java Hibernate:无法获取检索到的关联列表

Question

实体X具有实体Y的列表，实体Y具有实体Z的实例

X和Y之间的关系是一对一，Y和Z之间的关系是多对一

我想检索X，并将所有相关实体与它们一起检索

我应该编写什么HQL查询以便一次检索整个链。目前它的休眠模式。查找（“从X”）。 或者我用什么注释

X=服务提供商，Y=业务地点。java，Z=State。爪哇

我在下面注释了实体，并将整个链持久化到数据库中，但当我尝试检索Y（BusinessLocation）列表时，我得到了

没什么

我怎么把X和Y，Y和Z连接起来

下面是实体x、Y和Z

服务提供商。java

@Entity
public class ServiceProvider implements Serializable{

    private Long id;    
    private Set<BusinessLocation> businessLocations = new HashSet<BusinessLocation>();

    @Id
    @GeneratedValue
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }

    @OneToMany(mappedBy="serviceProvider", targetEntity=BusinessLocation.class, cascade=CascadeType.ALL, fetch=FetchType.EAGER)
    public Set<BusinessLocation> getBusinessLocations() {
        return businessLocations;
    }

    public void setBusinessLocations(Set<BusinessLocation> businessLocations) {
        this.businessLocations = businessLocations;
    }

    public boolean equals(Object obj) {
        if(!(obj instanceof ServiceProvider)) return false;
        ServiceProvider other = (ServiceProvider) obj;
        return new EqualsBuilder().append(businessLocations, other.businessLocations).isEquals();
    }
}

商务地点。java

@Entity
public class BusinessLocation implements Serializable{

    private Long id;
    private String address;
    private String city;
    private State state;
    private String pincode;
    private ServiceProvider serviceProvider;

    public BusinessLocation() {     
    }

    @Id
    @GeneratedValue
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getCity() {
        return city;
    }
    public void setCity(String city) {
        this.city = city;
    }

    @ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(name="state_id")
    public State getState() {
        return state;
    }
    public void setState(State state) {
        this.state = state;
    }   
    public void setPincode(String pincode) {
        this.pincode = pincode;
    }

    public String getPincode() {
        return pincode;
    }

    @ManyToOne
    @JoinColumn(name="serviceProvider_id")
    public ServiceProvider getServiceProvider() {
        return serviceProvider;
    }
    public void setServiceProvider(ServiceProvider serviceProvider) {
        this.serviceProvider = serviceProvider;
    }

    public boolean equals(Object obj) {
        if( !(obj instanceof BusinessLocation)) return false;
        BusinessLocation other = (BusinessLocation) obj;        
        return new EqualsBuilder().append(address, other.address).append(city, other.city).append(state, other.state).append(pincode, 

other.pincode).append(serviceProvider, other.serviceProvider).isEquals();
    }

    public int hashCode() {
        return new HashCodeBuilder().append(address).append(city).append(state).append(pincode).append(serviceProvider).toHashCode();
    }
}

状态。java

@Entity
public class State implements Serializable {

    private Long id;
    private String abbreviatedName;
    private String name;
    private List<BusinessLocation> businessLocations;

    @Id
    @GeneratedValue 
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getAbbreviatedName() {
        return abbreviatedName;
    }
    public void setAbbreviatedName(String abbreviatedName) {
        this.abbreviatedName = abbreviatedName;
    }
    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }


    @OneToMany(mappedBy="state", targetEntity=BusinessLocation.class, cascade=CascadeType.ALL, fetch=FetchType.EAGER)
    public List<BusinessLocation> getBusinessLocations() {
        return businessLocations;
    }
    public void setBusinessLocations(List<BusinessLocation> businessLocations) {
        this.businessLocations = businessLocations;
    }

    public boolean equals(Object obj) {
        if(! (obj instanceof State)) return false;
        State other = (State) obj;
        return new EqualsBuilder().append(abbreviatedName, other.abbreviatedName).append(name, other.name).append(businessLocations, 

other.businessLocations).isEquals();
    }

    public int hashCode() {
        return new HashCodeBuilder().append(name).append(abbreviatedName).append(businessLocations).toHashCode();
    }

}

有人能帮我吗

谢谢

Answer 1

I have the entities annotated below and I am having the whole chain persisted into database but when i try to retrieve the list of Y (BusinessLocation), I get... nothing

您应该激活SQL日志记录以查看发生的情况并检查数据，因为注释部分看起来是正确的：

• 在ServiceProvider和BusinessLocation之间的一对多是EAGER
• BusinessLocation和State之间的多对一是EAGER（默认情况下）

因此，整个链条都应该被急切地收回。如果情况并非如此，您可能希望检查数据和SQL，因此建议

作为即时关联的替代方法，您可以使用FETCH JOIN预取相关数据：

FROM ServiceProvider provider
  INNER JOIN FETCH provider.businessLocations location
  LEFT JOIN FETCH location.state

但是请注意，JPA1.0不允许JPQL中使用nested join fetches，这是特定于Hibernate的

参考文献

• Hibernate核心参考指南
  • 14.3. Associations and joins
• JPA1.0规范
  • 第9.1.22节“多通注释”
  • 第4.4.5.3节“获取连接”

Answer 2

那么：

Query q - entityManager.createQuery("Select x from ServiceProvider x inner join x.businessLocations as y and inner join y.state as z where x.id = ?1");