PU. before initialcontext
org.apache.naming.NamingContext jdbc
org.apache.tomcat.jdbc.pool.DataSource postgres
PU.After Context list

ERROR: org.hibernate.connection.DatasourceConnectionProvider - Could not find datasource: jdbc/postgres
javax.naming.NameNotFoundException: Name jdbc is not bound in this Context
   at org.apache.naming.NamingContext.lookup(NamingContext.java:770)
   at org.apache.naming.NamingContext.lookup(NamingContext.java:153)
   at org.apache.naming.SelectorContext.lookup(SelectorContext.java:152)
   at javax.naming.InitialContext.lookup(InitialContext.java:392)
   at org.hibernate.connection.DatasourceConnectionProvider.configure(DatasourceConnectionProvider.java:75)
   at org.hibernate.connection.ConnectionProviderFactory.newConnectionProvider(ConnectionProviderFactory.java:137)
   at org.hibernate.ejb.InjectionSettingsFactory.createConnectionProvider(InjectionSettingsFactory.java:29)
   at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:89)
   at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2101)
   at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1325)
   at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:867)
   at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:669)

   private static EntityManagerFactory buildEntityManagerFactory(){
      EntityManagerFactory em = null;
      
      System.out.println("PU. before initialcontext");
      try {
         Context ctx1 = (Context) new InitialContext().lookup("java:comp/env");
         listContext(ctx1, "");
          System.out.println("PU.After Context list");         
               
      } catch (NamingException nae) {
         System.out.println("PU. NAE Message = " + nae.getMessage());
         nae.printStackTrace();
      }      
   
      try{
         em = Persistence.createEntityManagerFactory("manager1");         
      } catch(Exception e){
         e.printStackTrace();
      }
      return em;
   }

   private static final void listContext(Context ctx, String indent) {
      try {
         NamingEnumeration list = ctx.listBindings("");
         while (list.hasMore()) {
             Binding item = (Binding) list.next();
             String className = item.getClassName();
             String name = item.getName();
             System.out.println(indent + className + " " + name);
             Object o = item.getObject();
             if (o instanceof javax.naming.Context) {
          listContext((Context) o, indent + " ");
             }
         }
      } catch (NamingException ex) {
         System.out.println("JNDI failure: " + ex);
         ex.printStackTrace();
      }
   }

<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="manager1">

      <jta-data-source>jdbc/postgres</jta-data-source>
      
      <!-- By default, Bean Validation (and Hibernate Validator) is activated -->       
      <properties>
         <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
         <property name="hibernate.hbm2ddl.auto" value="validate"/>
         <property name="hibernate.id.new_generator_mappings" value="true"/>
         
           <!-- Enable c3p0 connection pool management -->
           <property name="hibernate.c3p0.min_size" value="5"/>
           <property name="hibernate.c3p0.max_size" value="20"/>
           <property name="hibernate.c3p0.timeout" value="1800"/>
           <property name="hibernate.c3p0.max_statements" value="50"/>
          
           <!-- Enable Hibernate's automatic session context management -->
         <property name="current_session_context_class" value="thread"/>

      </properties>
   
   </persistence-unit>
</persistence>