Weblog for the AMIS Technology corner
Posts tagged aop
Configure JDeveloper 11g to work with Spring 2.5 and AOP
Dec 12th
In a recent article I described the interaction between JavaServer Faces (1.2) and Spring Framework (2.5.x): http://technology.amis.nl/blog/6655/spring-a-surprise-on-a-jsf-developer-how-spring-beans-can-become-jsf-managed-beans. I created a JDeveloper 11g web application that I ran on the integrated WebLogic Server 11g (10..3.2). In this article I will explain the configuration steps I had to go through for making JDeveloper and WebLogic run my simple JSF/Spring application.
1. Create a new generic JDeveloper application; set the project name and add the JSF library
2. Install the JDeveloper Spring extension through the Check for Updates facility under Help in the main menu
Spring a surprise on a JSF developer – how Spring beans can become “JSF Managed Beans”
Dec 11th
Recently I was looking at a JavaServer Faces application, that did something relatively simple – but was exhibiting strange behavior. The output shown on the page (and this is a simplified version of the real life situation) was:
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I had been asked to look into the situation and correct it. Before starting to make any changes I decided to familiarize myself with the application as it currently was. And then they almost tricked me.
The JSF page had a simple outputText component with an EL Expression in its value attribute. Something like:
<h:outputText value="#{someBean.property}"/>
I decided to take a look at the code for that bean, to understand the logic behind deriving the value of the outputText. So I first opened the faces-config.xml file to find the managed bean declaration that would tell me which class definition was behind the bean included in the EL expression. However, the faces-config.xml did not contain any managed bean definitions at all. None. And yes, I tried to see whether the web.xml specified any other faces-config.xml alternatives. But it did not.
Slowly it dawned on me Read the rest of this entry »
Pulling the rug from under your feet while keeping standing – Using the Hot Swappable Target Source in Spring AOP
Jun 19th
Spring AOP offers a wealth of new options in programming as well as designing Java applications. A somewhat more advanced feature is the Hot Swappable Target Source. The concept of a hot swappable target source is linked to the use of proxies instead of concrete object implementations, which is the heart of standard, run-time JDK based AOP. To advise an object with aspects, such as described in my previous post Getting into Spring AOP – Implementing simple business logic on top of Domain Objects using Aspect Oriented Programming, a proxy is created. This proxy intercepts method calls intended for the underlying target object and applies aspects for all specified pointcuts. Usually the wrapped target object still gets called somewhere in the middle of executing all the aspects that were advised. Note that the code using the proxy is not aware of the fact that it is not using a 'normal' implementation of the interface it is programmed against but instead a proxy. It does not matter for the code; only when you ask for the myobject.getClass() will get quite another classname than you would expect. However myobject instanceof interface will still result in true. Suppose we have advised an object implementing the Employee interface. The advise adds some validation logic that is executed just prior to invoking the set-methods on the Employee interface (for example to ensure that Salesmen do not get paid too much and that no employee is called John Doe). Since the code using the object is now in reality using a proxy that itself refers a 'real' EmployeeImpl object (EmployeeImpl is a class that implements the Employee interface), it should theoretically be possible to swap one EmployeeImpl currently use as proxy target with another one. Without the program noticing it, it would all of a sudden deal with a completely new underlying object. We will first show that such a thing is indeed possible – and in a fairly simple manner, and then we will discuss why you might one to do something like that. Read the rest of this entry »
