Develop Reference

JPA AttributeConverter search predicate in specification

I am trying to have a class that has a certain list of objects (specified by another class) persisted in the database as a string (use JPA Converter - all good).
And then I want to use Specification to search inside that string.
What is the best way to create the predicates? I don't seem to understand the connection bettween the AttributeConverter and the Expression in the Specification.
The parent class:
#Entity #Table
public class A {
#Column #Id #GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
#Column
private String name;
#Enumerated(EnumType.STRING)
private SomeType type;
#Column(length=1000) #Convert(converter = BConverter.class)
private List<B> bList;
private Integer no;
}
The listed object class:
public class B{
private String type;
private Integer quantity;
}
The converter:
#Converter
public class BConverter implements AttributeConverter<List<B>, String> {
private static final String SEPARATOR = ":";
private static final String LIST_SEPARATOR = ";";
#Override public String convertToDatabaseColumn(List<B> bList) {
return bList.stream().map(e->convertToString(e)).collect(Collectors.joining(LIST_SEPARATOR));
}
#Override public List<B> convertToEntityAttribute(String str) {
if(str==null || str.isEmpty() ) return null;
return Arrays.stream(str.split(LIST_SEPARATOR)).map(e->convertFromString(e)).collect(Collectors.toList());
}
private String convertToString(B b){
if(entity==null) return null;
return b.getType().toString() +SEPARATOR+ b.getQuantity().toString();
}
private B convertFromString(String subStr){
if(subStr==null || subStr.isEmpty() ) return null;
String[] pair = subStr.split(SEPARATOR);
return new B(pair[0],Integer.valueOf(pair[1]));
}
}
In the database should look something like:
Table A:
id: 1;
name: "Some Name";
type: "THISTYPE";
blist: "TYPE1:11;TYPE2:22";
no: 0;
id: 2;
name: "Other Name";
type: "THISTYPE";
blist: "TYPE1:45;TYPE2:56";
no: 12;
I would then like to create Specifications to search over this table for the attributes inside the bList.
For example, search by an entity that contains a B object where type=TYPE1 and a quantity>=30.
public static Specification<A> customSpecification(String type, Integer value) {
return (root, query, builder) -> ///?????????
}
Is there a way to use such specifications where the DB attribute is a String but JAVA only sees the objects?

Getting entity from table without having primary key in Hibernate

I'm currently working on a project where I'm trying to get a list of enities from table which does not have a primary key (dk_systemtherapie_merkmale). This table is 1:n related to another table (dk_systemtherapie). See the screenshot for the table structure.
When getting an entry for dk_systemtherapie, the program fetches the Collection "dkSystemtherapieMerkmalesById". However, the first table entry is fetched as often as the number of actual entries in the table is. It never fetches the other entries from dk_systemtherapie_merkmale. I assume it has something to do with the fact that hibernate can't differ between the entries, but I don't know how to fix it.
Table schema
I've created two corresponding entity classes, dk_systemtherapie:
#Entity
#Table(name = "dk_systemtherapie", schema = "***", catalog = "")
public class DkSystemtherapieEntity {
private int id;
private Collection<DkSystemtherapieMerkmaleEntity> dkSystemtherapieMerkmalesById;
#Id
#Column(name = "id")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
#OneToMany(mappedBy = "dkSystemtherapieByEintragId")
public Collection<DkSystemtherapieMerkmaleEntity> getDkSystemtherapieMerkmalesById() {
return dkSystemtherapieMerkmalesById;
}
public void setDkSystemtherapieMerkmalesById(Collection<DkSystemtherapieMerkmaleEntity> dkSystemtherapieMerkmalesById) {
this.dkSystemtherapieMerkmalesById = dkSystemtherapieMerkmalesById;
}
}
Here the second one, which is accessing the table without a primary key, dk_systhemtherapie_merkmale:
#Entity #IdClass(DkSystemtherapieMerkmaleEntity.class)
#Table(name = "dk_systemtherapie_merkmale", schema = "***", catalog = "")
public class DkSystemtherapieMerkmaleEntity implements Serializable {
#Id private Integer eintragId;
#Id private String feldname;
#Id private String feldwert;
private DkSystemtherapieEntity dkSystemtherapieByEintragId;
#Basic
#Column(name = "eintrag_id")
public Integer getEintragId() {
return eintragId;
}
public void setEintragId(Integer eintragId) {
this.eintragId = eintragId;
}
#Basic
#Column(name = "feldname")
public String getFeldname() {
return feldname;
}
public void setFeldname(String feldname) {
this.feldname = feldname;
}
#Basic
#Column(name = "feldwert")
public String getFeldwert() {
return feldwert;
}
public void setFeldwert(String feldwert) {
this.feldwert = feldwert;
}
#Id
#ManyToOne
#JoinColumn(name = "eintrag_id", referencedColumnName = "id")
public DkSystemtherapieEntity getDkSystemtherapieByEintragId() {
return dkSystemtherapieByEintragId;
}
public void setDkSystemtherapieByEintragId(DkSystemtherapieEntity dkSystemtherapieByEintragId) {
this.dkSystemtherapieByEintragId = dkSystemtherapieByEintragId;
}
}

I assume the problem is releated to the fact that Hibernate is using the following annotation as the one and only id for fetching data from database.
#Id
#ManyToOne
#JoinColumn(name = "eintrag_id", referencedColumnName = "id")
public DkSystemtherapieEntity getDkSystemtherapieByEintragId() {
return dkSystemtherapieByEintragId;
}
This leads to the problem that when getting more than one entry with the same id (as the id is not unique), you will get the number of entries you would like to but hibernate is always fetching the first entry for this id. So in fact you are getting dublicate entries.
So how to fix this?
According to this question: Hibernate and no PK, there are two workarounds which are actually only working when you don't have NULL entries in your table (otherwise the returning object will be NULL as well) and no 1:n relationship. For my understanding, hibernate is not supporting entities on tables without primary key (documentation). To make sure getting the correct results, I would suggest using NativeQuery.
Remove the Annotations and private DkSystemtherapieEntity dkSystemtherapieByEintragId; (incl. beans) from DkSystemtherapieMerkmaleEntity.java und add a constructor.
public class DkSystemtherapieMerkmaleEntity {
private Integer eintragId;
private String feldname;
private String feldwert;
public DkSystemtherapieMerkmaleEntity(Integer eintragId, String feldname, String feldwert) {
this.eintragId = eintragId;
this.feldname = feldname;
this.feldwert = feldwert;
}
public Integer getEintragId() {
return eintragId;
}
public void setEintragId(Integer eintragId) {
this.eintragId = eintragId;
}
public String getFeldname() {
return feldname;
}
public void setFeldname(String feldname) {
this.feldname = feldname;
}
public String getFeldwert() {
return feldwert;
}
public void setFeldwert(String feldwert) {
this.feldwert = feldwert;
}
}
Remove private Collection<DkSystemtherapieMerkmaleEntity> dkSystemtherapieMerkmalesById; (incl. beans) from DkSystemtherapieEntity.java.
Always when you need to get entries for a particular eintrag_id, use the following method instead of the Collection in DkSystemtherapieEntity.java.
public List<DkSystemtherapieMerkmaleEntity> getDkSystemtherapieMerkmaleEntities(int id) {
Transaction tx = session.beginTransaction();
String sql = "SELECT * FROM dk_systemtherapie_merkmale WHERE eintrag_id =:id";
List<Object[]> resultList;
resultList = session.createNativeQuery(sql)
.addScalar("eintrag_id", IntegerType.INSTANCE)
.addScalar("feldname", StringType.INSTANCE)
.addScalar("feldwert", StringType.INSTANCE)
.setParameter("id", id).getResultList();
tx.commit();
List<DkSystemtherapieMerkmaleEntity> merkmale = new ArrayList<>();
for (Object[] o : resultList) {
merkmale.add(new DkSystemtherapieMerkmaleEntity((Integer) o[0], (String) o[1], (String) o[2]));
}
return merkmale;
}
Call getDkSystemtherapieMerkmaleEntities(dkSystemtherapieEntityObject.getid()) instead of getDkSystemtherapieMerkmalesById().

spring data native query interesting bug with Lob column

I have an entity:
#Entity public class KnowledgeBase {
private Long id;
private String link;
private String content;
#Id
#SequenceGenerator(name = "knowledgebase_id_generator", sequenceName = "knowledgebase_id_sequence", allocationSize = 1)
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "knowledgebase_id_generator")
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getLink() {
return link;
}
public void setLink(String link) {
this.link = link;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}
And I have a spring data repository
#Repository public interface KnowledgeBaseRepository
extends AbstractRepository<KnowledgeBase, Long> {
#Query(value = "SELECT c.id as id,c.link as link, c.content as content"
+ " from knowledgebase c where content=?1", nativeQuery = true)
List<KnowledgeBase> findRelevantRecords(String searchString);
}
Please note that
where content=?1
is just a sample, where clause was different for testing.
The issue is if I run this repository method, everything just fine, but content column contains large text amount, I want it to be lazy loaded. If I do that I get error that value is wrong for Long: ''. So my entity is:
#Lob #Basic(fetch = LAZY) String content;
If I remove this, everything just fine.
How to prevent content column from being loaded every time and have spring data repository search properly?

try this:
Create a constructor in your entity which accepts only the required fields
public class KnowledgeBase{
//default constructor
public KnowledgeBase(){}
public KnowledgeBase(Long id,String link){
this.id=id;
this.link=link;
}
}
and use this constructor signature in your query in your repository
#Query(value = "SELECT new #{#entityName} (c.id as id,c.link as link) from #{#entityName} c "
+ " from knowledgebase c where content=?1", nativeQuery = true)
List<KnowledgeBase> findRelevantRecordsWithoutContent(String searchString);

IN and = operator in JPA query language

I have a problem regarding jpa query.
There are two tables i.e. Post table and Tag table
There is many to many relationship between Post and Tag
Now I want to write a query such that when multiple tags are chosen then all the posts associated with those tags should be selected.
For example,
post1 has tags friends and motivation
post2 has tags motivation and pune
post3 has tag boxing
if tags friends and pune are chosen then post1 and post 2 should be retrieved
if tag boxing is chosen then only post 3 should be retrieved
if tags boxing and motivation are chosen then all three posts should be retrieved.
I tried following things
SELECT DISTINCT p FROM Post p JOIN p.tags tags WHERE p.tags IN :tags
but it gives validator error that
The state field path 'p.tags' cannot be resolved to a collection type.
If I try like this
SELECT DISTINCT p FROM Post p JOIN p.tags tags WHERE p.tags = :tags
then it complies fine but after passing a list of tags it gives error
java.lang.IllegalArgumentException: You have attempted to set a value of type class java.util.ArrayList for parameter tags with expected type of class com.justme.model.entities.Tag from query string SELECT DISTINCT p FROM Post p JOIN p.tags tags WHERE p.tags = :tags.
Thank you for reading this much :) can you please guide me on this?
how can I achieve the results mentioned above?
my persistence provider is eclipseLink
This is Post entity
#Entity
#NamedQueries({
#NamedQuery(name = "Post.selectAllPosts", query = "SELECT p FROM Post p ORDER BY p.dateCreated DESC"),
#NamedQuery(name = "Post.selectPostForUser", query = "SELECT p FROM Post p WHERE p.user = :user ORDER BY p.dateCreated DESC"),
#NamedQuery(name = "Post.selectPostsByTags", query = "SELECT DISTINCT p FROM Post p JOIN p.tags tags WHERE p.tags IN :tags") })
public class Post implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int idpost;
#Lob
private String content;
private String title;
// bi-directional many-to-one association to User
#ManyToOne(cascade = CascadeType.PERSIST)
#JoinColumn(name = "iduser")
private User user;
// bi-directional many-to-many association to Tag
#ManyToMany(cascade = CascadeType.PERSIST)
#JoinTable(name = "post_tag", joinColumns = #JoinColumn(name = "idpost"), inverseJoinColumns = #JoinColumn(name = "idtag"))
private List<Tag> tags = new ArrayList<Tag>();
#Temporal(TemporalType.DATE)
private Date date = null;
#Temporal(TemporalType.TIMESTAMP)
private Date dateCreated = new Date();
public Post() {
}
public int getIdpost() {
return this.idpost;
}
public void setIdpost(int idpost) {
this.idpost = idpost;
}
public String getContent() {
return this.content;
}
public void setContent(String content) {
this.content = content;
}
public String getTitle() {
return this.title;
}
public void setTitle(String title) {
this.title = title;
}
public User getUser() {
return this.user;
}
public void setUser(User user) {
this.user = user;
}
public List<Tag> getTags() {
return this.tags;
}
public void setTags(List<Tag> tags) {
this.tags = tags;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public Date getDateCreated() {
return dateCreated;
}
public void setDateCreated(Date dateCreated) {
this.dateCreated = dateCreated;
}
#Override
public String toString() {
return "Post [idpost=" + idpost + ", content=" + content + ", title="
+ title + ", date=" + date + "]";
}
}
This is Tag Entity
#Entity
#NamedQueries({
#NamedQuery(name = "Tag.selectTags", query = "SELECT tag FROM Tag tag WHERE tag.tagName LIKE :keyword"),
#NamedQuery(name = "Tag.selectMatchingTags", query = "SELECT t.tagName FROM Tag t WHERE t.tagName LIKE :keyword"),
#NamedQuery(name = "Tag.selectTagByName", query = "SELECT tag FROM Tag tag WHERE tag.tagName = :tagName"),
#NamedQuery(name = "Tag.selectTagsForAllPosts", query = "SELECT DISTINCT tag FROM Tag tag, Post post JOIN tag.posts posts WHERE post.user = :user")})
public class Tag implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private int idtag;
private String tagName;
// bi-directional many-to-many association to Post
#ManyToMany(mappedBy = "tags", cascade = CascadeType.PERSIST)
private List<Post> posts;
public Tag() {
}
public Tag(String tagName) {
this.tagName = tagName;
}
public int getIdtag() {
return this.idtag;
}
public void setIdtag(int idtag) {
this.idtag = idtag;
}
public String getTagName() {
return this.tagName;
}
public void setTagName(String tagName) {
this.tagName = tagName;
}
public List<Post> getPosts() {
return this.posts;
}
public void setPosts(List<Post> posts) {
this.posts = posts;
}
#Override
public String toString() {
return tagName;
}
}

Try:
...
#NamedQuery(name = "Post.selectPostsByTags", query =
"SELECT DISTINCT p FROM Post p JOIN p.tags tags WHERE tags IN (:tags)") })
public class Post implements Serializable {
...
Use it like this:
#PersistenceContext
public EntityManager em;
...
List<Tag> ltags = new ArrayList<Tag>();
ltags.add(tagOne);
ltags.add(tagTwo);
List<?> list = em.createNamedQuery("Post.selectPostsByTags")
.setParameter("tags", ltags)
.getResultList();
for (Object object : list) {
System.out.println("Results: "+object);
}

multiple language support data from db

My application has entities with nameEn and nameDe for english and german. But only english being used now. Since there are so many entities available, I wanted to have a generic class which can return the selected language entries,but for multiple entries my approach didn't work.
#Entity
#Table(name="employee")
public class Employee implements java.io.Serializable {
// Fields
private Integer id;
private String nameEn;
private String nameDe;
//Getter, Setter Methods
}
#Entity
#Table(name="address")
public class Address implements
java.io.Serializable {
private String descriptionEn;
private String descriptionDe;
}
public interface ILabelText {
String getNameEn();
String getNameDe();
String getDescriptionEn();
String getDescriptionDe();
}
public abstract class LabelText implements ILabelText, Serializable {
private static final long serialVersionUID = 1L;
protected String descriptionEn;
protected String descriptionDe;
private Logger log = Logger.getLogger(LabelText.class);
String language = FacesContext.getCurrentInstance().getViewRoot().getLocale().getLanguage();
public String getDescription() {
log.info("Language Selected is " + language);
if (language.equals("De")) {
return getDescriptionDe();
} else {
return getDescriptionEn();
}
}
public String getName() {
log.info("Language Selected is " + language);
if (language.equals("De")) {
return getNameDe();
} else {
return getNameEn();
}
}
}
//In Xhtml, based on selected locale, display value accordingly
<h:outputText value="#{emp.getName()}" />
<h:outputText value="#{add.getDescription()}" />

You can create an entity Lang like this
#Entity
public class Lang implements Serializable
{
#Id #GeneratedValue(strategy=GenerationType.IDENTITY)
private long id;
#NotNull
private String key;
#NotNull
private String translation;
}
and use it in your Address like this
#OneToMany(cascade = CascadeType.ALL, fetch=FetchType.EAGER)
#MapKey(name = "key")
protected Map<String, Lang> name;
Then you are able to access the correct language in JSF:
<h:outputText value="#{emp.name[userLocale].translation}" />
The expression userLocale should be resolved to your language key (en, de, ...) or can be hardcoded e.g. #{emp.name['en'].translation}.

Is more easy you create a table with translations:
e.g:
People -> All of your persons
PersonTranslations
People | id
PersonTranslations | locale; person_id;
then on your Person class you set the language for all attributes on predicate
Person.description (this will search on PersonTranslation using a person_id key, and a locale)
some like that PersonTranslation.find(1, 'en');