Friday Mar 21, 2014

Starting with Oracle Coherence and Incubator projects

I had a chance to play with Oracle Coherence and even when everything seems to be documented, it took me a while to find all necessary informations to really get started, so I decided to share my steps. The main goal of this HOWTO will be building all samples from Coherence Incubator project, branch develop-12 (requires latest Coherence – 12.1.2).

Getting Coherence

Coherence 12.1.2 can be downloaded from [here]. I’m using stand-alone install, but I’m pretty sure that everything should be mostly the same (from Coherence point of view). Downloaded zip archive contains coherence_121200.jar, so lets execute that. Oh, and I almost forgot – I’m using Java 8:

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$ java -version
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)

And I’m on Mac OS X 10.9.2 (latest Mavericks). Installation process is pretty straightforward, you just execute java -jar ./coherence_121200.jar and use the wizard to install what you need. I choose samples to be included, but I won’t be referring to them in this post. Remember where you set your Oracle Home directory, it contains all the installed artefacts and we need to use it in next step.

Let’s assume the installation is done without any issues (I did not experienced any) and we are in Oracle_Home directory somewhere on our file system. Another thing I forgot to mention – you will need Apache Maven to be able to compile/execute projects from Incubator. I have Maven 3.1.1:

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$ mvn -v
Apache Maven 3.1.1 (0728685237757ffbf44136acec0402957f723d9a; 2013-09-17 17:22:22+0200)
Maven home: /Users/pavel/opt/apache-maven-3.1.1
Java version: 1.8.0, vendor: Oracle Corporation
Java home: /Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "mac os x", version: "10.9.2", arch: "x86_64", family: "mac"

Following information is taken from document available here:http://docs.oracle.com/middleware/1212/core/MAVEN.pdf.

Firstly, you need to install oracle-maven-sync plugin. It will install Coherence into your local maven repository. It is capable to publishing these artefacts to your company maven repository or something like that, but that won’t be covered here. Please see linked document to see more details about it if required.

The plugin gets installed by executing following command:

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mvn install:install-file -DpomFile=./oracle_common/plugins/maven/com/oracle/maven/oracle-maven-sync/12.1.2/oracle-maven-sync.12.1.2.pom -Dfile=./oracle_common/plugins/maven/com/oracle/maven/oracle-maven-sync/12.1.2/oracle-maven-sync.12.1.2.jar

I assume that this command is executed from Oracle_Home directory. You will need to adjust paths if that is not your case. Then you should see something similar to:

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[INFO] Scanning for projects...
[INFO]                                                                        
[INFO] ------------------------------------------------------------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-install-plugin:2.4:install-file (default-cli) @ standalone-pom ---
[INFO] Installing /Users/pavel/coherence/Oracle/Middleware/Oracle_Home/oracle_common/plugins/maven/com/oracle/maven/oracle-maven-sync/12.1.2/oracle-maven-sync.12.1.2.pom to /Users/pavel/.m2/repository/com/oracle/maven/oracle-maven-sync/12.1.2-0-0/oracle-maven-sync-12.1.2-0-0.jar
[INFO] Installing /Users/pavel/coherence/Oracle/Middleware/Oracle_Home/oracle_common/plugins/maven/com/oracle/maven/oracle-maven-sync/12.1.2/oracle-maven-sync.12.1.2.pom to /Users/pavel/.m2/repository/com/oracle/maven/oracle-maven-sync/12.1.2-0-0/oracle-maven-sync-12.1.2-0-0.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.349s
[INFO] Finished at: Fri Mar 21 15:26:37 CET 2014
[INFO] Final Memory: 3M/81M
[INFO] ------------------------------------------------------------------------

Now we are ready to install Coherence binaries to our local maven repository:

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Oracle_Home $ mvn -X com.oracle.maven:oracle-maven-sync:push -Doracle-maven-sync.oracleHome=.  -Doracle-maven-sync.testingOnly=false

Output is quite long, but if you see “BUILD SUCESS”, you can be sure that coherence jars are now installed in local maven repository. If there is some error, it is most likely related to incorrect directory, so try to play with “-Doracle-maven-sync.oracleHome” property and get it right.

Getting Coherence Incubator projects

This is an easy part. Coherence incubator is hosted on github – you obviously need git for that.

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git clone git@github.com:coherence-community/coherence-incubator.git

thats it. Git created directory coherence-incubator where all the projects are. Little inconvenient is that the version which we want to get is in the branch, so we need to execute:

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git checkout origin/develop-12 -b develop-12

Previous command checkouts remote branch “develop-12″ and saves it as local branch with the same name. It is not a must to create local branch, but it is easier to deal with that. Also, we will need to make some changes to get it running and you can store then in your local branch.

I’m not exactly sure why, but the project references Coherence version 12.1.2-0-1, but oracle-maven-sync plugin installs version 12.1.2-0-0, so the project can’t compile without modifications. Also, coherence-jvisualvm references binaries deployed on netbeans maven repository which is not mentioned anywhere, so we need to add it for maven to be able to download these dependencies. My complete patch is:

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diff --git a/pom.xml b/pom.xml
index 785741e..c4d951a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -137,11 +137,18 @@
<junit.version>4.10</junit.version>
<miglayout.version>3.6</miglayout.version>
<mockito.version>1.9.0</mockito.version>
-        <oracle.coherence.version>12.1.2-0-1</oracle.coherence.version>
+        <oracle.coherence.version>12.1.2-0-0</oracle.coherence.version>
<oracle.tools.version>1.2.2</oracle.tools.version>
<powermock.version>1.4.12</powermock.version>
</properties>
+    <repositories>
+        <repository>
+            <id>netbeans</id>
+        </repository>
+    </repositories>
+
<dependencyManagement>
<dependencies>
<dependency>

Now, we are finally ready for

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mvn -fae clean install

The “-fae” is here for trying to build everything possible, even when some project fails to build or test, which unfortunately happens. See my current results:

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[INFO] Coherence Incubator ............................... SUCCESS [1.284s]
[INFO] Coherence Incubator Common ........................ SUCCESS [30.717s]
[INFO] Coherence Incubator Command Pattern ............... SUCCESS [7.556s]
[INFO] Coherence Incubator Command Pattern (examples) .... SUCCESS [3.357s]
[INFO] Coherence Incubator Functor Pattern ............... SUCCESS [3.828s]
[INFO] Coherence Incubator Functor Pattern (examples) .... SUCCESS [2.577s]
[INFO] Coherence Incubator JVisualVM Plugin .............. SUCCESS [18.846s]
[INFO] Coherence Incubator Processing Pattern ............ SUCCESS [14.535s]
[INFO] Coherence Incubator Processing Pattern (examples) . SUCCESS [2.018s]
[INFO] Coherence Incubator Messaging Pattern ............. SUCCESS [8.903s]
[INFO] Coherence Incubator Messaging Pattern (functional tests)  SUCCESS [1:52.155s]
[INFO] Coherence Incubator Event Distribution Pattern .... SUCCESS [44.490s]
[INFO] Coherence Incubator Push Replication Pattern ...... SUCCESS [2.198s]
[INFO] Coherence Incubator Push Replication Pattern (functional tests)  FAILURE [6:49.643s]
[INFO] Coherence Incubator Push Replication Pattern (examples)  SUCCESS [1.645s]
[INFO] Coherence Incubator Push Replication Pattern *Web (examples)  SUCCESS [0.013s]
[INFO] Coherence Incubator Web Server .................... SUCCESS [2.058s]
[INFO] Coherence Incubator Web Application ............... SUCCESS [6.210s]
[INFO] Coherence Incubator Web Application Test .......... FAILURE [1:27.214s]
[INFO] Coherence Incubator Distribution .................. SUCCESS [13.540s]
[INFO] Coherence Incubator Site .......................... SUCCESS [0.019s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 12:53.648s
[INFO] Finished at: Fri Mar 21 16:30:09 CET 2014
[INFO] Final Memory: 58M/210M
[INFO] ------------------------------------------------------------------------

Anyway, as you can see, most of the projects can compile and are working properly. I was interested mainly in Messaging pattern, which works as expected, so I did not do any further inquiries about in Replication pattern and Web app tests.

And that’s it. If you are interested in any of these patterns or project, see sources and tests, there are usually “hello world” like samples which are perfect for learning. Also, if you happen to discover the reason for test failures I’m getting, feel free to add comment or send me a note to pavel.bucek [at] oracle.com and I’ll update the article.

Tuesday Mar 18, 2014

WebSocket API in JDK 8 - MessageHandler issue

JDK 8 is not yet released and it is already causing some headaches for JSR 356 implementors. The issue described in this article will be about the most famous and anticipated JDK 8 feature – lambda expressions and its impact to one part of WebSocket API.

Lambda expressions usable in WebSocket API can be diminished to just a replacement for standard anonymous classes; there might be some places where you can use method references, but not in the case of message handler. Following text is mainly about addMessageHandler method:

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public interface Session extends Closeable {
void addMessageHandler(MessageHandler handler) throws IllegalStateException;
}

There are multiple use cases when addMessageHandler method is used – for example, in any endpoint based on programmatic API, which is typically true on client side. Then you have code like:

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public class MyEndpoint extends Endpoint {
@Override
public void onOpen(Session session, EndpointConfig config) {
session.addMessageHandler(new MessageHandler.Whole<String>() {
@Override
public void onMessage(String message) {
// handle message
}
});
}
}

which always works as expected. JDK 8 introduces lambda expressions which can (not only!) replace too verbose anonymous classes, when they have only single method – which is true for MessageHandler.Whole interface. So when that code is opened in IDE supporting Java 8, it will usually say something like “anonymous class can be replaced with lambda expression” and recommends that action to be done. The resulting code will be:

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public class MyEndpoint extends Endpoint {
@Override
public void onOpen(javax.websocket.Session session, EndpointConfig config) {
session.addMessageHandler((MessageHandler.Whole<String>) message -> {
// handle message
});
}
}

It is nicer, part of the information is hidden, but my guess is it might not be seen as a drawback for most cases. And 3 lines of code were saved, so thumbs up! Well.. there is the last thing.. it doesn’t work.

Lambda expressions are not anonymous classes. Anonymous class can be replaced by using lambda expression and it still compiles, but the generic parameter is lost, or at least there is no way how to obtain it via standard reflection API. And that is the problem for any JSR 356 implementation – type parameter here is used for selecting appropriate Decoder (another part of the API). Any lambda expression used instead regular generic anonymous class will be treaded as MessageHandler.Whole<Object>.

What can we do with this? Surprisingly, not much. I will try to file a backwards compatibility issue/challenge agains JDK 8, but from the initial reactions on jdk8-dev mailing list, it does not seem like something anybody is willing to fix. There is one nice constructive proposal from Simone Bordet, which would at least make the variant with lambda not compilable. That would be great workaround (which will require WebSocket API 1.0.1 release and potentially changes in other APIs), but I still consider this being an issue which should be fixed in more generic way. And last but not least – I don’t think that new version of JDK should break any existing working API.

I’ll keep this post updated whenever I got additional information. Feel free to comment or suggest a solution!

EDIT:
Credit for discovering this issue should go to user ayyrk, reporter of TYRUS-302

Thursday Mar 06, 2014

Tyrus 1.5

New version of Tyrus was released today, so let’s do a quick summary of what is new compared to previous version and so on.

What’s new?

Maven archetype was (finally) added, so if you want to generate simple application, test it and maybe start playing with the code and modifying it to something more complex, you can. All you need is maven and little space on your hard drive. Then you can execute following command:

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mvn archetype:generate -DarchetypeArtifactId=tyrus-archetype-echo \
-DarchetypeGroupId=org.glassfish.tyrus.archetypes -DinteractiveMode=false \
-DgroupId=com.example -DartifactId=echo -Dpackage=com.example \
-DarchetypeVersion=1.5

and the project should be created.

What’s fixed?

  • Close reason for dropped connection is now 1006, as it should be.
  • Standalone Server is not leaking daemon threads any more.
  • Java SE 8 runtime issues.
  • “Host” header parsing issue which caused failed handshakes when using IPv6 localhost address ([::1]).
  •  Internal InputStream implementation now correctly returns ‘-1′ to InputStream#read() only when end of input is reached. Thanks Raghu for contributing the fix!

Java SE 8 related issue is worth a short explanation, since the change introduced by this fix goes beyond SE 8. Original problem was about some bug in Java SE 7 which somehow corrected Tyrus behaviour, so it was not noticed by our tests – bridge methods are not returned from Class.getMethods() call there. This was fixed in Java SE 8 and it caused some troubles in Tyrus implementation, because we just did not expect them to be returned.

The other part of this issue was correcting Tyrus in terms of handling inherited methods. JSR 356 describes how these should be handled in little bit cryptic way, but it basically states that annotations are not inherited, which is already defined in Java language specification. Unfortunately, Tyrus prior this version was considering annotated methods (@OnOpen, @OnMessage, …) only from the very same class as the registered one, so inherited methods were always ignored. This is now changed, so you can have something like:

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public class BaseEndpoint {
@OnOpen
public void onOpen(Session session) throws IOException {
// do something.
}
}
@ServerEndpoint("/echo")
public class EchoEndpoint extends BaseEndpoint {
@OnMessage
public void echo(Session session, String message) throws IOException {
// do something else.
}
}

both methods – onOpen and onMessage will be considered as part of EchoEndpoint class. Please note that annotations are still not inherited, so if you for example declare BaseEndpoint class as abstract with onOpen method annotated with @OnOpen, overriding method won’t be called by Tyrus unless you “re-add” @OnOpen annotation to new method:

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public abstract class BaseEndpoint {
public abstract void onOpen(Session session) throws IOException;
}
@ServerEndpoint("/echo")
public class EchoEndpoint extends BaseEndpoint {
@OnOpen // this has to be here!
@Override
public void onOpen(Session session) throws IOException {
// do something.
}
}

Feel free to ask here or send us a note to users@tyrus.java.net if you have any questions related to this release or anything related to our WebSocket implementation.

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Pavel Bucek-Oracle

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