[英]Correct Initialization of Hibernate Lazy collections
我是否正確初始化了惰性集合? 我的主要目標是進行數據庫查詢並初始化一個惰性集合,以便沒有數據庫會話的方法可以使用它。
我當前的方法有效,但似乎多次查詢數據庫。 任何人都可以確認這是正確的或告訴我正確的方法。
服務類方法
public void testing() {
try {
List<User> users = test();
for (User user : users) {
System.out.println(user);
Set<UserGroupMapping> userGroupMapping = user.getUserGroupMappings();
for (UserGroupMapping userGroupMapping : userGroupMapping) {
System.out.println(userGroupMapping);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
@Transactional(value = "transactionManager", propagation = Propagation.REQUIRED, isolation = Isolation.DEFAULT, readOnly = true)
private List<User> test() {
return dao.findUsers();
}
道類方法
@Transactional(value = "transactionManager", propagation = Propagation.MANDATORY, isolation = Isolation.DEFAULT, readOnly = true)
public List<User> findUsers() {
Criteria criteria = getCesSession().createCriteria(User.class);
criteria.setFetchMode("userGroupMappings", FetchMode.SELECT);
@SuppressWarnings("unchecked")
List<User> list = (List<User>) criteriaList(criteria);
for (User user : list) {
Set<UserGroupMapping> b = user.getUserGroupMappings();
Hibernate.initialize(b);
for (UserGroupMapping userGroupMapping : b) {
Hibernate.initialize(userGroupMapping.getGroup());
}
}
return list;
}
用戶實體
@Entity
@Table(name = "[User]", schema = "dbo", catalog = "Test", uniqueConstraints = @UniqueConstraint(columnNames = "userName"))
public class User extends DatabaseObject {
private Long userId;
private Set<UserGroupMapping> userGroupMappings = new HashSet<UserGroupMapping>(
0);
@Id
@Column(name = "userId", unique = true, nullable = false)
public Long getUserId() {
return this.userId;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "user")
public Set<UserGroupMapping> getUserGroupMappings() {
return this.userGroupMappings;
}
集團實體
@Entity
@Table(name = "[Group]", schema = "dbo", catalog = "Test", uniqueConstraints = @UniqueConstraint(columnNames = "name"))
public class Group extends DatabaseObject {
private Long groupId;
private Set<GroupRoleMapping> groupRoleMappings = new HashSet<GroupRoleMapping>(0);
private Set<UserGroupMapping> userGroupMappings = new HashSet<UserGroupMapping>(0);
@Id
@Column(name = "groupId", unique = true, nullable = false)
public Long getGroupId() {
return this.groupId;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "group")
public Set<GroupRoleMapping> getGroupRoleMappings() {
return this.groupRoleMappings;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "group")
public Set<UserGroupMapping> getUserGroupMappings() {
return this.userGroupMappings;
}
用戶組映射實體
@Entity
@Table(name = "UserGroupMapping", schema = "dbo", catalog = "Test", uniqueConstraints = @UniqueConstraint(columnNames = "userId"))
public class UserGroupMapping extends DatabaseObject {
private Long userGroupMappingId;
private Group group;
private User user;
@Id
@Column(name = "userGroupMappingId", unique = true, nullable = false)
public Long getUserGroupMappingId() {
return this.userGroupMappingId;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "groupId", nullable = false)
public Group getGroup() {
return this.group;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "userId", unique = true, nullable = false)
public User getUser() {
return this.user;
}
}
日志
DEBUG: 15:19:22.251 -
/* criteria query */ select
this_.userId as userId1_17_0_,
this_.createdBy as createdB2_17_0_,
this_.dateCreated as dateCrea3_17_0_,
this_.dateUpdated as dateUpda4_17_0_,
this_.name as name5_17_0_,
this_.password as password6_17_0_,
this_.updatedBy as updatedB7_17_0_,
this_.userName as userName8_17_0_
from
CES_SIT.dbo.[User] this_
Hibernate:
/* criteria query */ select
this_.userId as userId1_17_0_,
this_.createdBy as createdB2_17_0_,
this_.dateCreated as dateCrea3_17_0_,
this_.dateUpdated as dateUpda4_17_0_,
this_.name as name5_17_0_,
this_.password as password6_17_0_,
this_.updatedBy as updatedB7_17_0_,
this_.userName as userName8_17_0_
from
CES_SIT.dbo.[User] this_
DEBUG: 15:19:39.159 -
select
usergroupm0_.userId as userId7_17_0_,
usergroupm0_.userGroupMappingId as userGrou1_15_0_,
usergroupm0_.userGroupMappingId as userGrou1_15_1_,
usergroupm0_.createdBy as createdB2_15_1_,
usergroupm0_.dateCreated as dateCrea3_15_1_,
usergroupm0_.dateUpdated as dateUpda4_15_1_,
usergroupm0_.groupId as groupId6_15_1_,
usergroupm0_.updatedBy as updatedB5_15_1_,
usergroupm0_.userId as userId7_15_1_
from
CES_SIT.dbo.UserGroupMapping usergroupm0_
where
usergroupm0_.userId=?
Hibernate:
select
usergroupm0_.userId as userId7_17_0_,
usergroupm0_.userGroupMappingId as userGrou1_15_0_,
usergroupm0_.userGroupMappingId as userGrou1_15_1_,
usergroupm0_.createdBy as createdB2_15_1_,
usergroupm0_.dateCreated as dateCrea3_15_1_,
usergroupm0_.dateUpdated as dateUpda4_15_1_,
usergroupm0_.groupId as groupId6_15_1_,
usergroupm0_.updatedBy as updatedB5_15_1_,
usergroupm0_.userId as userId7_15_1_
from
CES_SIT.dbo.UserGroupMapping usergroupm0_
where
usergroupm0_.userId=?
DEBUG: 15:19:39.176 - Preparing collection intializer : [com.bdo.ces.entities.User.userGroupMappings#1]
DEBUG: 15:19:39.176 - Starting ResultSet row #0
DEBUG: 15:19:39.177 - Found row of collection: [com.bdo.ces.entities.User.userGroupMappings#1]
DEBUG: 15:19:39.177 - Resolving associations for [com.bdo.ces.entities.UserGroupMapping#1]
DEBUG: 15:19:39.177 - Done materializing entity [com.bdo.ces.entities.UserGroupMapping#1]
DEBUG: 15:19:39.177 - 1 collections were found in result set for role: com.bdo.ces.entities.User.userGroupMappings
DEBUG: 15:19:39.177 - Collection fully initialized: [com.bdo.ces.entities.User.userGroupMappings#1]
DEBUG: 15:19:39.177 - 1 collections initialized for role: com.bdo.ces.entities.User.userGroupMappings
DEBUG: 15:19:39.177 - Done loading collection
DEBUG: 15:19:39.177 - Initializing proxy: [com.bdo.ces.entities.Group#1]
DEBUG: 15:19:39.177 -
select
group0_.groupId as groupId1_16_0_,
group0_.createdBy as createdB2_16_0_,
group0_.dateCreated as dateCrea3_16_0_,
group0_.dateUpdated as dateUpda4_16_0_,
group0_.description as descript5_16_0_,
group0_.name as name6_16_0_,
group0_.updatedBy as updatedB7_16_0_,
group0_.visible as visible8_16_0_
from
CES_SIT.dbo.[
Group] group0_ where
group0_.groupId=?
Hibernate:
select
group0_.groupId as groupId1_16_0_,
group0_.createdBy as createdB2_16_0_,
group0_.dateCreated as dateCrea3_16_0_,
group0_.dateUpdated as dateUpda4_16_0_,
group0_.description as descript5_16_0_,
group0_.name as name6_16_0_,
group0_.updatedBy as updatedB7_16_0_,
group0_.visible as visible8_16_0_
from
CES_SIT.dbo.[
Group] group0_ where
group0_.groupId=?
使用 KC 進行測試================================
道類方法
@Transactional(value = "transactionManager", propagation = Propagation.MANDATORY, isolation = Isolation.DEFAULT, readOnly = true)
public List<User> findUsers() {
Criteria criteria = getCesSession().createCriteria(User.class);
criteria.setFetchMode("userGroupMappings", FetchMode.JOIN);
criteria.createAlias("userGroupMappings", "userGroupMappings",
JoinType.LEFT_OUTER_JOIN);
@SuppressWarnings("unchecked")
List<User> list = (List<User>) criteriaList(criteria);
Hibernate.initialize(list);
for (User user : list) {
Set<UserGroupMapping> b = user.getUserGroupMappings();
Hibernate.initialize(b);
for (UserGroupMapping userGroupMapping : b) {
Hibernate.initialize(userGroupMapping.getGroup());
}
}
return list;
}
日志
DEBUG: 17:40:19.989 -
/* criteria query */ select
this_.userId as userId1_17_1_,
this_.createdBy as createdB2_17_1_,
this_.dateCreated as dateCrea3_17_1_,
this_.dateUpdated as dateUpda4_17_1_,
this_.name as name5_17_1_,
this_.password as password6_17_1_,
this_.updatedBy as updatedB7_17_1_,
this_.userName as userName8_17_1_,
usergroupm1_.userId as userId7_17_3_,
usergroupm1_.userGroupMappingId as userGrou1_15_3_,
usergroupm1_.userGroupMappingId as userGrou1_15_0_,
usergroupm1_.createdBy as createdB2_15_0_,
usergroupm1_.dateCreated as dateCrea3_15_0_,
usergroupm1_.dateUpdated as dateUpda4_15_0_,
usergroupm1_.groupId as groupId6_15_0_,
usergroupm1_.updatedBy as updatedB5_15_0_,
usergroupm1_.userId as userId7_15_0_
from
CES_SIT.dbo.[User] this_
left outer join
CES_SIT.dbo.UserGroupMapping usergroupm1_
on this_.userId=usergroupm1_.userId
Hibernate:
/* criteria query */ select
this_.userId as userId1_17_1_,
this_.createdBy as createdB2_17_1_,
this_.dateCreated as dateCrea3_17_1_,
this_.dateUpdated as dateUpda4_17_1_,
this_.name as name5_17_1_,
this_.password as password6_17_1_,
this_.updatedBy as updatedB7_17_1_,
this_.userName as userName8_17_1_,
usergroupm1_.userId as userId7_17_3_,
usergroupm1_.userGroupMappingId as userGrou1_15_3_,
usergroupm1_.userGroupMappingId as userGrou1_15_0_,
usergroupm1_.createdBy as createdB2_15_0_,
usergroupm1_.dateCreated as dateCrea3_15_0_,
usergroupm1_.dateUpdated as dateUpda4_15_0_,
usergroupm1_.groupId as groupId6_15_0_,
usergroupm1_.updatedBy as updatedB5_15_0_,
usergroupm1_.userId as userId7_15_0_
from
CES_SIT.dbo.[User] this_
left outer join
CES_SIT.dbo.UserGroupMapping usergroupm1_
on this_.userId=usergroupm1_.userId
select
group0_.groupId as groupId1_16_0_,
group0_.createdBy as createdB2_16_0_,
group0_.dateCreated as dateCrea3_16_0_,
group0_.dateUpdated as dateUpda4_16_0_,
group0_.description as descript5_16_0_,
group0_.name as name6_16_0_,
group0_.updatedBy as updatedB7_16_0_,
group0_.visible as visible8_16_0_
from
CES_SIT.dbo.[
Group] group0_ where
group0_.groupId=?
Hibernate:
select
group0_.groupId as groupId1_16_0_,
group0_.createdBy as createdB2_16_0_,
group0_.dateCreated as dateCrea3_16_0_,
group0_.dateUpdated as dateUpda4_16_0_,
group0_.description as descript5_16_0_,
group0_.name as name6_16_0_,
group0_.updatedBy as updatedB7_16_0_,
group0_.visible as visible8_16_0_
from
CES_SIT.dbo.[
Group] group0_ where
group0_.groupId=?
DEBUG: 17:40:38.189 -
select
group0_.groupId as groupId1_16_0_,
group0_.createdBy as createdB2_16_0_,
group0_.dateCreated as dateCrea3_16_0_,
group0_.dateUpdated as dateUpda4_16_0_,
group0_.description as descript5_16_0_,
group0_.name as name6_16_0_,
group0_.updatedBy as updatedB7_16_0_,
group0_.visible as visible8_16_0_
from
CES_SIT.dbo.[
Group] group0_ where
group0_.groupId=?
Hibernate:
select
group0_.groupId as groupId1_16_0_,
group0_.createdBy as createdB2_16_0_,
group0_.dateCreated as dateCrea3_16_0_,
group0_.dateUpdated as dateUpda4_16_0_,
group0_.description as descript5_16_0_,
group0_.name as name6_16_0_,
group0_.updatedBy as updatedB7_16_0_,
group0_.visible as visible8_16_0_
from
CES_SIT.dbo.[
Group] group0_ where
group0_.groupId=?
DEBUG: 17:40:38.197 - Starting ResultSet row #0
決賽============================
使用此代碼使其工作我仍然不確定這是否是最好的方法,但它僅在一個查詢中加載了惰性集合。 我還在 [userGroupMappings.group] 中加入了惰性對象以使其工作。
我以為 Hibernate.initialize() 會為我做到這一點,但事實並非如此。
**Dao Class Method**
@Transactional(value = "transactionManager", propagation = Propagation.MANDATORY, isolation = Isolation.DEFAULT, readOnly = true)
public List<User> findUsers() {
Criteria criteria = getCesSession().createCriteria(User.class);
criteria.createCriteria("userGroupMappings", "userGroupMappings",
JoinType.LEFT_OUTER_JOIN);
criteria.createCriteria("userGroupMappings.group", "userGroupMappings.group",
JoinType.LEFT_OUTER_JOIN);
@SuppressWarnings("unchecked")
List<User> list = (List<User>) criteriaList(criteria);
return list;
}
由於User - UserGroupMapping
1-n 映射,您有 n + 1 選擇問題,描述為here 。 這就是為什么你有這么多的疑問。
您可以通過對 UserGroupMapping 執行左外部聯接來避免這種情況。
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