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Maven + Apache Felix + CXF + DOSGi: An Example of DOSGi Service

Maksim Sorokin — Sun, 18 Sep 2011 22:04:29 +0000

Link in series

Link to two Felix instances

Here is yet another post in Maven + Apache Felix + CXF + DOSGi series.

Here I will show how to use Apache CXF DOSGi for cosuming remote services. You may see the sources on my GitHub account.

We will have three projects dosgiRemote.service, dosgiRemote.service.api and dosgiRemote.consumer. dosgiRemote.service.api provides an interface for a service. dosgiRemote.service provides implementation for the service. dosgiRemote.consume will consume the service.
dosgiRemote.service.api has to be shared between dosgiRemote.service and dosgiRemote.consumer as both has to know which service they are publishing and consuming. dosgiRemote.service.api and dosgiRemote.service will run in one OSGi container. dosgiRemote.service.api and dosgiRemote.consumer will run in another OSGi container. You may see how to do that in Eclipse in the previous post.

dosgiRemote.service.api contains the following interface to a service:

package dk.sorokin.maksim.dosgiRemote.service.api;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("greeter")
public interface Greeter {

  @GET
  @Path("sayHello/{name}")
  @Produces(MediaType.TEXT_PLAIN)
  String sayHello(@PathParam("name") String name);
}

dosgiRemote.service provides the following implementation:

package dk.sorokin.maksim.dosgiRemote.internal.service;

import dk.sorokin.maksim.dosgiRemote.service.api.Greeter;

public class GreeterImpl implements Greeter {

  public String sayHello(String name) {
    return "Hello, " + name;
  }
}

Also, dosgiRemote.service registers a service in the following way:

package dk.sorokin.maksim.dosgiRemote.internal;

import java.util.Dictionary;
import java.util.Hashtable;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

import dk.sorokin.maksim.dosgiRemote.internal.service.GreeterImpl;
import dk.sorokin.maksim.dosgiRemote.service.api.Greeter;

public class Activator implements BundleActivator {

  public void start(BundleContext context) throws Exception {
    Dictionary restProps = new Hashtable();

    restProps.put("service.exported.interfaces", "*");
    restProps.put("service.exported.configs", "org.apache.cxf.rs");
    restProps.put("service.exported.intents", "HTTP");
    restProps.put("org.apache.cxf.rs.address", "http://localhost:8080/");
    context.registerService(Greeter.class.getName(), new GreeterImpl(), restProps);
  }

  public void stop(BundleContext context) throws Exception {
    //
  }
}

dosgiRemote.consumer will have OSGI-INF\remote-service\remote-services.xml, according to DOSGi documentation:



  
    
    *
    org.apache.cxf.rs
    HTTP
    http://localhost:8080

And the Activator class for dosgiRemote.consumer will be:

package dk.sorokin.maksim.dosgiRemote.consumer.internal;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;

import dk.sorokin.maksim.dosgiRemote.service.api.Greeter;

public class Activator implements BundleActivator {

  @Override
  public void start(BundleContext context) throws Exception {
    ServiceTracker serviceTracker = new ServiceTracker(context, Greeter.class.getName(), null) {
      @Override
      public Object addingService(ServiceReference reference) {
        Object result = super.addingService(reference);

        Object svc = context.getService(reference);
        if (svc instanceof Greeter) {
          final Greeter greeter = (Greeter) svc;
          System.out.println(greeter.sayHello("Max"));
        }

        return result;
      }
    };
    serviceTracker.open();
  }

  public void stop(BundleContext context) throws Exception {
    //
  }
}

We will have two startup configuration for Apache Felix, as described above. The first one:

felix.auto.deploy.action=install,start
felix.log.level=1

org.osgi.framework.storage.clean=onFirstInit

felix.auto.start.1 = \
 assembly:/C:/projects/dosgiRemote/dosgiRemote.service.api/target/classes \
 assembly:/C:/projects/dosgiRemote/dosgiRemote.service/target/classes

And the second one:

felix.auto.deploy.action=install,start
felix.log.level=1

org.osgi.framework.storage.clean=onFirstInit

felix.auto.start.1 = \
 assembly:/C:/projects/dosgiRemote/dosgiRemote.service.api/target/classes \
 assembly:/C:/projects/dosgiRemote/dosgiRemote.service/target/classes

Launch the first configuration and then the second. You should see the following message in the console:

Hello, Max

You could also see the same message in the browser on http://localhost:8080/greeter/sayHello/Max.

You may pass objects as well. Refer to previous posts to do that.

You can take the sources from may GitHub account.

Mule ESB: Building a Self-Contained Standalone Web App with Maven

Maksim Sorokin — Fri, 29 Jul 2011 10:44:19 +0000

This example demonstrates how to build standalone self-contained Mule ESB web application, which can be deployed to a Java web container, e.g. Tomcat. The sources used are taken from Mule ESB "hello" example, which is distributed together with Mule.

You can obtain the sources from this post on my github:
https://github.com/mah01/examples/tree/master/muleHelloStandalone

I will just show the keypoints of the application and changes, that were different from "hello" application in Mule distributable.

First of all, the pom.xml file. We download all required Mule dependencies in order to run the example. Note, that we use Mule Maven repository, because for some reason Mule artifacts has transitive dependencies on OSGified versions of certain libraries, which are not contained in Maven Central:


  4.0.0

  dk.sorokin.maksim
  muleHelloStandalone
  1.0.0-SNAPSHOT
  war

  Self-Contained Standalone Mule Hello World
  The sources for this application were copied from Mule distributable

  
    3.1.2
  

  
    
      
        src/main/app
      
      
        src/main/resources
      
    
  

  
    
      org.codehaus.groovy
      groovy-all
      1.8.1
    

    
      org.mule
      mule-core
      ${mule.version}
    

    
      org.mule
      mule-core
      ${mule.version}
      test
      test-jar
    

    
      org.mule.modules
      mule-module-builders
      ${mule.version}
    

    
      org.mule.modules
      mule-module-scripting
      ${mule.version}
    

    
      org.mule.transports
      mule-transport-vm
      ${mule.version}
    

    
      org.mule.transports
      mule-transport-servlet
      ${mule.version}
    

    
      org.mule.transports
      mule-transport-stdio
      ${mule.version}
    
  

  
    
      mule-deps
      Mule Dependencies
      http://dist.codehaus.org/mule/dependencies/maven2

And then we also add log4j.properties to src/main/java:

log4j.rootLogger=INFO, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %-5p %x - %m\n

And our web.xml looks like:



  mule.esb

  
    org.mule.config
    mule-config.xml
  

  
    org.mule.config.builders.MuleXmlBuilderContextListener

All other sources are copied directly from Mule "hello" example (the whole src folder).

Build the application with maven with mvn clean install and deploy the war to Tomcat (or other container).
Then go to http://localhost:8888/?name=Max. You should see the following message:

Hello Max, how are you?

IzPack with Maven

Maksim Sorokin — Thu, 10 Jun 2010 07:19:58 +0000

What does Maven? Maven builds a project. What does IzPack? IzPack builds an installer. Naturally, one would like to use Maven to control IzPack. Here is an example of a simple application which uses Maven and IzPack to create an installer for an application.

We start by creating a pom.xml:


  4.0.0

  test
  test18
  Test IzPack and maven
  0.0.1-SNAPSHOT
  pom

  
    ${project.build.directory}\staging
    4.3.2
  

  
    
      
      
        org.codehaus.izpack
        izpack-maven-plugin
        1.0-alpha-5
        
          
            package
            
              izpack
            
            
              ${staging.dir}
            
          
        
        
          
            org.codehaus.izpack
            izpack-standalone-compiler
            ${izpack.standalone.compiler.version}
          
        
      

      
        maven-resources-plugin
        2.4.2
        
          
            copy-resources
            validate
            
              copy-resources
            
            
              UTF-8
              ${staging.dir}
              
                
                  src/main/resources

Provided Maven packaging is pom since we don't want to produce any application jars. IzPack will create a executable jar file by itself.
And we are using two plugings. One is Maven IzPack plugin. And another one is used to copy installation files to the "staging" directory. Staging directory it is where all needed resources are copied. Executable jar will be created from it afterwards.

And then in the src/main/resources we create a install.xml configuration file which configures our installation:





  
    Test Installer
    1
    
    1.6

    
  

  
    
      
      
    
  

  
    
  

  
    
    
  

  
    
      Test Installation

All the detailed about this install.xml configuration file can be found on IzPack documentation page.

And now we are ready to go. Run mvn install and in target folder you will find an installer! It will consist of two panels -- Hello Panel and Finish Panel. Nothing fancy. But you have to start somewhere!

Multirow and Multicolumn Spanning in Latex

Maksim Sorokin — Sat, 22 May 2010 08:55:33 +0000

Miltirow and multicolumn table spanning now with colors!

or more complex example:

And here how we do that for simple variant:

\documentclass[12pt]{article}
\usepackage{multirow}
\usepackage{colortbl}
\definecolor{kugray5}{RGB}{224,224,224}

\begin{document}

\begin{figure}
  \centering
  \begin{tabular}{|c|c|c|c|c|c|c|c|c|}
    \hline
    \multicolumn{1}{|>{\columncolor{kugray5}}c|}{}&\multicolumn{4}{c|}{Rank}&\multirow{2}{*}{Total}\\
    \arrayrulecolor{kugray5}
    \arrayrulecolor{black}
    \cline{2-5}
    \multicolumn{1}{|>{\columncolor{kugray5}}c|}{}&A&B&C&Other&\\
    \hline
    type 2&8&14&5&2&29\\
    \hline
  \end{tabular}
  \caption{Distribution of the types by rank}
  \label{fig:typeDistribution}
\end{figure}

\end{document}

And for more complex one:

\documentclass[12pt]{article}
\usepackage{multirow}
\usepackage{colortbl}
\definecolor{kugray5}{RGB}{224,224,224}

\begin{document}

\begin{figure}
  \centering
  \begin{tabular}{|c|c|c|c|c|c|c|c|c|}
    \hline
    \multicolumn{2}{|>{\columncolor{kugray5}}c|}{}&\multicolumn{4}{c|}{Rank}&\multirow{2}{*}{Total}\\
    \arrayrulecolor{kugray5}
    \arrayrulecolor{black}
    \cline{3-6}
    \multicolumn{2}{|>{\columncolor{kugray5}}c|}{}&A&B&C&Other&\\
    \hline
    \multirow{2}{*}{Type}&type 1&10&21&6&3&40\\
    \cline{2-7}
                         &type 2&8&14&5&2&29\\
    \hline
    \multicolumn{2}{|c|}{Total}&18&35&11&5&69\\
    \hline
  \end{tabular}
  \caption{Distribution of the types by rank}
  \label{fig:typeDistribution}
\end{figure}

\end{document}

Config Files in Haskell

Maksim Sorokin — Sun, 09 May 2010 08:09:41 +0000

Here is an easy and simple way to read configuration files in Haskell using ConfigFile package.

Here is a simple configuration file test.cfg example:

key: value

And here is the program which reads the configuration file:

import Data.ConfigFile
import Data.Either.Utils

main =
 do val <- readfile emptyCP "test.cfg"
    let cp = forceEither val
    putStrLn $ forceEither $ get cp "" "key"

Haskell and MySQL

Maksim Sorokin — Sat, 24 Apr 2010 09:38:48 +0000

In this post I will describe how to connect and use MySQL with Haskell.

In this example we will use Ubuntu machine. We will use MySQL driver for HDBC from HackageDB.

First, we need to install MySQL server:

sudo apt-get install mysql-server

Then we need MySQL client library:

sudo apt-get install libmysqlclient-dev

Then, we install HDBC MySQL driver using Cabal:

http://hackage.haskell.org/package/HDBC-mysql

And you are ready to write some code!

module DatabaseTest where

import Database.HDBC
import Database.HDBC.MySQL

main =
   do conn <- connectMySQL defaultMySQLConnectInfo {
                  mysqlHost = "localhost",
                  mysqlDatabase = "db",
                  mysqlUser = "user",
                  mysqlPassword = "pass",
                  mysqlUnixSocket = "/var/run/mysqld/mysqld.sock" }
      quickQuery conn "INSERT INTO test VALUES (1)" []

JPA Persistence With GlassFish

Maksim Sorokin — Fri, 26 Feb 2010 22:20:32 +0000

So you want to use javax.persistence. Here is how you can configure it and run with GlassFish.

In this example we will use MySQL database.
First, we will need to configure GlassFish JDBC resources. In GlassFish administration portal go to "Resources->JDBC->Connection Pools". Create new Connection Pool with name examplePool. Set Resource Type to java.sql.Driver; Database Vendor to MySql, com.mysql.jdbc.Driver.
Then go to "Resources->JDBC->JDBC Resources". Add new resource with JNDI Name jdbc/example. Set Pool Name to examplePool.

In the application under src/main/resource META-INF folder should be created. And inside META-INF folder persistence.xml file added with following content:


    
  
    ${jtaDataSource}

Where ${jtaDataSource} should be jdbc/example. Or you can enable filtering in Maven pom.xml file and specify jdbc/example there So afterwards it would be easier to change and maintain it:


  ...
  
    
      src/main/resources
      true
    
  
  ...

...

  jdbc/example

You are ready to go! Create Entity:

@Entity
@Table(name = "pencils")
public class Pencil {
  @Id
  private int id;

  @Column
  private String color;

  public int getId() {
    return id;
  }

  public String getColor() {
    return color;
  }
}

Inject javax.persistence.PersistenceContext:

@PersistenceContext
private EntityManager em;

And you can create queries:

Query q = em.createQuery("select p from Pencil p where p.color=:color");
q.setParameter("color", "blue");

Java EE 6 Injection With Dynamic Parameter

Maksim Sorokin — Fri, 19 Feb 2010 18:08:40 +0000

Say, you want to inject an object using @javax.inject.Inject. And you would like to pass additional dynamic parameter upon initialization. You can do the following trick.

For instance you want to inject and object which depends on some input. In current case let it be Pencil object, which needs to be initialized with color.

public class Pencil {
  private Color color;

  void init(Color color) {
    this.color = color;
  }

  public void draw() {
    //
  }
}

In this case when you inject the Pencil, you have to call init(Color) explicitly, which is kind off error-prone. What you can do is create a PencilProducer which would create Pencil objects with desired color.

public class PencilProducer {
  @Inject private Instance pencilInstance;

  public Pencil produce(Colour color) {
    Pencil pencil = pencilInstance.get();
    pencil.init(color);
    return pencil;
  }
}

In this case PencilProducer will create new Pencil object every time it is called. And in the application you simply inject PencilProducer and call produce method when needed.

This may seem to be too straight and dirty, but hey -- no new keyword!

Servlet 3.0 Without Configuration Hell

Maksim Sorokin — Sun, 07 Feb 2010 16:41:23 +0000

Servlets 3.0 become easier.

Lets try simple InfoServlet example.

Our web.xml will look like:



  info

And our InfoServlet.java would look like:

package example; 

import java.io.IOException;
import java.io.PrintWriter; 

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; 

@WebServlet(urlPatterns = { "/info" })
public class InfoServlet extends HttpServlet { 

  private static final long serialVersionUID = 5585664118773284494L; 

  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,
      IOException {
    doPost(request, response);
  } 

  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException,
      IOException {
    PrintWriter out = response.getWriter();
    out.println("Info Servlet!");
    out.close();
  }
}

And that is it.

Why "InfoServlet"? Because it can be easily combined with earlier post about Maven versioning. In InfoServlet you can read a file with a version and show on a web page.