Hi there I am new to JPA and got following error as
In attribute 'employees', the "mapped by" value 'project_id' cannot be resolved to an attribute on the target entity.
with following code
#Entity
#Table(name = "project")
public class Project {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "project_id")
protected int id;
#Column(name = "project_name")
protected String name;
#ManyToMany(mappedBy = "project_id")
protected List<Employee> employees;
#Entity
#Table(name = "employee")
public class Employee {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "employee_id")
protected int id;
#Column(name = "employee_name")
protected String name;
#ManyToMany(targetEntity = Project.class)
#JoinTable(name = "project_employee", joinColumns = #JoinColumn(name = "project_id"), inverseJoinColumns = #JoinColumn(name = "employee_id"))
protected List<Project> projects;
Here If I am trying to map the inverse entity it says that attribute not found.
Please help me to solve this
As the message says your mappedBy value is wrong. It should be the name of the FIELD/PROPERTY on the other side of the BIDIRECTIONAL relation, that links back to this class. e.g Project.employees claims to link back via field Employee.project_id, yet that doesn't exist. Instead mappedBy should be projects. This would be found in any basic JPA docs
Related
I'm trying to create a favorites table between a user and a business, but I don't want to use the entire entity, just the ids, how can this be done in JPA? Something like this:
#Data
#Entity
#Table(name = "favorite", schema = "public" , uniqueConstraints = {
#UniqueConstraint(columnNames = {"user_id", "business_id"})
})
public class Favorite {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "appuser_id")
#NotNull
private UUID appuser_id;
#Column(name = "business_id")
#NotNull
private Long businessId;
}
instead of:
#Data
#Entity
#Table(name = "favorite", schema = "public" , uniqueConstraints = {
#UniqueConstraint(columnNames = {"user_id", "business_id"})
})
public class Favorite {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "appuser_id", referencedColumnName="id")
private AppUser appUser;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "business_id", referencedColumnName="id")
private Business business;
}
Problem is, solution #1 has no foreign key ref of any kind, is there a way to do this? I would really prefer my result objects to only have ids and not the entire user / business entities every time.
I know I can make a dto with ids only and manually set it up / workaround, but I'd like an answer to this problem if one exists.
I need help with resolving our problem with naming FK in JPA. We have one embeddable entity e.g. Foo which is used as collection in another one entity Bar.
embeddable entity:
#Embeddable
public class Foo{
#Column(name = "foo1")
private String foo1;
#Column(name = "foo2")
private String foo2;
}
main entity:
#Entity
#Table(name = "Bar")
public class Bar {
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
#Id
private Long id;
#ElementCollection
#CollectionTable(name = "foos", joinColumns = #JoinColumn(name = "bar_id", foreignKey = #ForeignKey(name = "foo_bar_fk"), nullable = false))
private List<Bar> bars;
}
When I generated tables in database (postgres) foreign key is called fdk44l345k64 instead foo_bar_fk. Can you tell me how to fix it? Thanks.
The situation: I have a class with a Map like this:
#Entity
public class Bar {
#Id
#GeneratedValue
private Long id;
#ManyToMany(cascade = CascadeType.ALL)
#JoinTable(name = "fooMap",
joinColumns = #JoinColumn(name = "One_ID", referencedColumnName = "ID") ,
inverseJoinColumns = #JoinColumn(name = "Two_ID", referencedColumnName = "ID") )
#MapKeyJoinColumn(name = "Bar")
private Map<FooOne, FooTwo> fooMap;
}
with key/value-classes like this (FooTwo looks more or less the same):
#Entity
public class FooOne {
#Id
#GeneratedValue
private Long id;
#Basic
private String name;
If I populate the map and try to persist it, I get the following exception:
UnitOfWork(117839394)--java.lang.IllegalStateException: During synchronization >a new object was found through a relationship that was not marked cascade >PERSIST: jpa.test.minimalExample.FooOne#2e4389ed.
because JPA cascades only to the target of the -toMany association which is the value entity.
Does JPA in general or EclipseLink as implementation offer any form of annotation to cascade actions to the key class of this map? What are my options here ?
I know adding a reference to FooOne in the FooTwo-class works (like this):
#Entity
public class FooTwo {
#Id
#GeneratedValue
private Long id;
#OneToOne(cascade = cascadeType.ALL)
private FooOne foo1;
}
I would rather not add any additional fields to my classes if I can avoid it.
I followed by tutorial : http://www.codejava.net/frameworks/hibernate/hibernate-one-to-one-mapping-with-foreign-key-annotations-example
I have following code:
#Entity
#Table(name = DomainConstant.TABLE_USER)
public class User{
#Id
#Column(name = DomainConstant.DOMAIN_USER_ID)
#GeneratedValue
private Long userId;
private UserActivationCode userActivationCode;
///////////////////// CONSTRUCTOR....
/// STANDARD GET AND SET....
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = DomainConstant.DOMAIN_ACTIVATION_LINK_ID)
public UserActivationCode getUserActivationCode() {
return userActivationCode;
}
}
#Entity
#Table(name = DomainConstant.TABLE_USER_ACTIVATON_LINK)
public class UserActivationCode {
#Id
#Column(name = DomainConstant.DOMAIN_ACTIVATION_LINK_ID)
#GeneratedValue
private Long userActivationCodeId;
#Column(name = DomainConstant.DOMAIN_ACTIVATION_DATE)
#Temporal(javax.persistence.TemporalType.DATE)
private Date date;
#Column(name = DomainConstant.DOMAIN_ACTIVATION_CODE)
private String code;
///////////////////// CONSTRUCTOR....
/// STANDARD GET AND SET....
}
When I save the User object it does not make record in UserActivationCode, why?
Like this:
User newUser = new User();
newUser.setUserActivationCode(new UserActivationCode("this is example"));
userDao.save(newUser);
I have record only in user table.
Can you tell me why?
Your problem is that you are mixing access types. In the User entity you have specified #Id on a field (private Long userId) whereas you have defined the join mapping on a property (the getter to UserActivationCode). If you specify the join mapping on the field, it should work as is.
#Entity
#Table(name = DomainConstant.TABLE_USER)
public class User{
#Id
#Column(name = DomainConstant.DOMAIN_USER_ID)
#GeneratedValue
private Long userId;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = DomainConstant.DOMAIN_ACTIVATION_LINK_ID)
private UserActivationCode userActivationCode;
///////////////////// CONSTRUCTOR....
/// STANDARD GET AND SET....
public UserActivationCode getUserActivationCode() {
return userActivationCode;
}
}
For more information on access and access types, see Access, Java EE 7
I've tried to read through the QueryDSL docs but I am still very confused. I'm accustomed to writing a lot of SQL, but this is my first real crack at using QueryDSL w/ JPQL (JPA2).
I have the following entity:
#Entity
public class Provider implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Long id;
#Version
#Column(name = "version")
private Integer version;
private String name;
#ManyToMany(cascade=CascadeType.ALL)
#JoinTable(name = "provider_contact", joinColumns = #JoinColumn(name = "contact_id", referencedColumnName = "id"), inverseJoinColumns = #JoinColumn(name = "provider_id", referencedColumnName = "id"))
#OrderColumn
private Collection<Contact> contact;
}
where Contact is a simple entity with an id for a pk.
#Entity
public class Contact {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Long id;
/**
* User first name
*/
#NotNull
private String firstName;
/**
* User last name
*/
#NotNull
private String lastName;
}
I'm trying to write a query which returns a Contact object given a specific Contact.id and Provider.id. If the Contact object is not a part of the Provider's Contact collection, I'm looking for a null value.
I've tried the following:
public Contact getContact( long providerId, long contactId ){
Predicate p = QProvider.provider.id.eq(providerId).and(QContact.contact.id.eq(contactId));
JPQLQuery query = new JPAQuery(em);
return query.from(QProvider.provider).innerJoin(QProvider.provider.contact).where(p).singleResult(QContact.contact);
}
but I'm getting the following error:
Caused by: java.lang.IllegalArgumentException: Undeclared path 'contact'. Add this path as a source to the query to be able to reference it.
at com.mysema.query.types.ValidatingVisitor.visit(ValidatingVisitor.java:78)
at com.mysema.query.types.ValidatingVisitor.visit(ValidatingVisitor.java:30)
at com.mysema.query.types.PathImpl.accept(PathImpl.java:94)
I'm presuming it has something to do with the fact that my predicate references QContact.contact direction and not part of the QProvider.provider.contact object, but I'm really at a loss as to figure out how this should be done.
Am I even on the right track? I'm not even sure my join is correct either.
This should work
public Contact getContact(long providerId, long contactId) {
QProvider provider = QProvider.provider;
QContact contact = QContact.contact;
return new JPAQuery(em).from(provider)
.innerJoin(provider.contact, contact)
.where(provider.id.eq(providerId), contact.id.eq(contactId))
.singleResult(contact);
}