[HELP]Failed to execute pipeline.

[Milkwayboat]

The error stack I got:       Failed to execute pipeline. org.apache.cocoon.ProcessingException: Failed to execute pipeline.: java.lang.NullPointerException Original Exception: java.lang.NullPointerException          at org.apache.xml.serializer.ToStream.ensurePrefixIsDeclared(ToStream.java:2675)           at org.apache.xml.serializer.ToStream.startElement(ToStream.java:1777)           at org.apache.xalan.transformer.TransformerIdentityImpl.startElement(TransformerIdentityImpl.java:1073)           at org.apache.cocoon.xml.AbstractXMLPipe.startElement(AbstractXMLPipe.java:130)           at org.apache.cocoon.xml.AbstractXMLPipe.startElement(AbstractXMLPipe.java:130)           at org.apache.cocoon.transformation.AbstractSAXTransformer.startTransformingElement(AbstractSAXTransformer.java:692)           at org.apache.cocoon.transformation.SQLTransformer.start(SQLTransformer.java:801)           at org.apache.cocoon.transformation.SQLTransformer.executeQuery(SQLTransformer.java:340)           at org.apache.cocoon.transformation.SQLTransformer.endExecuteQueryElement(SQLTransformer.java:493)           at org.apache.cocoon.transformation.SQLTransformer.endTransformingElement(SQLTransformer.java:774)           at org.apache.cocoon.transformation.AbstractSAXTransformer.endElement(AbstractSAXTransformer.java:358)   What I did:      1. I copied the "mysql-connector-java-3.0.11-stable-bin.jar" to $COCOON_HOME/WEB-INF/lib 2. add the following to the web.xml    <!-- For MySQL Driver: -->         com.mysql.jdbc.Driver 3. add the following to the cocoon.xconf   <jdbc name="YourPoolName">     <pool-controller min="5" max="10"/>     <dburl>jdbc:mysql://boss.mylab.org:3306/tbdb?autoReconnect=true</dburl>     <user>YourUsername</user>     <password>YourPassword</password>   </jdbc>     in fact I am not quite sure the port number, database name, user name and password above.    A>  the database server doesn't require an user name or password to use the database, but it dos require an account to login in to the OS, I don't know  how to set the user and password to the OS ?    B> also, I don't know if the port number is right? Is it just a random un-used one, or there is a specific port number for mysql in unix?    C> I am not sure the database name too. After I login on to the server by ssh, I can type               mysql               use tbdb and then, I can inquery the table I want, so is "tbdb"  the one I should set after the port number?   4: here is what I add to the sitemap.xmap    <map:match pattern="allUsers">       <map:generate src="allUsers.xml" />       <map:transform type="sql">         <map:parameter name="use-connection" value="YourPoolName" />         <map:parameter name="show-nr-of-rows" value="true" />         <map:parameter name="clob-encoding" value="UTF-8" />   </map:transform>     <map:serialize type="xml" />   </map:match> 5, here is the allUsers.xml   <?xml version="1.0" ?>   <document>    <execute-query xmlns="http://apache.org/cocoon/SQL/2.0">  <query name="allUsers">   select uid from users;   </query>   </execute-query>   </document>   So I started the server and input the Url, the response is very very slow(about 5 minutes) and what I got the above error stack. Now I totally have no idea why   Thanks for your help and time!