erro ao inserir autor pela web

Tathiana, pelo que me parece nao esta conseguindo injetar o entityManager, isso pode ocorrer por nao ter livraria no seu persistence.xml

Verifique primeiro seu persistence.xml, depois verifique se a conexao do banco de dados que seu persistence esta apontando esta funcionando.

se nao funcionar, posta aqui mais informacoes de como vc esta criando sua conexao pra poder te ajudar melhor.

Oi Diego, obrigada pela resposta! Acredito que não há erro com a conexão com o banco, pois a classe PopulaBanco funcionou perfeitamente e inseriu os contatos. vou posta o persistence.xml (estou usando oracle). Obrigada pela ajuda

<?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_2_0.xsd"
    version="2.0">

    <persistence-unit name="livraria" transaction-type="RESOURCE_LOCAL">

           <provider>org.hibernate.ejb.HibernatePersistence</provider>

        <class>br.com.caelum.livraria.modelo.Livro</class>
        <class>br.com.caelum.livraria.modelo.Autor</class>

         <properties>  
            <property name="hibernate.connection.url" value="jdbc:oracle:thin:@localhost:1521/XE"/> 
            <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver" />              
            <property name="hibernate.connection.username" value="system" />    
            <property name="hibernate.connection.password" value="root" /> 

               <property name="hibernate.dialect" value="org.hibernate.dialect.OracleDialect" />  
            <property name="hibernate.hbm2ddl.auto" value="update" />  
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true"/>
        </properties>
    </persistence-unit>

</persistence>

Bom dia Tathiana, Quando falei de conexao estava generalizando, pois me parece que o entityManager nao esta sendo injetado.

Me parece que seu persistence esta correto, mas so fiquei na duvida quanto ao "hibernate.dialect".. qual eh a versao do driver do oracle que voce esta utilizando? Qual eh o servidor que vc esta rodando ele (Jboss, tomcat...)??

Esse erro pode ser que ele nao esta injetando o entityManager pelo fato de nao estar encontrando o driver do oracle, que deve estar em seu servidor ou projeto.

Oi Diego, desculpe pela pergunta (talvez seja meio idiota), mas se eu estivesse com erro no driver do oracle, eu conseguiria gravar dados pelo hibernate (usando um método main)? Eu não entendo bem de hibernate, mas acredito que se o erro fosse no driver, eu não conseguiria persistir os objetos de nenhuma forma, estou certa? Estou usando o ojdbc6 e o tomcat8. Obrigada.

Oi Tathiana, por favor coloque o stacktrace inteiro, talvez tenha mais informações.

A única que sabemos que a EntityManagerFactory não conseguiu ser criada.

Obrigado, Nico

segue: mais uma vez, obrigada.

INFORMAÇÕES: Server startup in 16122 ms
Gravando autor teste
set 29, 2014 1:11:56 PM org.hibernate.annotations.common.Version <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {4.0.1.Final}
set 29, 2014 1:11:56 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {4.1.8.Final}
set 29, 2014 1:11:56 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
set 29, 2014 1:11:56 PM org.hibernate.cfg.Environment buildBytecodeProvider
INFO: HHH000021: Bytecode provider name : javassist
set 29, 2014 1:11:56 PM org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
INFO: HHH000402: Using Hibernate built-in connection pool (not for production use!)
set 29, 2014 1:11:56 PM com.sun.faces.lifecycle.InvokeApplicationPhase execute
ADVERTÊNCIA: #{autorBean.gravar}: javax.persistence.PersistenceException: [PersistenceUnit: livraria] Unable to build EntityManagerFactory
javax.faces.FacesException: #{autorBean.gravar}: javax.persistence.PersistenceException: [PersistenceUnit: livraria] Unable to build EntityManagerFactory
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:117)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:791)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1256)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:534)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)
Caused by: javax.faces.el.EvaluationException: javax.persistence.PersistenceException: [PersistenceUnit: livraria] Unable to build EntityManagerFactory
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:101)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:101)
    ... 29 more
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: livraria] Unable to build EntityManagerFactory
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:915)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:890)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:57)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)
    at br.com.caelum.livraria.dao.JPAUtil.getEntityManager(JPAUtil.java:21)
    at br.com.caelum.livraria.dao.DAO.adiciona(DAO.java:19)
    at br.com.caelum.livraria.bean.AutorBean.gravar(AutorBean.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:245)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:277)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
    ... 30 more
Caused by: org.hibernate.service.classloading.spi.ClassLoadingException: Specified JDBC Driver oracle.jdbc.OracleDriver class not found
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.configure(DriverManagerConnectionProviderImpl.java:107)
    at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.buildJdbcConnectionAccess(JdbcServicesImpl.java:223)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:89)
    at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
    at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:77)
    at org.hibernate.cfg.Configuration.buildSettingsInternal(Configuration.java:2283)
    at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2279)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1748)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:94)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:905)
    ... 45 more
Caused by: org.hibernate.service.classloading.spi.ClassLoadingException: Unable to load class [oracle.jdbc.OracleDriver]
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:141)
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.configure(DriverManagerConnectionProviderImpl.java:104)
    ... 59 more
Caused by: java.lang.ClassNotFoundException: Could not load requested class : oracle.jdbc.OracleDriver
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl$1.findClass(ClassLoaderServiceImpl.java:99)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:138)
    ... 60 more

set 29, 2014 1:11:56 PM org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: Servlet.service() for servlet [Faces Servlet] in context with path [/livraria] threw exception [javax.persistence.PersistenceException: [PersistenceUnit: livraria] Unable to build EntityManagerFactory] with root cause
java.lang.ClassNotFoundException: Could not load requested class : oracle.jdbc.OracleDriver
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl$1.findClass(ClassLoaderServiceImpl.java:99)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.hibernate.service.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:138)
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.configure(DriverManagerConnectionProviderImpl.java:104)
    at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.buildJdbcConnectionAccess(JdbcServicesImpl.java:223)
    at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure(JdbcServicesImpl.java:89)
    at org.hibernate.service.internal.StandardServiceRegistryImpl.configureService(StandardServiceRegistryImpl.java:75)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService(AbstractServiceRegistryImpl.java:159)
    at org.hibernate.service.internal.AbstractServiceRegistryImpl.getService(AbstractServiceRegistryImpl.java:131)
    at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:77)
    at org.hibernate.cfg.Configuration.buildSettingsInternal(Configuration.java:2283)
    at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2279)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1748)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:94)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:905)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:890)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:57)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)
    at br.com.caelum.livraria.dao.JPAUtil.getEntityManager(JPAUtil.java:21)
    at br.com.caelum.livraria.dao.DAO.adiciona(DAO.java:19)
    at br.com.caelum.livraria.bean.AutorBean.gravar(AutorBean.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.apache.el.parser.AstValue.invoke(AstValue.java:245)
    at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:277)
    at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:87)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:101)
    at javax.faces.component.UICommand.broadcast(UICommand.java:315)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:791)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1256)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:534)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1081)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:658)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

set 29, 2014 1:11:57 PM org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [null]

Achamos o vilão:

Specified JDBC Driver oracle.jdbc.OracleDriver class not found

O seu driver está na pasta WEB-INF/lib?

Abs, Nico

Perfect! Muito obrigada Nico! Era isso mesmo! Tava na lib mas não no web-inf