PersistenceUnit的java部署[…]失败。关闭此PersistenceUnit的所有工厂
我在调用hentMeldinger（）时不断遇到此错误
public class Kontroll {
private EntityManagerFactory emf;
Kontroll() {
emf = Persistence.createEntityManagerFactory("meldingsTing");
}
public List<Melding> hentMeldinger() {
EntityManager em = emf.createEntityManager();
TypedQuery<Melding> query = em.createQuery("SELECT o FROM Melding o",
Melding.class);// FIKS
List<Melding> meldinger = query.getResultList();
em.close();
return meldinger;
}
}
例外情况报告：
message Exception [EclipseLink-28019] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.EntityManagerSetupException
description The server encountered an internal error that prevented it from fulfilling this request.
exception
javax.persistence.PersistenceException: Exception [EclipseLink-28019] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Deployment of PersistenceUnit [meldingsTing] failed. Close all factories for this PersistenceUnit.
Internal Exception: Exception [EclipseLink-0] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.IntegrityException
Descriptor Exceptions:
---------------------------------------------------------
Exception [EclipseLink-63] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: The instance creation method [no.hib.dat104.oblig1.Melding.<Default Constructor>], with no parameters, does not exist, or is not accessible.
Internal Exception: java.lang.NoSuchMethodException: no.hib.dat104.oblig1.Melding.<init>()
Descriptor: RelationalDescriptor(no.hib.dat104.oblig1.Melding --> [DatabaseTable(MELDING)])
Runtime Exceptions:
---------------------------------------------------------
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.createDeployFailedPersistenceException(EntityManagerSetupImpl.java:820)
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:760)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:204)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:304)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:336)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:302)
no.hib.dat104.oblig1.Kontroll.lagreMelding(Kontroll.java:32)
no.hib.dat104.oblig1.MeldingServlet.doPost(MeldingServlet.java:83)
javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
根本原因：
Exception [EclipseLink-28019] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Deployment of PersistenceUnit [meldingsTing] failed. Close all factories for this PersistenceUnit.
Internal Exception: Exception [EclipseLink-0] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.IntegrityException
Descriptor Exceptions:
---------------------------------------------------------
Exception [EclipseLink-63] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: The instance creation method [no.hib.dat104.oblig1.Melding.<Default Constructor>], with no parameters, does not exist, or is not accessible.
Internal Exception: java.lang.NoSuchMethodException: no.hib.dat104.oblig1.Melding.<init>()
Descriptor: RelationalDescriptor(no.hib.dat104.oblig1.Melding --> [DatabaseTable(MELDING)])
Runtime Exceptions:
---------------------------------------------------------
org.eclipse.persistence.exceptions.EntityManagerSetupException.deployFailed(EntityManagerSetupException.java:238)
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.createDeployFailedPersistenceException(EntityManagerSetupImpl.java:820)
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:760)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:204)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:304)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:336)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:302)
no.hib.dat104.oblig1.Kontroll.lagreMelding(Kontroll.java:32)
no.hib.dat104.oblig1.MeldingServlet.doPost(MeldingServlet.java:83)
javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause
Exception [EclipseLink-0] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.IntegrityException
Descriptor Exceptions:
---------------------------------------------------------
Exception [EclipseLink-63] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: The instance creation method [no.hib.dat104.oblig1.Melding.<Default Constructor>], with no parameters, does not exist, or is not accessible.
Internal Exception: java.lang.NoSuchMethodException: no.hib.dat104.oblig1.Melding.<init>()
Descriptor: RelationalDescriptor(no.hib.dat104.oblig1.Melding --> [DatabaseTable(MELDING)])
Runtime Exceptions:
---------------------------------------------------------
org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:696)
org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:632)
org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.initializeDescriptors(DatabaseSessionImpl.java:568)
org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.postConnectDatasource(DatabaseSessionImpl.java:799)
org.eclipse.persistence.internal.sessions.DatabaseSessionImpl.loginAndDetectDatasource(DatabaseSessionImpl.java:743)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryProvider.login(EntityManagerFactoryProvider.java:239)
org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:685)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:204)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:304)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:336)
org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:302)
no.hib.dat104.oblig1.Kontroll.lagreMelding(Kontroll.java:32)
no.hib.dat104.oblig1.MeldingServlet.doPost(MeldingServlet.java:83)
javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
我的问题是，在查看此错误报告时，我不知道从何处开始。我已经试了几个小时了，但对我来说毫无意义。如果有人能从中理解som并加以解释，那就太棒了，但解决问题才是最好的
# 1 楼答案
对于JPA实体，至少必须包括
default constructor (no-arg constructor)