CrudGen

Compile-time annotation processor for Spring Boot 3 and 4. Annotate a JPA/Mongo entity or a use-case class; CrudGen generates repositories, services, REST controllers, immutable DTOs, and MapStruct mappers.

Features

• Compile-time generation — The processor runs in the javac annotation-processing round and emits plain .java sources. No runtime bytecode weaving, no reflection-based code paths in generated controllers or services.
• N+1-safe JPA reads — When RepoType.JPA is used and the Read DTO includes relation=true fields, generated repositories expose @EntityGraph read methods; services call them on get / getAll / getPaged. Relation binding stays out of MapStruct mappers.
• JSON Patch updates — With "Update" in dtos, generated controllers expose PATCH /{id} and PATCH /batch consuming application/json-patch+json, applying patches via zjsonpatch and validating the merged DTO.
• Configurable surface per type — dtos, controllerPath, service, extend* / custom*, and @EndpointGen control which layers and endpoints are generated. Empty controllerPath skips controller, DTOs, and mapper; customRepo / customService / customController swap in your implementations.

Quick comparison (before / after)

Before — annotated entity only

@Entity
@CrudGen(
    controllerPath = "/api/widgets",
    dtos = { "Read", "Create" },
    securityService = false,
    lifecycleHooks = false,
    openApi = false,
    logging = false
)
public class Widget {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @DTOField(dto = "Read")
    @DTOField(dto = "Create")
    @NotBlank @Size(max = 200)
    private String name;
}

After — one compileJava pass

com.example.app/
├── WidgetRepository.java      # JpaRepository (+ @FindBy / @FindAllBy when declared)
├── WidgetService.java         # @Service, @Transactional mutations
├── WidgetController.java      # @RestController under controllerPath
├── WidgetReadDTO.java         # immutable; Bean Validation mirrored from entity fields
├── WidgetCreateDTO.java
├── WidgetMapper.java          # MapStruct @Mapper(componentModel = "spring")
└── WidgetMapperImpl.java      # MapStruct annotation-processor output

Representative generated code:

@Repository
public interface WidgetRepository extends JpaRepository<Widget, Long>, JpaSpecificationExecutor<Widget> {}

@Service
public class WidgetService {
  public Widget get(Long id) { return repo.findById(id).orElse(null); }
  @Transactional public Widget create(Widget entity) { return repo.save(entity); }
}

@RestController
@RequestMapping("/api/widgets")
public class WidgetController {
  @GetMapping("/{id}")
  public ResponseEntity<WidgetReadDTO> get(@PathVariable Long id) {
    Widget entity = service.get(id);
    if (entity == null) throw new ResponseStatusException(NOT_FOUND, "Entity with id " + id + " not found.");
    return ResponseEntity.ok(mapper.get(entity));
  }
  @PostMapping("/")
  public ResponseEntity<WidgetReadDTO> create(@Valid @RequestBody WidgetCreateDTO dto) { /* ... */ }
}

@Mapper(componentModel = "spring")
public interface WidgetMapper {
  WidgetReadDTO get(Widget entity);
  Widget create(WidgetCreateDTO dto);
}

public class WidgetReadDTO {
  @NotBlank @Size(max = 200)
  private final String name;
  @JsonCreator
  public WidgetReadDTO(@JsonProperty("name") String name) { this.name = name; }
}

Coordinates: io.github.bariskokulu:crudgen:1.1.1
Bytecode: Java 17 (your app JDK and Spring Boot version are independent).

What the library does

Area	Annotations
Entity CRUD	@CrudGen on a class with @Id
DTOs + validation mirror	@DTOField + dtos = {Read, Create, Update}
Field queries	@FindBy, @FindAllBy
JSON Patch updates	"Update" in dtos + zjsonpatch on compile classpath
FK relations in API	@DTOField(relation = true) + {Entity}RelationApplier
Persistence backends	RepoType.JPA, MONGO, PLAIN
Custom / extended layers	customRepo, customService, customController, extend*
Use-case HTTP	@EndpointGen + @Endpoint
Cross-cutting	CrudGenSecurityService, EntityLifecycleCallbacks (optional)

Install

Gradle (Kotlin DSL)

dependencies {
    compileOnly("io.github.bariskokulu:crudgen:1.1.1")
    annotationProcessor("org.projectlombok:lombok:1.18.42")           // if used
    annotationProcessor("org.mapstruct:mapstruct-processor:1.5.5.Final") // Boot 4: 1.6.3
    annotationProcessor("io.github.bariskokulu:crudgen:1.1.1")
}

Maven — provided dependency + annotationProcessorPaths: Lombok → MapStruct → CrudGen.

Minimal usage

@Entity
@CrudGen(
    controllerPath = "/api/widgets",
    dtos = { "Read", "Create" },
    securityService = false,
    lifecycleHooks = false,
    openApi = false,
    logging = false
)
public class Widget {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @DTOField(dto = "Read")
    @DTOField(dto = "Create")
    @NotBlank
    private String name;
}

Generates repository, service, controller, Read/Create DTOs, and mapper. Step-by-step recipes: docs/EXAMPLES.md.

Documentation

Doc	Content
docs/EXAMPLES.md	Minimal → full usage (inline code)
docs/ANNOTATIONS.md	Every annotation parameter
docs/DECISION-TREE.md	What gets generated and when
docs/TROUBLESHOOTING.md	Build and runtime failures

Agent skills (Cursor + Claude): .cursor/skills/crudgen/SKILL.md and .claude/skills/crudgen/SKILL.md — keep identical when the processor changes.

Requirements

Your application

• Java 17+ for compiling against the processor; runtime JDK is your choice.
• Spring Boot 3.2+ or 4.0+ with Web MVC and (for entities) Spring Data JPA or Mongo, or RepoType.PLAIN with your repository implementation.
• MapStruct 1.5.5.Final (Boot 3) or 1.6.3 (Boot 4) when controllerPath is set.
• JSON Patch only if Update is in dtos: zjsonpatch 0.4.x (Jackson 2) or 0.6.2+ (Jackson 3).
• Bean Validation: processor mirrors javax.validation or jakarta.validation from your compile classpath.

Stack	Web starter	MapStruct	zjsonpatch (Update DTO)
Boot 3	spring-boot-starter-web	1.5.5.Final	com.flipkart.zjsonpatch:zjsonpatch:0.4.16
Boot 4	spring-boot-starter-webmvc	1.6.3	io.github.vishwakarma:zjsonpatch:0.6.2

Security and lifecycle (optional)

Defaults: securityService = true, lifecycleHooks = true. The processor may emit:

• com.bariskokulu.crudgen.security.CrudGenSecurityService
• com.bariskokulu.crudgen.lifecycle.EntityLifecycleCallbacks<T>

Implement in your application, or set both flags to false on every @CrudGen / @EndpointGen type so the interfaces are not generated.

License

Apache License 2.0 — LICENSE.