jpa-2.0

I am using JPA 2.0 and hibernate. I have a User class and a Group class as follows: public class User implements Serializable { @Id @Column(name="USER_ID") private String userId; @ManyToMany @JoinTable(name = "USER_GROUP", joinColumns = { @JoinColumn(name = "GROUP_ID") }, inverseJoinColumns = { @JoinColumn(name = "USER_ID") } ) private Set<Group> groupList; //get set methods } public class Group { @Id @Column(name="GROUP_ID") private String groupId; @ManyToMany(mappedBy="groupList") private Set<User> memberList; //get set methods } And then, I create a user and group and then assign the user

Which of the following collection types do you use in your JPA domain model and why: java.util.Collection java.util.List java.util.Set I was wondering whether there are some ground rules for this. UPDATE I know the difference between a Set and a List . A List allows duplicates and has an order and a Set cannot contain duplicate elements and does not define order. I'm asking this question in the context of JPA. If you strictly follow the definition, then you should always end up using the Set type, since your collection is stored in relational database, where you can't have duplicates and where

I have 1 entity call Item in which I want to be able to link parent items to children. to use a join table to create a parent/child relationship. I haven't been able to get any good documentation on. So if anyone has any thoughts I'm all ears. Here is what I have... which works most of the time. public class Item implements java.io.Serializable { @Id private Long id; @ManyToOne(optional = true, fetch = FetchType.LAZY) @JoinTable(name = "ITEMTOITEM", joinColumns = { @JoinColumn(name = "ITEMID") }, inverseJoinColumns = { @JoinColumn(name = "PARENTITEMID") } ) private Item parent; @OneToMany

Is it true that @JoinColumn can be used on both side of One to One relationship in JPA ? I was under impression that it should be always used in owning side of One to One relationship as owning side will have foreign key column and this annotation define the attribute of foreign key column . Please clarify if my understanding is not correct . Edit #1 - I wanted to know , In which scenario we will be using @JoinColumn annotation on both side of one to one relationship ? The OneToOne relationship is not necessarily bi-directional. A bi-directional OneToOne relationship happens when a reference

I want to find a record by date. In entity and database table, datatype is timestamp. I used Oracle database. @Entity public class Request implements Serializable { @Id private String id; @Version private long version; @Temporal(TemporalType.TIMESTAMP) @Column(name = "CREATION_DATE") private Date creationDate; public Request() { } public Request(String id, Date creationDate) { setId(id); setCreationDate(creationDate); } public String getId() { return id; } public void setId(String id) { this.id = id; } public long getVersion() { return version; } public void setVersion(long version) { this

how do I force hibernate to generate db schema such that it converts CamelCase into Underscores (using HBM)? Eg. I have: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="cz.csas.pdb.be.model.product.passive"> <class name="foo.BarBaz"> <id name="barBazId"> <generator class="sequence"/> </id> <property name="extractContactType"/> <!-- ... --> </class> </hibernate-mapping> And I want hibernate to create table like this (oracle): CREATE TABLE

I have a bidirectional one-to-many relationship with the following entity classes: 0 or 1 client <-> 0 or more product orders When persisting the client entity I want the associated product order entities to be persisted, too (as their foreign key to the "parent" client may have been updated). Of course all required CASCADE options are set on the client side. But it does not work if a newly created client is persisted for the first time while referencing an existing product order as in this scenario: product order '1' is created and persisted. Works fine. client '2' is created and product

Is it possible to store a list of integers in a single field of the respective entity table with standard JPA 2? Something like: @Entity @Table(name="tbl_myentities") public class MyEntity { @ElementaryCollection @Column(name="vals") // in table tbl_myentities private List<Integer> vals; Thanks MrKiane It is not possible to store multiple values in a single field. Whats the reason behind storing them in a single field? A way could be to use a field of type String and add all integers there in a comma separated list and join/explode in getters and setters: private String vals; public setVals