# Defining Entities

{% hint style="warning" %}
**This is the manual for older MicroStream versions (Version < 5.0).**

**The new documentation (Version >= 5.0) is located at:**

[https://docs.microstream.one/](https://docs.microstream.one/manual)
{% endhint %}

The entity types are just simple interfaces with value methods, which have following requirements:

* A return type, no void
* No parameters
* No type parameters
* No declared checked exceptions

You are not limited otherwise. Use any types you want. Inheritance and generics are supported as well.&#x20;

#### Entities

{% tabs %}
{% tab title="Beeing.java" %}

```java
public interface Beeing<B>
{
	public B partner();
}
```

{% endtab %}

{% tab title="Named.java" %}

```java
public interface Named
{
	public String name();
}
```

{% endtab %}

{% tab title="Animal.java" %}

```java
public interface Animal extends Beeing<Animal>, Entity
{
	public String species();
}
```

{% endtab %}

{% tab title="Pet.java" %}

```java
public interface Pet extends Animal, Named
{
}
```

{% endtab %}

{% tab title="Human.java" %}

```java
public interface Human extends Beeing<Human>, Named, Entity
{
}
```

{% endtab %}
{% endtabs %}

There is one base type (`Beeing`), one feature interface (`Named`) and three entities (`Animal`, `Pet`, `Human`).

#### Generated Code

The code generator takes care of the three entities, and its output looks like this:

{% tabs %}
{% tab title="AnimalEntity.java" %}

```java
public class AnimalEntity extends EntityLayerIdentity implements Animal
{
	protected AnimalEntity()
	{
		super();
	}

	@Override
	protected Animal entityData()
	{
		return (Animal)super.entityData();
	}

	@Override
	public final String species()
	{
		return this.entityData().species();
	}

	@Override
	public final Animal partner()
	{
		return this.entityData().partner();
	}
}
```

{% endtab %}

{% tab title="AnimalData.java" %}

```java
public class AnimalData extends EntityData implements Animal
{
	private final String species;
	private final Animal partner;

	protected AnimalData(final Animal entity,
		final String species,
		final Animal partner)
	{
		super(entity);

		this.species = species;
		this.partner = partner;
	}

	@Override
	public String species()
	{
		return this.species;
	}

	@Override
	public Animal partner()
	{
		return this.partner;
	}
}
```

{% endtab %}

{% tab title="AnimalCreator.java" %}

```java
public interface AnimalCreator extends Entity.Creator<Animal, AnimalCreator>
{
	public AnimalCreator species(String species);

	public AnimalCreator partner(Animal partner);

	public static AnimalCreator New()
	{
		return new Default();
	}

	public static AnimalCreator New(final Animal other)
	{
		return new Default().copy(other);
	}

	public class Default
		extends Entity.Creator.Abstract<Animal, AnimalCreator>
		implements AnimalCreator
	{
		private String species;
		private Animal partner;

		protected Default()
		{
			super();
		}

		@Override
		public AnimalCreator species(final String species)
		{
			this.species = species;
			return this;
		}

		@Override
		public AnimalCreator partner(final Animal partner)
		{
			this.partner = partner;
			return this;
		}

		@Override
		protected EntityLayerIdentity createEntityInstance()
		{
			return new AnimalEntity();
		}

		@Override
		public Animal createData(final Animal entityInstance)
		{
			return new AnimalData(entityInstance,
				this.species,
				this.partner);
		}

		@Override
		public AnimalCreator copy(final Animal other)
		{
			final Animal data = Entity.data(other);
			this.species = data.species();
			this.partner = data.partner();
			return this;
		}
	}
}
```

{% endtab %}

{% tab title="AnimalUpdater.java" %}

```java
public interface AnimalUpdater extends Entity.Updater<Animal, AnimalUpdater>
{
	public static boolean setSpecies(final Animal animal, final String species)
	{
		return New(animal).species(species).update();
	}

	public static boolean setPartner(final Animal animal, final Animal partner)
	{
		return New(animal).partner(partner).update();
	}

	public AnimalUpdater species(String species);

	public AnimalUpdater partner(Animal partner);

	public static AnimalUpdater New(final Animal animal)
	{
		return new Default(animal);
	}

	public class Default
		extends Entity.Updater.Abstract<Animal, AnimalUpdater>
		implements AnimalUpdater
	{
		private String species;
		private Animal partner;

		protected Default(final Animal animal)
		{
			super(animal);
		}

		@Override
		public AnimalUpdater species(final String species)
		{
			this.species = species;
			return this;
		}

		@Override
		public AnimalUpdater partner(final Animal partner)
		{
			this.partner = partner;
			return this;
		}

		@Override
		public Animal createData(final Animal entityInstance)
		{
			return new AnimalData(entityInstance,
				this.species,
				this.partner);
		}

		@Override
		public AnimalUpdater copy(final Animal other)
		{
			final Animal data = Entity.data(other);
			this.species = data.species();
			this.partner = data.partner();
			return this;
		}
	}
}
```

{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="PetEntity.java" %}

```java
public class PetEntity extends EntityLayerIdentity implements Pet
{
	protected PetEntity()
	{
		super();
	}

	@Override
	protected Pet entityData()
	{
		return (Pet)super.entityData();
	}

	@Override
	public final String species()
	{
		return this.entityData().species();
	}

	@Override
	public final Animal partner()
	{
		return this.entityData().partner();
	}

	@Override
	public final String name()
	{
		return this.entityData().name();
	}
}
```

{% endtab %}

{% tab title="PetData.java" %}

```java
public class PetData extends EntityData implements Pet
{
	private final String species;
	private final Animal partner;
	private final String name   ;

	protected PetData(final Pet entity,
		final String species,
		final Animal partner,
		final String name   )
	{
		super(entity);

		this.species = species;
		this.partner = partner;
		this.name    = name   ;
	}

	@Override
	public String species()
	{
		return this.species;
	}

	@Override
	public Animal partner()
	{
		return this.partner;
	}

	@Override
	public String name()
	{
		return this.name;
	}
}
```

{% endtab %}

{% tab title="PetCreator.java" %}

```java
public interface PetCreator extends Entity.Creator<Pet, PetCreator>
{
	public PetCreator species(String species);

	public PetCreator partner(Animal partner);

	public PetCreator name(String name);

	public static PetCreator New()
	{
		return new Default();
	}

	public static PetCreator New(final Pet other)
	{
		return new Default().copy(other);
	}

	public class Default
		extends Entity.Creator.Abstract<Pet, PetCreator>
		implements PetCreator
	{
		private String species;
		private Animal partner;
		private String name   ;

		protected Default()
		{
			super();
		}

		@Override
		public PetCreator species(final String species)
		{
			this.species = species;
			return this;
		}

		@Override
		public PetCreator partner(final Animal partner)
		{
			this.partner = partner;
			return this;
		}

		@Override
		public PetCreator name(final String name)
		{
			this.name = name;
			return this;
		}

		@Override
		protected EntityLayerIdentity createEntityInstance()
		{
			return new PetEntity();
		}

		@Override
		public Pet createData(final Pet entityInstance)
		{
			return new PetData(entityInstance,
				this.species,
				this.partner,
				this.name   );
		}

		@Override
		public PetCreator copy(final Pet other)
		{
			final Pet data = Entity.data(other);
			this.species = data.species();
			this.partner = data.partner();
			this.name    = data.name   ();
			return this;
		}
	}
}
```

{% endtab %}

{% tab title="PetUpdater.java" %}

```java
public interface PetUpdater extends Entity.Updater<Pet, PetUpdater>
{
	public static boolean setSpecies(final Pet pet, final String species)
	{
		return New(pet).species(species).update();
	}

	public static boolean setPartner(final Pet pet, final Animal partner)
	{
		return New(pet).partner(partner).update();
	}

	public static boolean setName(final Pet pet, final String name)
	{
		return New(pet).name(name).update();
	}

	public PetUpdater species(String species);

	public PetUpdater partner(Animal partner);

	public PetUpdater name(String name);

	public static PetUpdater New(final Pet pet)
	{
		return new Default(pet);
	}

	public class Default
		extends Entity.Updater.Abstract<Pet, PetUpdater>
		implements PetUpdater
	{
		private String species;
		private Animal partner;
		private String name   ;

		protected Default(final Pet pet)
		{
			super(pet);
		}

		@Override
		public PetUpdater species(final String species)
		{
			this.species = species;
			return this;
		}

		@Override
		public PetUpdater partner(final Animal partner)
		{
			this.partner = partner;
			return this;
		}

		@Override
		public PetUpdater name(final String name)
		{
			this.name = name;
			return this;
		}

		@Override
		public Pet createData(final Pet entityInstance)
		{
			return new PetData(entityInstance,
				this.species,
				this.partner,
				this.name   );
		}

		@Override
		public PetUpdater copy(final Pet other)
		{
			final Pet data = Entity.data(other);
			this.species = data.species();
			this.partner = data.partner();
			this.name    = data.name   ();
			return this;
		}
	}
}
```

{% endtab %}
{% endtabs %}

{% tabs %}
{% tab title="HumanEntity.java" %}

```java
public class HumanEntity extends EntityLayerIdentity implements Human
{
	protected HumanEntity()
	{
		super();
	}

	@Override
	protected Human entityData()
	{
		return (Human)super.entityData();
	}

	@Override
	public final Human partner()
	{
		return this.entityData().partner();
	}

	@Override
	public final String name()
	{
		return this.entityData().name();
	}
}
```

{% endtab %}
{% endtabs %}