObjectMapper（没有自定义@JsonCreator）是否可以将这个Json解组到提供的Java Dto？

Question

I have two Java classes:

public class Request
{
    private List<Item> subItems;

    public Request()
    {
    }

    public List<Item> getSubItems()
    {
        return subItems;
    }

    public void setSubItems(List<Item> subItems)
    {
        this.subItems = subItems;
    }
}

class Item
{
    private String name;
    private String functionName;

    //...elided...
}

The subItems that will be passed can be complex (include a function) or simple (just a name). There can be a mix of these. To simplify the JSON, I'd like to be able to accept the following:

JSON:

{
  "subItems": [
    {
      "name": "complexType",
      "function": "someFunction"
    },
    "simpleType"
  ]
}

and then have this turned into the equivalent of the following instance:

Request request = new Request();
request.setSubItems(
    Arrays.asList(
        new Item( "complexType", "SomeFunction" ),
        new Item( "simpleType" )
    )
);

Is this possible with Jackson/ObjectMapper? What settings and annotations would I need?

Answer 1

If your Item class has a string constructor, it will be called with the "simpleType" value.

class Item {
    private String name;
    private String functionName;

    public Item() {
    }

    public Item(String name) {
        this.name = name;
    }

    // getters and setters here
}

Full demo

public class Request {
    public static void main(String[] args) throws IOException {
        String json = "{\"subItems\":[" +
                          "{\"name\":\"complexType\",\"functionName\":\"SomeFunction\"}," +
                          "\"simpleType\"" +
                      "]}";
        Request request = new ObjectMapper().readValue(json, Request.class);
        System.out.println(request);
    }

    private List<Item> subItems;
    public Request() {
    }
    public Request(Item... subItems) {
        this.subItems = Arrays.asList(subItems);
    }
    public List<Item> getSubItems() {
        return this.subItems;
    }
    public void setSubItems(List<Item> subItems) {
        this.subItems = subItems;
    }
    @Override
    public String toString() {
        return "Request [subItems=" + this.subItems + "]";
    }
}

class Item {
    private String name;
    private String functionName;
    public Item() {
    }
    public Item(String name) {
        this.name = name;
    }
    public Item(String name, String functionName) {
        this.name = name;
        this.functionName = functionName;
    }
    public String getName() {
        return this.name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getFunctionName() {
        return this.functionName;
    }
    public void setFunctionName(String functionName) {
        this.functionName = functionName;
    }
    @Override
    public String toString() {
        return "Item [name=" + this.name + ", functionName=" + this.functionName + "]";
    }
}

Output

Request [subItems=[Item [name=complexType, functionName=SomeFunction], Item [name=simpleType, functionName=null]]]