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.