Java Reference
In-Depth Information
C H A P T E R 4
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Servlet Container and Frameworks
Now that you've set up your development environment and configured the SDK, it's
time to look at the design of your application. Out of the box, App Engine uses the
Java Servlet standard for web applications, but you may be able to use your favorite
framework as well. In this chapter we'll look at different libraries and frameworks that
run in App Engine. You'll build a small application with servlets and JavaServer (JSP)
pages as well as applications using Spring MVC and Adobe Flex with GraniteDS.
Choosing a Framework
Choosing the best application framework almost always generates a heated debate.
There are pros and cons for each framework, and every developer has an opinion. Some
developers may prefer a robust Enterprise JavaBeans (EJB) framework while others
prefer a lightweight, agile approach. To ensure that your application will run within the
App Engine server runtime environment, App Engine imposes some constraints that
enable applications to run “nicely” together and be scalable across multiple distributed
runtime instances.
While Google doesn't officially support the libraries or frameworks that run on App
Engine, it does take a community-oriented approach to compatibility. While many
frameworks will run seamlessly on App Engine, others will not. Some frameworks will
require modifications, and there is an active and vibrant community dedicated to
interoperability.
Popular Java libraries and frameworks are listed in Table 4-1. Frameworks marked
as compatible should work out-of-the-box with some minor configuration changes or
code tweaks. Ones marked “Semi-compatible” typically include some features that
will not operate properly due to App Engine restrictions (for example, writing to the
file system, multithreading). Most incompatible frameworks fail to run due to their
reliance on classes not supported by App Engine.
