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Message-ID: <4B2B6FC6.3030708@gmail.com>
Date: Fri, 18 Dec 2009 20:04:22 +0800
From: Willem Jiang <willem.jiang@gmail.com>
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To: dev@camel.apache.org
Subject: Re: svn commit: r892199 -
 /camel/trunk/components/camel-protobuf/src/main/java/org/apache/camel/dataformat/protobuf/ProtobufDataFormat.java
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Hi Claus,

Thanks for point issue out.
I added a lock on loading the class, it should be better now ;)

Willem
Claus Ibsen wrote:
> On Fri, Dec 18, 2009 at 11:20 AM, Claus Ibsen <claus.ibsen@gmail.com> wrote:
>> Hi
>>
>> Actually the AtomicBoolean cannot safely be used for initializing code blocks?
>>
>> You can still have concurrent threads invoking the boolean and one
>> thread will see it as false and the other as true.
>> What it helps is that there are only one ever that sees it as false
>> and therefore only one thread that will initialize it.
>>
>> But in the mean time another thread could have seen it as true, but
>> its still not initialized because the first thread is currently doing
>> that.
>> e.g. there are no locks.
>>
>> You have to use the synchronized or a Lock object.
>>
>> See for example camel-jaxb and how it use the synchronized.
>>
>> Its not bad to use as synchronized is heavily optimized in JDK6.
>>
>>
>> A better idea would be to implements Service (extends ServiceSupport)
>> and do initialization in the start method.
>> I am pretty sure Camel will invoke these start/stop on data formats as
>> well. Could you try that? If not we should get that done.
>> Then all kind of initialization can be done using the Service interface.
>>
> 
> Ah yeah you need to do it at runtime sine you need access to CamelContext.
> I wonder if implementing CamelContextAware is sufficient?
> 
> 
>>
>>
>> On Fri, Dec 18, 2009 at 10:54 AM,  <ningjiang@apache.org> wrote:
>>> Author: ningjiang
>>> Date: Fri Dec 18 09:54:30 2009
>>> New Revision: 892199
>>>
>>> URL: http://svn.apache.org/viewvc?rev=892199&view=rev
>>> Log:
>>> CAMEL-2148 using the ClassResolver from the CamelContext to load class
>>>
>>> Modified:
>>>    camel/trunk/components/camel-protobuf/src/main/java/org/apache/camel/dataformat/protobuf/ProtobufDataFormat.java
>>>
>>> Modified: camel/trunk/components/camel-protobuf/src/main/java/org/apache/camel/dataformat/protobuf/ProtobufDataFormat.java
>>> URL: http://svn.apache.org/viewvc/camel/trunk/components/camel-protobuf/src/main/java/org/apache/camel/dataformat/protobuf/ProtobufDataFormat.java?rev=892199&r1=892198&r2=892199&view=diff
>>> ==============================================================================
>>> --- camel/trunk/components/camel-protobuf/src/main/java/org/apache/camel/dataformat/protobuf/ProtobufDataFormat.java (original)
>>> +++ camel/trunk/components/camel-protobuf/src/main/java/org/apache/camel/dataformat/protobuf/ProtobufDataFormat.java Fri Dec 18 09:54:30 2009
>>> @@ -20,10 +20,12 @@
>>>  import java.io.InputStream;
>>>  import java.io.OutputStream;
>>>  import java.lang.reflect.Method;
>>> +import java.util.concurrent.atomic.AtomicBoolean;
>>>
>>>  import com.google.protobuf.Message;
>>>  import com.google.protobuf.Message.Builder;
>>>
>>> +import org.apache.camel.CamelContext;
>>>  import org.apache.camel.CamelException;
>>>  import org.apache.camel.Exchange;
>>>  import org.apache.camel.InvalidPayloadException;
>>> @@ -34,6 +36,8 @@
>>>  public class ProtobufDataFormat implements DataFormat {
>>>
>>>     private Message defaultInstance;
>>> +    private String instanceClassName;
>>> +    private AtomicBoolean setDefaultInstanceHasBeenCalled = new AtomicBoolean(false);
>>>
>>>     /**
>>>      * @param defaultInstance
>>> @@ -51,11 +55,15 @@
>>>
>>>     public void setInstanceClass(String className) throws Exception {
>>>         ObjectHelper.notNull(className, "ProtobufDataFormat instaceClass");
>>> -        Class<?> instanceClass = ObjectHelper.loadClass(className);
>>> +        instanceClassName = className;
>>> +    }
>>> +
>>> +    protected Message loadDefaultInstance(String className, CamelContext context) throws CamelException, ClassNotFoundException {
>>> +        Class<?> instanceClass = context.getClassResolver().resolveMandatoryClass(className);
>>>         if (Message.class.isAssignableFrom(instanceClass)) {
>>>             try {
>>>                 Method method = instanceClass.getMethod("getDefaultInstance", new Class[0]);
>>> -                defaultInstance = (Message) method.invoke(null, new Object[0]);
>>> +                return (Message) method.invoke(null, new Object[0]);
>>>             } catch (Exception ex) {
>>>                 throw new CamelException("Can't set the defaultInstance of ProtobufferDataFormat with "
>>>                                          + className + ", caused by " + ex);
>>> @@ -64,7 +72,6 @@
>>>             throw new CamelException("Can't set the defaultInstance of ProtobufferDataFormat with "
>>>                   + className + ", as the class is not a subClass of com.google.protobuf.Message");
>>>         }
>>> -
>>>     }
>>>
>>>     /*
>>> @@ -82,8 +89,15 @@
>>>      * java.io.InputStream)
>>>      */
>>>     public Object unmarshal(Exchange exchange, InputStream inputStream) throws Exception {
>>> +
>>>         if (this.defaultInstance == null) {
>>> -            throw new CamelException("There is not defaultInstance for protobuf unmarshaling");
>>> +            if (instanceClassName == null) {
>>> +                throw new CamelException("There is not defaultInstance for protobuf unmarshaling");
>>> +            } else {
>>> +                if (!setDefaultInstanceHasBeenCalled.getAndSet(true)) {
>>> +                    defaultInstance = loadDefaultInstance(instanceClassName, exchange.getContext());
>>> +                }
>>> +            }
>>>         }
>>>         Builder builder = this.defaultInstance.newBuilderForType().mergeFrom(inputStream);
>>>         if (!builder.isInitialized()) {
>>>
>>>
>>>
>>
>>
>> --
>> Claus Ibsen
>> Apache Camel Committer
>>
>> Author of Camel in Action: http://www.manning.com/ibsen/
>> Open Source Integration: http://fusesource.com
>> Blog: http://davsclaus.blogspot.com/
>> Twitter: http://twitter.com/davsclaus
>>
> 
> 
>