JSON Schema to POJO: Enterprise Contract-First

The Standard: jsonschema2pojo

<plugin>
<groupId>org.jsonschema2pojo</groupId>
<artifactId>jsonschema2pojo-maven-plugin</artifactId>
<configuration>
<sourceDirectory>src/main/resources/schema</sourceDirectory>
<targetPackage>com.example.types</targetPackage>
</configuration>
</plugin>

plugins {
id "org.jsonschema2pojo" version "1.2.1"
}

jsonSchema2Pojo {
targetPackage = 'com.example.types'
useLongIntegers = true
}

Enforcing Validation (JSR-303)

A schema isn't just structure; it's rules. By enabling JSR-303, your generated POJOs will include standard validation annotations.

// Schema Property
"email": {
"type": "string",
"format": "email",
"minLength": 5
}

// Generated Java
@NotNull
@Size(min = 5)
@Pattern(regexp = "...")
public String email;

Handling "OneOf" Polymorphism

JSON Schema oneOf allows a field to be a User OR a Company. Java handles this through Interfaces and Jackson Polymorphism.

@JsonTypeInfo(
use = JsonTypeInfo.Id.NAME,
include = JsonTypeInfo.As.PROPERTY,
property = "type"
)
@JsonSubTypes({
@Type(value = User.class, name = "user"),
@Type(value = Company.class, name = "company")
})
public interface Actor { ... }

Modern Dates (Java 8)

Don't get stuck with java.util.Date. Force the generator to use modern java.time types.

// Gradle Config
customDateType = "java.time.LocalDate"
customDateTimeType = "java.time.LocalDateTime"

Reducing Boilerplate (Lombok)

Generated POJOs can be extremely verbose. While jsonschema2pojo doesn't strictly depend on Lombok, you can configure it to be cleaner:

• Set includeConstructors = true for easier instantiation.
• Set includeHashcodeAndEquals = true for Value Object semantics.
• Or, generated the source to a separate folder and let your IDE collapse it.

Contract-First vs. Code-First