Java 使用具有一对多关系的 CriteriaBuilder 的 Spring Data JPA 规范
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Spring Data JPA Specification using CriteriaBuilder with a one to many relationship
提问by Andrew Mairose
I have a Userentity, a UserToApplicationentity, and an Applicationentity.
我有一个User实体，一个UserToApplication实体，一个Application实体。
A single Usercan have access to more than one Application. And a single Applicationcan be used by more than one User.
一个人User可以访问多个Application。而且一个人Application可以多人使用User。
Here is the Userentity.
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 */
}
Here is the UserToApplicationentity.
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;
}
}
And here is the Applicationentity.
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 */
}
I have the following Specificationthat I use to search for a Userby firstNm, lastNm, and email.
我有以下的Specification，我用它来搜索User的firstNm，lastNm和email。
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);
}
};
}
}
And here is the User_metamodel that I have so far.
这是User_我目前拥有的元模型。
@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;
}
Now, I would like to also pass in a list of application IDs to the Specification, such that its method signature would be:
现在，我还想将应用程序 ID 列表传递给Specification，使其方法签名为：
public static Specification<User> findByFirstNmLastNmEmailApp(String firstNm, String lastNm, String email, Collection<Long> appIds)
So, my question is, if I add the @OneToManymapping to the User_metamodel for the Collection<Application> applicationsfield of my Userentity, then how would I reference it in the Specification?
所以，我的问题是，如果我将@OneToMany映射添加到实体字段的User_元模型中，那么我将如何在?Collection<Application> applicationsUserSpecification
My current Specificationwould be similar to the following SQL query:
我的当前Specification将类似于以下 SQL 查询：
select * from user u
where lower(first_nm) like '%firstNm%'
and lower(last_nm) like '%lastNm%'
and lower(email) like '%email%';
And what I would like to achieve in the new Specificationwould be something like this:
我想在新版本中实现的目标Specification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);
Is it possible to do this kind of mapping in the metamodel, and how could I achieve this result in my Specification?
是否可以在元模型中进行这种映射，我如何在我的Specification?
采纳答案by Andrew Mairose
I found a solution. To map a one to many attribute, in the metamodel I added the following:
我找到了解决方案。为了映射一对多属性，我在元模型中添加了以下内容：
public static volatile CollectionAttribute<User, Application> applications;
I also needed to add a metamodel for the Applicationentity.
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;
}
Then in my Specification, I could access the applicationsfor a user, using the .join()method on the Root<User>instance. Here is the PredicateI formed.
然后在 my 中Specification，我可以applications使用实例.join()上的方法访问用户的Root<User>。这是Predicate我组建的。
final Predicate appPredicate = root.join(User_.applications).get(Application_.applicationId).in(appIds);
Also, it is worth noting that my Specificationas it is written in the question will not work if any of the input values are empty. A null Predicatepassed to the .and()method of CriteriaBuilderwill cause a NullPointerException. So, I created an ArrayListof type Predicate, then added each Predicateto the list if the corresponding parameter was non-empty. Finally, I convert the ArrayListto an array to pass it to the .and()function of the CriteriaBuilder. Here is the final Specification:
另外，值得注意的是，Specification如果任何输入值为空，则问题中所写的my将不起作用。Predicate传递给 的.and()方法的nullCriteriaBuilder将导致NullPointerException. 因此，我创建了一个ArrayListof type Predicate，然后Predicate如果相应的参数非空，则将每个都添加到列表中。最后，我转换ArrayList到一个数组将它传递到.and()的功能CriteriaBuilder。这是决赛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()]));
}
};
}
}
