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Subject: Re: AW: [sdo] New HelperProvider implementation
Hi Frank, Attached is a variant of SDOImplementation. I have taken this class and split it into two classes: SDO and HelperContextFactory (in commonj.sdo.helper). SDO implementors would be responsible for providing a subclass of HelperContextFactory. To create a HelperContext, a user would need to do the following: HelperContext hc = SDO.getHelperContextFactory(String).createHelperContext(); This has a similar feel to JPA where users do the following: EntityManager em = Persistence.createEntityManagerFactory(String).createEntityManager(); -Blaise Blaise Doughan wrote: 49918D50.4090503@oracle.com" type="cite">Hi Frank, |
/** * <copyright> * * Service Data Objects * Version 3.0 * Licensed Materials * * (c) Copyright BEA Systems, Inc., International Business Machines Corporation, * Oracle Corporation, Primeton Technologies Ltd., Rogue Wave Software, SAP AG., * Software AG., Sun Microsystems, Sybase Inc., Xcalia, Zend Technologies, * 2005-2008. All rights reserved. * * </copyright> * */ package commonj.sdo.helper; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.security.AccessController; import java.security.PrivilegedAction; import java.util.HashMap; public class SDO { private static ImplementationResolver implementationResolver; public static ImplementationResolver getImplementationResolver() { if (null == implementationResolver) { implementationResolver = new DefaultImplementationResolver(); } return implementationResolver; } public static void setImplementationResolver(ImplementationResolver anImplementationResolver) { implementationResolver = anImplementationResolver; } public static HelperContextFactory getHelperContextFactory() { return getImplementationResolver().getHelperContextFactory(); } public static HelperContextFactory getHelperContextFactor(String implName) { return getImplementationResolver().getHelperContextFactory(implName); } public static interface ImplementationResolver { /** * The name of the system property that will be checked for an implementation name. */ static final String PROPERTY_NAME = "commonj.sdo.helper.HelperContextFactory"; /** * The name of the resource that is used for service location. */ static final String SERVICE_RESOURCE_NAME = "META-INF/services/" + PROPERTY_NAME; HelperContextFactory getHelperContextFactory(); HelperContextFactory getHelperContextFactory(String implName); } private static class DefaultImplementationResolver implements ImplementationResolver { /** * Locate and instantiate the default HelperContextFactory. * * @see getInstance(String) */ public HelperContextFactory getHelperContextFactory() { return getHelperContextFactory(null); } /** * Locate and instantiate a HelperContextFactory. <p/> If the specified * implName is not null, attempt to instantiate an implementation class * with that name. If implName is null, then the name of the * implementation to use is determined by the value of the * "commonj.sdo.helper.HelperContextFactory" system property. If this is not * set or this code does not have permission to read it then the name * will be retrieved from the * META-INF/services/commonj.sdo.helper.HelperContextFactory resource. <p/> * Name lookup and class loading is done using first the Thread's * current context classloader and then, if that is not set, not * readable, or does not provide an implementation, using the * classloader used to load the HelperContextFactory class itself. <p/> * * @param implName * The name of the implementation class. * @return A singleton instance of the selected HelperContextFactory. */ public HelperContextFactory getHelperContextFactory(String implName) { if (implName == null) { implName = getImplementationName(); } ClassLoader cl = getContextClassLoader(); if (cl != null) { HelperContextFactory impl = getHelperContextFactory(cl, implName); if (impl != null) { return impl; } } cl = HelperContextFactory.class.getClassLoader(); HelperContextFactory impl = getHelperContextFactory(cl, implName); if (impl != null) { return impl; } return null; } /** * Map from implementation classes to their corresponding singleton instances. */ protected final HashMap<Class, HelperContextFactory> instanceMap = new HashMap<Class, HelperContextFactory>(); protected HelperContextFactory getHelperContextFactory(ClassLoader cl, String implName) { try { if (implName == null) { implName = getImplementationName(cl); if (implName == null) return null; } Class instanceClass = cl.loadClass(implName); HelperContextFactory instance = instanceMap.get(instanceClass); if (instance == null) { instance = (HelperContextFactory) instanceClass.newInstance(); instanceMap.put(instanceClass, instance); } return instance; } catch (Exception e) { return null; } } protected String getImplementationName(ClassLoader cl) throws IOException { InputStream is = cl.getResourceAsStream(SERVICE_RESOURCE_NAME); if (is == null) return null; InputStreamReader in = new InputStreamReader(is, "UTF-8"); BufferedReader reader = new BufferedReader(in, 128); try { String line; while ((line = reader.readLine()) != null) { int i = line.indexOf('#'); if (i != -1) { line = line.substring(0, i); } line = line.trim(); if (line.length() > 0) return line; } return null; } finally { reader.close(); } } protected String getImplementationName() { try { return (String)AccessController.doPrivileged(new PrivilegedAction() { public Object run() { return System.getProperty(PROPERTY_NAME); } }); } catch (SecurityException e) { return null; } } protected ClassLoader getContextClassLoader() { try { return (ClassLoader)AccessController.doPrivileged(new PrivilegedAction() { public Object run() { return Thread.currentThread().getContextClassLoader(); } }); } catch (SecurityException e) { return null; } } } }
/** * <copyright> * * Service Data Objects * Version 3.0 * Licensed Materials * * (c) Copyright BEA Systems, Inc., International Business Machines Corporation, * Oracle Corporation, Primeton Technologies Ltd., Rogue Wave Software, SAP AG., * Software AG., Sun Microsystems, Sybase Inc., Xcalia, Zend Technologies, * 2005-2008. All rights reserved. * * </copyright> * */ package commonj.sdo.helper; import java.util.Map; import commonj.sdo.helper.HelperContext; import commonj.sdo.impl.ExternalizableDelegator.Resolvable; public abstract class HelperContextFactory { public HelperContextFactory() { } /** * Gets the implementation's default HelperContext. * @return a HelperContext object */ public abstract HelperContext getDefaultHelperContext(); /** * Create a new HelperContext in this implementation. * @return a HelperContext object */ public abstract HelperContext createHelperContext(); /** * Create a new HelperContext in this implementation. * @param properties - Properties required to initialize the HelperContext. * @return a HelperContext object */ public abstract HelperContext createHelperContext(Map properties); /** * Create a new HelperContext in this implementation. * @param classLoader - The class loader for the generated static classes (if any). * @return a HelperContext object */ public abstract HelperContext createHelperContext(ClassLoader classLoader); /** * Create a new HelperContext in this implementation. * @param classLoader - The class loader for the generated static classes (if any). * @param properties - Properties required to initialize the HelperContext. * @return a HelperContext object */ public abstract HelperContext createHelperContext(ClassLoader classLoader, Map properties); protected abstract Resolvable resolvable(); protected abstract Resolvable resolvable(Object target); }
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