Quick Start

Add Dependency

Add Catatumbo as a dependency to your project.

Maven

<dependency>
  <groupId>com.jmethods</groupId>
  <artifactId>catatumbo</artifactId>
  <version>2.3.0</version>
</dependency>

Gradle

dependencies {
    compile 'com.jmethods:catatumbo:2.3.0'
}

Define Model Class

Model classes can either use classic JavaBeans Pattern or Builder Pattern. In either case, note that the model class is annotated with @Entity. Also, the id field is annotated as @Identifier.

Classic JavaBeans Pattern

import java.time.LocalDate;

import com.jmethods.catatumbo.Entity;
import com.jmethods.catatumbo.Identifier;

@Entity
public class Person {
  @Identifier
  private long id;
  private String name;
  private LocalDate birthDate;

  public long getId() {
    return id;
  }

  public void setId(long id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public LocalDate getBirthDate() {
    return birthDate;
  }

  public void setBirthDate(LocalDate birthDate) {
    this.birthDate = birthDate;
  }

}

Builder Pattern

@Entity
public class Person {
  @Identifier
  private final long id;
  private final String name;
  private final LocalDate birthDate;

  private Person(Builder builder) {
    this.id = builder.id;
    this.name = builder.name;
    this.birthDate = builder.birthDate;
  }

  public long getId() {
    return id;
  }

  public String getName() {
    return name;
  }

  public LocalDate getBirthDate() {
    return birthDate;
  }

  public static Builder newBuilder() {
    return new Builder();
  }

  public static class Builder {
    private long id;
    private String name;
    private LocalDate birthDate;

    public Builder setId(long id) {
      this.id = id;
      return this;
    }

    public Builder setName(String name) {
      this.name = name;
      return this;
    }

    public Builder setBirthDate(LocalDate birthDate) {
      this.birthDate = birthDate;
      return this;
    }

    public Person build() {
      return new Person(this);
    }

  }

}

Create DAO

Now let's create a simple DAO to create, read, update and delete Person entities.

import com.jmethods.catatumbo.EntityManager;
import com.jmethods.catatumbo.EntityManagerFactory;

public class PersonDAO {

  public static PersonDAO instance = new PersonDAO();
  private EntityManager em;

  private PersonDAO() {
    em = EntityManagerFactory.getInstance().createDefaultEntityManager();
  }

  public Person create(Person person) {
    return em.insert(person);
  }

  public Person update(Person person) {
    return em.update(person);
  }

  public void delete(Person person) {
    em.delete(person);
  }

  public Person read(long id) {
    return em.load(Person.class, id);
  }

}

Insert an Entity

Classic JavaBeans Pattern

import java.time.LocalDate;

public class CreatePerson {

  public static void main(String[] args) {
    Person person = new Person();
    person.setName("John Doe");
    person.setBirthDate(LocalDate.of(1990, 2, 15));
    PersonDAO dao = PersonDAO.getInstance();
    person = dao.create(person);
    System.out.printf("Person entity with ID %d was created successfully", person.getId());
  }

}

Builder Pattern

import java.time.LocalDate;

public class CreatePerson {

  public static void main(String[] args) {
    Person person = Person.newBuilder().setName("John Doe").setBirthDate(LocalDate.of(1990, 2, 15))
        .build();
    PersonDAO dao = PersonDAO.getInstance();
    person = dao.create(person);
    System.out.printf("Person entity with ID %d was created successfully", person.getId());
  }

}

When you run either of the CreatePerson programs, a new entity will be created in Google Cloud Datastore. The console should have something like this:

Person entity with ID 5754272234864640 was created successfully

Log into Google Cloud Console and make sure the new Person entity is created as shown below: