REST service in 5 minutes (using Java)

I remember these days when building something similar in Java required much more body movements, and maybe this was the reason to why some start-ups have chosen other weak typing languages with all their fancy Web frameworks for rapid bootstrapping. This isn't the case anymore, see how easy is creating a REST service that supports all CRUD operations in Java:

1. Define your task model:

/**
 * Task model
 */
@Entity
public class Task {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private long id;
  private String text;
  private Date created = new Date();
  private Date completed;

  public String getText() {
    return text;
  }

  public void setText(String text) {
    this.text = text;
  }

  public Date getCreated() {
    return created;
  }

  public void setCreated(Date created) {
    this.created = created;
  }

  public Date getCompleted() {
    return completed;
  }

  public void setCompleted(Date completed) {
    this.completed = completed;
  }
}

2. Tell what operations on tasks you're going to support:

/**
 * This class defines DB operations on Task entity
 */
public interface TaskRepository extends PagingAndSortingRepository<Task> {
  // Magic method name automatically generates needed query
  public List<Task> findByCompletedIsNull();
}

3. Configure your application:

/**
 * This class is responsible for:
 *  - Setting up DB connection and ORM
 *  - Initializing REST service for all found entities
 *  - Starting Spring application (main entry point)
 */
@ComponentScan
@Configuration
@EnableAutoConfiguration
@EnableJpaRepositories
@EnableTransactionManagement
public class Application extends RepositoryRestMvcConfiguration {

  @Bean
  public DataSource dataSource() throws PropertyVetoException {
    MySQLDataSource dataSource = new MySQLDataSource();
    dataSource.setDatabaseName("taskdb");
    dataSource.setUserName("user");
    dataSource.setPassword("pass");
    return dataSource;
  }

  @Bean
  public LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource) {
    HibernateJpaVendorAdapter jpaVendorAdapter = new HibernateJpaVendorAdapter();
    // Database tables will be created/updated automatically due to this:
    jpaVendorAdapter.setGenerateDdl(true);
    jpaVendorAdapter.setDatabase(Database.MYSQL);

    LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
    entityManagerFactoryBean.setDataSource(dataSource);
    entityManagerFactoryBean.setJpaVendorAdapter(jpaVendorAdapter);
    entityManagerFactoryBean.setPackagesToScan(getClass().getPackage().getName());
    return entityManagerFactoryBean;
  }

  @Bean
  public PlatformTransactionManager transactionManager() {
    return new JpaTransactionManager();
  }

  public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
  }
}

That's all! After invoking this application, you'll get a task complete REST service for free. Let's test it:

Create a new task:

~$ curl -X POST -H "Content-Type: application/json" -d '{"text":"Implement simplest REST Java application"}' http://localhost:8080/tasks

See the task contents:

~$ curl  http://localhost:8080/tasks/1

{
  "text" : "Implement simplest REST Java application",
  "created" : 1395665199000,
  "completed" : null,
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/tasks/1"
    }
  }
}

Create another task:

~$ curl -X POST -H "Content-Type: application/json" -d '{"text":"Go home"}' http://localhost:8080/tasks

Find all tasks:

~$ curl  http://localhost:8080/tasks

{
  "_links" : {
    "self" : {
      "href" : "http://localhost:8080/tasks{?page,size,sort}",
      "templated" : true
    },
    "search" : {
      "href" : "http://localhost:8080/tasks/search"
    }
  },
  "_embedded" : {
    "tasks" : [ {
      "text" : "Implement simplest REST Java application",
      "created" : 1395665199000,
      "completed" : null,
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/tasks/1"
        }
      }
    }, {
      "text" : "Go home",
      "created" : 1395665359000,
      "completed" : null,
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/tasks/2"
        }
      }
    } ]
  },
  "page" : {
    "size" : 20,
    "totalElements" : 2,
    "totalPages" : 1,
    "number" : 0
  }
}

(pay an attention to how easy is it implementing pagination using this REST service!)

Mark the first task as complete:

~$ curl -X PATCH -H "Content-Type: application/json" -d "{\"completed\":$(($(date +%s)*1000))}" http://localhost:8080/tasks/1

Find incomplete tasks:

~$ curl  http://localhost:8080/tasks/search/findByCompletedIsNull

{
  "_embedded" : {
    "tasks" : [ {
      "text" : "Go home",
      "created" : 1395665359000,
      "completed" : null,
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/tasks/2"
        }
      }
    } ]
  }
}

Pretty easy and yet powerful, huh?

For more information and instructions for how to compile and run this application, see source code on GitHub.