In this tutorial, you will learn using MapStruct for mapping/converting Java objects, JPA and Hibernate entity to DTO and vice versa. Let's get started to build a RESTful APIs example with Spring Boot and MySQL to see how MapStruct playing in the context.
What you'll need
- JDK 8+ or OpenJDK 8+
- Maven 3+
- MySQL Server 5+ or Docker CE 18+
Init project structure and MapStruct
Project structure
├── src
│ └── main
│ ├── java
│ │ └── com
│ │ └── hellokoding
│ │ └── springboot
│ │ └── restful
│ │ ├── product
│ │ │ ├── Product.java
│ │ │ ├── ProductAPI.java
│ │ │ ├── ProductDTO.java
│ │ │ ├── ProductMapper.java
│ │ │ ├── ProductRespository.java
│ │ │ └── ProductService.java
│ │ └── Application.java
│ └── resources
│ └── application.properties
├── Dockerfile
├── docker-compose.yml
└── pom.xml
Setting up MapStruct
MapStruct is a Java annotation processor for generating bean mapping classes.
To set up, add MapStruct dependency into pom.xml and configure annotationProcessorPaths of maven-compiler-plugin. Full project dependencies and build plugins as below
Define JPA and Hibernate Entity, DTO, Repository, and Service
DTO, stands for Data Transfer Object, is a design pattern used for customizing/aggregating data input and output so reducing the number of call to remote API.
Using MapStruct
Define MapStruct Mapper
To using MapStruct, you have to define a @Mapper interface which declares any required mapping methods to map between entity and DTO
Here you only define simple method signatures, converting Entity to DTO, DTO to Entity, List of Entity to List of DTOs. MapStruct will generate implementation code for you during build time.
Using MapStruct on REST API
Inject your previous defined @Mapper interface into REST API and start using its methods.
Wow! what a clean REST API without writing a single mapping/converting logic :)
Config and Run
Application Configurations
hk-mysql refers to Docker Compose service defined in the below docker-compose.yml file
spring.jpa.hibernate.ddl-auto=create allows JPA/Hibernate auto create database and table schema for you.
On production environment, you may like to disable the DDL Auto feature by using spring.jpa.hibernate.ddl-auto=validate or spring.jpa.hibernate.ddl-auto=none (default). Check out this example as one of the approaches Database Migration/Evolution Example with Flyway and JPA/Hibernate
Run with Docker
Prepare Dockerfile for Java/Spring Boot application and docker-compose.yml for MySQL Server
Type the below command at the project root directory, make sure your local Docker is running
docker-compose up
Access to MySQL Server docker container by issuing below bash command and key in hellokoding on Enter password:
docker exec -it hk-mysql mysql -p
Run with JDK/OpenJDK, Maven and MySQL Server local
Update hk-mysql on application.properties to localhost and type the below command at the project root directory
mvn clean spring-boot:run
Test with curl
Create a new product
curl -i -H "Content-Type: application/json" -X POST -d '{"name":"Hello Koding","description": "Simple coding examples and tutorials","price":"1"}' http://localhost:8080/api/v1/products
Find all products
curl -i http://localhost:8080/api/v1/products