Help loading XML config file via Init Servlet

[James Dekker]

Hello,

I am using the Apache Commons Digester to load an XML config file via a servlet with init params...

I keep getting this error when I start Tomcat 5.5.9 and have deployed the war file via my build script:

INFO: Deploying web application archive coffeebreak.war
2007-01-14 03:10:33,050 WARN [org.coffeebreak.logging.Log4jInitServlet] - Loaded: log4j.properties file
attributes-config.xml not found, /Developer/JavaTools/tomcat/jakarta-tomcat-5.5.9/bin/WEB-INF/classes/org/coffeebreak/config/attributes-config.xml
2007-01-14 03:10:33,074 WARN [org.coffeebreak.helper.AttributeBeanXmlConfigHelper] - rules: null
org.apache.commons.digester.xmlrules.XmlLoadException
at org.apache.commons.digester.xmlrules.FromXmlRuleSet$URLXMLRulesLoader.loadRules(FromXmlRuleSet.java:199)
at org.apache.commons.digester.xmlrules.FromXmlRuleSet.addRuleInstances(FromXmlRuleSet.java:176)
at org.apache.commons.digester.xmlrules.FromXmlRuleSet.addRuleInstances(FromXmlRuleSet.java:141)
at org.apache.commons.digester.Digester.addRuleSet(Digester.java:1998)
at org.apache.commons.digester.xmlrules.DigesterLoader.createDigester(DigesterLoader.java:80)
at org.coffeebreak.helper.AttributeBeanXmlConfigHelper.parse(AttributeBeanXmlConfigHelper.java:29)
at org.coffeebreak.config.XmlConfigInitServlet.init(XmlConfigInitServlet.java:22)
at javax.servlet.GenericServlet.init(GenericServlet.java:211)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1091)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:925)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3857)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4118)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:788)
at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:677)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:473)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1102)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:683)
at org.apache.catalina.startup.Catalina.start(Catalina.java:537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:271)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:409)
Caused by: java.lang.NullPointerException
at org.apache.commons.digester.xmlrules.FromXmlRuleSet$URLXMLRulesLoader.loadRules(FromXmlRuleSet.java:197)
... 33 more
java.lang.NullPointerException
at org.apache.commons.digester.xmlrules.FromXmlRuleSet$URLXMLRulesLoader.loadRules(FromXmlRuleSet.java:197)
at org.apache.commons.digester.xmlrules.FromXmlRuleSet.addRuleInstances(FromXmlRuleSet.java:176)
at org.apache.commons.digester.xmlrules.FromXmlRuleSet.addRuleInstances(FromXmlRuleSet.java:141)
at org.apache.commons.digester.Digester.addRuleSet(Digester.java:1998)
at org.apache.commons.digester.xmlrules.DigesterLoader.createDigester(DigesterLoader.java:80)
at org.coffeebreak.helper.AttributeBeanXmlConfigHelper.parse(AttributeBeanXmlConfigHelper.java:29)
at org.coffeebreak.config.XmlConfigInitServlet.init(XmlConfigInitServlet.java:22)
at javax.servlet.GenericServlet.init(GenericServlet.java:211)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1091)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:925)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3857)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4118)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:788)
at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:677)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:473)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1102)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:683)
at org.apache.catalina.startup.Catalina.start(Catalina.java:537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:271)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:409)
java.lang.NullPointerException
at org.coffeebreak.helper.AttributeBeanXmlConfigHelper.parse(AttributeBeanXmlConfigHelper.java:38)
at org.coffeebreak.config.XmlConfigInitServlet.init(XmlConfigInitServlet.java:22)
at javax.servlet.GenericServlet.init(GenericServlet.java:211)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1091)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:925)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3857)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4118)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:788)
at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:677)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:473)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1102)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:683)
at org.apache.catalina.startup.Catalina.start(Catalina.java:537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:271)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:409)
2007-01-14 03:10:33,687 WARN [org.coffeebreak.config.ErrorInitServlet] - Loaded: error.properties
INFO: Server startup in 15130 ms

As one can see there's an obvious pathing issue:

/Developer/JavaTools/tomcat/jakarta-tomcat-5.5.9/bin/WEB-INF/classes/org/coffeebreak/config/attributes-config.xml

As one can see there's an obvious pathing issue.

Where does the tomcat_home/bin/... come from? The "bin" directory is not supposed to be there!

Here's the specific target from my build script which places attributes-config.xml into tomcat_home/WEB-INF/classes/org/coffeebreak/config:

<target name="static" depends="prepare">
        <!-- Copy web files -->
<copy todir="${webapp.build.dir}/">
        <fileset dir="web" />
        </copy>
        <!-- Copy webapp configuration files -->
<copy todir="${webapp.build.dir}/WEB-INF/">
        <fileset dir="etc" />
        </copy>
<!-- Copy library files -->
<copy todir="${webapp.build.dir}/WEB-INF/lib/">
       <fileset dir="lib" />
</copy>
    <!-- Copy properties files -->
    <copy todir="${webapp.build.dir}/WEB-INF/classes/">
    <fileset dir="props" />
    </copy>
    <!-- Copy config files -->
    <copy todir="${webapp.build.dir}/WEB-INF/classes/org/coffeebreak/config/">
    <fileset dir="config" />
    </copy>
    <!-- Copy rules files -->
    <copy todir="${webapp.build.dir}/WEB-INF/classes/org/coffeebreak/helper/">
    <fileset dir="rules" />
    </copy>
</target>

Here's my deployment descriptor (web.xml) file:

<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd">
 
<web-app>
 
    <display-name>Coffee Break</display-name>
    <description>
        CoffeeBreak Application
    </description>
 
    <servlet>
      <servlet-name>CoffeeBreakServlet</servlet-name>
      <servlet-class>org.coffeebreak.CoffeeBreakServlet</servlet-class>
    </servlet>
 
    <servlet-mapping>
      <servlet-name>CoffeeBreakServlet</servlet-name>
      <url-pattern>/app</url-pattern>
    </servlet-mapping>
   
    <servlet>
       <servlet-name>log4j-init</servlet-name>
       <servlet-class>org.coffeebreak.logging.Log4jInitServlet</servlet-class>
       <init-param>
           <param-name>log4j-init-file</param-name>
           <param-value>WEB-INF/classes/log4j.properties</param-value>
       </init-param>
       <load-on-startup>1</load-on-startup>
   </servlet>
  
   <servlet>
       <servlet-name>xml-config</servlet-name>
       <servlet-class>org.coffeebreak.config.XmlConfigInitServlet</servlet-class>
       <init-param>
           <param-name>xml-config-file</param-name>
           <param-value>WEB-INF/classes/org/coffeebreak/config/attributes-config.xml</param-value>
       </init-param>
       <load-on-startup>2</load-on-startup>
   </servlet>
  
    <servlet>
       <servlet-name>error-init</servlet-name>
       <servlet-class>org.coffeebreak.config.ErrorInitServlet</servlet-class>
       <init-param>
           <param-name>error-init-file</param-name>
           <param-value>WEB-INF/classes/error.properties</param-value>
       </init-param>
       <load-on-startup>3</load-on-startup>
   </servlet>
   
</web-app>

Here's my init servlet for the XML file:

package org.coffeebreak.config;
 
import org.apache.log4j.Logger;
import org.coffeebreak.helper.AttributeBeanXmlConfigHelper;
 
import java.io.File;
 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
 
public class XmlConfigInitServlet extends HttpServlet {
    public void init() throws ServletException {
        String file = getInitParameter("xml-config-file");
        File xmlConfigFile = new File(file);
        if (!xmlConfigFile.exists()) {
            System.out.println("attributes-config.xml not found, "
                    + xmlConfigFile.getAbsolutePath());
        }
 
        try {
            // Configure Digester from XML ruleset
            AttributeBeanXmlConfigHelper.parse(xmlConfigFile);
 
            Logger.getLogger(this.getClass()).warn(
                    "Finished parsing the config file.");
        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

My helper file (which is showing that the rules file is not loading):

package org.coffeebreak.helper;
 
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
 
import org.apache.commons.digester.Digester;
import org.apache.commons.digester.xmlrules.DigesterLoader;
import org.apache.log4j.Logger;
import org.coffeebreak.model.AttributeBean;
import org.xml.sax.SAXException;
 
public class AttributeBeanXmlConfigHelper {
 
    private static List<AttributeBean> attributeConfigList = null;
 
    public static void parse(File xmlConfigFile) throws IOException,
            SAXException {
        URL rules = AttributeBeanXmlConfigHelper.class
                .getResource("attributes-rules.xml");
        Logger.getLogger(AttributeBeanXmlConfigHelper.class).warn(
                "rules: " + rules);
        Digester digester = null;
        try {
            digester = DigesterLoader.createDigester(rules);
        }
        catch (Throwable e) {
            e.printStackTrace();
            e.getCause().printStackTrace();
        }
 
        // Push empty List onto Digester's Stack
        attributeConfigList = new ArrayList<AttributeBean>();
        digester.push(attributeConfigList);
 
        // Parse the XML document
        InputStream input = new FileInputStream(xmlConfigFile);
        digester.parse(input);
    }
 
    public static List<AttributeBean> getConfig() {
        return attributeConfigList;
    }
}

What could I possibly be doing wrong?

Why is it stating this when I start Tomcat:

attributes-config.xml not found, /Developer/JavaTools/tomcat/jakarta-tomcat-5.5.9/bin/WEB-INF/classes/org/coffeebreak/config/attributes-config.xml

it should be without the "bin" directory, like this:

/Developer/JavaTools/tomcat/jakarta-tomcat-5.5.9/WEB-INF/classes/org/coffeebreak/config/attributes-config.xml

Why is the rules file coming out as null?

2007-01-14 03:10:33,074 WARN [org.coffeebreak.helper.AttributeBeanXmlConfigHelper] - rules: null

Sincerely,

James Dekker
[ January 14, 2007: Message edited by: James Dekker ]

[Ulf Dittmer]

In web applications, never use relative paths to files, always absolute paths. What the relative path might be is unspecifed, ans sometimes unpredictable, and it varies from one container to the next.

You can convert a relative path to an absolute one like this:

absolutePath = conf.getServletContext().getRealPath("/") + relativePath
[ January 14, 2007: Message edited by: Ulf Dittmer ]

[James Dekker]

Mr. Dittmer,

The problem with getRealPath() is that if you set unpackWars="false" then the file returns as null. getRealPath() is raw File I/O.

What am I doing wrong with my code? Why isn't it finding the xml config file?

Sincerely,

JD

[Bear Bibeault]

If you are not unpacking the wars, then you cannot expect the files to live anywhere on the file-system. If you need the files in the file system, don't use unpacked wars.

If you want to read a resource without unpacking, you may wish to explore the getResourceAsStream() method of ServletContext.

[James Dekker]

Bear,

When I tried your suggestion (using getServletContext()), I got a different error...

Here's my change:

public class XmlConfigInitServlet extends HttpServlet {
    public void init() throws ServletException {
        String file = getServletContext().getInitParameter("xml-config-file");
        File xmlConfigFile = new File(file);
        if (!xmlConfigFile.exists()) {
            System.out.println("attributes-config.xml not found, "
                    + xmlConfigFile.getAbsolutePath());
        }
 
        try {
            // Configure Digester from XML ruleset
            AttributeBeanXmlConfigHelper.parse(xmlConfigFile);
 
            Logger.getLogger(this.getClass()).warn(
                    "Finished parsing the config file.");
        }
        catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}

Here's the error message:

INFO: Deploying web application archive coffeebreak.war
2007-01-14 15:53:41,989 WARN [org.coffeebreak.logging.Log4jInitServlet] - Loaded: log4j.properties file
2007-01-14 15:53:42,010 ERROR [org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/coffeebreak]] - StandardWrapper.Throwable
java.lang.NullPointerException
at java.io.File.<init>(File.java:194)
at org.coffeebreak.config.XmlConfigInitServlet.init(XmlConfigInitServlet.java:14)
at javax.servlet.GenericServlet.init(GenericServlet.java:211)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1091)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:925)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3857)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4118)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:788)
at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:677)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:473)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1102)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:683)
at org.apache.catalina.startup.Catalina.start(Catalina.java:537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:271)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:409)
2007-01-14 15:53:42,028 ERROR [org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/coffeebreak]] - Servlet /coffeebreak threw load() exception
java.lang.NullPointerException
at java.io.File.<init>(File.java:194)
at org.coffeebreak.config.XmlConfigInitServlet.init(XmlConfigInitServlet.java:14)
at javax.servlet.GenericServlet.init(GenericServlet.java:211)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1091)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:925)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3857)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4118)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:788)
at org.apache.catalina.startup.HostConfig.deployWARs(HostConfig.java:677)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:473)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1102)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:683)
at org.apache.catalina.startup.Catalina.start(Catalina.java:537)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:271)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:409)
2007-01-14 15:53:42,118 WARN [org.coffeebreak.config.ErrorInitServlet] - Loaded: error.properties
INFO: Server startup in 13302 ms

When I tried to use the getResourceAsStream() method, by doing this:

InputStream file = getServletContext().getResourceAsStream("xml-config-file");
        File xmlConfigFile = new File(file);
        if (!xmlConfigFile.exists()) {
            System.out.println("attributes-config.xml not found, "
                    + xmlConfigFile.getAbsolutePath());
        }

I got this error message in Eclipse:

The constructor File(InputStream) is undefined.

Thank you for your insight!

Sincerely,

James
[ January 14, 2007: Message edited by: James Dekker ]