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javajsonjsonschemajsonschema2pojo

JSON Schema multiple instances of a property

I'm trying to define a json schema where there are multiple properties that instances of the same object for a Java application endpoint.

A simple example of what I'm trying to do is this

{
"$schema": "http://json-schema.org/draft-07/schema",
"type": "object",

"properties": {
    "last": {
        "$ref": "#/$def/node"
    },
    "next": {
        "$ref": "#/$def/node"
    }
},
"$def": {
    "node": {
        "type": "object",
        "properties": {
            "item": "object"
        }
    }
}}

The issue is that when I pass this into jsonschema2pojo, it interprets this as last and next being distinct classes rather than instances of a common node object.

-----------------------------------com.example.Last.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Last {

@SerializedName("item")
@Expose
public Object item;

}

-----------------------------------com.example.Next.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Next {

@SerializedName("item")
@Expose
public Object item;

}

-----------------------------------com.example.Node.java-----------------------------------

package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Node {

@SerializedName("last")
@Expose
public Last last;
@SerializedName("next")
@Expose
public Next next;

}

Is it possible to have multiple instances of a property in json-schema and would I express this? Or is this a limitation of the jsonschema2pojo tool/plugin? Or does json-schema require multiple instances be placed into an array?

Solution

  • It seems you have to force the same type being used by declaring a specific "javaType" in your definition, which is unfortunately tool-specific (which is something you wanted to avoid according to your comments).

    The following worked on jsonschema2pojo.org:

    Input: JSON Schema

    {
  "type": "object",
  "properties": {
      "last": {
        "$ref": "#/definitions/node"
      },
      "next": {
        "$ref": "#/definitions/node"
      }
  },
  "definitions": {
      "node": {
          "javaType" : "com.example.Node",
          "type": "object",
          "properties": {
            "item": {}
          }
      }
  }
}

    Output: com.example.Example.java

    package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Example {

    @SerializedName("last")
    @Expose
    public Node last;
    @SerializedName("next")
    @Expose
    public Node next;

}

    Output: com.example.Node.java

    package com.example;

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

public class Node {

    @SerializedName("item")
    @Expose
    public Object item;

}