Is it possible to implement Pattern querying with JPA Criteria API?
In my case, regex patterns are stored into a quick bag property; and I'm trying to avoid using native queries (e.g. PostgreSQL POSIX support).
#Entity #Table(name = "rcp")
public class Recipient {
#Id #Column(name = "rcp_email_id")
#Email
private String email;
#CollectionTable(joinColumns = #JoinColumn(name = "rcp_email_fk"))
#ElementCollection(fetch = EAGER)
#Convert(converter = PatternConverter.class)
private Set<Pattern> rules = new HashSet<>();
...
}
So I figured I could use the Criteria API but failed to properly develop the technlogy, obviously:
#AllArgsConstructor
public class RecipientSpecification implements Specification<Recipient> {
private String sample;
#Override
public Predicate toPredicate(Root<Recipient> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
return builder.exists(root.join("rules").as(Pattern.class).matcher(sample).find());
}
}
I thought I could work on the join with a cast and execute the Java Pattern logic by casting the properties, which I realize to be dumb now because it has no sense from the JPA DSL point of view. It doesn't even compile! But is there a proper way to proceed?
Thanks in advance
Related
In SDN+OGM I used the following method to extend the base repository with additional functionality, specifically I want a way to find or create entities of different types (labels):
#NoRepositoryBean
public class MyBaseRepository<T> extends SimpleNeo4jRepository<T, String> {
private final Class<T> domainClass;
private final Session session;
public SpacBaseRepository(Class<T> domainClass, Session session) {
super(domainClass, session);
this.domainClass = domainClass;
this.session = session;
}
#Transactional
public T findOrCreateByName(String name) {
HashMap<String, String> params = new HashMap<>();
params.put("name", name);
params.put("uuid", UUID.randomUUID().toString());
// we do not use queryForObject in case of broken data with non-unique names
return this.session.query(
domainClass,
String.format("MERGE (x:%s {name:$name}) " +
"ON CREATE SET x.creationDate = timestamp(), x.uuid = $uuid " +
"RETURN x", domainClass.getSimpleName()),
params
).iterator().next();
}
}
This makes it so that I can simply add findOrCreateByName to any of my repository interfaces without the need to duplicate a query annotation.
I know that SDN 6 supports the automatic creation of a UUID very nicely through #GeneratedValue(UUIDStringGenerator.class) but I also want to add the creation date in a generic way. The method above allows to do that in OGM but in SDN the API changed and I am a bit lost.
Well, sometimes it helps to write down things. I figured out that the API did not change that much. Basically the Session is replaced with Neo4jOperations and the Class is replaced with Neo4jEntityInformation.
But even more important is that SDN 6 has #CreatedDate which makes my entire custom code redundant.
I'm changing our identity strategy and we're using an ID that is generated before the Entity is written to the database. This change is causing some of our tests to fail due to the way we're mocking some service calls.
TimeLog timeLog = buildTimeLog('123456', mockEmployeeId);
TimeLog mockTimeLog = buildTimeLog('123456', mockEmployeeId);
when(this.timeLogService.save(mockTimeLog)).thenReturn(timeLog);
When the test makes the call to the Controller, the bound entity in the Controller gets a different ID than the mock that is expected because the Entity generates the ID. Whereas before, the database generated the ID so the mocks worked.
If there is a way to tell Mockito to ignore a property in the expectation? That would solve the problem and the test would still be valid. Otherwise, other approaches are welcome.
You can't tell mockito to ignore a property in an expectation because it's using the java "equals" method... You can define an equals method in TimeLog that igonres ID but I suspect that won't give you what you want. The other approach is, instead of trying to tell mockito what not to verify, define explicitly what it is to verify using a hamcrest matcher. Define a hamcrest matcher which just matches the fields you want to verify i.e. all fields other than ID. So something like:
private class TimeLogMatcher extends TypeSafeMatcher<TimeLog> {
private final EmployeeId employeeId;
public TimeLogMatcher(EmployeeId employeeId) {
this.employeeId = employeeId;
}
#Override
public void describeTo(Description description) {
description.appendText("TimeLog with employeeId=" + employeeId);
}
#Override
public boolean matchesSafely(TimeLog item) {
return employeeId.equals(item.getEmployeeId());
}
}
And then instead of calling whatever your "buildTimeLog" method is doing call into the mockito Matchers class like:
TimeLog timeLog = Matchers.argThat(new TimeLogMatcher(mockEmployeeId));
Or alternatively you could always use an Answer object:
when(this.timeLogService.save(any(TimeLog.class)).thenAnswer(new Answer<TimeLog> {
public TimeLog answer(InvocationOnMock invocation) throws Throwable {
TimeLog receivedTimeLog = invocation.getArgumentAt(0, TimeLog.class);
assertThat(receivedTimeLog.getEmployeeId(), equalTo(mockEmployeeId));
return timeLog;
}
});
Does that all make sense?
I am trying to implement a three-way join relationship in JPA 2.0 (using annotations).
My domain is as follows:
I had a look at the #JoinTable annotation and I am not sure how to use it in order to implement the relationship.
Can anyone please provide clues or code samples?
If I understand your question well, you actually have another Entity, let's call it AdvertisementAssignment. Then, this entity should have OneToOne association with each of your 3-way counterparts.
#Entity
#Table(name = "ADV_ASSIGNMENTS")
public class AdvertisementAssignment {
private Advertisement advertisement;
private TimeSlot timeSlot;
private Day day;
// other properties definition (e.g. id, assigner etc.)
// define constructor
#OneToOne(cascade = CascadeType.ALL)
public Advertisement getAdvertisement() {
return this.advertisement;
}
public void setAdvertisement(Advertisement advertisement) {
this.advertisement = advertisement;
}
// same for 'timeSlot' and 'day' properties
}
I have a problem. I'm learning JPA. I'm using embedded OpenEJB container in unit tests, but only working is #OneToMany(fetch=EAGER). Otherwise is the collection allways null. I haven't found, how the lazy strategy works, how the container fills the data and in which circumstances triggers the container the loading action?
I have read, that the action triggers when the getter is being called. But when I have the code:
#OneToMany(fetch = LAZY, mappedBy="someField")
private Set<AnotherEntities> entities = new Set<AnotherEntities>();
...
public Set<AnotherEntities> getEntities() {
return entities;
}
I'm always getting null. I thing, the LAZY strategy cannot be tested with embedded container. The problem might be also in the bidirectional relation.
Does have anybody else similar expiriences with the JPA testing?
Attachments
The real test case with setup:
#RunWith(UnitilsJUnit4TestClassRunner.class)
#DataSet("dataSource.xml")
public class UnitilsCheck extends UnitilsJUnit4 {
private Persister prs;
public UnitilsCheck() {
Throwable err = null;
try {
Class.forName("org.hsqldb.jdbcDriver").newInstance();
Properties props = new Properties();
props.setProperty(Context.INITIAL_CONTEXT_FACTORY, "org.apache.openejb.client.LocalInitialContextFactory");
props.put("ds", "new://Resource?type=DataSource");
props.put("ds.JdbcDriver", "org.hsqldb.jdbcDriver");
props.put("ds.JdbcUrl", "jdbc:hsqldb:mem:PhoneBookDB");
props.put("ds.UserName", "sa");
props.put("ds.Password", "");
props.put("ds.JtaManaged", "true");
Context context = new InitialContext(props);
prs = (Persister) context.lookup("PersisterImplRemote");
}
catch (Throwable e) {
e.printStackTrace();
err = e;
}
TestCase.assertNull(err);
}
#Test
public void obtainNickNamesLazily() {
TestCase.assertNotNull(prs);
PersistableObject po = prs.findByPrimaryKey("Ferenc");
TestCase.assertNotNull(po);
Collection<NickNames> nicks = po.getNickNames();
TestCase.assertNotNull(nicks);
TestCase.assertEquals("[Nick name: Kutyafája, belongs to Ferenc]", nicks.toString());
}
}
The bean Presister is the bean mediating access to the entity beans. The crucial code of class follows:
#PersistenceUnit(unitName="PhonePU")
protected EntityManagerFactory emf;
public PhoneBook findByPrimaryKey(String name) {
EntityManager em = emf.createEntityManager();
PhoneBook phonebook = (PhoneBook)em.find(PhoneBook.class, name);
em.close();
return phonebook;
}
Entity PhoneBook is one line of phone book (also person). One person can have zero or more nick names. With EAGER strategy it works. With LAZY the collection is allways null. May be the problem is in the detaching of objects. (See OpenEJB - JPA Concepts, part Caches and detaching.) But in the manual is written, that the collection can be sometimes (more like manytimes) empty, but not null.
The problem is in the life cycle of an entity. (Geronimo uses OpenJPA, so le't see OpenJPA tutorial, part Entity Lifecycle Management.) The application uses container managed transactions. Each method call on the bean Persiser runs in an own transation. And the persistency context depends on the transaction. The entity is disconnected from its context at the end of the transaction, thus at the end of the method. I tried to get the entity and on second line in the same method to get the collection of nick names and it worked. So the problem was identifyed: I cannot get additionally any entity data from the data store without re-attaching the entity to some persistency context. The entity is re-attached by the EntityManager.merge() method.
The code needs more correctures. Because the entity cannot obtain the EntityManager reference and re-attach itself, the method returning nick names must be moved to the Persister class. (The comment Heureka marks the critical line re-attaching the entity.)
public Collection<NickNames> getNickNamesFor(PhoneBook pb) {
//emf is an EntityManagerFactory reference
EntityManager em = emf.createEntityManager();
PhoneBook pb = em.merge(pb); //Heureka!
Collection<NickNames> nicks = pb.getNickNames();
em.close();
return nicks;
}
The collection is then obtained in this way:
//I have a PhoneBook instance pb
//pb.getNickNames() returns null only
//I have a Persister instance pe
nicks = pe.getNickNames(pb);
That's all.
You can have a look at my second question concerning this topic I'have asked on this forum. It is the qustion OpenJPA - lazy fetching does not work.
How I would write the code
#Entity
public class MyEntity {
#OneToMany(fetch = LAZY, mappedBy="someField")
private Set<AnotherEntities> entities;
// Constructor for JPA
// Fields aren't initalized here so that each em.load
// won't create unnecessary objects
private MyEntity() {}
// Factory method for the rest
// Have field initialization with default values here
public static MyEntity create() {
MyEntity e = new MyEntity();
e.entities = new Set<AnotherEntities>();
return e;
}
public Set<AnotherEntities> getEntities() {
return entities;
}
}
Idea no 2:
I just thought that the order of operations in EAGER and LAZY fetching may differ i.e. EAGER fetching may
Declare field entities
Fetch value for entities (I'd assume null)
Set value of entities to new Set<T>()
while LAZY may
Declare field `entities
set value of entities to new Set<T>()
Fetch value for entities (I'd assume null)'
Have to find a citation for this as well.
Idea no 1: (Not the right answer)
What if you'd annotate the getter instead of the field? This should instruct JPA to use getters and setters instead of field access.
In the Java Persistence API, an entity can have field-based or
property-based access. In field-based access, the persistence provider
accesses the state of the entity directly through its instance
variables. In property-based access, the persistence provider uses
JavaBeans-style get/set accessor methods to access the entity's
persistent properties.
From The Java Persistence API - A Simpler Programming Model for Entity Persistence
How can I send JPA generated entities over an JAX WS web service without getting the
an XML infinite cycle exception because of the cycle of references in those entities?
Any idea? I found this MOXy that can do it...partially. But i already have the entities generated and to manually add XmlTransient and such annotations to each of them it's crazy.
Do you have any other idea how to do it?
Thanks!
EclipseLink JAXB (MOXy) can handle this with its bidirectional mapping with #XmlInverseReference:
import javax.persistence.*;
#Entity
public class Customer {
#Id
private long id;
#OneToOne(mappedBy="customer", cascade={CascadeType.ALL})
private Address address;
}
and
import javax.persistence.*;
import org.eclipse.persistence.oxm.annotations.*;
#Entity
public class Address implements Serializable {
#Id
private long id;
#OneToOne
#JoinColumn(name="ID")
#MapsId
#XmlInverseReference(mappedBy="address")
private Customer customer;
}
For more information see:
http://bdoughan.blogspot.com/2010/07/jpa-entities-to-xml-bidirectional.html
http://wiki.eclipse.org/EclipseLink/Examples/MOXy/JPA
You can also use MOXy's externalized representation of the metadata for this. For more information see:
XML to Java mapping tool - with mapping descriptor
http://wiki.eclipse.org/EclipseLink/Examples/MOXy/EclipseLink-OXM.XML
make your getCustomer #XmlTransient
#XmlTransient
public Customer getCustomer() {
...