protected static Digester createDigester() 
{
        long t1 = System.currentTimeMillis();
        // Initialize the digester
        Digester digester = new Digester();
        digester.setValidating(false);
        digester.setClassLoader(StoreRegistry.class.getClassLoader());
        // Configure the actions we will be using
        digester.addObjectCreate("Registry",
                "org.apache.catalina.storeconfig.StoreRegistry", "className");
        digester.addSetProperties("Registry");
        digester
                .addObjectCreate("Registry/Description",
                        "org.apache.catalina.storeconfig.StoreDescription",
                        "className");
        digester.addSetProperties("Registry/Description");
        digester.addRule("Registry/Description", new StoreFactoryRule(
                "org.apache.catalina.storeconfig.StoreFactoryBase",
                "storeFactoryClass",
                "org.apache.catalina.storeconfig.StoreAppender",
                "storeAppenderClass"));
        digester.addSetNext("Registry/Description", "registerDescription",
                "org.apache.catalina.storeconfig.StoreDescription");
        digester.addCallMethod("Registry/Description/TransientAttribute",
                "addTransientAttribute", 0);
        digester.addCallMethod("Registry/Description/TransientChild",
                "addTransientChild", 0);
        long t2 = System.currentTimeMillis();
        if (log.isDebugEnabled())
            log.debug("Digester for server-registry.xml created " + (t2 - t1));
        return (digester);
}

Create and configure the Digester we will be using for setup store registry.

 public StoreRegistry getRegistry() 
{
             
        return registry;
}

 public URL getRegistryResource() 
{
        return registryResource;
}

 public  void load() 
{
        InputStream is = null;
        Throwable error = null;
        registryResource = null ;
        try {
            String configUrl = getConfigUrl();
            if (configUrl != null) {
                is = (new URL(configUrl)).openStream();
                if (log.isInfoEnabled())
                    log
                            .info("Find registry server-registry.xml from system property at url "
                                    + configUrl);
                ;
                registryResource = new URL(configUrl);
            }
        } catch (Throwable t) {
            // Ignore
        }
        if (is == null) {
            try {
                File home = new File(getCatalinaBase());
                File conf = new File(home, "conf");
                File reg = new File(conf, "server-registry.xml");
                is = new FileInputStream(reg);
                if (log.isInfoEnabled())
                    log.info("Find registry server-registry.xml at file "
                            + reg.getCanonicalPath());
                ;
                registryResource = reg.toURL() ;
            } catch (Throwable t) {
                // Ignore
            }
        }
        if (is == null) {
            try {
                is = StoreLoader.class
                        .getResourceAsStream("/org/apache/catalina/storeconfig/server-registry.xml");
                if (log.isInfoEnabled())
                    log
                            .info("Find registry server-registry.xml at classpath resource");
                registryResource = StoreLoader.class
                    .getResource("/org/apache/catalina/storeconfig/server-registry.xml");
            } catch (Throwable t) {
                // Ignore
            }
        }
        if (is != null) {
            try {
                synchronized (digester) {
                    registry = (StoreRegistry) digester.parse(is);
                }
            } catch (Throwable t) {
                error = t;
            } finally {
                try {
                    is.close();
                } catch (IOException e) {
                }
            }
        }
        if ((is == null) || (error != null)) {
            log.error(error);
        }
}

Load from defaults
• System Property URL catalina.storeregistry
• File $catalina.base/conf/server-registry.xml
• class resource org/apache/catalina/storeconfig/server-registry.xml

 public  void load(String aURL) 
{
        synchronized (digester) {
            File aRegistryFile = serverFile(aURL);
            try {
                registry = (StoreRegistry) digester.parse(aRegistryFile);
                registryResource = aRegistryFile.toURL();
            } catch (IOException e) {
                log.error(e);
            } catch (SAXException e) {
                log.error(e);
            }
        }
}

Load Description from external source

 protected File serverFile(String aFile) 
{
        if (aFile == null || (aFile != null && aFile.length() <  1))
            aFile = "server-registry.xml";
        File file = new File(aFile);
        if (!file.isAbsolute())
            file = new File(System.getProperty("catalina.base") + "/conf",
                    aFile);
        try {
            file = file.getCanonicalFile();
        } catch (IOException e) {
            log.error(e);
        }
        return (file);
}

 public  void setRegistry(StoreRegistry registry) 
{
        this.registry = registry;
}