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Many modern, and particularly Spring-based libraries, cannot function correctly in Sakai's current ClassLoader environment, since in component code the context ClassLoader is incorrectly set to the most recent webapp which serviced a request. The concept of the context ClassLoader was introduced in Java 2, and an increasing number of libraries are relying on it. With an incorrect context ClassLoader, many packages, such as Alfresco, or ActiveMQ cannot be used without a good deal of custom coding, in the case of Alfreso a prohibitive amount. At a lower level, the incorrect ClassLoader causes unexpected effects with many Spring-based techniques (resource loading, creating proxies etc.) which steepen the learning curve for developers who are familiar with Spring but not Sakai. (For example, transaction proxies in a component can only be defined against targets which have an interface in shared space.) Correcting the context ClassLoader is one of the functions that could be achieved by a proxy-based design (see below).
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