To find an object from entity with primary key we use em.find(Person.class, <Id>).
I'm using JPA EclipseLink and I have a Person entity which has a composite primary key(#classId),
the Person entity:
#Entity
#IdClass(PersonId.class)
public class Person {
#Id
private int id;
#Id
private String name;
public String getName() {
return name;
}
// getters & setters
}
and the PersonID:
public class PersonId implements Serializable {
private static final long idVersionUID = 343L;
private int id;
private String name;
// must have a default construcot
public PersonId() {
}
public PersonId(int id, String name) {
this.id = id;
this.name = name;
}
//getters & setters
//hachCode & equals
}
How to use em.find to get a Person object?
I found the solution :
PersonId personeId = new PersonId(33, "Jhon");
Person persistedPerson = em.find(Person.class, personeId);
System.out.println(persistedPerson.getID() + " - " + persistedPerson.getName());
Related
Need make a relationship between same table. Example: the object "category" have subcategories and the subcategorie have other subcategorie.
In MySQL make a column and point to primary key of same table, but, howto make in JPA?
My code is:
#Entity
#Table(name = "objects")
public class JObject {
private long id;
private String name;
private JObject parentJObject;
private Set<JObject> jObjects;
public JObject(){
}
public JObject(long id){
this.id = id;
}
public JObject(String name){
this.name = name;
}
public JObject(String name, JObject parentJObject){
this.name = name;
this.parentJObject = parentJObject;
}
#Null
#JoinColumn(name="parent_object_id", referencedColumnName="id")
#ManyToOne(cascade=CascadeType.ALL)
public JObject getParentJObject() {
return parentJObject;
}
public void setParentJObject(JObject parentJObject) {
this.parentJObject = parentJObject;
}
#Null
#OneToMany(mappedBy = "parentJObject", cascade = CascadeType.ALL)
public Set<JObject> getJObjects() {
return jObjects;
}
public void setJObjects(Set<JObject> jObjects) {
this.jObjects = jObjects;
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
#NotNull
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
And the making objects:
JObject jObjectcategories = new JObject("Demo 1");
Set categoriesJObjects = new HashSet<JObject>(){{
add(new JObject("Demo 1.1", jObjectcategories));
}};
jObjectcategories.setJObjects(categoriesJObjects);
jObjectDao.save(new HashSet<JObject>() {{
add(jObjectcategories);
}});
But does not works. The log says:
List of constraint violations:[ ConstraintViolationImpl{interpolatedMessage='It has to be null', propertyPath=JObjects, rootBeanClass=class a.b.c.models.JObject, messageTemplate='{javax.validation.constraints.Null.message}'} ]
You need to be consistent in where you place your JPA annotations: either all on fields, or all on getters. But not mixed as you're doing.
The OneToOne should be a ManyToOne according to your description, since several objects share the same parent.
And the cascade ALL doesn't make sense: you don't want to delete a parent when a child is deleted.
I have a class hierarchy for JPA entities with the base class being a MappedSuperclass which has one ID defined. I am trying to use a composite key in a subclass however that does not seem to work
My code looks like this
#MappedSuperclass
public class BaseEntity implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "id")
protected Long id;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
}
#Entity
#EntityListeners(EntityBaseListener.class)
#Inheritance(strategy=InheritanceType.JOINED)
#Table(name = "catalog_entity")
public class BaseCatalogEntity extends BaseEntity {
#Column(name = "created_at", nullable = false)
#Temporal(TemporalType.TIMESTAMP)
private Date createdAt;
#Column(name = "updated_at", nullable = false)
#Temporal(TemporalType.TIMESTAMP)
private Date updatedAt;
public void setCreatedAt(Date date)
{
createdAt = date;
}
public void setUpdatedAt(Date date)
{
updatedAt = date;
}
public Date getCreatedAt() {
return createdAt;
}
public Date getUpdatedAt() {
return updatedAt;
}
}
#Entity
#Table(schema = "student_catalog")
#IdClass(value = StudentCatalog.StudentCatalogPK.class)
public class StudentCatalog extends BaseCatalogEntity {
#Id
#Column(name = "name", nullable = false, length = 100)
private String name;
#Id
#Column(name = "version", nullable = false)
private Integer version;
#Column(name = "description" , length = 255)
private String description;
#Column(name = "vendor" , length = 50)
private String vendor;
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;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getVendor() {
return vendor;
}
public void setVendor(String vendor) {
this.vendor = vendor;
}
public static class StudentCatalogPK implements Serializable {
private Long id;
private String name;
private Integer version;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
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;
}
#Override
public boolean equals(Object obj) {
boolean result = false;
if(obj != null && (obj instanceof StudentCatalogPK)) {
StudentCatalogPK other = (StudentCatalogPK)obj;
result = (Objects.equals(this.id, other.id) && Objects.equals(this.name, other.name) &&
Objects.equals(this.version, other.version));
}
return result;
}
#Override
public int hashCode() {
return (27780 + (this.id != null ? this.id.hashCode() : 0) +
(this.version != null ? this.version.hashCode() : 0) +
(this.name != null ? this.name.hashCode() : 0));
}
}
}
I get the following exception:
Exception Description: Invalid composite primary key specification. The names of the primary key fields or properties in the primary key class [com.example.jpa.StudentCatalog$StudentCatalogPK] and those of the entity bean class [class com.example.jpa.StudentCatalog] must correspond and their types must be the same. Also, ensure that you have specified ID elements for the corresponding attributes in XML and/or an #Id on the corresponding fields or properties of the entity class.
I am using Eclipselink 2.5.1. Is there a way I can get this to work without changing the BaseEntity and BaseCatalogEntity classes?
It is not legal in JPA to redefine the id in subclasses. This would lead to ambiguities in the table mappings as well as in polymorphic queries.
The desire to extend the key defined in a superclass is a common issue when business keys are used for DB identity. I would advise to use only surrogate keys (like UUID) for DB identity and business keys for instance identity.
Under following conditions:
your base entity should use TABLE_PER_CLASS inheritance (and as I can see it is)
your base entity (composite key) key is of the same type as that one you want to have in your derived class (so there should be also composite key of String and Integer).
You can use #AttributeOverride annotation under class declaration, removing #Id fields from it:
#AttributeOverride(name = "id", column = #Column(name = "NAME"))
This - in result, can change column name in derived entity's table and that's the most you can acheive.
When using #MappedSuperClass, it would be advisable to make the BaseEntity Class as abstract and then extending the Base class from other Entity classes.
Cleaner approach keeping inheritance in mind and designing your application.
I have a problem to handle mapping object relationship for mysql tables.
I have 2 tables shown below:
Device
-----------
deviceId PK
deviceName
ApkInfo
--------
id PK
packageName
appName
deviceId FK
And then here are my classes:
#Entity
#Table(name="Device")
public class Device implements Serializable {
#Column
#Id
private String deviceId;
#Column
private String deviceName;
//getters and setters
}
#Entity
#Table(name="ApkInfos")
public class ApkInfo implements Serializable {
#Column
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private int id;
#Column
#Id
private String packageName;
#Column
private String appName;
#Column
#Temporal(TemporalType.TIMSTAMP)
private Date installDate;
#ManyToOne
#JoinColumn(name="deviceId" referencedColumnName="deviceId")
private Device device;
//getters and setters
}
This works for me, but I want to use compound key, deviceId and packageName, in ApkInfos table.
#Entity
#Table(name="ApkInfos")
public class ApkInfo implements Serializable {
#Colum(instable=false, updatable=false)
#Id
private String deviceId;
#Column
private String packageName;
#Column
private String appName;
#ManyToOne
#JoinColumn(name="deviceId" referencedColumnName="deviceId")
private Device device;
//getters and setters
}
But when I tried to save an entity using Spring Data JPA repository, I got an error:
org.springframework.dao.InvalidAccessApiUsageException: Class must not
be null, nested exception is java.lang.IllegalArgumentException: Class
must not be null
ApkInfo apkInfo = new ApkInfo();
apkInfo.setDeviceId("1234");
apkInfo.setPackageName("aaa");
apkInfo.setAppName("myapp");
apkInfo.setInstallDate(new Date());
apkInfo.setDevice(new Device("1234"));
repository.save(apkInfo);
And device has the deviceID '1234' already exists in the Device table.
I created a separate primary key class added #IdClass in the ApkInfo class. It works fine now, thanks. I am going to have a look at EmbeddedId more later.
I added #IdClass at the entity class and #Id for the packageName property. Also I made insert, update false for the One-to-many column.
#Entity
#Table(name="ApkInfos")
#IdClass(ApkInfo.class)
public class ApkInfo implements Serializable {
#Column #Id private String deviceId;
#Column #Id private String packageName;
#ManyToOne
#JoinColumn(name="deviceId" referencedColumnName="deviceId", insetable=false, updatable=false)
private Device device;
//getters and setters missing
}
Primary key class has only setters and overrides equals and hasCode methods.
public class ApkInfo implements Serializable {
private String deviceId;
private String packageName;
public ApkInfo(){}
public ApkInfo (String deviceId, String packageName){
this.deviceId = deviceId;
this.packageName = packageName;
}
public String getDeviceId(){
return this.deviceId;
}
public String getPackageName(){
return this.packageName;
}
#Override
public boolean equals(Object obj){
return (obj!=null &&
obj instanceof ApkInfoPk &&
deviceId.equals(((ApkInfoPk)obj).getDeviceId()) &&
packageNames.equals(((ApkInfoPk)obj).getPackageName()) );
}
#Override
public int hashCode(){
super.hashCode();
}
}
I want to copy the entity's UUID, generated at run time to another field.
The entity id is generated via the code described bellow:
package eclipselink.example;
public class UUIDSequence extends Sequence implements SessionCustomizer {
public UUIDSequence() {
super();
}
public UUIDSequence(String name) {
super(name);
}
#Override
public Object getGeneratedValue(Accessor accessor,
AbstractSession writeSession, String seqName) {
return UUID.randomUUID().toString().toUpperCase();
}
...
public void customize(Session session) throws Exception {
UUIDSequence sequence = new UUIDSequence("system-uuid");
session.getLogin().addSequence(sequence);
}
}
Persitence.xml:
property name="eclipselink.session.customizer" value="eclipselink.example.UUIDSequence"
The entity:
public abstract class MyEntity{
private String id;
private String idCopy;
#Id
#Basic(optional = false)
#GeneratedValue(generator="system-uuid")
#XmlElement(name = "ID")
public String getId() {
return id;
}
}
How can I instruct JPA (Eclipse-link) to copy the UUID generated at runtime to idCopy field as well?
I'm not 100% sure this will work (I don't know if EclipseLink calls the setter or assigns the field directly), but give this a try:
public abstract class MyEntity{
private String id;
private String idCopy;
#Id
#Basic(optional = false)
#GeneratedValue(generator="system-uuid")
#XmlElement(name = "ID")
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
this.idCopy = id;
// or
// this.setIdCopy(id);
}
}
I'm struggling to successfully implement a OneToOne mapping on my play framework application.
examples I have are:
#Entity
public class Profile extends GenericModel {
#Id
#GeneratedValue(generator = "foreignGenerator")
#GenericGenerator(name = "foreignGenerator", strategy = "foreign",
parameters = #Parameter(name = "property", value = "user"))
public static int id;
#OneToOne(mappedBy="profile", cascade = {CascadeType.ALL})
public static User user;
}
and :
#Entity
public class User extends Model {
#Required
public String firstName;
#Required
public String surname;
}
in this setup it throws:
org.hibernate.AnnotationException: No identifier specified for entity: models.Profile
EDIT: As per Christian Boariu's answer, I have modified Profile to what you have suggested and User to:
#Entity
public class User extends GenericModel {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
public Long user_id;
#Required
public String firstName;
#Required
public String surname;
#OneToOne(cascade = {CascadeType.ALL})
#PrimaryKeyJoinColumn(name = "user_id", referencedColumnName = "profile_id")
public Profile profile;
public Profile getProfile() {
return profile;
}
public void setProfile(Profile profile) {
this.profile = profile;
}
}
Also added getter/setter to Profile:
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
But I am now getting hibernate.id.IdentifierGenerationException: null id generated for:class models.Profile.. not sure how to correct?
The problem is about your Id definition.
It should not be static.
Also, user should not be static as well.
UPDATE:
So your class should be like this:
#Entity
public class Profile extends GenericModel {
#Id
#GeneratedValue(generator = "foreignGenerator")
#GenericGenerator(name = "foreignGenerator", strategy = "foreign",
parameters = #Parameter(name = "property", value = "user"))
public int id;
#OneToOne(mappedBy="profile", cascade = {CascadeType.ALL})
public User user;
}
Fixed. suggesstions, as above fixed the #OneToOne issue and the hibernate.id.IdentifierGenerationException: null id generated for:class models.Profile was due to trying to persist an entity with a null id - due to using #primaryKeyJoin, so changed to #JoinColumn