NamespacePackageResolver.java

/*
 * JBoss, Home of Professional Open Source
 * 
 * Distributable under LGPL license. See terms of license at gnu.org.
 */
package org.jboss.seam.init;

import java.net.URI;

import org.jboss.seam.log.LogProvider;
import org.jboss.seam.log.Logging;

/**
 * <p>Converts an <a href="http://www.w3.org/TR/xml-names/">XML namespace</a> to a Java package name.</p>
 * 
 * @author <a href="mailto:eric DOT jung AT yahoo DOT com">Eric H. Jung</a>
 */
public class NamespacePackageResolver {
    private static final String JAVA_SCHEME = "java";
    
    @SuppressWarnings("unused")
   private static final LogProvider log = 
        Logging.getLogProvider(NamespacePackageResolver.class);
    
    
    /**
     * <p>Converts an XML namespace, <code>ns</code>, to a Stringified package name
     *
     * @param ns the xml namespace to convert
     * 
     * @returns a namespace descriptor
     */
    public String resolve(final String ns) {
        try {
            return parseURI(new URI(ns));
        } catch (Exception e) {
            // the exact exception doesn't matter here.  The caller
            // can log if needed
            return null;
        }
    }
    
    private String parseURI(URI uri) {
        if (!uri.isAbsolute()) {
            throw new IllegalArgumentException(uri + " is not an absolute URI");
        }
		
        return uri.isOpaque() ? parseOpaqueURI(uri) : parseHierarchicalURI(uri);
    }
    
    /**
     * java:package 
     * seam:component
     * seam:package:prefix
     */
    private String parseOpaqueURI(URI uri) {
        if (uri.getScheme().equalsIgnoreCase(JAVA_SCHEME)) {
            return uri.getSchemeSpecificPart();
        }
        throw new IllegalArgumentException("Unrecognized scheme in " + uri);
    }
    
    private String parseHierarchicalURI(URI uri) {
        String scheme = uri.getScheme().toLowerCase();
        if (!scheme.equals("http") && !scheme.equals("https")) {
            throw new IllegalArgumentException("Hierarchical URLs must use http or https scheme " + uri);
        }
	
        StringBuffer buf = new StringBuffer();
	
        appendToPackageName(buf, hostnameToPackage(uri.getHost()));
        appendToPackageName(buf, pathToPackage(uri.getPath()));
	
        return buf.toString();
    }
    
    /**
     * Convert path elements to package names in forward order
     */
    private String pathToPackage(String path) {
        StringBuffer buf = new StringBuffer();
	
        if (path != null) {
            String[] pathElements = path.split("/");
            for (int i = 1, len = pathElements.length; i < len; i++) {
                appendToPackageName(buf, pathElements[i]);
            }
        }
	
        return buf.toString();
    }
	
    private String hostnameToPackage(String hostname) {
        StringBuffer result = new StringBuffer(); 
	
        String[] subdomains = hostname.split("\\.");
        
        //Iterate through the subdomains in reverse converting each to a package name. 
        for (int i = subdomains.length - 1; i >= 0; i--) {
            String subdomain = subdomains[i];
            if (i > 0 || !subdomain.equalsIgnoreCase("www")) {
                appendToPackageName(result, subdomain);
            }
        }
        
        return result.toString();
    }	
    
    private void appendToPackageName(StringBuffer buf, String subdomain) {
        if (subdomain.length()>0) {
            subdomain = makeSafeForJava(subdomain);
            
            if (buf.length() > 0) {
                buf.append('.');
            }
            
            buf.append(subdomain);
        }
    }
    
    /**
     * Converts characters in <code>subdomain</code> which aren't java-friendly
     * into java-friendly equivalents. Right now, we only support the conversion
     * of hyphens ("-") to underscores ("_"). We could do other things like toLowerCase(),
     * but there are instances of upper-case package names in widespread use even by the
     * likes of IBM (e.g., <a href="http://publib.boulder.ibm.com/infocenter/db2luw/v8/index.jsp?topic=/com.ibm.db2.udb.dc.doc/dc/r_jdbcdrivers.htm">
     * COM.ibm.db2 classnames</a>).
     * 
     * @param subdomain
     * @return
     */
    private String makeSafeForJava(String subdomain) {
        return subdomain.replace("-", "_");
    }
}