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[英]Error relationship persistence using Spring Data JPA in a many to one
[英]Spring Data JPA Specification using CriteriaBuilder with a one to many relationship
我有一个User
实体,一个UserToApplication
实体和一个Application
实体。
单个User
可以访问多个Application
。 并且单个Application
可以由多个User
。
这是User
实体。
@Entity
@Table(name = "USER", schema = "UDB")
public class User {
private Long userId;
private Collection<Application> applications;
private String firstNm;
private String lastNm;
private String email;
@SequenceGenerator(name = "generator", sequenceName = "UDB.USER_SEQ", initialValue = 1, allocationSize = 1)
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "generator")
@Column(name = "USER_ID", unique = true, nullable = false)
public Long getUserId() {
return userId;
}
public void setUserId(Long userId) {
this.userId = userId;
}
@OneToMany(mappedBy = "user", fetch = FetchType.LAZY)
public Collection<Application> getApplications() {
return applications;
}
public void setApplications(Collection<Application> applications) {
this.applications = applications;
}
/* Other getters and setters omitted for brevity */
}
这是UserToApplication
实体。
@Entity
@Table(name = "USER_TO_APPLICATION", schema = "UDB")
public class Application {
private Long userToApplicationId;
private User user;
private Application application;
@SequenceGenerator(name = "generator", sequenceName = "UDB.USER_TO_APP_SEQ", initialValue = 0, allocationSize = 1)
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "generator")
@Column(name = "USER_TO_APPLICATION_ID", unique = true, nullable = false)
public Long getUserToApplicationId() {
return userToApplicationId;
}
public void setUserToApplicationId(Long userToApplicationId) {
this.userToApplicationId = userToApplicationId;
}
@ManyToOne
@JoinColumn(name = "USER_ID", referencedColumnName = "USER_ID", nullable = false)
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@ManyToOne
@JoinColumn(name = "APPLICATION_ID", nullable = false)
public Application getApplication() {
return application;
}
}
这是Application
实体。
@Entity
@Table(name = "APPLICATION", schema = "UDB")
public class Application {
private Long applicationId;
private String name;
private String code;
/* Getters and setters omitted for brevity */
}
我有以下Specification
,我用firstNm
, lastNm
和email
搜索User
。
public class UserSpecification {
public static Specification<User> findByFirstNmLastNmEmail(String firstNm, String lastNm, String email) {
return new Specification<User>() {
@Override
public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
final Predicate firstNmPredicate = null;
final Predicate lastNmPredicate = null;
final Predicate emailPredicate = null;
if (!StringUtils.isEmpty(firstNm)) {
firstNmPredicate = cb.like(cb.lower(root.get(User_.firstNm), firstNm));
}
if (!StringUtils.isEmpty(lastNm)) {
lastNmPredicate = cb.like(cb.lower(root.get(User_.lastNm), lastNm));
}
if (!StringUtils.isEmpty(email)) {
emailPredicate = cb.like(cb.lower(root.get(User_.email), email));
}
return cb.and(firstNmPredicate, lastNmPredicate, emailPredicate);
}
};
}
}
这是我到目前为止的User_
元模型。
@StaticMetamodel(User.class)
public class User_ {
public static volatile SingularAttribute<User, String> firstNm;
public static volatile SingularAttribute<User, String> lastNm;
public static volatile SingularAttribute<User, String> email;
}
现在,我还想将一个应用程序ID列表传递给Specification
,这样它的方法签名就是:
public static Specification<User> findByFirstNmLastNmEmailApp(String firstNm, String lastNm, String email, Collection<Long> appIds)
所以,我的问题是,如果我添加了@OneToMany
映射到User_
元模型的Collection<Application> applications
我的领域User
的实体,那么我将如何引用它的Specification
?
我当前的Specification
类似于以下SQL查询:
select * from user u
where lower(first_nm) like '%firstNm%'
and lower(last_nm) like '%lastNm%'
and lower(email) like '%email%';
我想在新Specification
实现的是这样的:
select * from user u
join user_to_application uta on uta.user_id = u.user_id
where lower(u.first_nm) like '%firstNm%'
and lower(u.last_nm) like '%lastNm%'
and lower(u.email) like '%email%'
and uta.application_id in (appIds);
是否可以在元模型中执行此类映射,如何在Specification
实现此结果?
我找到了解决方案。 要映射一个到多个属性,在元模型中我添加了以下内容:
public static volatile CollectionAttribute<User, Application> applications;
我还需要为Application
实体添加元模型。
@StaticMetamodel(Application.class)
public class Application_ {
public static volatile SingularAttribute<Application, Long> applicationId;
}
然后在我的Specification
,我可以使用Root<User>
实例上的.join()
方法访问用户的applications
。 这是我形成的Predicate
。
final Predicate appPredicate = root.join(User_.applications).get(Application_.applicationId).in(appIds);
此外,值得注意的是,如果任何输入值为空,我在问题中写的Specification
将不起作用。 传递给CriteriaBuilder
的.and()
方法的null Predicate
将导致NullPointerException
。 因此,我创建了一个Predicate
类型的ArrayList
,然后如果相应的参数非空,则将每个Predicate
添加到列表中。 最后,我将ArrayList
转换为数组,以将其传递给CriteriaBuilder
的.and()
函数。 这是最终Specification
:
public class UserSpecification {
public static Specification<User> findByFirstNmLastNmEmailApp(String firstNm, String lastNm, String email, Collection<Long> appIds) {
return new Specification<User>() {
@Override
public Predicate toPredicate(Root<User> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
final Collection<Predicate> predicates = new ArrayList<>();
if (!StringUtils.isEmpty(firstNm)) {
final Predicate firstNmPredicate = cb.like(cb.lower(root.get(User_.firstNm), firstNm));
predicates.add(firstNmPredicate);
}
if (!StringUtils.isEmpty(lastNm)) {
final Predicate lastNmPredicate = cb.like(cb.lower(root.get(User_.lastNm), lastNm));
predicates.add(lastNmPredicate);
}
if (!StringUtils.isEmpty(email)) {
final Predicate emailPredicate = cb.like(cb.lower(root.get(User_.email), email));
predicates.add(emailPredicate);
}
if (!appIds.isEmpty()) {
final Predicate appPredicate = root.join(User_.applications).get(Application_.applicationId).in(appIds);
predicates.add(appPredicate);
}
return cb.and(predicates.toArray(new Predicate[predicates.size()]));
}
};
}
}
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