需要将Postgresql 9.1 DB连接到Tomcat 8服务器的帮助吗

我想知道是否有任何教程教我如何将POSTGRESQL 9.1 DB连接到Windows上的Tomcat 8服务器。我找到了这个教程，但我没有完全理解它，没有真正的DBA经验。我目前正试图在Tomcat中运行一个连接到POSTGRESQL数据库的web应用程序。web应用出现在我的浏览器中，但当我尝试登录时，我收到以下错误：

===========> Msg.initMsg: No DB Connection [12]
===========> PreparedStatementProxy.init: SELECT Name, PO_Name FROM AD_Element WHERE UPPER(ColumnName)=? [12]
java.lang.IllegalStateException: DB.getConnectionRO - @NoDBConnection@
    at org.compiere.util.DB.createConnection(DB.java:451)
    at org.compiere.util.DB.getConnectionRO(DB.java:381)
    at org.compiere.db.PreparedStatementProxy.init(PreparedStatementProxy.java:66)
    at org.compiere.db.PreparedStatementProxy.<init>(PreparedStatementProxy.java:44)
    at org.compiere.db.ProxyFactory.newCPreparedStatement(ProxyFactory.java:54)
    at org.compiere.util.DB.prepareStatement(DB.java:744)
    at org.compiere.util.DB.prepareStatement(DB.java:713)
    at org.compiere.util.Msg.getElement(Msg.java:479)
    at org.compiere.util.Msg.translate(Msg.java:574)
    at org.compiere.util.Msg.translate(Msg.java:617)
    at org.compiere.util.Msg.parseTranslation(Msg.java:664)

10:16:44.368     ManagerBase.processExpires: Start expire sessions StandardManager at 1433341004368 sessioncount 0 [32]
10:16:44.369     ManagerBase.processExpires: End expire sessions StandardManager processingTime 1 expired sessions: 0 [32]

任何帮助都将不胜感激

将以下内容添加到context.xml：

<Context>
     <Resource name="jdbc/postgres" auth="Container"
      type="javax.sql.DataSource" driverClassName="org.postgresql.Driver"
      url="jdbc:postgresql://127.0.0.1:5432/a1ehr"
      username="adempiere" password="abc123" maxTotal="20" maxIdle="10" maxWaitMillis="-1"/>

<WatchedResource>WEB-INF/web.xml</WatchedResource>
<WatchedResource>${catalina.base}/conf/web.xml</WatchedResource>

</Context>

并将以下内容添加到Web.xml：

   <resource-ref>
    <description>a1ehr</description>
    <res-ref-name>jdbc/postgres</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
   </resource-ref>

---

我得到了NullPointerException。我无法复制错误以给出完整的消息。

这允许mt登录到应用程序中，但仍在修复错误。我不知道你走了多远

 cd /home/postgres/Adempiere/postgresql/8.1.4/pgdata
 edit pg_hba.conf 

 # CAUTION: Configuring the system for local "trust" authentication allows
 # any local user to connect as any PostgreSQL user, including the database
 # superuser. If you do not trust all your local users, use another
 # authentication method.
 # TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD
 # "local" is for Unix domain socket connections only
 local   all         all                               trust
 # IPv4 local connections:
 host    all         all         127.0.0.1/32          trust
 # IPv6 local connections:
 host    all         all         ::1/128               trust
 host all all {Set your IP}/32 trust