Java 使用Hibernate条件获取相同的对象

我有两个对象。一个是Company，另一个是Country。Company对象有一些属性，其中两个与Country对象相关，称为“controllerCountry”和“RegistrCountry”。当我使用Hibernate条件获取公司时，有一个n+1查询（实际上不是）问题

我的公司目标代码：

public class Company implements Serializable{

private Country controllerCountryArea;

private Country registCountryArea;

@ManyToOne(targetEntity = Country.class,optional=true)
@JoinColumn(name="controller_country",referencedColumnName="code",insertable=false,updatable=false)
@LazyToOne(LazyToOneOption.PROXY)
public Country getControllerCountryArea() {
    return controllerCountryArea;
}

public void setControllerCountryArea(Country controllerCountryArea) {
    this.controllerCountryArea = controllerCountryArea;
}

@ManyToOne(targetEntity = Country.class,optional=true)
@JoinColumn(name="regist_country",referencedColumnName="code",insertable=false,upda         table=false)
@LazyToOne(LazyToOneOption.PROXY)
public Country getRegistCountryArea() {
    return registCountryArea;
}

public void setRegistCountryArea(Country registCountryArea) {
    this.registCountryArea = registCountryArea;
}
}

public class Country implements Serializable {

private static final long serialVersionUID = 3070416090656703733L;

private Integer id;
private String code;
private String numcode;


@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

@Column(name="CODE")
public String getCode() {
    return code;
}

public void setCode(String code) {
    this.code = code;
}

@Column(name="NUMCODE")
public String getNumcode() {
    return numcode;
}

public void setNumcode(String numcode) {
    this.numcode = numcode;
}
}

我的国家/地区目标代码：

public class Company implements Serializable{

private Country controllerCountryArea;

private Country registCountryArea;

@ManyToOne(targetEntity = Country.class,optional=true)
@JoinColumn(name="controller_country",referencedColumnName="code",insertable=false,updatable=false)
@LazyToOne(LazyToOneOption.PROXY)
public Country getControllerCountryArea() {
    return controllerCountryArea;
}

public void setControllerCountryArea(Country controllerCountryArea) {
    this.controllerCountryArea = controllerCountryArea;
}

@ManyToOne(targetEntity = Country.class,optional=true)
@JoinColumn(name="regist_country",referencedColumnName="code",insertable=false,upda         table=false)
@LazyToOne(LazyToOneOption.PROXY)
public Country getRegistCountryArea() {
    return registCountryArea;
}

public void setRegistCountryArea(Country registCountryArea) {
    this.registCountryArea = registCountryArea;
}
}

public class Country implements Serializable {

private static final long serialVersionUID = 3070416090656703733L;

private Integer id;
private String code;
private String numcode;


@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
public Integer getId() {
    return id;
}

public void setId(Integer id) {
    this.id = id;
}

@Column(name="CODE")
public String getCode() {
    return code;
}

public void setCode(String code) {
    this.code = code;
}

@Column(name="NUMCODE")
public String getNumcode() {
    return numcode;
}

public void setNumcode(String numcode) {
    this.numcode = numcode;
}
}

我的查询代码：

Criteria criteria = this.getSession().createCriteria(Company.class);
List list = criteria.list()

我从控制台获取select SQL：

Hibernate: select this_.id as id14_2_, this_.controller_country as controller10_14_2_, this_.regist_country as regist28_14_2_,  countryare2_.id as id4_0_, countryare2_.CODE as CODE4_0_,  countryare2_.NUMCODE as NUMCODE4_0_, countryare3_.id as id4_1_, countryare3_.CODE as CODE4_1_,  countryare3_.NUMCODE as NUMCODE4_1_ from ps_ctf_company this_ left outer join PS_CTF_DICT_country countryare2_ on this_.controller_country=countryare2_.CODE left outer join PS_CTF_DICT_country countryare3_ on this_.regist_country=countryare3_.CODE order by this_.code asc
Hibernate: select countryare0_.id as id4_0_, countryare0_.CODE as CODE4_0_, countryare0_.NUMCODE as NUMCODE4_0_ from PS_CTF_DICT_country countryare0_ where countryare0_.CODE=?
Hibernate: select countryare0_.id as id4_0_, countryare0_.CODE as CODE4_0_, countryare0_.NUMCODE as NUMCODE4_0_ from PS_CTF_DICT_country countryare0_ where countryare0_.CODE=?
Hibernate: select countryare0_.id as id4_0_, countryare0_.CODE as CODE4_0_, countryare0_.NUMCODE as NUMCODE4_0_ from PS_CTF_DICT_country countryare0_ where countryare0_.CODE=?
Hibernate: select countryare0_.id as id4_0_, countryare0_.CODE as CODE4_0_, countryare0_.NUMCODE as NUMCODE4_0_ from PS_CTF_DICT_country countryare0_ where countryare0_.CODE=?
Hibernate: select countryare0_.id as id4_0_, countryare0_.CODE as CODE4_0_, countryare0_.NUMCODE as NUMCODE4_0_ from PS_CTF_DICT_country countryare0_ where countryare0_.CODE=?

---

事实上，第一个sql就是我想要的，它得到了预期的5个结果（ues'left join'得到了'controllerCountry'和'RegistrCountry'）。我不明白为什么还有其他5个sql。如果问题是n+1-query，则应该有其他10个sql（5个sql用于选择“controllerCountry”，另一个用于选择“RegistrCountry”）。有人能告诉我发生了什么，以及如何通过一个sql获得结果。

我想您需要的是快速加载，您可以使用以下操作：

@ManyToOne(targetEntity = Country.class, fetch=FetchType.EAGER)
@JoinColumn(name="controller_country",referencedColumnName="code",insertable=false,updatable=false)
public Country getControllerCountryArea() {
    return controllerCountryArea;
}

---

另一个集合也是如此。

这是因为在第一个查询中，

对
WHERE
子句中的条件和可选匹配执行JOIN

。您必须指示

条件

立即取孩子。你可以这样做。至于未来，这是一个很好的例子