I have an entity TagLabel
it looks like this:
#Entity
#Table(name = "tag_label")
public class TagLabelDB implements Persistable<Long> {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private Long labelId;
#Column(name = "study_instance_UID")
private String stuInsUID;
#Column(name = "tag")
private String tag;
...
I would like to receive a list of distinct tag fields
List tags from JpaRepository
something like:
#Query("SELECT DISTINCT t.tag FROM TagLabelDB t")
List<String> findDistinctTags();
The code above works fine,
but I wouldn't like to use #Query
But Method name, Projection or Specification?...
It looks as a simple question, but I couldn't figure it out...
Distinct keyword can occur in any place of the subject between find (and the other keywords) and by. It means that you can't use distinct like
List<String> findDistinctTagLabelDB();
Related
I am trying to read data from another table based on the value of one of the fields in the current entity. But somehow I am facing an issue selecting multiple fields inside the formula.
#Entity
#Table(name = "contacts")
#Data
#Builder
#NoArgsConstructor
#AllArgsConstructor
public class ContactInfo {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private Long id;
#Column(name = "name")
private String name;
#Column(name = "url")
private String imageUrl;
//Not working
#Formula("(select code,area from areas where area_id=id)")
private Map<String, String> vals;
//working
#Formula("(select code from areas where area_id=id)")
private String someVal;
}
is there any way that I can use the formula for retrieving multiple columns of data with multiple rows?
Thanks for your help.
I'm not sure you can retrieve like Map<string, String>. Suppose you declare another field how you going to retrieve. you can receive as a List instead of Map<st..., str..>.
Instead of #Formulae, you can use #OneToMany & #ManyToOne. through a Bi-direction connection, you achieve your scenario.
This looks more like it should be using JPA's ElementCollection mapping to the Area table, with a MapKeyColumn mapping:
public class ContactInfo {
..
#ElementCollection
#MapKeyColumn(name="code")//key
#Column(name="area") //value
#CollectionTable(name="areas",
joinColumns=#JoinColumn(name="area_id"))//fk from Areas->contacts.id
private Map<String, String> vals;
..
See this for some more information and examples.
I have got three classes as mentioned below. I am trying to create a specification to filter data where there is a match in the linked table.
public class Album {
private Long id;
private List<AlbumTag> albumTags;
}
public class Tag {
private Long id;
private String category;
}
public class AlbumTag{
private Long id;
private Album album;
private Tag tag;
}
In the schema given above what I am trying to find is a list of all albums from Album table with the link in AlbumTag. The SQL that I want to achieve, doesn't have to be same, is below
select *
from Album A
where (A.Id in (select [AT].AlbumId
from AlbumTag [AT]))
What I have tried so far which is not working, of course, is below
public class AlbumWithTagSpecification implements Specification<Album> {
#Override
public Predicate toPredicate(Root<Album> root, CriteriaQuery<?> cq, CriteriaBuilder cb) {
final Subquery<Long> personQuery = cq.subquery(Long.class);
final Root<Album> album = personQuery.from(Album.class);
final Join<Album, AlbumTag> albumTags = album.join("albumTags");
personQuery.select((albumTags.get("album")).get("id"));
personQuery.where(cb.equal(album.get("id"), (albumTags.get("album")).get("id")));
return cb.in(root.get("id")).value(personQuery);
}
}
Using spring boot and spring data JPA, you can prefer entity relationship to fetch the data.
1.Annotate the domain class with the entity relationship which given below:
#Entity
#Table(name="Album")
public class Album {
#Id
#Column(name="id")
private Long id;
#OneToMany(targetEntity = AlbumTag.class, mappedBy = "album")
private List<AlbumTag> albumTags;
//getter and setter
}
#Entity
#Table(name="Tag")
public class Tag {
#Id
#Column(name="id")
private Long id;
#Column(name="category")
private String category;
//getter and setter
}
#Entity
#Table(name="AlbumTag")
public class AlbumTag{
#Id
#Column(name="id")
private Long id;
#ManyToOne(optional = false, targetEntity = Album.class)
#JoinColumn(name = "id", referencedColumnName="id", insertable = false, updatable = false)
private Album album;
#ManyToOne(optional = false, targetEntity = Tag.class)
#JoinColumn(name = "id", referencedColumnName="id", insertable = false, updatable = false)
private Tag tag;
//getter and setter
}
2.use the spring data to fetch the details using the below:
Album album = ablumRepository.findOne(1); // get the complete details about individual album.
List<AlbumTag> albumTags = ablum.getAlbumTags(); // get the all related albumTags details for particular album.
I hope this will help you to solve it.
Subqueries in JPA only really work with CriteriaBuilder.exists() so i would try:
public Predicate toPredicate(Root<Album> root, CriteriaQuery<?> cq, CriteriaBuilder cb) {
final Subquery<Long> subQuery = cq.subquery(Long.class);
final Root<AlbumTag> albumTag = subQuery.from(AlbumTag.class);
// it doesn't really matter what we select
subQuery.select(cb.literal(1));
subQuery.where(cb.equal(root.get("id"), (albumTag.get("album")).get("id")));
return cb.exists(subQuery);
}
which is equivalent to
select *
from Album A
where exists(
select 1 from AlbumTag AT
where AT.AlbumId = A.Id
)
Well, I wouldn't go for in operation in this case - it just complicates the query and the specification. The problem you described is actually matter of joining records from Table A with related records from Table B so the query in your case would be like:
SELECT a from Album a join AlbumTag at on a.id = at.albumId - as you needed it will return all albums that have album tags. Inner join explained
So in your case I would create this "factory" method that would create for you this specification.
public static Specification<Album> withTags() {
return new Specification<Album>() {
#Override
public Predicate toPredicate(Root<Album> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
return root.join("albumTags").getOn();
}
};
}
Also I would suggest you to have a look at static metamodel library from hibernate - link to introduction. It generates for you static model from your entity classes that helps you avoid creating queries/specifications using hardcoded strings.
creteria query for join tables
CriteriaQuery<Album> query = cb.createQuery(Album.class);
Root<Album> album = query.from(Teacher.class);
Join<Album, AlbumTag> tag = teacher.join("id");
query.select(tag).where(cb.equal(album.get("album")));
List<Album> results = em.createQuery(query).getResultList();
for (Album al : results) {
System.out.println("album-->+al.get(name));
}
This looks like a classic many to many example. The three classes you have map directly to the tables you would expect in the database. JPA is an Object Relational Mapping (ORM) library which means we can structure the classes in a more OO style and map to the underlying relational database.
The AlbumTag class can be omitted and the #ManyToMany relationship added to both Album and Tag.
public class Album {
private Long id;
#ManyToMany
#JoinTable(name="AlbumTag",
joinColumns=
#JoinColumn(name="album", referencedColumnName="id"),
inverseJoinColumns=
#JoinColumn(name="tag", referencedColumnName="id"))
private List<Tag> tags;
}
public class Tag {
private Long id;
private String category;
#ManyToMany(mappedBy="tags")
private List<Album> albums;
}
To find albums by Tag you would first retrieve the Tag from the repository using something like findById(1l); or findByCategory("Rock"); and then simply call getAlbums() on the Tag object.
Note: One slight difference here is that the AlbumTag table would have only two columns (album and tag). The extra id column on AlbumTag is unnecessary since the combination of album and tag would be a unique id and you would never need to find by id in this table anyway.
Since you are using spring-data-jpa you should really take advantage of the features it provides.
My first question is related to your entity classes. I do not understand why is it necesary to store a list of album tags in the album class. Since you have a join table this information is reduntant.
Secondly you should adnotate your entity clases:
#Entity
public class Album {
#Id
#Column
private Long id;
}
#Entity
public class Tag {
#Id
#Column
private Long id;
#Column
private String category;
}
#Entity
#Table
public class AlbumTag{
#Id
#Column
private Long id;
#ManyToOne
#JoinColumn
private Album album;
#ManyToOne
#JoinColumn
private Tag tag;
}
Next you should create repositories for your entity classes.
interface AlbumRepository extends JpaRepository<Album, Long>{
#Query
("select DISTINCT(a) from AlbumTag at "+
"join at.album a "
"where at.tag is not null")
List<Album> findAlbumWithTag();
}
Then simply call the repository function which will return a list of albums which have at least one tag.
I am trying to use Hibernate Criteria api to fetch only the topics based on the USER_ID but have no idea how to do it using the criteria.
My Tables are "topic_users" (below)
and "topics" table (below)
I know how to do it using SQL, this would be something like:
SELECT TOPICNAME
FROM topic_users INNER JOIN topics on topic_users.TOPICS_TOPICS_ID = topics.TOPICS_ID
WHERE topic_users.USER_ID = 1
This will return all TOPICNAME of USER_ID 1 which is exactly what I want but how I can do this with Hibernate Criteria. So far I have this in my Repository class (see below) but this will only return a highly nested JSON array. I could loop through the objects, use a DTO and build my response or try the Hibernate createSQLQuery method that will let me call a native SQL statement directly (haven't tried that yet)...but I am trying to learn the Criteria so I hope anyone can answer my query.
#Repository("userTopicsDao")
public class UserTopicsDaoImpl extends AbstractDao<Integer, UserTopics>implements UserTopicsDao {
#Override
public List<UserTopics> findMyTopics(int userId) {
Criteria crit = createEntityCriteria();
crit.add(Restrictions.eq("userId", userId));
List<UserTopics> userTopicsList = (List<UserTopics>)crit.list();
return userTopicsList;
}
and my TOPIC_USERS Entity where I have mapped the TOPICS
#Entity
#Table(name="TOPIC_USERS")
public class UserTopics {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
#Column(name="TOPICUSER_ID")
private Integer id;
#Column(name="USER_ID")
private Integer userId;
#OneToMany(fetch = FetchType.EAGER)
#JoinColumn(name = "TOPICS_ID")
private Set<Topics> topicsUser;
//getter and setters
Ok starting from the ground up.. you entity classes should look like this:
#Entity
#Table(name="TOPIC_USERS")
public class UserTopics {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
#Column(name="TOPICUSER_ID")
private Integer id;
#Column(name="USER_ID")
private Integer userId;
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "TOPICS_TOPICS_ID")
private Topics topics;
Your Topics class should look like this:
#Entity
#Table(name="TOPICS")
public class Topic {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
#Column(name="TOPICUS_ID")
private Integer id;
#Column(name="TOPICNAME")
private Integer topicName;
#OneToMany(mappedBy = "topics")
private Set<UserTopics> userTopics;
Finally the Criteria:
Version 1) You get entire entity:
Criteria c = session.createCriteria(Topics.class, "topics");
c.createAlias("topics.userTopics", "userTopics");
c.add(Restrictions.eq("userTopics.userId", userId));
return c.list(); // here you return List<Topics>
Version 2) You project only the topicname:
Criteria c = session.createCriteria(Topics.class, "topics");
c.createAlias("topics.userTopics", "userTopics");
c.add(Restrictions.eq("userTopics.userId", userId));
c.setProjection(Projections.property("topics.topicName"));
List<Object[]> results = (List<Object[]>)c.list();
// Here you have to manually get the topicname from Object[] table.
}
I am trying to use hibernate annotations for getting data from a MySQL database table which doesn't have a primary key defined.
However the fact is 2 columns of that table together are unique in the table. How can I achieve the same using hibernate annotation?
This is my code
#Entity
#Table(name = "coc_order_view")
public class CoCOrderDetailsTest {
#EmbeddedId
private MyJoinClassKey key;
#Column(name = "coupon_code")
private String couponCode;
some other columns and their getters and setters .....
#Embeddable
public class MyJoinClassKey implements Serializable {
private static final long serialVersionUID = -5L;
#Column(name = "product_id")
private int productId;
#Column(name = "order_id")
private int orderId;
gettes and setters....
And here is my criteria query
Criteria criteria = getHibernatetemplate().getSession().createCriteria(CoCOrderDetailsTest.class);
criteria.add(Restrictions.eq("status", "New"));
ArrayList<CoCOrderDetailsTest> orderDet = (ArrayList<CoCOrderDetailsTest>) getHibernatetemplate().get(criteria);
I am unable to get all the values from db. Kindly suggest some solutions.
After reading through your question again not sure this will help. You can't have a table without primary key(s). Read the first couple of paragraphs in this article
That said, if you can alter the table and add primary keys on those fields you need to add #IdClass annotation to your class signature for CoCOrderDetailsTest and then get rid of the #embeddable and #embeddedId notation in your classes.
Another alternative, if you can add a field to the table, would be to use an #GeneratedValue on that added primary key field and of course annotate it with #Id.
If you can't alter the table then you can't use JPA and you'll have to use JDBC.
See http://docs.oracle.com/javaee/5/api/javax/persistence/IdClass.html
A working example:
#Entity
#Table(name = "player_game_log")
#IdClass(PlayerGameLogId.class)
public class PlayerGameLog {
#Id
#Column(name = "PLAYER_ID")
private Integer playerId;
#Id
#Column(name = "GAME_ID")
private String gameId;
....
and the id class (note there are no annotations on the id class)....
public class PlayerGameLogId implements Serializable {
private static final long serialVersionUID = 1L;
private Integer playerId;
private String gameId;
Try:
String hql = "FROM CoCOrderDetailsTest WHERE status = :status";
Query query = session.createQuery(hql);
query.setParameter("status","New");
List results = query.list();
I usually use EntityManager rather than session so I'm not familiar with this syntax - and I have typically added a type to the list to be returned - like:
List<CoCOrderDetailsTest> results = query.list();
In my case I have a SQL query which looks like:
select * from event_instance where (object_id, object_type) in
(<LIST OF TUPLES RETRIEVED FROM SUBQUERY>);
I want to map this on Hibernate Entities and I have a problem with this query. My mapping looks like that:
#Entity
#Table(name="event_instance")
public class AuditEvent {
<OTHER_FIELDS>
#Column( name = "object_type", nullable = false)
private String objectType;
#Column( name ="object_id" , nullable = false)
private Integer objectId;
}
and second entity:
#Entity
#Table(schema = "els" ,name = "acg_objects")
public class AcgObject implements Serializable{
#Id
#Column(name = "acg_id")
private String acgId;
#Id
#Column(name="object_type")
private String objectType;
#Id
#Column(name="object_id")
private Integer objectId;
<OTHER FIELDS>
}
I already run query for getting AcgObjects and for my DAO I'm getting List only thing I want to do is query a touple using criteria like:
crit.add(Restrictions.in("objectType,objectId",<List of tuples>);
Is it possible? I was trying to use #Embedded object but don't know how exactly construct a query for it. Please help
You can do that not in standard SQL nor using criteria; you have to split in two distinct restrictions or using a Session.SQLQuery() if you want to use specific RDBMS (look at SQL WHERE.. IN clause multiple columns for an explanation)