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Subject: Re: AW: [sdo] New HelperProvider implementation
Hi Frank,
I'm still looking for ways to have the default resolver handle OSGi
(nothing to propose yet). The pluggable resolver approach is something
I have borrowed from the EclipseLink JPA team.
Thinking about the SDOImplementation class more, I think it requires
some additional createHelperContext methods. I have attached the
updated class, the new create methods are also shown below:
/**
* 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);
-Blaise
Frank Budinsky wrote:
> Hi Blaise,
>
> I think that the added flexibility of a pluggable resolver approach sounds
> good. I also think we should also try to make the default resolver handle
> all the cases we can think of so that needing to plug in a custom resolver
> will be less likely. Is there something else that we should/could do in
> the default resolver to handle the OSGi case?
>
> Thanks,
> Frank
>
>
>
>
> Blaise Doughan <blaise.doughan@oracle.com>
> 02/06/2009 12:13 PM
>
> To
> Frank Budinsky/Toronto/IBM@IBMCA
> cc
> sdo@lists.oasis-open.org
> Subject
> Re: AW: [sdo] New HelperProvider implementation
>
>
>
>
>
>
> Hi Frank,
>
> What about making the implementation look-up more pluggable? Attached is
> a modified version of SDOImplementation that provides a plug-in mechanism
> for looking up implementations (ImplmentationResolver). By default it
> behaves exactly as what you proposed. The plugin-mechanism would allow
> the behaviour to be changed for other environments such as OSGi.
>
> -Blaise
>
> Blaise Doughan wrote:
> Hi Frank,
>
> Along with your proposed changes the following would be required to
> ExternalizableDelegator (also attached).
>
> public ExternalizableDelegator()
> {
> delegate = SDOImplementation.getInstance().resolvable();
> }
>
> public ExternalizableDelegator(Object target)
> {
> delegate = SDOImplementation.getInstance().resolvable(target);
> }
>
>
> I think in general this means that the HelperContext used for
> deserialization will become:
> SDOImplementation.getInstance().getDefaultContext();
>
> As opposed to:
> HelperProvider.getDefaultContext();
>
> -Blaise
>
>
>
> Frank Budinsky wrote:
> Hi Guys,
>
> Since we'd like to get rid of all the INSTANCE fields for SDO-96, I was
> thinking that all the static getXXXHelper() methods in HelperProvider
> should also go. Once we remove all this, I think we're not left with much
> interesting content in HelperProvider, so I think that maybe we should
> just deprecate the entire class HelperProvider, and replace it with a
> clean new API. I've attached my first pass at this, class
> SDOImplementation. I've deprecated HelperProvider, but made it a subclass
> of SDOImplementation, for backward compatibility. Comments welcome.
>
> Thanks,
> Frank.
>
>
>
>
>
>
>
> Frank Budinsky/Toronto/IBM@IBMCA
> 01/13/2009 10:51 AM
>
> To
> sdo@lists.oasis-open.org
> cc
>
> Subject
> Re: AW: [sdo] New HelperProvider implementation
>
>
>
>
>
>
> Hi Ron,
>
> Thanks for looking at it. You're right that is is a partial resolution to
> SDO-96. My thinking was that SDO-96 is one of the issues that we can
> resolve in the virtual F2F, but I wanted to get some starting material for
>
>
> discussion on the table before that. I think there are several aspects to
> the issue that we'll want to discuss in detail.
>
> One thing that I definitely had intended this class to do, but forgot, was
>
>
> to allow more that one impl/service to be located. I've attached a
> slightly modified version here.
>
>
>
> Thanks,
> Frank.
>
>
>
>
> "Barack, Ron" <ron.barack@sap.com>
> 01/13/2009 10:01 AM
>
> To
> Frank Budinsky/Toronto/IBM@IBMCA, <sdo@lists.oasis-open.org>
> cc
>
> Subject
> AW: [sdo] New HelperProvider implementation
>
>
>
>
>
>
> Hi Frank,
>
> I'm guessing that this is a partial resolution to SDO-96, is that right?
> If not, what is the issue that is being addressed here.
>
> I think holding the information in a file in meta-inf is OK, certainly an
> improvement over what we have now, but in order to handle the
> bootstrapping problem, I think we need some additional options. The
> problem with having things in a file in meta-inf is that it doesn't really
>
>
> change the situation about having only one SDO on the classpath, which the
>
>
> user always gets, no matter what.
>
> A lot of systems allow specifying the implementation class through the
> API... InitialContext is a famous example of this. Others allow
> configuration through system properties ("-D"s). I think SDO should allow
>
>
> for all 3 configuration options, with the API given highest priority,
> System properties second, the mechanism which you provide third, and the
> fallback solution should be the fixed class name constant, as you have
> given it.
>
> Best Regards,
> Ron
>
>
> -----Ursprüngliche Nachricht-----
> Von: Frank Budinsky [mailto:frankb@ca.ibm.com]
> Gesendet: Montag, 12. Januar 2009 22:57
> An: sdo@lists.oasis-open.org
> Betreff: [sdo] New HelperProvider implementation
>
> Hi Guys,
>
> Attached is a proposed new implementation for class HelperProvider. The
> advantages of this impl are:
>
> 1. It allows SDO implementations be registered as a Java Service Provider
> -
> http://java.sun.com/j2se/1.4.2/docs/guide/jar/jar.html#Service%20Provider
> 2. Implementations should not need to replace this impl, but instead
> simply plug in an subclass with necessary overrides.
> 3. I believe it's backward compatible with the previous version.
>
> Please take a look at this impl, and let me know what you think. Maybe we
> can discuss in tomorrow's call?
>
> Thanks,
> Frank.
>
>
> ---------------------------------------------------------------------
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>
>
> [attachment "HelperProvider.java" deleted by Frank Budinsky/Toronto/IBM]
> ---------------------------------------------------------------------
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>
>
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>
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> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php /**
> * <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.impl;
>
> 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;
>
> import commonj.sdo.helper.HelperContext;
> import commonj.sdo.impl.ExternalizableDelegator.Resolvable;
>
> /**
> * Central access to an implementation of SDO.
> */
> public abstract class SDOImplementation
> {
> /**
> * 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();
>
> 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 SDOImplementation getInstance() {
> return getImplementationResolver().getInstance();
> }
>
> public static SDOImplementation getInstance(String implName) {
> return getImplementationResolver().getInstance(implName);
> }
>
> protected SDOImplementation()
> {
> }
>
> protected abstract Resolvable resolvable();
>
> protected abstract Resolvable resolvable(Object target);
>
> 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.impl.SDOImplementation";
>
> /**
> * The name of the resource that is used for service location.
> */
> static final String SERVICE_RESOURCE_NAME =
> "META-INF/services/commonj.sdo.impl.SDOImplementation";
>
> SDOImplementation getInstance();
>
> SDOImplementation getInstance(String implName);
>
> }
>
> private static class DefaultImplementationResolver implements
> ImplementationResolver {
>
> /**
> * Locate and instantiate the default SDOImplementation.
> * @see getInstance(String)
> */
> public SDOImplementation getInstance()
> {
> return getInstance(null);
> }
>
> /**
> * Locate and instantiate an SDOImplementation.
> * <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.impl.SDOImplementation" 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.impl.SDOImplementation 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 SDOImplementation class
> itself.
> * <p/>
> * @param implName The name of the implementation class.
> * @return A singleton instance of the selected SDOImplementation.
> */
> public SDOImplementation getInstance(String implName)
> {
> if (implName == null) {
> implName = getImplementationName();
> }
> ClassLoader cl = getContextClassLoader();
> if (cl != null) {
> SDOImplementation impl = getInstance(cl, implName);
> if (impl != null) {
> return impl;
> }
> }
> cl = SDOImplementation.class.getClassLoader();
> SDOImplementation impl = getInstance(cl, implName);
> if (impl != null) {
> return impl;
> }
> return null;
> }
>
> /**
> * Map from implementation classes to their corresponding singleton
> instances.
> */
> protected final HashMap<Class, SDOImplementation> instanceMap = new
> HashMap<Class, SDOImplementation>();
>
> protected SDOImplementation getInstance(ClassLoader cl, String
> implName)
> {
> try {
> if (implName == null) {
> implName = getImplementationName(cl);
> if (implName == null)
> return null;
> }
> Class instanceClass = cl.loadClass(implName);
> SDOImplementation instance = instanceMap.get(instanceClass);
> if (instance == null) {
> instance =
> (SDOImplementation)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;
> }
> }
>
> }
>
> }
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe from this mail list, you must leave the OASIS TC that
> generates this mail. Follow this link to all your TCs in OASIS at:
> https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php
>
>
/**
* <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.impl;
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;
import java.util.Map;
import commonj.sdo.helper.HelperContext;
import commonj.sdo.impl.ExternalizableDelegator.Resolvable;
/**
* Central access to an implementation of SDO.
*/
public abstract class SDOImplementation
{
/**
* 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);
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 SDOImplementation getInstance() {
return getImplementationResolver().getInstance();
}
public static SDOImplementation getInstance(String implName) {
return getImplementationResolver().getInstance(implName);
}
protected SDOImplementation()
{
}
protected abstract Resolvable resolvable();
protected abstract Resolvable resolvable(Object target);
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.impl.SDOImplementation";
/**
* The name of the resource that is used for service location.
*/
static final String SERVICE_RESOURCE_NAME = "META-INF/services/commonj.sdo.impl.SDOImplementation";
SDOImplementation getInstance();
SDOImplementation getInstance(String implName);
}
private static class DefaultImplementationResolver implements ImplementationResolver {
/**
* Locate and instantiate the default SDOImplementation.
* @see getInstance(String)
*/
public SDOImplementation getInstance()
{
return getInstance(null);
}
/**
* Locate and instantiate an SDOImplementation.
* <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.impl.SDOImplementation" 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.impl.SDOImplementation 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 SDOImplementation class itself.
* <p/>
* @param implName The name of the implementation class.
* @return A singleton instance of the selected SDOImplementation.
*/
public SDOImplementation getInstance(String implName)
{
if (implName == null) {
implName = getImplementationName();
}
ClassLoader cl = getContextClassLoader();
if (cl != null) {
SDOImplementation impl = getInstance(cl, implName);
if (impl != null) {
return impl;
}
}
cl = SDOImplementation.class.getClassLoader();
SDOImplementation impl = getInstance(cl, implName);
if (impl != null) {
return impl;
}
return null;
}
/**
* Map from implementation classes to their corresponding singleton instances.
*/
protected final HashMap<Class, SDOImplementation> instanceMap = new HashMap<Class, SDOImplementation>();
protected SDOImplementation getInstance(ClassLoader cl, String implName)
{
try {
if (implName == null) {
implName = getImplementationName(cl);
if (implName == null)
return null;
}
Class instanceClass = cl.loadClass(implName);
SDOImplementation instance = instanceMap.get(instanceClass);
if (instance == null) {
instance = (SDOImplementation)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;
}
}
}
}
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