dot kam - be kind, do good - Part 12 dot kam

boot / ubuntu — Comments Off
29
Nov 10

Install Alternate Ubuntu Image from USB

UNetbootin allows you to create bootable Live USB drives for Ubuntu, Fedora, and other Linux distributions without burning a CD.

Unfortunately it does not work by default with Alternate Ubuntu Images. In order to make it work:

1. download an alternate image: Ubuntu Alternative Downloads
2. write an image to USB drive using UNetbootin
3. boot from this new USB on the target host
4. select the menu item “Default”
5. DON’T press ENTER
6. press TAB
7. add the “cdrom-detect/try-usb=true” before the “- -”
8. press ENTER

Now it will actually look into USB to install the system rather than looking for CD-ROM or trying the whole OS from the network.

aspectj / maven / spring — Comments Off
12
Oct 10

Running Spring AspectJ Tests with Maven

You need to use a real AspectJ aspect with Spring, where you would like to inject some dependencies into this aspect as a Spring container starts up.

Here is an AspectJ aspect:

@Aspect
public class VeryImportantAspect {
    ...
    public void setSomeDependency( SomeDependency dependency ) {
        this.dependency = dependency;
    }
    ...
}

Now let’s define it as a bean and inject “someDependency”:

<bean id="veryImportantAspect" 
         class="org.dotkam.VeryImportantAspect"
         factory-method="aspectOf">
 
         <property name="someDependency" ref="someDependency"/>
</bean>

Notice factory-method=”aspectOf” that tells Spring to use a real AspectJ ( not Spring AOP ) aspect to create this bean. In reality, if the “VeryImportantAspect” was already woven in, it will have an “aspectOf” method.

Hence if you get this error at some point:

No matching factory method found: factory method 'aspectOf()'

That would mean that the aspect was not woven by AspectJ weaver.

We also need to tell Spring to use load time weaving:

<context:load-time-weaver/>

If you run with the above configuration without doing anything, you would get a following error:

ClassLoader does NOT provide an 'addTransformer(ClassFileTransformer)' method

That tells you ( well not explicitly :) ) to include a “spring-instrument.jar” javaagent.

So at this point two things need to be added: AspectJ weaver and Spring Instrument agent. Build / Continues integration server does not use any IDE, so it is not as simple as downloading AspectJ plugin for IDEA / Eclipse and including VM arguments in Run Configurations… It is simpler: just add the two in your POM file.

Adding an AspectJ plugin:

<plugin>
     <groupId>org.codehaus.mojo</groupId>
     <artifactId>aspectj-maven-plugin</artifactId>
     <version>1.3</version>
     <executions>
         <execution>
             <configuration>
                <source>1.6</source>
                <target>1.6</target>
            </configuration>                     
             <goals>
                 <goal>compile</goal>       <!-- use this goal to weave all your main classes -->
                 <goal>test-compile</goal>  <!-- use this goal to weave all your test classes -->
             </goals>
         </execution>
    </executions>
</plugin>

Adding a Spring Instrument agent to participate in a test execution:

<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-surefire-plugin</artifactId>
	<version>2.4</version>
	<configuration>
            <forkMode>once</forkMode>
            <argLine>
                 -javaagent:"${settings.localRepository}/org/springframework/spring-instrument/${spring.framework.version}/spring-instrument-${spring.framework.version}.jar"
	    </argLine>
            <useSystemClassloader>true</useSystemClassloader>
	</configuration>
</plugin>

And all that work, just too see a couple of lines from Maven:

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------

design-patterns / humans / software — Comments Off
06
Oct 10

Humans + Software = Zero

FACT:

Humans are stateful and mutable beings that have no problems processing many things concurrently and share state with others + they are usually “coupled”

GOAL:

And yet in software design we strive for being stateless, immutable and decoupled.

CONCLUSION I:

Humans should not design software

CONCLUSION II:

If humans were designed by software, that project sucked ( according to the GoF teachings )

CONCLUSION III:

Humans are not software, they are maybe… hardware

CONCLUSION IV:

Good software is going to lead to the race of Inhumans

CONCLUSION V:

Humans + Software = 0

hibernate / java / spring — Comments Off
26
Sep 10

Money Making Project

For the past several years most of my projects were based on Spring and Hibernate. And what I keep seeing is how people struggle to understand how the two are working together.

So going from project to project, I have to repeat the same spiel over and over again to get people up to speed.

Since I believe that the most effective way to LEARN is to DO, I create simple examples for people to play with / to complete / to analyze, etc..

So “Money Making Project” is one of such examples. It comfortably lives at github’s luxury apartments, so anybody can “git clone” / “fork” and play with it.

Besides making money, this project also demos things such as:

A way to structure a project

Maven based structure ( hence can be easily used by gradle ). Configuration and property files organized under “META-INF/conf”, “META-INF/props”, etc..

A way to separate Spring configs

“tx-spring-config.xml”, “persistence-spring-config.xml”, “service-spring-config.xml”, “repository-spring-config.xml” and “application-context.xml” that includes them all

Properties via PropertyPlaceholderConfigurer

<context:property-placeholder location="classpath:META-INF/props/env.properties"/>

Hibernate overall configuration file

That is injected into AnnotationSessionFactoryBean

Hibernate Named Queries

That are linked to the Hibernate overall config

<mapping resource="META-INF/conf/hibernate/mapping/startup-bank-named-queries.xml"/>

Spring’s DAO / Hibernate Exception Translation

Via @Repository and “PersistenceExceptionTranslationPostProcessor”

Simple CRUD Repository

public interface MoneyRepository {
 
    public void make( MoneyRoll moneyRoll );        // C
    public MoneyRoll find( Long id );                       // R
    public void update( MoneyRoll moneyRoll );     // U
    public void takeOut( MoneyRoll moneyRoll );    // D
}

with a Hibernate based implementation

Transaction Management with Spring AOP

Declarative, on a Service Level, using “aop:config”, “tx:advice” namespaces

Spring Testing

With SpringJUnit4ClassRunner, ContextConfiguration, etc..

Using Embeded in-memory H2 Database for Testing

<jdbc:embedded-database id="dataSource" type="H2"/>

Hibernate Logging

Most useful hibernate “log4j.logger” properties

Demoing how important Transaction is for Hibernate Sessions

“HibernateSessionNotBoundToThreadIntegrationTest” for the second (after LazyInitializationException ) most common Hibernate exception: “No Hibernate Session bound to thread, and configuration does not allow creation of non-transactional one here”

money / spel / spring — Comments Off
10
Sep 10

Spring Expression Language: Calling a Method with Parameters

Have you ever wanted to win $1,000,000 with a single SpEL ( Spring Expression Language ) call? Well, now you can, and here is how.

Let’s say there is a Lottery that deposits money to a winner’s bank account and congratulates the winner:

private class Lottery {
    // ...
    public String congratulateWinner( String name, BigDecimal amount, Date date ) {
    	String now = new SimpleDateFormat( "MM-dd-yyyy" ).format( date );
    	String cash = new DecimalFormat( "$#,###,###" ).format( amount.doubleValue() );
 
    	return "Congratulations " + name + "! " +
    	       "Today is " + now + ", and it's your lucky day, because " +
    	       "you just won " + cash + "!";
    }
}

Here is how to make Anatoly win money with SpEL:

"congratulateWinner( 'Anatoly', #amount, #date )"

( of course, let’s not forget to set an amount to at least a million dollars ).

And here is a million dollar unit test:

@Test
public void shouldInvokeMethodWithParameters() {
 
    Lottery lottery = new Lottery();
 
    GregorianCalendar calendar = new GregorianCalendar();
    calendar.set( 2010, 8, 10 );
 
    BigDecimal amount = BigDecimal.valueOf( 1000000.00 );
 
    // letting SPEL know about the "lottery", the "amount" won, and the "date"
    EvaluationContext context = new StandardEvaluationContext( lottery );
    context.setVariable( "amount", amount );
    context.setVariable( "date", calendar.getTime() );
 
    ExpressionParser parser = new SpelExpressionParser();
 
    // using '#' to identify a variable ( NOTE: #this, #root are reserved variables )
    Expression exp = parser.parseExpression( "congratulateWinner( 'Anatoly', #amount, #date )" );
 
    String congratulations = ( String ) exp.getValue( context );	
    assertEquals( "Congratulations Anatoly! " + 
                  "Today is 09-10-2010, and it's your lucky day, because you just won $1,000,000!", 
                  congratulations );
}

(!) Do not write code that does not earn you money :)

kam
one of those blogs

Install Alternate Ubuntu Image from USB

Running Spring AspectJ Tests with Maven

Humans + Software = Zero

Money Making Project

Spring Expression Language: Calling a Method with Parameters

here is more about

kamone of those blogs

Install Alternate Ubuntu Image from USB

Running Spring AspectJ Tests with Maven

Humans + Software = Zero

Money Making Project

Spring Expression Language: Calling a Method with Parameters

here is more about

kam
one of those blogs