Java Jackson @JsonPropertyDescription Example

1. Introduction

Jackson provides a multitude of annotations to enhance the serialization and deserialization process of Java objects. The @JsonPropertyDescription annotation is particularly useful for documentation purposes. It allows you to associate a description with a JSON property, which can then be extracted using the schema generation module to generate JSON schemas with these descriptions. Although it doesn't affect the serialization/deserialization process directly, it provides a clear way to document the intended use or meaning of a particular property.

2. Example Steps

1. Add the required Jackson library dependencies to your project.

2. Create a Java class (POJO) and annotate fields with @JsonPropertyDescription.

3. Generate the JSON schema using Jackson's schema generation module.

4. Print or examine the generated schema to view the property descriptions.

3. Java Jackson @JsonPropertyDescription Example

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.module.jsonSchema.JsonSchema;
import com.fasterxml.jackson.module.jsonSchema.JsonSchemaGenerator;
import com.fasterxml.jackson.annotation.JsonPropertyDescription;

public class JsonPropertyDescriptionExample {

    public static void main(String[] args) {
        ObjectMapper mapper = new ObjectMapper();
        JsonSchemaGenerator schemaGen = new JsonSchemaGenerator(mapper);
        JsonSchema schema = schemaGen.generateSchema(User.class);

        try {
            String schemaAsString = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(schema);
            System.out.println(schemaAsString);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    static class User {
        @JsonPropertyDescription("The unique identifier of the user.")
        private String userId;

        @JsonPropertyDescription("The full name of the user.")
        private String name;

        // Constructor, getters, setters and other methods...
    }
}

Output:

{
  "type" : "object",
  "id" : "urn:jsonschema:com:example:JsonPropertyDescriptionExample:User",
  "properties" : {
    "userId" : {
      "type" : "string",
      "description" : "The unique identifier of the user."
    },
    "name" : {
      "type" : "string",
      "description" : "The full name of the user."
    }
  }
}

4. Step By Step Explanation

1. We began by setting up a User class containing two fields: userId and name.

2. The fields in the User class are annotated with @JsonPropertyDescription to provide descriptions for the corresponding JSON properties.

3. In the main method, a JsonSchemaGenerator is created using an ObjectMapper.

4. This generator is then used to produce a JsonSchema object for the User class.

5. Finally, the schema object is converted to a pretty-printed JSON string and printed to the console. This JSON schema will contain the descriptions set by the @JsonPropertyDescription annotations.