JPA @NamedEntityGraph使用

@NamedEntityGraph的使用时为了解决sql查询过多的问题

@Entity
@Table(name="s_person")
@NamedEntityGraph(name="person.all",attributeNodes={@NamedAttributeNode("address"),@NamedAttributeNode("cards")})
public class Person {
	
	@GeneratedValue(generator = "uuid2")
        @GenericGenerator(name = "uuid2", strategy = "uuid2")
	@Id
	private String id;
	private String username;
	private String age;
	
	@OneToOne
	@JoinColumn(name="address_id",referencedColumnName="id")
	private Address address;
	
	
	
	@OneToMany(fetch=FetchType.EAGER)
	@JoinTable(name="s_person_card",joinColumns={@JoinColumn(name="p_id")}
	,inverseJoinColumns={@JoinColumn(name="c_id")})
	private List<Cards> cards;
	
	public List<Cards> getCards() {
		return cards;
	}
	public void setCards(List<Cards> cards) {
		this.cards = cards;
	}
	
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}

}

接口

public interface PersonRepository extends JpaRepository<Person, String>{

	@EntityGraph(value = "person.all" , type=EntityGraphType.FETCH)
	Person findById(String id);

}

当去查询person的时候会自动查询Adress和Cards里面的内容，且只发出一条sql语句，这样就解决了是使用关联查询导致sql查询过多的问题