The services that this bundle activator enables a bundle to provide are: *
The algorithm to find the implementations of the abstract parsers * is derived from the JAR file specifications, specifically the Services API. *
An XMLParserActivator assumes that it can find the class file names of the factory classes * in the following files: *
If either of the files does not exist, XMLParserActivator assumes that the parser does not * support that parser type. * *
XMLParserActivator attempts to instantiate both the SAXParserFactory and the * DocumentBuilderFactory. It registers each factory with the framework along with service * properties: *
Individual parser implementations may have additional features, properties, or attributes * which could be used to select a parser with a filter. These can be added by extending this class and overriding the * setSAXProperties and setDOMProperties methods. */ public class XMLParserActivator implements BundleActivator, ServiceFactory { /** Context of this bundle */ private BundleContext context; /** Filename containing the SAX Parser Factory Class name. Also used as the basis for the SERVICE_PID registration property. */ public static final String SAXFACTORYNAME = "javax.xml.parsers.SAXParserFactory"; /** Filename containing the DOM Parser Factory Class name. Also used as the basis for the SERVICE_PID registration property. */ public static final String DOMFACTORYNAME = "javax.xml.parsers.DocumentBuilderFactory"; /** Path to the factory class name files */ private static final String PARSERCLASSFILEPATH = "/META-INF/services/"; /** Fully qualified path name of SAX Parser Factory Class Name file */ public static final String SAXCLASSFILE = PARSERCLASSFILEPATH + SAXFACTORYNAME; /** Fully qualified path name of DOM Parser Factory Class Name file */ public static final String DOMCLASSFILE = PARSERCLASSFILEPATH + DOMFACTORYNAME; /** SAX Factory Service Description */ private static final String SAXFACTORYDESCRIPTION = "A JAXP Compliant SAX Parser"; /** DOM Factory Service Description */ private static final String DOMFACTORYDESCRIPTION = "A JAXP Compliant DOM Parser"; /** Service property specifying if factory is configured to support validating parsers. * The value is of type Boolean. */ public static final String PARSER_VALIDATING = "parser.validating"; /** Service property specifying if factory is configured to support namespace aware parsers. * The value is of type Boolean. */ public static final String PARSER_NAMESPACEAWARE = "parser.namespaceAware"; /** Key for parser factory name property - this must be saved in the parsers properties hashtable * so that the parser factory can be instantiated from a ServiceReference */ private static final String FACTORYNAMEKEY = "parser.factoryname"; /** * Called when this bundle is started so the Framework can perform the bundle-specific * activities necessary to start this bundle. This method can be used to register services or to * allocate any resources that this bundle needs. * *
This method must complete and return to its caller in a timely manner. * *
This method attempts to register a SAX and DOM parser with the Framework's service registry. * * @param context The execution context of the bundle being started. * @exception java.lang.Exception If this method throws an exception, this bundle is marked * as stopped and the Framework will remove this bundle's listeners, unregister all services * registered by this bundle, and release all services used by this bundle. * @see Bundle#start */ public void start(BundleContext context) throws Exception { this.context = context; Bundle parserBundle = context.getBundle(); try { // check for sax parsers registerSAXParsers(getParserFactoryClassNames(parserBundle.getResource(SAXCLASSFILE))); // check for dom parsers registerDOMParsers(getParserFactoryClassNames(parserBundle.getResource(DOMCLASSFILE))); } catch (IOException ioe) { // if there were any IO errors accessing the resource files containing the class names ioe.printStackTrace(); throw new FactoryConfigurationError(ioe); } } /** *
This method has nothing to do as all open service registrations will * automatically get unregistered when the bundle stops. * * @param context The execution context of the bundle being stopped. * @exception java.lang.Exception If this method throws an exception, * the bundle is still marked as stopped, and the Framework will * remove the bundle's listeners, unregister all services * registered by the bundle, and release all services * used by the bundle. * @see Bundle#stop */ public void stop(BundleContext context) throws Exception { } /** * Given the URL for a file, reads and returns the parser class names. There may be * multiple classes specified in this file, one per line. There may also be * comment lines in the file, which begin with "#". * * @param parserUrl The URL of the service file containing the parser * class names * @return A vector of strings containing the parser class names or null if parserUrl * is null * @throws IOException if there is a problem reading the URL input stream */ private Vector getParserFactoryClassNames(URL parserUrl) throws IOException { Vector v = new Vector(1); if (parserUrl!=null) { String parserFactoryClassName = null; InputStream is = parserUrl.openStream(); BufferedReader br = new BufferedReader(new InputStreamReader(is)); while (true) { parserFactoryClassName = br.readLine(); if (parserFactoryClassName==null) { break; // end of file reached } String pfcName = parserFactoryClassName.trim(); if (pfcName.length()==0) { continue; // blank line } int commentIdx = pfcName.indexOf("#"); if (commentIdx == 0) { // comment line continue; } else if (commentIdx<0) { // no comment on this line v.addElement(pfcName); } else { v.addElement(pfcName.substring(0, commentIdx).trim()); } } return v; } else { return null; } } /** * Register SAX Parser Factory Services with the framework. * * @param parserFactoryClassNames - a Vector of String objects containing the names of the parser Factory Classes * @throws FactoryConfigurationError if thrown from getFactory */ private void registerSAXParsers(Vector parserFactoryClassNames) throws FactoryConfigurationError { if (parserFactoryClassNames!=null) { Enumeration e = parserFactoryClassNames.elements(); int index = 0; while (e.hasMoreElements()) { String parserFactoryClassName = (String)e.nextElement(); // create a sax parser factory just to get it's default properties. It will never be used since // this class will operate as a service factory and give each service requestor it's own SaxParserFactory SAXParserFactory factory = (SAXParserFactory)getFactory(parserFactoryClassName); Hashtable properties = new Hashtable(7); // figure out the default properties of the parser setDefaultSAXProperties(factory, properties, index); // store the parser factory class name in the properties so that it can be retrieved when getService is called // to return a parser factory properties.put(FACTORYNAMEKEY, parserFactoryClassName); // release the factory factory = null; // register the factory as a service context.registerService(SAXFACTORYNAME, this, properties); index++; } } } /** *
Set the SAX Parser Service Properties. By default, the following properties * are set: *
Set the customizable SAX Parser Service Properties. * *
This method attempts to instantiate a validating parser and a namespaceaware * parser to determine if the parser can support those features. The appropriate properties are then set * in the specified properties object. * *
This method can be overridden to add additional SAX2 features and properties. If you want to be able * to filter searches of the OSGi service registry, this method must put a key, value pair into the properties object * for each feature or property. For example, * * properties.put("http://www.acme.com/features/foo", Boolean.TRUE); * * @param factory - the SAXParserFactory object * @param properties - the properties object for the service */ public void setSAXProperties(SAXParserFactory factory, Hashtable properties) { SAXParser parser = null; // check if this parser can be configured to validate boolean validating = true; factory.setValidating(true); factory.setNamespaceAware(false); try { parser = factory.newSAXParser(); } catch (Exception pce_val) { validating = false; } // check if this parser can be configured to be namespaceaware boolean namespaceaware = true; factory.setValidating(false); factory.setNamespaceAware(true); try { parser = factory.newSAXParser(); } catch (Exception pce_nsa) { namespaceaware = false; } // set the factory values factory.setValidating(validating); factory.setNamespaceAware(namespaceaware); // set the OSGi service properties properties.put(PARSER_NAMESPACEAWARE, new Boolean(namespaceaware)); properties.put(PARSER_VALIDATING, new Boolean(validating)); } /** * Register DOM Parser Factory Services with the framework. * * @param parserFactoryClassNames - a Vector of String objects containing the names of the parser Factory Classes * @throws FactoryConfigurationError if thrown from getFactory */ private void registerDOMParsers(Vector parserFactoryClassNames) throws FactoryConfigurationError { if (parserFactoryClassNames!=null) { Enumeration e = parserFactoryClassNames.elements(); int index = 0; while (e.hasMoreElements()) { String parserFactoryClassName = (String)e.nextElement(); // create a dom parser factory just to get it's default properties. It will never be used since // this class will operate as a service factory and give each service requestor it's own DocumentBuilderFactory DocumentBuilderFactory factory = (DocumentBuilderFactory)getFactory(parserFactoryClassName); Hashtable properties = new Hashtable(7); // figure out the default properties of the parser setDefaultDOMProperties(factory, properties, index); // store the parser factory class name in the properties so that it can be retrieved when getService is called // to return a parser factory properties.put(FACTORYNAMEKEY, parserFactoryClassName); // release the factory factory = null; // register the factory as a service context.registerService(DOMFACTORYNAME, this, properties); index++; } } } /** * Set the DOM parser service properties. * * By default, the following properties are set: *
Set the customizable DOM Parser Service Properties. * *
This method attempts to instantiate a validating parser and a namespaceaware * parser to determine if the parser can support those features. The appropriate properties are then set * in the specified props object. * *
This method can be overridden to add additional DOM2 features and properties. If you want to be able * to filter searches of the OSGi service registry, this method must put a key, value pair into the properties object * for each feature or property. For example, * * properties.put("http://www.acme.com/features/foo", Boolean.TRUE); * * @param factory - the DocumentBuilderFactory object * @param props - Hashtable of service properties. */ public void setDOMProperties(DocumentBuilderFactory factory, Hashtable props) { DocumentBuilder parser = null; // check if this parser can be configured to validate boolean validating = true; factory.setValidating(true); factory.setNamespaceAware(false); try { parser = factory.newDocumentBuilder(); } catch (Exception pce_val) { validating = false; } // check if this parser can be configured to be namespaceaware boolean namespaceaware = true; factory.setValidating(false); factory.setNamespaceAware(true); try { parser = factory.newDocumentBuilder(); } catch (Exception pce_nsa) { namespaceaware = false; } // set the factory values factory.setValidating(validating); factory.setNamespaceAware(namespaceaware); // set the OSGi service properties props.put(PARSER_VALIDATING, new Boolean(validating)); props.put(PARSER_NAMESPACEAWARE, new Boolean(namespaceaware)); } /** * Given a parser factory class name, instantiate that class. * * @param parserFactoryClassName A String object containing the name of the parser factory class * @return a parserFactoryClass Object * @pre parserFactoryClassName!=null */ private Object getFactory(String parserFactoryClassName) throws FactoryConfigurationError { Exception e = null; try { return Class.forName(parserFactoryClassName).newInstance(); } catch (ClassNotFoundException cnfe) { e = cnfe; } catch (InstantiationException ie) { e = ie; } catch (IllegalAccessException iae) { e = iae; } throw new FactoryConfigurationError(e); } /** * Creates a new XML Parser Factory object. * *
A unique XML Parser Factory object is returned for each call to this method. * *
The returned XML Parser Factory object will be configured for validating * and namespace aware support as specified in the service properties of the * specified ServiceRegistration object. * * This method can be overridden to configure additional features in the returned * XML Parser Factory object. * * @param bundle The bundle using the service. * @param registration The ServiceRegistration object for the service. * @return A new, configured XML Parser Factory object or null if a configuration * error was encountered */ public Object getService(Bundle bundle, ServiceRegistration registration) { ServiceReference sref = registration.getReference(); String parserFactoryClassName = (String) sref.getProperty(FACTORYNAMEKEY); try { // need to set factory properties Object factory = getFactory(parserFactoryClassName); if (factory instanceof SAXParserFactory) { ((SAXParserFactory)factory).setValidating(((Boolean)sref.getProperty(PARSER_VALIDATING)).booleanValue()); ((SAXParserFactory)factory).setNamespaceAware(((Boolean)sref.getProperty(PARSER_NAMESPACEAWARE)).booleanValue()); } else if (factory instanceof DocumentBuilderFactory) { ((DocumentBuilderFactory)factory).setValidating(((Boolean)sref.getProperty(PARSER_VALIDATING)).booleanValue()); ((DocumentBuilderFactory)factory).setNamespaceAware(((Boolean)sref.getProperty(PARSER_NAMESPACEAWARE)).booleanValue()); } return factory; } catch (FactoryConfigurationError fce) { fce.printStackTrace(); return null; } } /** * Releases a XML Parser Factory object. * * @param bundle The bundle releasing the service. * @param registration The ServiceRegistration object for the service. * @param service The XML Parser Factory object returned by a previous call to the getService method. */ public void ungetService(Bundle bundle, ServiceRegistration registration, Object service) { } }