Develop Reference

Cannot resolve column name

I'm using JPA with hibernate under my small resteasy project deployed on wildfly.
I've got my persistence.xml file under directory:
resources/META-INF/
<?xml version="1.0" encoding="UTF-8" ?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0">
<persistence-unit name="PostgresDS" transaction-type="JTA">
<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
<jta-data-source>java:jboss/datasources/PostgresDS</jta-data-source>
<properties>
<property name="hibernate.hbm2ddl.auto" value="create-drop"/>
</properties>
</persistence-unit>
</persistence>
So I'm dropping and creating database each time on startup.
When typing annotation #Column(name="SomeName") I've got error that
"Cannot resolve column "Name" "
and as fix I'm supposed to attach data-source.
Should I prepare some hibernate config file(attaching data-source didn't help), maybe disabling some validation ?

Get all available persistence-unit names defined in persistence.xml

I have persistence.xml as below (just an example) and I want to retrieve set of all persistence-unit names. In this example a,b and c
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="1.0">
<persistence-unit name="a">
</persistence-unit>
<persistence-unit name="b">
</persistence-unit>
<persistence-unit name="c">
</persistence-unit>
</persistence>

You can get all persistence unit names using this code.
List<ParsedPersistenceXmlDescriptor> persistenceUnits = PersistenceXmlParser.locatePersistenceUnits(new Properties());
for (ParsedPersistenceXmlDescriptor descriptor : persistenceUnits) {
AVAILABLE_MODULES_LIST.add(descriptor.getName());
}
For me it works fine.

Ljava.lang.String class cannot be resolved in persistence.xml

I am using JBoss Developer Studio. I have a project with a persistence.xml file. The file is perfect to me, but I keep getting this error on the tab that lists all the Problems of my project.
Class "[Ljava.lang.String;#22ec7158" cannot be resolved
I include the picture for a better context.
When I click on the error, so that it takes me to the place where the error is happening, it takes me to the end of the file.
Persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="Persistence">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<jta-data-source>java:jboss/datasources/MemberOfferDS</jta-data-source>
<class>com.bbb.memberoffer.model.SycsCoordinator</class>
<class>com.bbb.aicweb.memberoffer.model.SycsCoordinatorPhoneNumber</class>
<class>com.bbb.memberoffer.model.SycsCoordinatorClub</class>
<class>com.bbb.memberoffer.model.SycsCoordinatorSecurityGroup</class>
<class>com.bbb.memberoffer.model.SycsCoordinatorClubPk</class>
<class>com.bbb.memberoffer.model.PhoneNumberType</class>
<class>com.bbb.memberoffer.model.Club</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<!-- Not sure if this is the right one to use or not? -->
<property name='hibernate.show_sql' value='true' />
<property name='hibernate.format_sql' value='true' />
<property name="hibernate.dialect" value="org.hibernate.dialect.SQLServerDialect"/>
</properties>
</persistence-unit>
</persistence>

You may have solved this already, however, in my case the problem was caused by referencing a class in a element that no longer existed.
EDIT: The exact reason for this type of error message is that the error generator is trying to run a toString() on a String array when it generates the error message.

Why Eclipse dont generate complete persistence.xml?

I have Vaadin project with JPA 2.1 + EclipseLink + MySQL.
In eclipse in project settings I set connection to base and drivers correctly. Without problem I "generate Entities from Tables", but persistence.xml haven't info about driver, connection, login, pass to DB.
My auto generate persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="RadiologicalWarehouse">
<class>pl.intibs.rw.entitites.Message</class>
<class>pl.intibs.rw.entitites.Part</class>
<class>pl.intibs.rw.entitites.Role</class>
<class>pl.intibs.rw.entitites.Sample</class>
<class>pl.intibs.rw.entitites.SampleHistory</class>
<class>pl.intibs.rw.entitites.User</class>
</persistence-unit>
</persistence>
If I run my application with simple query, I get of course exception:
javax.servlet.ServletException: com.vaadin.server.ServiceException: javax.persistence.PersistenceException: Exception [EclipseLink-4021] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.DatabaseException
Exception Description: Unable to acquire a connection from driver [null], user [null] and URL [null]. Verify that you have set the expected driver class and URL. Check your login, persistence.xml or sessions.xml resource. The jdbc.driver property should be set to a class that is compatible with your database platform
com.vaadin.server.VaadinServlet.service(VaadinServlet.java:239)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
If JPA has defined the connection in the project, why does not generate this persistence automatically?
Screenshot settings JPA: http://i.imgur.com/T2oEdHA.png

Based on what I understand you have set parameters for the Jpa plugin to eclipse and this is much different to set the parameters to persistence provider. Firstly you have to decide what persitent provide use and specify it in the persistence.xml together with the others paramenters.
This is an example of persistence.xml with eclipseLink:
<persistence>
<persistence-unit name="myUnit">
<provider>yourProvider</provider>
<class>it.myCompany.domain.MyFirstClass</class>
<class>it.myCompany.domain.MySecondClassClass</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="${driverClass}" />
<property name="javax.persistence.jdbc.url" value="${connectionURL}" />
<property name="javax.persistence.jdbc.user" value="${username}" />
<property name="javax.persistence.jdbc.password" value="${password}" />
<property name="eclipselink.logging.level" value="info"/>
</properties>
<shared-cache-mode>NONE</shared-cache-mode>
</persistence-unit>
</persistence>

JPA Exception: No Persistence provider for EntityManager named MyJPAApplicationPU

I am newbie with JPA. I'm trying to run some sample code using JPA but I get the following exception:
javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyJPAApplicationPU
I put my exception message here,
INFO: Could not find any META-INF/persistence.xml file in the classpath
javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyJPAApplicationPU
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
at com.myJpa.TestJPA.setUp(TestJPA.java:30)
at com.myJpa.TestJPA.main(TestJPA.java:72)
Any help would be appreciated.

Well, the error is self explaining, you need to provide a META-INF/persistence.xml to use JPA. This file is used to define a "persistence unit". From the JPA 1.0 specification:
6.2.1 persistence.xml file
A persistence.xml file defines a
persistence unit. It may be used to
specify managed persistence classes
included in the persistence unit,
object/relational mapping information
for those classes, and other
configuration information for the
persistence unit and for the entity
manager(s) and entity manager factory
for the persistence unit. The
persistence.xml file is located in
the META-INF directory of the root
of the persistence unit. This
information may be defined by
containment or by reference, as
described below.
Here is a sample persistence.xml for a Java SE environment (using Hibernate as JPA provider):
<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0">
<persistence-unit name="MyJPAApplicationPU" transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<class>com.mycompany.Foo</class>
<class>com.mycompany.Bar</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<property name="hibernate.connection.provider_class" value="org.hibernate.connection.DriverManagerConnectionProvider" />
<property name="hibernate.connection.url" value="jdbc:hsqldb:mem:unit-testing-jpa"/>
<property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
<property name="hibernate.connection.username" value="sa"/>
<property name="hibernate.connection.password" value=""/>
<property name="hibernate.show_sql" value="true"/>
</properties>
</persistence-unit>
</persistence>
Some comments about the above file:
when running in a Java SE environment, you cannot rely on JTA and the transaction type must be RESOURCE_LOCAL (which is actually the default in a Java SE environment but specifying it make it more clear).
when running in a Java SE environment, you cannot use a JDNI data source and the provider will obtain connections directly from the JDBC driver so you must pass the relevant informations to the provider (driver class name, connection url, user, password). With JPA 1.0 the properties used to pass these metadata are provider specific.
To insure the portability of a Java SE application, it is necessary to explicitly list the managed persistence classes that are included in the persistence unit.

For JPA to work, you need META-INF/persistence.xml. I will assume this is a web-app, so this folder has to be in WEB-INF/classes/.
The persistence.xml file would look like this:
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0">
<persistence-unit name="MyJPAApplicationPU" transaction-type="RESOURCE_LOCAL">
</persistence-unit>
</persistence>

EntityManagerFactory emf = Persistence.createEntityManagerFactory("<JDBC connection>");
Check the correct JDBC Connection.