SpringDM笔记18-Designing OSGi Enterprise Applications
1. Organizing OSGi components
??? (1) ORGANIZING THE DEPENDENCIES
??? The WAR Structure:
??? ■ It’s a ZIP file
??? ■ Downloadable resources (images, JavaScript files) are located at the root of the WAR
??? ■ Application classes (servlet, web controllers) are located in WEB-INF/classes
??? ■ Libraries and frameworks (packaged as JAR files) are in WEB-INF/lib
??? Thanks to OSGi's sophisticated classloading mechanisms, OSGi supports this scenario out of the
??? box:
??? different versions of the same library can coexist in a container.
??? (2) ORGANIZING THE APPLICATION
??? Some guidelines for developing OSGi applications:
??? ■ Separate the static components from the dynamic components:
??? (1)Static components are bundles that define APIs by exporting interface-based Java packages.
??? These bundles don’t contain a Spring application context (or a BundleActivator) and don’t register
??? or reference any OSGi services.
??? (2)Dynamic components are bundles that import Java packages from static bundles, provide
??? implementations, and usually register OSGi services. As this is a Spring DM book, these bundles
??? are Spring-powered.
??? ■ Design Layered Application: （用SOA设计的思想设计）
??? Perhaps exporting the packages of data access object (DAO) interfaces is useless, because what
??? we’re really interested in is the business services. Remember, OSGi is sometimes referred to as
??? a service-oriented architecture (SOA) in a JVM. We can still define the service API, but the??
??? implementation can hide its inner workings. We can then reorganize our bundles in a simpler way
??? and gather the service implementation and data access layer in the same bundle—the backend
??? bundle.
2. Defining interactions between application bundles
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