I'm using ResultTransformer to select only particular properties from entity, just i don't need all properties from entity.
But the problem i faced is when a property is "one-to-many".
Here is a simple example.
#Entity
#Table(name = "STUDENT")
public class Student
{
private long studentId;
private String studentName;
private List<Phone> studentPhoneNumbers = new ArrayList<Phone>();
#Id
#GeneratedValue
#Column(name = "STUDENT_ID")
public long getStudentId()
{
return this.studentId;
}
#OneToMany(cascade = CascadeType.ALL)
#JoinTable(name = "STUDENT_PHONE", joinColumns = {#JoinColumn(name = "STUDENT_ID")}, inverseJoinColumns = {#JoinColumn(name = "PHONE_ID")})
public List<Phone> getStudentPhoneNumbers()
{
return this.studentPhoneNumbers;
}
#Column(name = "STUDENT_NAME", nullable = false, length = 100)
public String getStudentName()
{
return this.studentName;
}
Here is the class used by ResultTransformer for storing the selected properties.
public class StudentDTO
{
private long m_studentId;
private List<Phone> m_studentPhoneNumbers = new ArrayList<Phone>();
..
constructors and getters and setters..
And finally the Criteria code
Criteria criteria = session.createCriteria(Student.class)
.setProjection(Projections.projectionList()
.add(Projections.property("studentId"), "m_studentId")
.add(Projections.property("studentPhoneNumbers"), "m_studentPhoneNumbers"))
.setResultTransformer(Transformers.aliasToBean(StudentDTO.class));
List list = criteria.list();
StudentDTO p = (StudentDTO) list.get(0);
So, after i get StudentDTO object , only studenId is available, studentPhoneNumber is null ..
Does it mean ResultTransformer does not work with any relationships ? or my way is wrong
Any suggestions?
Thanks
I have run into this problem before. The transformers in hibernate generally lead to frustration. You can do a manual assignment as is suggested, or you can map the DTO class to the same table using hibernate. Just add the same annotation to your StudentDTO class as the Student class and then load it like normal. So student DTO would be:
#Entity
#Table(name = "STUDENT")
public class StudentDTO
{
private long studentId;
private String studentName;
private List<Phone> studentPhoneNumbers = new ArrayList<Phone>();
#Id
#GeneratedValue
#Column(name = "STUDENT_ID")
public long getStudentId()
{
return this.studentId;
}
#OneToMany(cascade = CascadeType.ALL)
#JoinTable(name = "STUDENT_PHONE", joinColumns = {#JoinColumn(name = "STUDENT_ID")}, inverseJoinColumns = {#JoinColumn(name = "PHONE_ID")})
public List<Phone> getStudentPhoneNumbers()
{
return this.studentPhoneNumbers;
}
Just leave out what you do not want to load.
Related
I'm trying to update a ManyToMany relationship using CriteriaUpdate.
The following are the entities;
#Entity
#Table(name = "COURSE")
public class Course {
#Id
#GeneratedValue
private String id;
private String name;
// Getters and setter...
}
#Entity
#Table(name = "STUDENT")
public class Student {
#Id
#GeneratedValue
private String id;
private String name;
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(name = "STUDENT_COURSE", joinColumns = {#JoinColumn(name = "STUDENT_ID")}, inverseJoinColumns = {#JoinColumn(name = "COURSE_ID")})
private Set<Course> courses = new HashSet<>();
// Getters and setter...
}
Below is the code in the DAO
void updateCourses(String studentId, Set<Course> courses){
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaUpdate<Student> criteriaUpdate = criteriaBuilder.createCriteriaUpdate(Student.class);
Root<Student> studentRoot = criteriaUpdate.from(Student.class);
criteriaUpdate.where(criteriaBuilder.equal(studentRoot.get("id"), studentId));
criteriaUpdate.set("courses", courses);
entityManager.createQuery(criteriaUpdate).executeUpdate();
}
The above code throws the following exception
java.lang.IllegalArgumentException: Attribute path for assignment must represent a singular attribute [null.courses]
How can I update using CriteriaUpdate?
I got a lot of answers and advice, tried changing my code according to these tips.
But, unfortunately, these tips helped only partially.
Now, when creating a new project and creating a new user, I can add the desired user to the set of projects, and the required project will be added to the set of users.
But the relationship between the desired project and the desired user will not appear in the project_user table.
Please help find the answer.
Entity Project
#Data
#Entity
#AllArgsConstructor
#NoArgsConstructor
#Table(name = "project")
public class Project {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column
private String name;
#Column
private String description;
#ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
#JoinTable(name = "project_users",
joinColumns = #JoinColumn(name = "project_id"),
inverseJoinColumns = #JoinColumn(name = "users_id"))
private Set<User> projectUserSet = new HashSet<>();
#ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
#JoinTable(name = "project_task",
joinColumns = #JoinColumn(name = "project_id"),
inverseJoinColumns = #JoinColumn(name = "task_id"))
private Set<Task> projectTaskSet = new HashSet<>();
public void addUserToProject(User user){
this.projectUserSet.add(user);
user.getUserProjectsSet().add(this);
}
public void addTasksToProject(Task task){
this.projectTaskSet.add(task);
task.getTasksProjectSet().add(this);
}
//constructors, hashCode, equals, toString
}
Entity User
#Data
#Entity
#AllArgsConstructor
#NoArgsConstructor
#Table(name = "users")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column
private String firstName;
#Column
private String lastName;
#ManyToMany(mappedBy = "projectUserSet", cascade = CascadeType.ALL)
private Set<Project> userProjectsSet = new HashSet<>();
#ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
#JoinTable(name = "users_task",
joinColumns = {#JoinColumn(name = "users_id")},
inverseJoinColumns = {#JoinColumn(name = "task_id")})
private Set<Task> userTasksSet = new HashSet<>();
public void addTaskToUser(Task task) {
this.userTasksSet.add(task);
task.getTasksUserSet().add(this);
}
//constructors, hashCode, equals, toString
}
project and user initialization
Project project1 = new Project("Project1", "Project1");
User user1 = new User("User1", "User1");
project1.addUserToProject(user1);
With code shown below, table project_user is populated, verified using H2 console. In order to avoid stack overflow, I had to modify method Project#addTaskToUser as shown below.
Please note that only code relevant to the question, is included.
Normally, issue should be described by some tests. In this case, I added a CommandLineRunner that runs at startup.
CascadeType.ALL is not recommended for many-to-many relations, hence I changed this in code shown below.
Tested using H2 in-memory db.
Project class
#Data
#Entity
public class Project {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private String description;
#ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
#JoinTable(name = "project_users",
joinColumns = #JoinColumn(name = "project_id"),
inverseJoinColumns = #JoinColumn(name = "users_id"))
private Set<MyUser> projectUserSet = new HashSet<>();
public void addUserToProject(User user) {
this.projectUserSet.add(user);
}
}
Project repo
public interface ProjectRepo extends JpaRepository<Project, Long> { }
User class
// cannot use #Data here because it will cause cyclic ref and stack overflow when accessing userProjectsSet
#Getter
#Setter
#Entity
#Table(name = "users")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String firstName;
private String lastName;
#ManyToMany(mappedBy="projectUserSet")
private Set<Project> userProjectsSet = new HashSet<>();
}
User repo
public interface UserRepo extends JpaRepository<User, Long> {}
In app class
#SpringBootApplication
public class MyApplication {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
#Bean
CommandLineRunner run(ProjectRepo projectRepo, EntityManagerFactory entityManagerFactory) {
return args -> {
var testUser = new User();
testUser.setFirstName("first-name");
testUser.setLastName("last-name");
var project = new Project();
project.setName("project-name");
project.setDescription("project-description");
project.addUserToProject(testUser);
projectRepo.save(project);
// get saved user and print some properties
var userInDb = entityManagerFactory.createEntityManager().find(User.class, testUser.getId());
System.out.println(userInDb.getFirstName()); // prints "first-name"
System.out.println(userInDb.getUserProjectsSet().size()); // prints "1"
};
}
}
I want to understand how to work with related entities in Hibernate.
There are two related entities:
#Entity
#Table(name = "usr")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(nullable = false)
private String username;
#Column(nullable = false)
private String password;
#Column(nullable = false)
private String email;
private boolean active;
#Enumerated(EnumType.STRING)
private Role role;
#OneToMany(fetch = FetchType.LAZY,
mappedBy = "responsibleUser", cascade = CascadeType.ALL)
private List<GrowBox> growBoxes;
//def-constructor , getters, setters
}
and
#Entity
#Table(name = "growBoxes")
public class GrowBox {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
Long id;
#Column(nullable = false)
private Integer length;
#Column(nullable = false)
private Integer width;
#Column(nullable = false)
private Integer height;
#OneToMany(fetch = FetchType.LAZY, mappedBy = "responsibleGrowBox", cascade = CascadeType.ALL)
private List<Plant> plants;
#OneToMany(fetch = FetchType.LAZY, mappedBy = "activeGrowBox", cascade = CascadeType.ALL)
private List<Sensor> sensors;
#ManyToOne
#JoinColumn(name = "user_id")
private User responsibleUser;
//def-constructor , getters, setters
}
I have registered mapping using annotations. Hope it is correct. And I want to find box by user Id, but don't know how HQL query should be written. 'Cause there is no "user_id" field in my Box Class. Instead there is "User responsibleUser" field. And smth like this won't work(should not)
#Autowired
SessionFactory sessionFactory;
#Override
public List<GrowBox> findByUser(Long userId) {
Session session = sessionFactory.openSession();
String hqlQuery = "from GrowBox where user_id =: userId";
Query query = session.createQuery(hqlQuery);
List growBoxes = query.getResultList();
session.flush();
session.close();
return growBoxes;
}
A HQL query would be
String hqlQuery = "from GrowBox gb where gb.responsibleUser.id =: userId";
I have four class; UserGroup, UserAccount, Role, UserGroupRoleRelation and my db is IBM DB2
#Entity
#Table(name = "USER_GROUP")
public class UserGroup implements Serializable {
#Id
#Column(name = "USER_GROUP_ID")
#GeneratedValue
private Long id;
......
..
#OneToMany(mappedBy = "userGroup", cascade = CascadeType.ALL, orphanRemoval = true)
private List<UserGroupRoleRelation> userAccountsRole = new ArrayList<UserGroupRoleRelation>();
}
#Entity
#Table(name = "ROLE")
public class Role implements Serializable {
#Id
#Column(name = "ROLE_ID")
#GeneratedValue
private Long id;
......
#OneToMany(mappedBy = "role")
private List<UserGroupRoleRelation> userAccountInGroup = new ArrayList<UserGroupRoleRelation>();
}
#Entity
#Table(name = "USER_GROUP_ROLE_LINE", uniqueConstraints = #UniqueConstraint(columnNames = { "ROLE_ID", "USER_GROUP_ID" }))
public class UserGroupRoleRelation {
#Id
#GeneratedValue
#Column(name = "RELATION_ID")
private Long relationId;
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "USER_ACCOUNT_USER_GROUP_ROLE_LINE", joinColumns = { #JoinColumn(name = "RELATION_ID") }, inverseJoinColumns = { #JoinColumn(name = "USER_ID") }, uniqueConstraints = #UniqueConstraint(columnNames = { "USER_ID", "RELATION_ID" }))
private List<UserAccount> userAccountList = new ArrayList<UserAccount>();
#ManyToOne
#JoinColumn(name = "USER_GROUP_ID")
private UserGroup userGroup;
#ManyToOne
#JoinColumn(name = "ROLE_ID")
private Role role;
}
#Entity
#Table(name = "USER_ACCOUNT")
public class UserAccount implements Serializable {
#Id
#Column(name = "USER_ID")
#GeneratedValue
private Long id;
.....
#ManyToMany(mappedBy = "userAccountList", cascade = CascadeType.ALL)
private List<UserGroupRoleRelation> rolesInGroup = new ArrayList<UserGroupRoleRelation>();
}
I wanna find usergroups of a useraccount and i prepared a method with criteria. its like;
#Override
#Transactional
public List<UserGroup> findUserGroupOf(UserAccount userAccount) {
Criteria criteria = getSession().createCriteria(UserGroup.class);
criteria.createAlias("userAccountsRole", "userAccountsRole");
criteria.add(Restrictions.eq("userAccountsRole.userAccountList", userAccount));
return criteria.list();
}
But when i try to get result of that method, DB2 gives to me DB2 SQL Error: SQLCODE=-313, SQLSTATE=07004, SQLERRMC=null, DRIVER=3.63.75
Probably its about creating alias on many to many relation. I dont know what should i do to create alias on many to many. How can I get result of that function?
Thank
#Override
#Transactional
public List<UserGroup> findUserGroupOf(UserAccount userAccount) {
Criteria criteria = getSession().createCriteria(UserGroup.class);
criteria.createAlias("userAccountsRole", "userAccountsRole");
criteria.createAlias("userAccountsRole.userAccountList", "userAccountList");
criteria.add(Restrictions.eq("userAccountList.id", userAccount.getId()));
return criteria.list();
}
It works for me. I mean criteria on "id". But I don't understand why I cant check equality on object instead of id when there is ManyToMany list
It is not of creating alias. You are passing an object to hibernate on which it can not make any criteria. You need to create bidirectional mapping for that.Or else if you your requirement is just to fetch the the list of UserAccountList of particular UserGroup class you can follow the below code.
#Override
#Transactional
public List<UserGroup> findUserGroupOf(long userGroupId) {
Criteria criteria = getSession().createCriteria(UserGroup.class);
criteria.add(Restrictions.eq("id",userGroupId));
criteria.createAlias("userAccountsRole", "uar");
criteria.setFetchMode("uar.userAccountList",FetchMode.JOIN);
return criteria.list();
}
I need to create a join table in my database using JPA annotations so the result will be this:
So far I just implemented 2 entities:
#Entity
#Table(name="USERS", schema="ADMIN")
public class User implements Serializable {
private static final long serialVersionUID = -1244856316278032177L;
#Id
#Column(nullable = false)
private String userid;
#Column(nullable = false)
private String password;
public String getUserid() {
return userid;
}
public void setUserid(String userid) {
this.userid = userid;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
#Entity
#Table(name="GROUPS", schema="ADMIN")
public class Group implements Serializable {
private static final long serialVersionUID = -7274308564659753174L;
#Id
#Column(nullable = false)
private String groupid;
public String getGroupid() {
return groupid;
}
public void setGroupid(String groupid) {
this.groupid = groupid;
}
}
Should i create another entity called USER_GROUP or i can just add some annotations, so the join table will be created automatically when i run create tables from entities(ORM)?
How should i annotate my entities to achieve the same as in the image?
You definitely shouldn't create User_Group entity as it's more the underlying database representation than the object oriented one.
You can achieve the join table by defining something like:
#Entity
#Table(name="USERS", schema="ADMIN")
public class User implements Serializable {
//...
#ManyToOne
#JoinTable(name="USER_GROUP")
Group group;
#Entity
#Table(name="GROUPS", schema="ADMIN")
public class Group implements Serializable {
//...
#OneToMany(mappedBy="group")
Set<User> users;
Edit: If you want to explicitly set the names of the columns you could use #JoinColumn elements as shown below:
#ManyToOne
#JoinTable(name="USER_GROUP",
joinColumns = #JoinColumn(name = "userid",
referencedColumnName = "userid"),
inverseJoinColumns = #JoinColumn(name = "groupid",
referencedColumnName = "groupid"))
Group group;
I would implement it this way:
#Entity
#Table(name="GROUPS", schema="ADMIN")
public class Group implements Serializable {
#OneToMany
#JoinTable(name = "USER_GROUP",
joinColumns = #JoinColumn(name = "groupid"),
inverseJoinColumns = #JoinColumn(name = "userid"))
private List<User> users;
}
Solution suggested by #PedroKowalski should work too, but then you'll have to keep a reference to Group entity in your User entity which is not always possible.
To have the same annotations like in your diagram you can do this in your User class:
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(name = "USER_GROUP",
joinColumns = { #JoinColumn(name = "userid") },
inverseJoinColumns = { #JoinColumn(name = "groupid") })
private List<Group> grups;
in your group class
#ManyToMany(fetch = FetchType.LAZY)
#JoinTable(name = "USER_GROUP",
joinColumns = { #JoinColumn(name = "groupid") },
inverseJoinColumns = { #JoinColumn(name = "userid") })
private List<User> users;
I'm wondering what is the point to create a Join Table in this way, considering that we can't access directly for queries?
JPA doesn't allow to make queries directly to the Join Table, so if the user want to do an operation on USER_GROUP, he has to creare a normal join query between users and groups; due to this, the join table USER_GROUP is useless.