On Fri, Dec 18, 2009 at 3:31 PM, William Tam <email.w...@gmail.com> wrote: > > > Claus Ibsen wrote: >> >> Hi >> >> Actually the AtomicBoolean cannot safely be used for initializing code >> blocks? >> > > I thought object construction and member initialization were atomic and > threadsafe but I am not an expert on that. >>
There are only a dozens expert on this matter, and all here are not experts. However Brian Goetz is such an expert and his book - Java concurrency in practice is a really good book. AtomicBoolean is just a volatile boolean that I guess is a bit optimized and it got that compareAndSet method that is guaranteed to happen atomic among threads. Anyway we had such a case with the camel-cxf component some months ago that had this bug, and causes a NPE under heavy load on startup. We fixed it by moving the initalization to the service doStart method. >> 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. >> >> >> >> >> On Fri, Dec 18, 2009 at 10:54 AM, <ningji...@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
