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Spring 3.0 on Google App Engine

Posted by Idris on April 19, 2009 at 1:27 PM Comments comments (28)

-- Note: If you just want the nitty gritty without my blabbing, ignore the first paragraph --

So last week I got the inspiration to try out Google App Engine after reading about the new Java support. I searched around to find some resources on getting Spring running on App Engine, but the resources were surprisingly scarce. Google points you to their "autoshoppe" example, which is a little incomplete in terms of setup and what libraries you need. Ironically, Spring Source's post about App Engine was talking about using Groovy, not Spring. Finally I found a blog entry by Sikeh. So I got a nice Hello World up and running on Spring 2, thanks to Sikeh, but I wasn't satisfied yet. I wanted Spring 3. Spring 2 is so... 2008. So I started bringing in some Spring 3 (M2) jars, played around a little more, did some Googling, and finally got Spring 3 up and running.

Here's how you'll need to setup the directory structure:

  1. Setup a Google App Engine project (I used the Eclipse plugin)
  2. Download Spring 3.0.0.M2 (or the latest version)
  3. Copy the following jar files from Spring into the /war/WEB-INF/lib directory:
  4. Spring also depends on the following jars, which you can search for around the internet, or download from my Spring Example git repository:
  5. Finally, you'll need to rename the commons-logging-1.1.1 jar to something else, like commons-logging.jar (thanks to Martin for this tip!)

Next, you'll need to configure your web.xml for Spring. In web.xml I added a catch-all mapping to my Spring dispatcher:

<servlet> <servlet-name>dispatcher</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>dispatcher</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping>

WARNING: If you use a catch-all (/*) url-pattern, the application will not work in development mode (locally), but will work on the AppEngine server. I believe this is a known bug.

For my dispatcher-servlet.xml: (also in /war/WEB-INF/)

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="" xmlns:xsi="" xmlns:p="" xmlns:context="" xsi:schemaLocation=""> <context:component-scan base-package="example.controllers" /> <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver" p:prefix="/WEB-INF/views/" p:suffix=".jsp" /> </beans>

You obviously want to change the base-package to whatever package you want. I use the InternalResourceViewResolver, and put all my views in /WEB-INF/views/. Finally, here's my (uninteresting) applicationContext.xml:

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" ""> <beans> </beans>

Now we're all done with setup! Just create a controller and a view. I made a simple hello.jsp view that outputs the request parameter "name". Here's the controller:

package example.controllers.hello; import org.springframework.stereotype.Controller; import org.springframework.ui.Model; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; @Controller public class HelloController { @RequestMapping("/hello/{name}") public String hello(@PathVariable String name, Model model) { model.addAttribute("name", name); return "hello/hello"; } }

So there you have it. Spring up and running on Google App Engine. You can see it in action at, or you can get the source at For now, this is all just a Hello Wold. I'll post more functionality later... Feel free to suggest topics in the comments!