public static XMLReader createXMLReader()

in jaxp-api-1.3/src/main/java/org/xml/sax/helpers/XMLReaderFactory.java [110:220]
61 lines of code
15 McCabe index (conditional complexity)

    public static XMLReader createXMLReader ()
    throws SAXException
    {
        String		className = null;
        ClassLoader	loader = NewInstance.getClassLoader ();
        
        // 1. try the JVM-instance-wide system property
        try { className = SecuritySupport.getSystemProperty (property); }
        catch (Exception e) { /* normally fails for applets */ }
        
        // 2. if that fails, try META-INF/services/
        if (className == null || className.length() == 0) {
            String      service = "META-INF/services/" + property;
            
	        try {
	            // If we are deployed into an OSGi environment, leverage it
	            Class<? extends XMLReader> spiClass = org.apache.servicemix.specs.locator.OsgiLocator.locate(XMLReader.class, property);
	            if (spiClass != null) {
	                return spiClass.newInstance();
	            }
	        } catch (Throwable e) {
	        }

            InputStream is = null;
            className = null;
            
            // First try the Context ClassLoader
            ClassLoader cl = SecuritySupport.getContextClassLoader();
            if (cl != null) {
                is = SecuritySupport.getResourceAsStream(cl, service);
                
                // If no provider found then try the current ClassLoader
                if (is == null) {
                    cl = XMLReaderFactory.class.getClassLoader();
                    is = SecuritySupport.getResourceAsStream(cl, service);
                }
            } else {
                // No Context ClassLoader or JDK 1.1 so try the current
                // ClassLoader
                cl = XMLReaderFactory.class.getClassLoader();
                is = SecuritySupport.getResourceAsStream(cl, service);
            }
            
            if (is != null) {
                
                // Read the service provider name in UTF-8 as specified in
                // the jar spec.  Unfortunately this fails in Microsoft
                // VJ++, which does not implement the UTF-8
                // encoding. Theoretically, we should simply let it fail in
                // that case, since the JVM is obviously broken if it
                // doesn't support such a basic standard.  But since there
                // are still some users attempting to use VJ++ for
                // development, we have dropped in a fallback which makes a
                // second attempt using the platform's default encoding. In
                // VJ++ this is apparently ASCII, which is a subset of
                // UTF-8... and since the strings we'll be reading here are
                // also primarily limited to the 7-bit ASCII range (at
                // least, in English versions), this should work well
                // enough to keep us on the air until we're ready to
                // officially decommit from VJ++. [Edited comment from
                // jkesselm]
                BufferedReader rd;
                try {
                    rd = new BufferedReader(new InputStreamReader(is, "UTF-8"), DEFAULT_LINE_LENGTH);
                } catch (java.io.UnsupportedEncodingException e) {
                    rd = new BufferedReader(new InputStreamReader(is), DEFAULT_LINE_LENGTH);
                }
                
                try {
                    // XXX Does not handle all possible input as specified by the
                    // Jar Service Provider specification
                    className = rd.readLine();
                } 
                catch (Exception x) {
                    // No provider found
                } 
                finally {
                    try { 
                        // try to close the reader. 
                        rd.close(); 
                    } 
                    // Ignore the exception. 
                    catch (IOException exc) {}
                }
            }
        }
        
        // 3. Distro-specific fallback
        if (className == null) {
            // BEGIN DISTRIBUTION-SPECIFIC
            
            // EXAMPLE:
            // className = "com.example.sax.XmlReader";
            // or a $JAVA_HOME/jre/lib/*properties setting...
            className = "org.apache.xerces.parsers.SAXParser";
            
            // END DISTRIBUTION-SPECIFIC
        }
        
        // do we know the XMLReader implementation class yet?
        if (className != null)
            return loadClass (loader, className);
        
        // 4. panic -- adapt any SAX1 parser
        try {
            return new ParserAdapter (ParserFactory.makeParser ());
        } catch (Exception e) {
            throw new SAXException ("Can't create default XMLReader; "
                    + "is system property org.xml.sax.driver set?");
        }
    }