使用JSON模式或等效模式验证Java POJO？

Question

It's there a way or technology like JSON schema in which I get a JSON description of the data structure and I can validate in JAVA if fits the description. I want something like JSON schema to validate incoming data, but I want to validate that the POJOs or Maps as Java objects, not the JSON document themselves.

Make the POJO a JSON just to validate it isn't a practical option, thanks!

is a way to do this with JSON schema or any other technologies?

UPDATE: SUMMARY AS far as I know: JSON Schema is a JSON document used to validate JSON documents. I want a schema written in JSON to validate Java POJOs.

the example below (I use the validate as a static function of class Validator ):

public static void main(String[] args) {
        String schema = "{\n" +
                "  \"type\": \"object\",\n" +
                "  \"properties\": {\n" +
                "    \"street_address\": { \"type\": \"string\" },\n" +
                "    \"city\":           { \"type\": \"string\" },\n" +
                "    \"state\":          { \"type\": \"string\" }\n" +
                "  },\n" +
                "  \"required\": [\"street_address\", \"city\", \"state\"]\n" +
                "}";
        Object foo = new Hashtable();

        ((Map)foo).put("street_address","first street");
        ((Map)foo).put("street_address","The city");
        ((Map)foo).put("street_address","Not the USA");

        Validator validator = new Validator(schema);

        if (Validator.validate(foo, schema)) {
            System.out.println("It's validated");
        } else
            System.err.println("It isn't validated");
    }

Answer 1

You are looking for the OPEN API: https://github.com/OAI/OpenAPI-Specification

This is the former SWAGGER TOOL ( https://swagger.io ) which allows to define objects in JSON / YAML / XML. This is used a lot to:

1. Document your APIs and the objects you can receive
2. Generate client stubs based on the structure defined in the JSON
3. Help create test suites by integrating the JSONs in other tools (ex: postman)
4. etc

This allow you not only to document your POJOs but many other things in additional. It is quite powerful.

Answer 2

I just came accross this project which does exactly what you are asking for: https://github.com/everit-org/json-schema

This is an example of a schema:

{
    "type" : "object",
    "properties" : {
        "rectangle" : {"$ref" : "#/definitions/Rectangle" }
    },
    "definitions" : {
        "size" : {
            "type" : "number",
            "minimum" : 0
        },
        "Rectangle" : {
            "type" : "object",
            "properties" : {
                "a" : {"$ref" : "#/definitions/size"},
                "b" : {"$ref" : "#/definitions/size"}
            }
        }
    }
}

Example JSON:

{
    "rectangle" : {
        "a" : -5,
        "b" : 5
    }
}

In this case the thrown ValidationException will point to #/rectangle/a .

try {
  schema.validate(rectangleSingleFailure);
} catch (ValidationException e) {
  // prints #/rectangle/a: -5.0 is not higher or equal to 0
  System.out.println(e.getMessage());
}

Answer 3

You can take a look at this library . You can validate Java POJO against JSON Schemas. It supports JSON schema v3 and v4.