Question

实体X具有实体Y的列表，而实体Y具有实体Z的实例。

X到Y之间的关系是OneToMany，Y到Z之间的关系是ManyToOne。

我想检索X并同时检索所有相关实体。

我写了什么HQL查询，以便我一次检索整个链。目前它的 hibernateTemplate.find（“来自X”）。或者我用它做什么宣布？

X = ServiceProvider，Y = BusinessLocations.java，Z = State.java

我有下面注释的实体，我将整个链保存到数据库中但是当我尝试检索Y（BusinessLocation）列表时，我得到了

没有

我该怎么做用Y和Y连接X和Z？

下面是实体x，Y和Z。

ServiceProvider.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();
    }
}

BusinessLocation.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();
    }
}

State.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();
    }

}

有人可以帮助我吗？

由于

Answer 1

怎么样：

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");

Answer 2

我在下面注释了实体，并且我将整个链保存到数据库中但是当我尝试检索Y（BusinessLocation）列表时，我得到......没有

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：

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

所以应该热切地检索整个链条。如果这不是正在发生的事情，您可能需要检查数据和SQL，因此建议。

作为EAGER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

但请注意，JPA 1.0不允许在JPQL中使用nested join fetches，这是特定于Hibernate的。

参考

Hibernate核心参考指南
- 14.3. Associations and joins
JPA 1.0规范
- 第9.1.22节“ManyToOne注释”
- 第4.4.5.3节“获取联接”

Hibernate：无法获取关联的List

2 个答案:

参考