I have a provider:user=1:N association modeled with entities, Hibernate/JPA.
Then I want to query a provider/user pair via restrictions on attributes of the dependent entity, like certain values for the attributes of the user, let’s say its id, date of birth, etc.
The logged sql has a proper join and all the attributes of the two entities in the select. I tried it manually, it returns the expected single row.
Thus, on entity level, I expect a single provider entity to be returned with the user list containing the queried user.
Indeed, the corresponding provider entity is returned, but when I then want to access the user via the provider’s user list, it hits the DB a second time and reads all users of the provider totally neglecting my restrictions of the query.
The observed behavior is the same for queries formulated with HQL, Hibernate Criteria (also with #Filter), JPA CriteriaBuilder.
What am I missing here?
Do those restrictions only affect the selection of the root entities (which is provider in my case)?
The problem is sketched on
https://docs.jboss.org/hibernate/orm/3.3/reference/en/html/querycriteria.html
Under 5.4 Associations it says:
The kittens collections held by the Cat instances returned by the previous two queries are not pre-filtered by the criteria. If you want to retrieve just the kittens that match the criteria, you must use a ResultTransformer.
Is this thus the intended behavior for this kind of API?
Or is there a convenient possibility to access just the restricted sub set of the dependent entities?
Regards,
Wolfgang
Here comes some source code to precise my verbal description above.
Provider and User table.
drop table EX_USER;
drop table EX_PROVIDER;
create table EX_PROVIDER
( id number(*,0) not null
,name varchar2(255) not null
,primary key (id)
);
insert into EX_PROVIDER (id,name) values (0 ,'Provider_A');
insert into EX_PROVIDER (id,name) values (1 ,'Provider_B');
commit;
create table EX_USER
( id number(*,0) not null
, ex_provider_id number(*,0) not null
,name varchar2(255)
,location varchar2(255)
,primary key (id)
,constraint ex_user_provider_fk foreign key(ex_provider_id) references EX_PROVIDER(id)
);
insert into EX_USER (id,ex_provider_id,name,location) values (0,0,'User_1','Munich');
insert into EX_USER (id,ex_provider_id,name,location) values (1,0,'User_2','Berlin');
insert into EX_USER (id,ex_provider_id,name,location) values (2,1,'User_3','Munich');
commit;
Entities generated with Eclipse "JPA Tools".
#Entity
#Table(name="EX_PROVIDER")
#NamedQuery(name="ExProvider.findAll", query="SELECT e FROM ExProvider e")
public class ExProvider implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#SequenceGenerator(name="EX_PROVIDER_ID_GENERATOR", sequenceName="KONST_SD_SEQ")
#GeneratedValue(strategy=GenerationType.SEQUENCE, generator="EX_PROVIDER_ID_GENERATOR")
private long id;
private String name;
//bi-directional many-to-one association to ExUser
#OneToMany(mappedBy="exProvider",fetch=FetchType.LAZY)
private Set<ExUser> exUsers=new HashSet<ExUser>();
public ExProvider() {
}
public long getId() {
return this.id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public Set<ExUser> getExUsers() {
return this.exUsers;
}
public void setExUsers(Set<ExUser> exUsers) {
this.exUsers = exUsers;
}
public ExUser addExUser(ExUser exUser) {
getExUsers().add(exUser);
exUser.setExProvider(this);
return exUser;
}
public ExUser removeExUser(ExUser exUser) {
getExUsers().remove(exUser);
exUser.setExProvider(null);
return exUser;
}
}
#Entity
#Table(name="EX_USER")
#NamedQuery(name="ExUser.findAll", query="SELECT e FROM ExUser e")
public class ExUser implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#SequenceGenerator(name="EX_USER_ID_GENERATOR", sequenceName="KONST_SD_SEQ")
#GeneratedValue(strategy=GenerationType.SEQUENCE, generator="EX_USER_ID_GENERATOR")
private long id;
private String location;
private String name;
//bi-directional many-to-one association to ExProvider
#ManyToOne(fetch=FetchType.LAZY)
#JoinColumn(name="EX_PROVIDER_ID")
private ExProvider exProvider;
public ExUser() {
}
public long getId() {
return this.id;
}
public void setId(long id) {
this.id = id;
}
public String getLocation() {
return this.location;
}
public void setLocation(String location) {
this.location = location;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public ExProvider getExProvider() {
return this.exProvider;
}
public void setExProvider(ExProvider exProvider) {
this.exProvider = exProvider;
}
}
My intention with the below code was to retrieve Provider 0 (Provider_A) containing User 1 (Berlin) in its user list.
#SuppressWarnings("unchecked")
private void demo() {
EntityManager em = null;
try {
em = emf.createEntityManager();
EntityTransaction tx = em.getTransaction();
try {
tx.begin();
Session session = (Session) em.getDelegate();
Criteria crit = session.createCriteria(ExProvider.class, "provider")
.createCriteria("exUsers", "user")
.add(Restrictions.eq("user.location","Berlin"))
;
List<ExProvider> providerList=(List<ExProvider>)crit.list();
logExProviderList(providerList);
tx.commit();
} finally {
if (tx!=null && tx.isActive()) tx.rollback();
}
} finally {
if (em!=null) em.close();
}
}
private void logExProviderList(List<ExProvider> providerList) {
for (ExProvider provider: providerList) {
logger.info("Criteria: provider=["+provider.getId()+"]");
for (ExUser user : provider.getExUsers()) {
logger.info("Criteria: user=["+user.getId()+"] name=["+user.getName()+"] location=["+user.getLocation()+"]");
}
}
}
The 1st SQL is what I expected. It is executed when crit.list() is called. On SQL level it returns the expected single row for Provider 0, User 1.
SELECT this_.id AS id43_1_,
this_.name AS name43_1_,
user1_.id AS id44_0_,
user1_.EX_PROVIDER_ID AS EX4_44_0_,
user1_.location AS location44_0_,
user1_.name AS name44_0_
FROM EX_PROVIDER this_
INNER JOIN EX_USER user1_
ON this_.id=user1_.EX_PROVIDER_ID
WHERE user1_.location=?;
However, this is not mapped to entity level as I expected. There, the restriction seems to affect the selection of the Provider only. When the user list is accessed, all users of the provider are read from DB neglecting the 'Berlin' restriction.
This was the same whether I used HQL, Hibernate Criteria (also with #Filter), JPA CriteriaBuilder.
SELECT exusers0_.EX_PROVIDER_ID AS EX4_43_1_,
exusers0_.id AS id1_,
exusers0_.id AS id44_0_,
exusers0_.EX_PROVIDER_ID AS EX4_44_0_,
exusers0_.location AS location44_0_,
exusers0_.name AS name44_0_
FROM EX_USER exusers0_
WHERE exusers0_.EX_PROVIDER_ID=?;
The log.
Criteria: provider=[0]
Criteria: user=[1] name=[User_2] location=[Berlin]
Criteria: user=[0] name=[User_1] location=[Munich]
I may achieve the expected result set using setResultTransformer(), but in this case the properly selected result is returned as some rows of entities.
#SuppressWarnings("unchecked")
private void demo() {
EntityManager em = null;
try {
em = emf.createEntityManager();
EntityTransaction tx = em.getTransaction();
try {
tx.begin();
Session session = (Session) em.getDelegate();
Criteria crit = session.createCriteria(ExProvider.class, "provider")
.createCriteria("exUsers", "user")
.add(Restrictions.eq("user.location","Berlin"))
.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
;
List<ExProvider> providerList=(List<ExProvider>)crit.list();
logExProviderMapList(providerList);
tx.commit();
} finally {
if (tx!=null && tx.isActive()) tx.rollback();
}
} finally {
if (em!=null) em.close();
}
}
private void logExProviderMapList(List providerList) {
Iterator iter = providerList.iterator();
while ( iter.hasNext() ) {
Map map = (Map) iter.next();
ExProvider provider = (ExProvider) map.get("provider");
if(provider!=null) {
logger.info("Criteria: provider=["+provider.getId()+"]");
}
ExUser user = (ExUser) map.get("user");
if(user!=null) {
logger.info("Criteria: user=["+user.getId()+"] name=["+user.getName()+"] location=["+user.getLocation()+"]");
}
}
}
The SQL is the same as the 1st SQL above.
SELECT this_.id AS id43_1_,
this_.name AS name43_1_,
user1_.id AS id44_0_,
user1_.EX_PROVIDER_ID AS EX4_44_0_,
user1_.location AS location44_0_,
user1_.name AS name44_0_
FROM EX_PROVIDER this_
INNER JOIN EX_USER user1_
ON this_.id=user1_.EX_PROVIDER_ID
WHERE user1_.location=?;
The log.
Criteria: provider=[0]
Criteria: user=[1] name=[User_2] location=[Berlin]
My question was and is, whether it is possible to get this result as proper entity tree with Provider_A containing exactly the User from Berlin in its list.
Thanks again,
Wolfgang B
I am using tje JPA criteria API to create an "IN" query. I want to select Courses that are in certain Categories. The Categories are supposed to end up in the IN part of the query.
This is the Course entity. It has a reference to a Category entity, because each Course is in one Category.
#Entity
public class Course implements DomainObject {
private Long id;
private Integer version;
private String name;
private Category category;
#Override
#Id
#GeneratedValue
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
#ManyToOne
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getVersion() {
return version;
}
public void setVersion(Integer version) {
this.version = version;
}
}
In my service I want to select Courses that are belong to certain (a list) of Categories.
public List<Course> findCourses(CourseFilter filter) {
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery<Course> criteriaQuery = criteriaBuilder.createQuery(Course.class);
Root<Course> root = criteriaQuery.from(Course.class);
List<Predicate> predicateList = new ArrayList<Predicate>();
if (!filter.getCategories().isEmpty()) {
Predicate predicate = root.get(Course_.category).in(filter.getCategories());
predicateList.add(predicate);
}
Predicate[] predicates = new Predicate[predicateList.size()];
predicateList.toArray(predicates);
criteriaQuery.where(predicates);
TypedQuery<Course> typedQuery = entityManager.createQuery(criteriaQuery);
return typedQuery.getResultList();
}
When the query executes on the last line of the method it throws an error:
HTTP Status 500 - Request processing failed; nested exception is
org.springframework.dao.InvalidDataAccessApiUsageException:
org.hibernate.TransientObjectException: object references an unsaved transient instance
save the transient instance before flushing:nl.codebasesoftware.produx.domain.Category;
nested exception is java.lang.IllegalStateException:
org.hibernate.TransientObjectException: object references an unsaved transient instance
save the transient instance before flushing: nl.codebasesoftware.produx.domain.Category
I am not even sure I am using the right way to create an IN query. I think the criteria API is terribly complicated. But before I worry about the IN query I would like to know why Hibernate is throwing this TransientObjectException. The filter.getCategories() call results in actual categories, filled with a primary key id, etc.
Added:
Here is how I get the Category instance that I use to later fetch Courses with. This is also a DAO method that is called via a #Service from a #Controller method.
public Category findByName(String name) {
CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<Category> query = builder.createQuery(Category.class);
Root<Category> root = query.from(Category.class);
Predicate predicate = builder.equal(root.get(Category_.urlTitle), name);
query.where(predicate);
TypedQuery<Category> typedQuery = entityManager.createQuery(query);
return getSingleResult(typedQuery);
}
So, Hibernate is telling me I am using Category objects that somehow reference an unsaved entity, but I don't see how. The Category that is returned from this method is just a Category that if fetched by Hibernate. I am not doing anything with it before I send it to the method that fetches Courses.
Here is my the controller method:
#RequestMapping(method = RequestMethod.GET, value = "/{categoryUrlName}")
public String setup(#PathVariable("categoryUrlName") String categoryUrlName, Model model){
// Fetch the category
Category category = categoryService.findByName(categoryUrlName);
// if no category found, throw a 404
if(category == null){
throw new ResourceNotFoundException();
}
// Fetch courses in this category
List<Course> courses = courseService.findCourses(category);
model.addAttribute("courses", courses);
model.addAttribute("category", category);
model.addAttribute("mainContent", "content/category");
return "main";
}
Before executing a query, Hibernate flushes the changes you made to persistent entities in the session. This ensures that the query will search on the latest state of all the entities. Unfortunately, one of the dirty entities that Hibernate tries to flush references a transient entity, and thus can't be flushed, which causes the exception. The exception doesn't come from the query itself, but from the flush before the execution of the query.
You probably did something like the following before executing the query:
Cat cat = em.find(Cat.class, catId); // cat is a persistent persistent entity
cat.setMate(new Mouse()); // the mouse has not been persisted, and cat references it.
I have a webservice that will be persisting and deleting data to a Database. I want to track in the database which usernames touched which rows of the database. In each table there are columns for usernames to be stored (update columns if you will). There are also triggers on the tables that will take a userID for the transaction and update that table with the username and password that attempted to insert. Is there a way in open JPA where I can get the username (which will be passed from the client) and update some kind of JPA object so that when JPA persists data, that user name will be thrown into the table?
One of the cleanest ways is to implement a common "mapped" superclass for your entities and use a method with #PrePersist annotation to populate the fields.
#MappedSuperclass
public class AuditedEntity {
#Id protected Integer id;
protected String lastUpdatedBy;
// Setters and getters here
#PreUpdate
#PrePersist
public void onChange() {
String user = .... // Do whatever is needed to get the current user
setLastUpdatedBy(user);
}
}
#Entity
public class Employee extends AuditedEntity {
// ....
}
Another option is to use a separate listener:
public interface AuditedEntity {
public static void setLastUpdatedBy(String username);
}
#Entity
#EntityListeners({ MyLogger.class, ... })
public class Employee implements AuditedEntity {
// ...
}
public class MyLogger {
#PreUpdate
#PrePersist
public void onChange(Object o) {
if(o instanceof AuditedEntity) {
String user = .... // Do whatever is needed to get the current user
((AuditedEntity) o).setLastUpdatedBy(user);
}
}
#PostPersist
#PostUpdate
public void logChange(Object o) {
// Log the successful operation
}
}
I've got stuck on the M:N relation between entity and strings. An user can have more than one role and each role can be assigned to more than one user. Role is just a string. Roles are contained in table with two columns: roleId and roleName.
I've created two entities, but I'm absolutely unable to made it work. First entity is the user:
#Entity
#Table(name="appUsers")
public class UserEntity {
#Id
private String login;
private String password;
#OneToMany(fetch=FetchType.EAGER,mappedBy="user") //we always need to load user's roles
private Collection<UsersToRoles> roles;
#Transient
private Collection<String> roleNames;
public String getLogin() {
return login;
}
public String getPassword() {
return password;
}
#PostLoad
void prepareRoleNames() {
roleNames = new HashSet<String>(roles.size());
for (UsersToRoles mapping : roles)
roleNames.add(mapping.getNameOfRole());
}
public Collection<String> getRoles() {
return roleNames;
}
}
The second is entity associated with connecting table:
#Entity
#IdClass(UsersToRolesId.class)
public class UsersToRoles {
#Id
#SuppressWarnings("unused")
#Column(name="login")
private String login;
#Id
#SuppressWarnings("unused")
#Column(name="roleId")
private int roleId;
#ElementCollection(fetch=FetchType.EAGER)
#CollectionTable(name="userRoles", joinColumns={#JoinColumn(name="roleId")})
private List<String> roleName;
#ManyToOne
#JoinColumn(name="login")
#SuppressWarnings("unused")
private UserEntity user;
public String getNameOfRole() {
if (roleName.isEmpty())
throw new CommonError("Role name for roleId=" + roleId, AppErrors.ACCESSOR_UNAVAILABLE);
return roleName.get(0);
}
}
class UsersToRolesId {
private String login;
private int roleId;
/**
* Implicit constructor is not public. We have to
* declare public non-parametric constructor manually.
*/
public UsersToRolesId() {
}
#Override
public int hashCode() {
return 17*login.hashCode() + 37*roleId;
}
#Override
public boolean equals(Object obj) {
if (!(obj instanceof UsersToRolesId))
return false;
UsersToRolesId ref = (UsersToRolesId)obj;
return (this.login.equals(ref.login) && this.roleId == ref.roleId);
}
}
And the problem is, that the roleName collection is always null. I'm unable to get it work. When I make a mistake in table name in #CollectionTable annotation, it still works. The JPA does not fetch the subcollection at all. It makes select from table of user joined with table UsersToRoles, but the join to table userRoles is missing.
Can I ever do that? Can I get eagerly collection of entities containing another eagerly fetched collections?
Your mapping is completely wrong. UsersToRoles has a roleId column. Thus it refers to a single role. How could it have a collection of role names? The login column is mapped twice in the entity. Moreover, this looks like a simple join table to me, without any other attribute than the roleId and the login, which are foreign keys to the IDs of User and Role, respectively.
You should have two entities : User and Role, with a ManyToMany association using the UsersToRoles table as join table. That's it. The UsersToRoles table should not be mapped as an entity: it's a pure join table.
JPA providers usually have a configuration property denoting default eager fetch depth, i.e. hibernate.max_fetch_depth for Hibernate. Check if you can see more when you increase it.
Also, think about your design. Fetching subcollections of a collection eagerly might be a good idea only in limited scenarios (performance-wise). When you annotate your entity like that, you're going to use eager fetching in all use cases. Perhaps you'd be better off with "lazy" and fetching it eagerly only explicitly, with a query with a JOIN FETCH clause?
I have 2 models: ContactGroup and Contact. ContactGroup contains many Contacts.
In the page, I have to display a list of groups and number of contacts in the correspondence group like this:
Group Foo (12 contacts)
Group Bar (20 contacts)
So I at server side I used a DTO ContactGroupInfo:
public class ContactGroupInfo {
private Integer contactCount;
private Long id;
private String name;
public Integer getContactCount() { return this.contactCount; }
public Long getId() { return this.id; }
public String getName() { return this.name; }
public void setContactCount(Integer count) { this.contactCount = count; }
public void setId(Long id) { this.id = id; }
public void setName(String name) { this.name = name; }
}
In this ContactGroupInfo, I added contactCount field which is not a field in ContactGroup entity.
And at client side, I used a ValueProxy:
#ProxyFor(value = ContactGroupInfo.class, locator = ContactGroupService.class)
public interface LightContactGroupProxy extends ValueProxy {
Integer getContactCount();
Long getId();
String getName();
void setContactCount(Integer count);
void setId(Long id);
void setName(String name);
}
So when server side returns to client side a list of LightContactGroupProxy, I stored that list a in ArrayList to render to a CellTable.
And here is the problem comes to me: when I need to edit the name of the group at client side, I can't edit the LightContactGroupProxy object directly.
So I have to send the new name to server to return a new LightContactGroupProxy with the new name. This is not effective because I have to count contacts again (althought I know the number of contacts does not change).
Or I have to send both the number of contacts and new name to server to create a new LightContactGroupProxy with the new name. This is not I want, because if LightContactGroupProxy has many other fields I have to send many fields.
I don't know why GWT teams designs the immutable proxy. So please, someone has experience on requestfactory please show me the correct way to handle ValueProxy returned from server so that we can use them to render and edit?
Thank you
Maybe you should try something like this :
ContactGroupContext ctx = requestFactory.newContactGroupContext();
LightContactGroupProxy editableProxy = ctx.edit(lightContactGroupProxy);
editableProxy.setName(newName);
ctx.saveInfoAndReturn(editableProxy).fire(receiver); // or just ctx.fire();
Anyway, I wouldn't use ValueProxy in this case, I would directly get the ContactGroup entities with a transiant property contactCount. The property could be a primitive, or a ValueProxy if you don't want it to be calculated every time a ContactGroup is requested.