A Programação Orientada a Aspectos (AOP) complementa a programação orientada a objetos, provendo uma nova forma de pensar sobre a arquitetura da aplicação.

Na programação orientada a objetos encapsulamos as responsabilidades em classes. Já na AOP, as responsabilidades são encapsuladas em um aspecto. Um aspecto permite a modularização de interesses que geralmente aparecem espalhados por várias classes do sistema (denominados de interesses transversais – crosscutting concerns), como o gerenciamento de transações, por exemplo.

Veja a imagem abaixo. Se compreendermos as linhas horizontais como classes, veremos que os interesses de segurança, transação, etc. são transversais, ou seja, repetidos entre várias classes. A AOP contribui no sentido de retirar essas funcionalidades das classes e encapsula-las em aspectos, sem alterar o comportamento do sistema.

Conceitos

Aspect: é a unidade modular (funcionalidade) que encapsula interesses que atravessam vários objetos dentro do sistema.

Join Point: é um ponto durante a execução do programa que poderá ser afetado pelo aspecto. Um join point pode ser, por exemplo, a execução de um método do programa.

Point Cut: é uma expressão escrita em uma linguagem específica para a finalidade de selecionar join points (pontos de execução).

Advice: quando um join point é atingido, e selecionado pelo point cut, uma ação será executada. Essa ação é determinada advice.

Objeto Alvo: é o objeto que está sendo interceptado por um ou mais aspectos.

Proxy AOP: é o objeto criado pelo framework AOP para implementar a ligação entre o aspecto e o objeto alvo.

Veja na imagem abaixo. Durante a execução do programa, vários join points serão “atingidos”. No suporte a @AspectJ do Spring Framework (veremos exemplos a seguir) um join point é sempre a execução de um método. Dessa forma, imagine que cada um dos 6 join points abaixo representem 6 diferentes métodos. Um point cut é uma expressão, em linguagem específica, que seleciona quais dos 6 métodos (join points) serão afetados pelo aspecto. Nesse caso, imagine que os 3 joint points verdes foram atingidos pela expressão pointcut. O advice é a ação que irá executar quando eles foram atingidos, nesse caso, o advice será executado 3 vezes.

Tipos de Advice

No AspectJ existem 5 tipos diferentes de advice:

• Before: ação do advice executa antes do join point.

• After returning: ação do advice executa depois do joint ser executado com sucesso, ou seja, sem lançar exceção.

• After throwing: ação do advice executa depois do joint ser executado com erro, ou seja, somente quando ele lançar uma exceção.

• After (finally): ação do advice executa depois do joint ser executado independente de ter causado ou não exceção.

• Around: advice que envolve a execução de um joint point. Com ele é possível codificar ações antes e depois do join point. Inclusive é possível alterar valores passados como parâmetro, como retorno, ou nem mesmo chamar o método do objeto alvo.

Exemplo concreto utilizando o suporte a @AspectJ com Spring

A partir da versão 2.0 do Spring Framework é suportado o uso do @AspectJ 5 de forma integrada ao seu container. Ainda é possível declarar aspectos por XML, como nas versões anteriores, porém agora é possível declarar aspectos com uso de anotações.

Para implementar um aspecto é necessário três coisas:

• Colocar os jars ‘aspectjrt.jar’ e ‘aspecjtweaver.jar’ no classpath, juntamente com os jars tradicionais do Spring.

• Declarar no applicationContext.xml o uso de aspectos com declaração por anotações, dessa forma:<aop:aspectj-autoproxy />.

• Criar uma classe anotada com @Aspect para definir o aspecto. Utilizar uma anotação de advice (before, after ou around) e definir uma expressão point cut para selecionar quais joint points o aspecto afetará.

Veja um exemplo abaixo:

Repare que a expressão “execution(* xyz.abc.ClienteDao.*(..))” é o point cut e a anotação @Before é o advice. A linguagem do point cut é específica do @AspectJ e sua documentação pode ser encontrada no site da biblioteca. Explicando a expressão em detalhes:

• execution: Qualquer execução de método.

• Primeiro asterisco da expressão: que tenha qualquer visibilidade e retorne qualquer tipo de parâmetro.

• xyz.abc: pacote que estão a(s) classe(s) que o point cut afetará.

• ClienteDao: a classe afetada pelo point cut.

• Segundo asterisco da expressão: qualquer método da classe ClienteDao.

• (..): O método pode ter qualquer quantidade de parâmetros, de qualquer tipo.

Dessa forma podemos dizer que o método ‘realizarAcao’ será executado antes que qualquer método da classe ClienteDao executar.

É importante lembrar que o suporte à @AspectJ do Spring, como mostrado no exemplo, só selecionará join points que forem beans gerenciados pelo Spring. Ou seja, no exemplo acima o 'ClienteDao' tem que ser um bean no application context do Spring.

No próximo artigo veremos como implementar uma solução simples de auditoria utilizando AOP com Spring e @AspectJ.

Abraços,
Michel Zanini.

Both Sends and Receives Need Transactions

Ludovic's helpful comment on yesterday's post confirms that we need to make sure both sends and receives are in transactions.  As of yesterday, we were only wrapping the message sends, but not receives, in a transaction -- at least that was what we were trying to do!  As it turns out, the transaction-wrappage of the sends was unsuccessful, while on the other hand we were accidentally successfully wrapping the receives!  Here's how it happened:

Wrapping Sends: If It Ain't A Bean...

As you may recall from yesterday, the pointcut I had defined for applying transaction advice to message sends was as follows:

[sourcecode language='xml']
       
[/sourcecode]

But as Keith points out, since my JndiBitronixTest class is not defined as a bean in my Spring beans files, the transaction advice will not be applied to the transactedSendMessage method execution.  Oops!  I didn't realize that Spring AOP advice applied only to beans!  Fixing that is easy enough: the transactedSendMessage method calls one layer down into the MessageSender class, which is defined as a bean.  We can just start the transaction there instead:

[sourcecode language='xml']
       
[/sourcecode]

Wrapping Receives: Forgotten Advice

I was looking in the main beans file to verify that MessageSender was defined as a bean when I saw a surprising thing:  I already had transactional advice on the message receives, including the following pointcut:

[sourcecode language='xml']
       
[/sourcecode]

This advice came along when I brought this code over from my original XA example manual test that runs only on an app server.  I consolidated this advice with the send advice into the spring-beans-bitronix.xml file to yield this advice:

[sourcecode language='xml']
   
       
           
       
   

   
       
       
   
[/sourcecode]

And this time both pointcuts point to classes that are Spring beans.  :)

Happy Path Seems to Work

Now our integration test can send a JMS message and the listener picks it up from the queue and writes it to the database, without exceptions or stack traces.  Furthermore, when I bump the log level to DEBUG for Bitronix classes, in my log4j.properties file:

[sourcecode language='php']
log4j.logger.bitronix.tm=DEBUG
[/sourcecode]

Then I see encouraging looking XA-type messages like the following:

[sourcecode language='php']
DEBUG bitronix.tm.BitronixTransaction  - committing, 2 enlisted resource(s)
DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to PREPARING
DEBUG bitronix.tm.journal.TransactionLogAppender  - between 19089 and 19193, writing a Bitronix TransactionLogRecord with status=PREPARING, recordLength=96, headerLength=28, time=1219154728262, sequenceNumber=11, crc32=-1825120209, gtrid=737072696E672D62746D0000011BDB48D3FF00000000, uniqueNames=XAOracleDS,activemq/QueueConnectionFactory
DEBUG bitronix.tm.journal.TransactionLogAppender  - disk journal appender now at position 19193
DEBUG bitronix.tm.twopc.AbstractPhaseEngine  - executing phase on 2 resource(s) enlisted in 1 position(s) in natural position order

...

DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to PREPARED
...

DEBUG bitronix.tm.twopc.Preparer  - successfully prepared 2 resource(s)
DEBUG bitronix.tm.BitronixTransaction  - 2 interested resource(s)
DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to COMMITTING (forced)
...

DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to COMMITTED

[/sourcecode]

There's Also a One-Phase Commit In There (and that's good)

Before I found that two-phase commit sequence in the log, I found another sequence farther up

[sourcecode language='php']

DEBUG bitronix.tm.BitronixTransaction  - committing, 1 enlisted resource(s)
DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to PREPARING
DEBUG bitronix.tm.journal.TransactionLogAppender  - between 18721 and 18813, writing a Bitronix TransactionLogRecord with status=PREPARING, recordLength=84, headerLength=28, time=1219154728200, sequenceNumber=7, crc32=-667556454, gtrid=737072696E672D62746D0000011BDB48D4AA00000003, uniqueNames=activemq/QueueConnectionFactory
DEBUG bitronix.tm.journal.TransactionLogAppender  - disk journal appender now at position 18813
DEBUG bitronix.tm.twopc.Preparer  - 1 resource enlisted, no prepare needed (1PC)
DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to PREPARED
DEBUG bitronix.tm.journal.TransactionLogAppender  - between 18813 and 18905, writing a Bitronix TransactionLogRecord with status=PREPARED, recordLength=84, headerLength=28, time=1219154728200, sequenceNumber=8, crc32=-2001767057, gtrid=737072696E672D62746D0000011BDB48D4AA00000003, uniqueNames=activemq/QueueConnectionFactory
DEBUG bitronix.tm.journal.TransactionLogAppender  - disk journal appender now at position 18905
DEBUG bitronix.tm.BitronixTransaction  - 1 interested resource(s)
DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to COMMITTING
DEBUG bitronix.tm.journal.TransactionLogAppender  - between 18905 and 18997, writing a Bitronix TransactionLogRecord with status=COMMITTING, recordLength=84, headerLength=28, time=1219154728200, sequenceNumber=9, crc32=236131807, gtrid=737072696E672D62746D0000011BDB48D4AA00000003, uniqueNames=activemq/QueueConnectionFactory
...

DEBUG bitronix.tm.BitronixTransaction  - changing transaction status to COMMITTED
[/sourcecode]

I worried about line 8 where it said that only one resource was enlisted and so only a one-phase commit (1PC) was needed -- "What happened to the database resource?" I wondered.  But then I remembered that this must be the message send (I tend to forget that that's being transacted too), and the send does not involve the database resource.

Next Steps

I'd still like to have my integration test query the database to verify that the record really made it in there.

Technical:

• Strong hands-on Java development experience, 5+ years
• Strong presentation tier skills, including HTML, CSS, Javascript, with Ajax and similar technologies a definite plus.
• UI Design and Usability testing skills
• Knowledge of Spring framework (web MVC, AOP and data access), Hibernate and JDBC
• Some experience with relational databases, preferably Sybase as plus
• Recent JSP / JSTL and Servlet experience ideally on Apache / Tomcat
• OO Development and Design Skills including UML and use of design patterns
• Experience of Spring Webflow  framework development a bonus
• Experience of developing on Linux / Unix platform
• Demonstrable experience of working in all phases of the development life cycle
• BS or MS in Computer Science or Engineering degree from a highly accredited academic institution

Non-technical:

• Good inter-personal skills with ability to communicate effectively both orally and in writing
• Must have the capacity to work effectively either in a team  or on his / her own
• Strong analytical and organisational skills.
• Must be able to adapt well to change.
• Must be able to demonstrate intellectual capacity to learn very quickly and adapt to complex situations in a fast paced and demanding environment.

laszlo_spiller@kellyservices.hu

execution(* com.example.MessageListener(..))

and getting this error:

java.lang.IllegalArgumentException: warning no match for this type name: com.example [Xlint:invalidAbsoluteTypeName]

I Googled this error (alas, my beloved Ask.com seems to have fewer of the stack trace errors indexed) and found a post to a Spring Framework support forum saying it was the pointcut expression that was incorrect.  And in The AspectJ^TM Programming Guide under Matching and Some Example Pointcuts it does look like there's supposed to be a method signature there in the pointcut expression, not just a class name.

Now that I understand the pointcut expressions a little more, I think I'll take out most of the wildcards for now (I'm leaving the ".." wildcard for the Message parameter for now because when I replaced that with Message, I got some kind of error):

[sourcecode language='xml']

   
   

[/sourcecode]

Now the deployment succeeds... but when my messagelistener throws a RuntimeException the message is still gone from the queue, so it doesn't seem to be rolling back correctly yet.  So that's where we'll start next time!

[sourcecode language='xml']

   
       
   

   
   

[/sourcecode]

When I deployed this, I got:

15:12:25,757 ERROR [ContextLoader] Context initialization failed
org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Unable to locate Spring NamespaceHandler for XML schema namespace [http://www.springframework.org/schema/aop]
Offending resource: class path resource [applicationContext.xml]

The AOP xmlns and schemaLocation looked right in the applicationContext.xml, so I did a web search for the error and...

An entry in the note19 blog gave me the idea to check to make sure my project includes the AOP portion of the Spring libraries in its dependencies... so I ended up adding both spring-aop and spring-aspects to my pom file.

I needed both

With only spring-aspects I still got the Unable to locate Spring NamespaceHandler error; with only spring-aop I got an exception (nested, of course :), to wit:

NoClassDefFoundError: org/aspectj/weaver/reflect/ReflectionWorld$ReflectionWorldException

But with both spring-aspects and spring-aop in my pom as dependencies, the error is gone!  Replaced by...

The next error

Now I get this:

16:18:30,896 ERROR [ContextLoader] Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'queueConnectionFactory': Initialization of bean failed; nested
exception is java.lang.IllegalArgumentException: warning no match for this type name: com.example [Xlint:invalidAbsoluteTypeName]

My queueConnectionFactory JNDI-lookup bean definition looks like this:

[sourcecode language='xml']

[/sourcecode]

And that definition has been working -- my messageListener has been getting messages using that queue connection factory.  So I suspect that somehow the AOP beans -- which look like this:

[sourcecode language='xml']

   
       
   

   
   

[/sourcecode]

-- are causing the problem.

If I comment out the

[sourcecode language='xml']

[/sourcecode]

line, the error goes away (but then of course the message receives don't roll back when a runtime exception is encountered either...)

Let's pursue this next time.

In this newest version I have added AOP support to cut down on cross cutting code and also the ability to delete staff members from the GridView, most of the time spent was fighting against the asp.net controls (suprise, surprise) such as the GridView and the ObjectDataSource, I'm not sure what the guy(s) who created the ObjectDataSource object was smoking at the time but it must have been stronger than just tobacco :-)

My next release I want to demonstrate adding some service support showing how we can re-use existing code so they become little more than a remote facade (in theory!).

It was blowing up...

When we started up an application context that had a Spring DefaultMessageListenerContainer, and the JMS Queue that listenercontainer pointed to already had messages in it, the messagelistenercontainer (fairly reproducibly, it seemed) called our listener before our listener's beans were all initialized by Spring (i.e., before it was "wired"). This resulted in a Java NullPointerException.

An indignant pause

Imagine! Not being able to trust a big-name Inversion of Control container like Spring to do its job properly! But before reporting a bug, we wanted to put a minimal test together demonstrating the problem.

Minimal... minimal...

Complicating factors were:

• The error was happening inside an AOP around advice method before it even got into the MessageListener's onMessage method; and
• The process was running on an application server

So... was the problem simply with Spring? Or was it something about the AOP setup? Or was it something that would only show up in the context of running on an app server? I (with Keith's help) came up with a plan to root out the cause of the error.

Diagnostic Test Plan

Level A: Message already in queue (NON app server, NON AOP version)

We'd try the simplest test first to see if we could reproduce the issue without being on an app server and without AOP.

• Create a small Java app that puts a text message in the JMS Queue
• Upon receiving a message, the Messagelistener (in a separate Java app) calls its helloWorld bean's sayHello() method, passing the string from the JMS text message. The listener thread would create the application context and then sleep for a while.

Level B: Add AOP advice

If Level A didn't reproduce the problem, we'd add AOP around advice to the MessageListener's onMessage method, and the around advice would need to internally use a Spring bean

Level C: Do Level A test in an app server environment
Level D: Do Level B test in an app server environment

Potential Post-D levels, if we still can't reproduce the problem:
- Maybe it only happens with JMS Object messages...?

An Unexpectedly Quick Resolution

I was getting the Level A test put together when Keith had a thought. Our Spring context bootstrap code - in what order were we loading things there?

We looked, and what do you know - the Spring context that contained the MessageListenerContainer that was starting up "too early" and blowing up if messages were already in the queue depended on something in another Spring context, which at that point our bootstrap code had not loaded yet. The problem was in our bootstrap code, a simple ordering problem!

Being new and slow with this stuff, it took me a while to write the test to confirm this, but that was the issue.

I was unsure about how to do this until recently seeing a post by Ayende http://www.ayende.com/Blog/archive/2008/05/05/Actively-enforce-your-conventions.aspx in it he references an article by Glenn Block whereby both of them came up with a unit test called PrismShouldNotReferenceUnity in the test they use reflection to check that there are indeed no references from the Prism assembly to the Unity assembly.

This is a great idea! You now have a repeatable test that can be run to make sure the conventions for your system are met, so armed with this technique I created the following test:

[sourcecode language='csharp']
[Test]
public void task_class_methods_should_be_marked_with_wrap_exception_attributes()
{
try
{
Assembly asm = Assembly.LoadFrom( "MCromwell.StaffIntranet.Task.dll" );
var wrapExceptionType = asm.GetType( "MCromwell.StaffIntranet.Task.Infrastructure.WrapExceptionWithAttribute" );
Assert.IsNotNull(wrapExceptionType);

foreach (Type current in asm.GetTypes())
{
if (current.FullName.StartsWith( "MCromwell.StaffIntranet.Task.Tasks." ) && (!current.IsInterface) && (!current.IsAbstract))
{
foreach (var method in current.GetMethods())
{
if ((method.IsPublic) && (method.DeclaringType.Name != "Object"))
{
if (method.GetCustomAttributes(wrapExceptionType, false).Length <= 0)
Assert.Fail("no wrap exception attribute found on type '{0}', method '{1}'", current.FullName,method.Name);
}
}
}
}
}
catch (ReflectionTypeLoadException rex)
{
foreach (var current in rex.LoaderExceptions)
Console.WriteLine(current.ToString());
throw;
}
catch (Exception ex)
{
Console.Error.Write(ex.Message);
throw;
}
}
[/sourcecode]

In here you can see by leveraging reflection I can browse all the public methods for my task layer classes and make sure they do indeed have a WrapExceptionWithAttribute the other cool thing is that by doing it this way I can freely add new classes and they will need to comply with the conventions set out or the testing will fail, cool eh!

One thing to point out is that if you start increasing the number of conventions and want a better way to control and report on, you probably want to look into something like FXCop or NDepend's CQL.

A lire aussi : le camembert résiste !
En savoir plus : www.inao.gouv.fr

[sourcecode language='csharp']
[Test]
public void Should_log_exception_if_exception_is_raised_when_deleting_session()
{
Guid id = Guid.Empty;
IAdministrationRepository mockRepository = CreateMock();

IServiceResolver mockResolver = CreateMock();
ILog mockLog = CreateMock();
Exception mockException = new Exception( "mock ex" );

using (Record)
{
SetupResult.For(mockResolver.Resolve())
.Return(mockLog);
SetupResult.For(mockRepository.FindLoginSessionBy(id))
.IgnoreArguments()
.Return(new LoginSession(id));
mockRepository.Delete(null);
LastCall.IgnoreArguments()
.Throw(mockException);
mockLog.Error(mockException);
}

using (PlayBack)
{
try
{
IoC.InitializeWith(mockResolver);
IAuthenticationTask sut = createSUT(mockRepository);
sut.InvalidateSessionFor(id);
}
catch { }
}
}
[/sourcecode]

And to fulfill this I then end up with cross cutting code to meet the test behaviour:

[sourcecode language='csharp']
try
{
//... work here
}
catch (Exception thrownException)
{
Log(thrownException);
throw new ProblemSavingStaffMemberException(thrownException);
}
[/sourcecode]

To try and cut down on this cross cutting code and to keep the tasks more lean I did some investigation into some AOP strategies.

My first reaction was... I'm using Castle Windsor so can I utilize it's built in AOP capabilities after changing some code and adding an interceptor I quickly found out this won't be possible as it doesn't support out or ref parameters and due to some of my task layer method using out parameters to pass back a notification object this choice was gone!

Next up I had a look at PostSharp the difference between them being that PostSharp adds code in after compilation whereas Windsor dynamically creates proxies at runtime. After looking at some examples I had an idea as to how to implement it so after installing PostSharp I created my object that will inject itself into other objects:

[sourcecode language='csharp']
[Serializable]
[AttributeUsage(AttributeTargets.All)]
public class TaskExceptionHandlerAttribute : OnMethodBoundaryAspect
{
public override void OnException(MethodExecutionEventArgs eventArgs)
{
Exception thrownException = eventArgs.Exception;
LogException(thrownException);
WrapExceptionWithAttribute wrapExceptionAttribute = RetrieveWrappingExceptionAttribute(eventArgs.Method);
if (wrapExceptionAttribute != null)
{
Type exceptionToWrapWith = wrapExceptionAttribute.WrapExceptionType;
Exception exceptionToThrow = (Exception)Activator.CreateInstance(exceptionToWrapWith, thrownException);
if (exceptionToThrow != null)
throw exceptionToThrow;
}
throw new TaskLayerException(thrownException);
}

private static WrapExceptionWithAttribute RetrieveWrappingExceptionAttribute(MethodBase method)
{
WrapExceptionWithAttribute wrapExceptionAttribute =
method.GetFirstCustomAttribute(typeof(WrapExceptionWithAttribute),false);
return wrapExceptionAttribute;
}

private static void LogException(Exception thrownException)
{
ILog log = IoC.Resolve();
log.Error(thrownException);
}
}
[/sourcecode]

In order to not have to place this object as an attribute on all the different task classes I can use the assembly attribute and give it a target using a name plus a wildcard:

[sourcecode language='csharp']
[assembly: TaskExceptionHandler(AttributeTargetTypes="MCromwell.StaffIntranet.Task.Tasks.*")]
[/sourcecode]

And that's it my methods are now injected with the PostSharp code after compilation to handle exceptions and at which point it will call my custom code very cool!

One thing you may have noticed is the use of another attribute that can be decorated on the task methods WrapExceptionWithAttribute this attribute takes a Type in it's constructor this Type is the exception that should wrap the thrown exception ideally we would like this attribute to be placed on all public task class methods so that we raise applicable exceptions depending on the task be performed although how do we enforce this convention?...

In my next post I will be demonstrating a technique that allows to enforce these types of conventions we want for our systems.

In Application:

Log.For(this).Info(...)

And Log class initialize different logging service might be passed in.

[sourcecode language="CSharp"]

public class Log
{
private static ILogFactory logFactory;

public static void InitializeLogFactory(ILogFactory logFactory)
{
Log.logFactory = logFactory;
}

public static ILog For(object itemThatRequiresLoggingServices)
{
return For(itemThatRequiresLoggingServices.GetType());
}

public static ILog For(Type type){

// This is IOC style, then we should not use logFactory field which needs to be passed in when using log.
// return DependencyResolver.GetImplementationOf().CreateFor(type);

return logFactory.CreateFor(type); ;
}
}

[/sourcecode]

If it's a simple console logging service, the implementation will be like this:

[sourcecode language="CSharp"]

public class ConsoleLogFactory : ILogFactory
{
public ILog CreateFor(Type type)
{
return new ConsoleLogger();
}

private class ConsoleLogger : ILog
{
public void Informational(string message)
{
System.Console.Out.WriteLine(message);
}

public void Informational(string messageFormat, params object[] args)
{
System.Console.Out.WriteLine(messageFormat, args);
}

[/sourcecode]

And the log4net factory will be this, in which the WireUpConfiguration() method is using singleton pattern.

[sourcecode language="CSharp"]
public class Log4NetLogFactory : ILogFactory
{
private ILog4NetInitialization initialization;
private bool initialized;

public Log4NetLogFactory(): this(new Log4NetInitialization())
{
}

public Log4NetLogFactory(string filename): this(new Log4NetInitialization(filename))
{
}

// using ILog4NetInitialization can enable logFactory read from different app config file.
public Log4NetLogFactory(ILog4NetInitialization initialization)
{
this.initialization = initialization;
}

public ILog CreateFor(Type typeThatRequiresLoggingServices)
{
WireUpConfiguration();
return new Log4NetLog(LogManager.GetLogger(typeThatRequiresLoggingServices));
}

private void WireUpConfiguration()
{
if (initialized) return;

initialization.Execute();
initialized = true;
}
}

[/sourcecode]

Finally, the log4netINitialization is this: (I don't think ILog4NetInitialization is necessary, in fact the whole Log4NetInitialization can also be moved into log4net Factory class even.)

[sourcecode language="CSharp"]
public class Log4NetInitialization : ILog4NetInitialization
{
private readonly XmlElement configuration;
public Log4NetInitialization(){}

public Log4NetInitialization(string filename)
{
XmlDocument document = new XmlDocument();
document.Load(filename);
configuration = document.DocumentElement;

}
public Log4NetInitialization(XmlElement configuration)
{
this.configuration = configuration;
}

public void Execute()
{
if (configuration == null) XmlConfigurator.Configure();
else XmlConfigurator.Configure(configuration);
}
}
[/sourcecode]

The benefit of all those work is, the front end is same based on different logging service implementation,

Log.For(this).Info(...)

Log.For(this).Debug(...)

Log.For(this).Fatal(...)

Log.For(this).Warn(...)

Log.For(this).Error(...)

To make it work with CSLA, I figured out there is a minor change needed. (The version I am working on in 3.0) The reason is WcfPortal actually doesn't throw exception, instead, it casts the exception to an object returning to WcfProxy. This means, It's WcfProxy at the client side throwing the exception. Apparently, Juval's logbook can only monitor exceptions on Wcf Host, not at the client. I had to add an

throw ex;

into WcfPortal's catching block to make CSLA framework can use this handy logBook tools.

[sourcecode language="CSharp"]
WcfPortal:
public WcfResponse Fetch(FetchRequest request)
{
Csla.Server.DataPortal portal = new Csla.Server.DataPortal();
object result;
try
{
result = portal.Fetch(request.ObjectType, request.Criteria, request.Context);
}
catch (Exception ex)
{
result = ex;
}
return new WcfResponse(result);
}

WcfProxy:
public DataPortalResult Fetch(Type objectType, object criteria, DataPortalContext context)
{
ChannelFactory cf = new ChannelFactory(_endPoint);
IWcfPortal svr = cf.CreateChannel();
WcfResponse response =
svr.Fetch(new FetchRequest(objectType, criteria, context));
cf.Close();

object result = response.Result;
if (result is Exception)
throw (Exception)result;
return (DataPortalResult)result;
}
[/sourcecode]

Thanks to Juval, this is almost exactly what our boss wants, the only thing missing is UserName and Client Machine information, and exception stack?

Most important, what's the reason WcfPortal doesn't throw exception? The explanation back from Rocky is, he wants to display the full stack of the error/exception so the exception on the server side is caught but not thrown out, instead this exception is passed to client as an parameter to the client side. Another ward, no exception will be thrown from CSLA at all! There is no way to use LogBook, unless we change CSLA framework.

Here is Andy's solution from CLSA forum:

That's what I do.. override OnDataPortalException.  You can do this in something like MyCompanyBusinessBase, and have all your classes inherit that subclass.  Rocky recommends creating such a subclass even if initially it doesn't add any behavior at all, because someday you will.

One thing to watch is that if you're doign different logging on server vs. client you need to check ExecutionLocation.  But it works great.

My exception handling actually builds up a message, drilling down to all InnerExceptions and emails the whole thing to me.  Very helpful to finding out where the exception is occuring.  If the email fails to send for some reason, my fallback is to log a message to the Windows Event Log.  This can be tricky to get going at first, because if you're remoting you'll need to manually add the Application Name to the registry so that your application can use that name (and you'll want to do this to distingish between your remoting application and other asp.net errors).

HTH
Andy

Bankerne har i stigende grad begyndt at flytte deres ydelser fra at være ren bankkontors tjenester på internettet. Dette er et naturligt skridt, da vi lever i et IT-samfundet. En af disse tjenester er at låne penge. De fleste lånegivare har åbnet muligheden for at bruge en hjemmeside til at anvende og prisen på forskellige lån.
Denne side vil fokus på at låne penge, men endnu mere om, hvordan det er muligt at låne penge online. Vi vil beskæftige sig med forskellige betingelser, omkostninger, at de fleste lånegivare have. Men vi altid anbefaler, at du altid læse alle de betingelser, samt data fra lånegivaren.

Lån penge online

Der er en række aktører på gæld markedet i dag, nogle er større långivere, mens andre er mindre og fokuserede på SMS, små lån.
Dette gør det vanskeligere at vælge, hvor de skal sætte deres lån. Hver långiver har forskellige betingelser, omkostninger og amorteringssätt på de lån, de yder.
Når alt kommer til alt, er det heller ikke sikkert, at denne særlige långiver du ønsker at have lån med tilskud netop dit lån.
Derfor kunne det være smart at forhøre behovene hos de mange lånegivare på samme tid, og sammenligne lån vil være billigst for dig.
Noget vigtigt, når du tager lån er, at man ser på de samlede omkostninger, de betingelser også bør læses i både en og to gange for at være sikker på at alt er igenomgått.

Når du ønsker at låne penge, hvad enten det er at låne penge online eller at gå til din lokale filial og få et lån, disse forskellige lånegivare forskellige krav til lånetagaren. Disse krav er, at lånegivaren ønsker at kunne se, at lånetagaren have mulighed for på en eller anden måde være i stand til at betale sagens omkostninger og renter på lånet, men også at det betaler sig / amortiseret i rette tid.
En person, der ikke behøver at have mulighed for at betale sagens omkostninger og tilbagebetalingstid på lånet er normalt ikke få et lån. Men der er visse formildende tidspunkter, hvor kan det stadig være muligt. Det er hvis du har en kautionist der kan give en garanti for lånet. Denne person indvilger i at tilbagebetale lån på mandag i det usandsynlige skulle løbe ind i finansielle trångsmål.

De personer, der har dårlig kreditværdighed kan også have problemer med at optage et lån, men vi ser på nogle långivere, der kan hjælpe dig med lån, selv om der er betalingsforsømmelse.

Forskellige typer af lån
Der er flere typer af obligationsmarkedet i Sverige. Her vil vi nævne et par af disse. Vi vil mere specifikt at gå i detaljer i hvert af de underordnede kan du finde her.

Lån penge online
I de sidste mange selv vidste, hvad der blev kaldt bankmand, og det gjorde sin bankärrende direkte på grenen. Men i dagens informationssamfund, så går mere og mere hyppigt til banken til at udføre deres bankärrende. Dette har banker / lånegivare opmærksomhed og er derfor begyndt at tilbyde tjenester til at låne penge online.

billigt Andelsboliglån

Ejendom Kredit er en af de mest almindelige lån i Sverige. De fleste af de mennesker, der køber et hjem tager en ejendom lån til at finansiere bostadsköpet.
En ejendomslån tendens til at være lånet blev ydet til den laveste rente, at når banken / lånegivaren har hjemme som sikkerhed, hvis det ikke er muligt at foretage betalinger.
Ejendom pengeinstitutter er normalt opdelt i Topplån, Bottenlån.

Kreditkort - Kreditlån
Kreditkort er mange der ikke ser som et lån, men det er en form for lån. Den låner penge fra kreditkortsbolaget i en vis periode til sent betale lånet tilbage.
Dette, sammen med ejendomslån er de mest almindelige typer af lån finner. Det er også det lån, der er mest er den letteste at gå glip af.

Låne penge på trods af betaling standard
Personer, der har dårlig kreditværdighed kan have store problemer at få større lån, for eksempel, bolig, bil eller andre lån til andre objekter. Der er én og andre långivere i danmark, der gør det muligt at opnå et lån er fastsat betalingsforsømmelse. Kravet fra lånegivaren i disse tilfælde er tilbøjelig til at være en garant og / eller at du kan vise, at der er kapital til at være i stand til at tilbagebetale lånet.

Vi håber du vil finde svarene her for at skitsere bekymring for, at lån penge online.

Setting Joseph Conrad’s classic novel to music.

by Siobhan Roberts

Published in the June 2008 issue.

brooklyn — On a November night, an audience gathered in the Great Room at American Opera Projects headquarters to get an early glimpse of an unlikely addition to the cultural canon: an opera based on Joseph Conrad’s Heart of Darkness. The librettist, London artist Tom Phillips (whose portrait of Iris Murdoch hangs in Britain’s National PortraitGallery), introduced the performance by offering interpretative outtakes from his umpteen readings of the classic novella, published in 1902.

Read full article: The Walrus Magazine » Joseph Conrad Heart of Darkness Musical » By Siobhan Roberts » Tom Phillips

Man kan låta proxies automatgenereras utifrån cache/flush annotations eller så kan man explicit skapa proxies per böna.

Ett varningens finger dock, även om det var mycket bekvämt kändes det inte helt moget. Ett ex är att det ännu (v0.9) inte går att flusha cachen på lägre nivå än cache/grupp nivå. Ännu allvarligare är att jag upplevde en minnesläcka i ramverkets interna metadata cachning, dvs cachningen av annotations. Att sluta använda annotations och istället använda proxy-konfiguration i xml går runt problemet. Ytterligare en frustration som tyder på att lösningen inte är helt genomarbetat beskrivs här
Sammanfattningsvis, bra tänkt men vänta gärna några versioner.