Understanding context.xml in tomcat 6

Question

I created a mainly empty dynamic web project in eclipse.

It has

• no servlets
• no jsp files

The web.xml is

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>testprojekt</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

and I added a context.xml to its META-INF folder

<?xml version="1.0" encoding="UTF-8"?>
<Context>
        <Parameter name="companyName" value="My Company, Incorporated"  override="false"/>
</Context>

I exported this project as a WAR file. With the following structure:

user@system:$ tree
.
|-- META-INF
|   |-- MANIFEST.MF
|   `-- context.xml
`-- WEB-INF
    |-- classes
    |-- lib
    `-- web.xml

4 directories, 3 files

When I deploy the project to a local tomcat (Apache Tomcat/6.0.20) Everything works as expected. Meaning, the context.xml is copied to /conf/Catalina/localhost and renamed to testprojekt.xml.

When I edit the testprojekt.xml to:

<?xml version="1.0" encoding="UTF-8"?>
<Context>
  <Parameter name="companyName" value="My BLAH Company, Incorporated"  override="false"/>
</Context>

I see the following output in the catalina.out:

02.11.2009 13:21:35 org.apache.catalina.startup.HostConfig checkResources
INFO: Undeploying context [/testprojekt]
02.11.2009 13:21:35 org.apache.catalina.core.StandardContext resourcesStart
SCHWERWIEGEND: Error starting static Resources
java.lang.IllegalArgumentException: Document base /opt/tomcat6/webapps/testprojekt does not exist or is not a readable directory
        at org.apache.naming.resources.FileDirContext.setDocBase(FileDirContext.java:142)
        at org.apache.catalina.core.StandardContext.resourcesStart(StandardContext.java:4048)
        at org.apache.catalina.core.StandardContext.start(StandardContext.java:4217)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:526)
        at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:630)
        at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:556)
        at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:491)
        at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1274)
        at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:296)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
        at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1337)
        at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601)
        at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
        at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590)
        at java.lang.Thread.run(Thread.java:619)
02.11.2009 13:21:35 org.apache.catalina.core.StandardContext start
SCHWERWIEGEND: Error in resourceStart()
02.11.2009 13:21:35 org.apache.catalina.core.StandardContext start
SCHWERWIEGEND: Error getConfigured
02.11.2009 13:21:35 org.apache.catalina.core.StandardContext start
SCHWERWIEGEND: Context [/testprojekt] startup failed due to previous errors
02.11.2009 13:21:35 org.apache.catalina.core.StandardContext stop
INFO: Container org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/testprojekt] has not been started

Why is that? Is that the expected result? What is the right way to change parameters in a context.xml?

Thank you in advance. Regards,

Answer 1

I think this is a bug in Tomcat. I filed a bug report but they claim it works as designed. Tomcat has 3 modes of deployment: Directory, WAR and Context Fragment. In your case, it gets confused when reloading.

Here is the sequence leading to the error,

1. When you deploy the WAR, the context fragment (META-INF/context.xml) is copied to conf/Catalina/[host] directory.
2. When you modifies the fragment, it correctly detects the change so redeployment is triggered.
3. However, it forgets this is a WAR deployment and treats it as Directory deployment. The directory is removed by undelpoy so you get the error.

If you only change the XML in META-INF, everything should work for you.