JPA-examples/README.md

JPA-examples

Entity annotation

@Entity
@Table
public final class MyEntityClass {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @Column
    private float primitiveField;

    @Column
    private String primitiveField2;

}

References to another entities

@Entity
@Table
public final class AnotherEntity {
    //...
    @ManyToMany(fetch = FetchType.EAGER)
    @JoinColumn(name = "my_entity_id", nullable = false)
    private Collection<MyEntityClass> entities;
}

Collection of primitives

//...
public final class AnotherEntity {
    //...
    @ElementCollection(fetch = FetchType.EAGER)
    private Set<String> stringSet;
}

Map field as another data type

//...
public final class AnotherEntity {
    //...
    @Column
    @JSONProperty
    @Convert(converter = CustomConverter.class)
    private CustomType settings;
}

public class CustomType {
    //...
}

/*
        Convert custom type to string and vise versa
 */
@Converter
public static class CustomConverter implements AttributeConverter<CustomType, String> {

    @Override
    public String convertToDatabaseColumn(CustomType customType) {
        // return ...
    }

    @Override
    public CustomType convertToEntityAttribute(String dbData) {
        // return ...
    }
}