November 22, 2011

How to Install Swedish BankID on Ubuntu 11.10 64-bits

First download the Swedish BankID program from https://install.bankid.com/.

Unzip the file.
$ tar -xvf BISP-.tar.gz

Install BankID
$ cd BISP-
sudo ./install..sh -i

The last part is only for 64-bit OS and that is to simulate your 32-bit Firefox pluging to run on your 64-bit OS. To do that you need the ia32-libs and nspluginwrapper packages. On a clean installed computer they are not installed.

To install them
$ sudo apt-get install ia32-libs nspluginwrapper

Then install the BankID plugin in Firefox.
$ sudo nspluginwrapper -i /usr/local/lib/personal/libplugins.so

Now restart Firefox and test your plugin via https://install.bankid.com/

To read more in depth of the installation, see http://ubuntu-se.org/wiki/NexusPersonal.

November 21, 2011

Can Programmers Learn Something from Industrial Design?

Another interest of mine is design and art. Which I will not write more about on this technical blog, but I recently got aquinted with the designer Dieter Rams (http://en.wikipedia.org/wiki/Dieter_Rams) who is interesting in many ways, but one thing that I think is of interest to share on this blog is his famous:

Ten Principles for Good Desing


1. Good design is innovative.

2. Good design makes a product useful.

3. Good design is aesthetic.

4. Good desing makes a product understandable.

5. Good design is unobtrusive.

6. Good design is honest.

7. Good design is long-lasting.

8. Good desing is thorough, down to the last detail.

9. Good design is environmentally-friendly.

10. Good design is as little design as possible.

Where my favourite is the last ”Good design is as little design as possible.”. Like James Bond would have said it ”Less is more.” Or maybe as a programmers would have put it ”KISS”.

You can read more of these principles here http://www.vitsoe.com/en/gb/about/dieterrams/gooddesign.

Is Oracle Making any Progress with Pushing Java Forword?

Well in one sense, Oracle have managed to release a new Java version 7, but there are still some differences to solve to make the work go faster and smother.

Read more about the Java 7 ballot
http://jcp.org/en/jsr/results?id=5111

and for the Java 8 ballot release.
http://jcp.org/en/jsr/results?id=5112

One can clearly see that the fighting of lawyers are still going on for the license of Java. I hope they solve it and comes to an agrement so that the evolving of Java progresses faster, than it has since Java 5.

For history of previous Java releases, please read
http://magnus-k-karlsson.blogspot.com/2010/10/jaoo-day-4-java-future-at-oracle.html

How to Disable the Overlay Scrollbar in Ubuntu 11.01 and 11.10

How to Disable the Overlay Scrollbar in Ubuntu 11.01 and 11.10

I like the new look of Unity, but there is one thing that keeps bugging me and that is the new Overlay Scrollbar. To remove it, do the following from the Terminal.

First you need to become root
$ sudo su

Then export the following setting:
$ echo export LIBOVERLAY_SCROLLBAR=0 > /etc/X11/Xsession.d/80overlayscrollbars

Last reboot and voilà the classical scrollbar is back.

February 28, 2011

Java Bug hangs the JVM

I'm not sure about publishing bugs, but I guess it's already out there and there is also a patch available. The problem is in java.lang.Double and the handling of maximum doouble value, i.e. 2.2250738585072012e-308. The following code will send the older JVM to an infinitive loop.
Double.parseDouble(2.2250738585072012e-308)

Ok, but is this really a problem? Yes, it is for Java server connected to Internet. Let's imagine a Bank Server written in Java and exposed/available from the Internet. And you can be quite certain there will some fields taking double as input. These html fields are all Strings, but when processing at the server they are parsed to Double. And this is a typical exploit scenario a hacker can use for hanging the server/DoS attack.

The solution is either patching your current JVM version or upgrading to the latest JVM, i.e. Java 6 Update 24.


http://blogs.oracle.com/security/2011/02/security_alert_for_cve-2010-44.html

This bug is foremost for server application, since desktop application can always be restarted, but if you want to upgrade your desktop java version, please go to http://java.com/.

February 23, 2011

Best Practice Aspect-Oriented Programming with JBoss AOP

In my recent project I have been working with JBoss AOP. There have been some pitfalls, I have fallen into and in this blog I will share those you.

First of all. Do not choose aspect-oriented programming to solve everyday Java problems. Example of good cases are:
  • Logging
  • Caching
  • Security
  • Error Handling
But why does AOP does not suites to solve common Java problem? Lets look at an example with Spring and AspectJ.

The Logic class:
public class FooPojo { public void setFoo(Object inparam) { /* logic goes here... */ } }
The Aspect class:
@Aspect public class FooAspect {
    @Before("execution(void set*(*))") public void handle() { /* logic goes here... */ }
}
Boilerplate XML configuration files
<beans>
    <aop:aspectj-autoproxy>
        <aop:include name="fooAspect" />
    </aop:aspectj-autoproxy>
    <bean id="fooAspect" class="se.msc.example.aop.FooAspect" />
</beans>

<beans>
    <import resource= "aspects-config.xml"/>
    <bean name="foo" class="se.msc.example.aop.FooPojo" />
</beans>


And now call it
((FooPojo) new ClassPathXmlApplicationContext(“application-config.xml”).getBean(“foo”)).setFoo(null);
The problem with the code above, is that in FooPojo there is no hint at all, that other code will be called. This can be very confusing for a junior programmer and also to a much more skilled programmer that is not familiar with AOP. So how to make AOP more clearer and more understandable? The answer is to look at other framework and how they have solved it. Take for example Spring. They use AOP very heavily under the hood, to solve common tasks as marking classes as transactional (@Transactional). And in J2EE, Oracle uses also Annotation, e.g. in JAX-WS they have the method Annotation @WebMethod, to signal that a method is a Web Service method. So lets copy that pattern, to write your own Annotation, as marker in the code that you want to apply apsect-oriented programming to. Our own Annotation, to trigger Aspect:
package se.msc.example.aop;

import static java.lang.annotation.ElementType.METHOD;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Cache Annotation.
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ METHOD })
public @interface Cache {

 String attribute() default "";
    // String value() default ""; if attribute name is 'value', you do not need to specify it 
}

Our Aspect. Here we use interface implementation. This solution works on JBoss 4.3.0 - 5.1.0:
package se.msc.example.aop;

import java.lang.annotation.Annotation;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.log4j.Logger;
import org.jboss.aop.advice.Interceptor;
import org.jboss.aop.joinpoint.Invocation;
import org.jboss.aop.joinpoint.MethodInvocation;

/**
 * Cache interceptor demo. See also jboss-aop.xml. 
 */
public class CacheInterceptor implements Interceptor {
 protected final Logger log = Logger.getLogger(this.getClass());
 private final ConcurrentHashMap<Long, Object> cache = new ConcurrentHashMap<Long, Object>();
 
 /**
  * @see org.jboss.aop.advice.Interceptor#getName()
  */
 public String getName() {
  return this.getClass().getSimpleName();
 }

 /**
  * @see org.jboss.aop.advice.Interceptor#invoke(Invocation)
  */
 public Object invoke(Invocation invocation) throws Throwable {
  Object rtnObject = beforeInvocation((MethodInvocation) invocation);
  if (rtnObject != null) {
   if (log.isDebugEnabled()) log.debug("CACHED.");
   return rtnObject; // if cached, return 
  }
  try {
   rtnObject = invocation.invokeNext();
   afterInvocation((MethodInvocation) invocation, rtnObject);
  } catch (Throwable t) {
   onInvocationException((MethodInvocation) invocation, t);
  }
  return rtnObject;
 }

 protected Object beforeInvocation(MethodInvocation invocation) throws Throwable {
  if (log.isDebugEnabled()) log.debug("beforeInvocation...");
  Object[] args = invocation.getArguments();
  // always check for null and array length, when using reflection
  if (args.length > 0 && args[0] != null && (args[0] instanceof Long)) return cache.get(args[0]);
  return null;
 }

 protected void afterInvocation(MethodInvocation invocation, Object rtnObject) throws Throwable {
  if (log.isDebugEnabled()) log.debug("afterInvocation...");
  if (rtnObject == null) return;
  Object[] args = invocation.getArguments();
  // always check for null and array length, when using reflection
  if (args.length > 0 && args[0] != null && (args[0] instanceof Long)) {
   if (log.isDebugEnabled()) log.debug("ADD id=" + args[0] + ", object='" + rtnObject + "'.");
   cache.put((Long) args[0], rtnObject);
  }
 }

 protected void onInvocationException(MethodInvocation invocation, Throwable invocationException)
         throws Throwable {
  if (log.isDebugEnabled()) log.debug("onInvocationException...");
  log.error("onInvocationException", invocationException);
  // if nothing we can do, re-throw
  throw invocationException;
 }
 
 // ----------------------- Helper Method -----------------------
 
 protected <t extends Annotation> T getMethodAnnotation(MethodInvocation invocation,
         Class<t> annotationClass) {
  return invocation.getMethod().getAnnotation(annotationClass);
 } 
}

The JBoss AOP configuration file, META-INF/jboss-aop.xml
<?xml version="1.0" encoding="UTF-8"?>
<aop xmlns="urn:jboss:aop-beans:1.0">
 <!-- Singleton Interceptor -->
 <!-- http://docs.jboss.com/aop/1.3/aspect-framework/reference/en/html_single/index.html -->
 <interceptor name="Cache" class="se.msc.example.aop.CacheInterceptor" scope="PER_VM" />
 <bind pointcut="all(@se.msc.example.aop.Cache)">
  <interceptor-ref name="Cache" />
 </bind>
</aop>

Now lets create a Test class, that we annotate with our own Annotation:
package se.msc.example.aop;

import java.util.HashMap;
import java.util.Map;

/**
 * Simulate DB Service.
 */
public class Dummy {
 private Map<Long, String> db = new HashMap<Long, String>();
 
 @Cache
 public String load(Long id) {
  if (!db.containsKey(id)) db.put(id, "NEW " + id);
  return db.get(id);
 }
 
 public void update(long id, String str) {
  db.put(id, str);
 }
}

And a Unit Test to verify it is working.
package se.msc.example.aop;

import java.util.HashMap;
import java.util.Map;

/**
 * Simulate DB Service.
 */
public class Dummy {
 private Map<Long, String> db = new HashMap<Long, String>();
 
 @Cache
 public String load(Long id) {
  if (!db.containsKey(id)) db.put(id, "NEW " + id);
  return db.get(id);
 }
 
 public void update(long id, String str) {
  db.put(id, str);
 }
}

And here is the maven pom.xml
<?xml version="1.0" encoding="UTF-8" ?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
 <modelversion>4.0.0</modelVersion>
 <groupid>se.msc.example</groupId>
 <artifactid>aop-demo</artifactId>
 <version>1.0-SNAPSHOT</version>
 <packaging>jar</packaging>
 <properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  <jbossaop.version>2.1.1.GA</jbossaop.version>
 </properties>
 <repositories>
  <repository>
   <id>repository.jboss.org</id>
   <name>Jboss Repository for Maven</name>
   <url>http://repository.jboss.org/maven2/</url>
  </repository>
 </repositories>
 <pluginrepositories>
  <pluginrepository>
   <id>repository.jboss.org</id>
   <name>Jboss Repository for Maven</name>
   <url>http://repository.jboss.org/maven2/</url>
  </pluginRepository>
 </pluginRepositories>
 <dependencies>
  <!-- JBoss 5.1.0.GA -->
  <dependency>
   <groupid>org.jboss.aop</groupId>
   <artifactid>jboss-aop</artifactId>
   <version>2.1.1.GA</version>
  </dependency>
  <!-- Test support -->
  <dependency>
   <groupid>junit</groupId>
   <artifactid>junit</artifactId>
   <version>4.8.1</version>
   <scope>test</scope>
  </dependency>
 </dependencies>
 <build>
  <pluginmanagement>
   <plugins>
    <plugin>
     <groupid>org.apache.maven.plugins</groupId>
     <artifactid>maven-compiler-plugin</artifactId>
     <version>2.0.2</version>
     <configuration>
      <source>1.6</source>
      <target>1.6</target>
      <!-- Plugin ignores default value 'project.build.sourceEncoding' -->
      <encoding>${project.build.sourceEncoding}</encoding>
     </configuration>
    </plugin>
    <plugin>
     <groupid>org.apache.maven.plugins</groupId>
     <artifactid>maven-jar-plugin</artifactId>
     <version>2.2</version>
     <configuration>
      <archive>
       <manifest>
        <!-- Adding Implementation And Specification Details -->
        <adddefaultimplementationentries>true</addDefaultImplementationEntries>
       </manifest>
      </archive>
     </configuration>
    </plugin>
    <plugin>
     <groupid>org.apache.maven.plugins</groupId>
     <artifactid>maven-surefire-plugin</artifactId>
     <version>2.4.3</version>
     <configuration>
      <!-- Konfiguration för AOP loadtime-weaving -->
      <argline>-javaagent:"${settings.localRepository}/org/jboss/aop/jboss-aop/${jbossaop.version}/jboss-aop-${jbossaop.version}.jar"</argLine>
     </configuration>
    </plugin>    
   </plugins>
  </pluginManagement>
 </build>
 <reporting>
  <plugins>
   <plugin>
    <groupid>org.codehaus.mojo</groupId>
    <artifactid>cobertura-maven-plugin</artifactId>
    <version>2.3</version>
   </plugin>
  </plugins>
 </reporting>
</project>

To make the example complete, we also need to supply a log4j configuration file.
<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE log4j:configuration PUBLIC "-//log4j/log4j Configuration//EN" "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
 <appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender">
  <param name="Target" value="System.out" />
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss.SSS} [%p] %c:%L - %m%n" />
  </layout>
 </appender>
 <appender name="FILE_APPENDER" class="org.apache.log4j.RollingFileAppender">
  <param name="File" value="/tmp/server.log" />
  <param name="Append" value="true" />
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="%d %-5p [%t] %C{2} (%F:%L) - %m%n" />
  </layout>
 </appender>
 <logger name="se.msc.example.aop">
  <level value="DEBUG" />
  <appender-ref ref="CONSOLE" />
 </logger>
 <root>
  <level value="WARN" />
  <appender-ref ref="CONSOLE" />
 </root>
</log4j:configuration>


To run/debug this inside Eclipse we need to copy the argLine from the maven pom file to the unit test file configuration.



For more about JBoss AOP Maven plugin , see http://community.jboss.org/wiki/JBossAOPMavenPlugin.