Spring Injection with Servlets: NoSuchBean - spring

Question

New to Spring, and working with Spring 3.2.5 trying to get injection to work with a servlet in a vanilla web app (i.e., it's not a Spring MVC web app - it's a pre-existing app I'm extending using the Spring framework). The container is Tomcat 7.0.47.
My problem is that I'm getting NoSuchBeanDefinitionException errors (No bean named 'MyServlet' is defined) when I hit the servlet. There are no errors at startup, so at least one of my beans (the ServiceImplementation bean) is getting successfully instantiated. The problem appears to be with finding the HttpRequestHandler-derived bean (MyServlet) when a new HTTP request comes in.
The full stack trace for the exception is:
org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'MyServlet' is defined
org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:570)
org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1114)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:279)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:198)
org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1121)
org.springframework.web.context.support.HttpRequestHandlerServlet.init(HttpRequestHandlerServlet.java:58)
com.random.webapp.MySpringServlet.init(Unknown Source)
javax.servlet.GenericServlet.init(GenericServlet.java:160)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
java.lang.Thread.run(Thread.java:662)
I followed this pattern for my setup:
http://andykayley.blogspot.com/2008/06/how-to-inject-spring-beans-into.html
...with one minor (I think) twist. I have a class derived from HttpRequestHandlerServlet so that I can override the init method with some application-specific stuff. The extension class looks like this:
public class MySpringServlet extends HttpRequestHandlerServlet
{
public void init() throws ServletException
{
super.init();
appSpecificInit();
}
}
The servlet I want injected looks like this:
public class MyServlet implements HttpRequestHandler
{
private IService _service = null;
public void setService( IService theService ) {
_service = theService;
}
#Override
public void handleRequest(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException
{
_service.DoSomething();
}
}
The implementation I want it injected with looks like this:
public class ServiceImplementation implements IService
{
#Override
public void DoSomething()
{
// some code goes here
}
}
These are the relevant entries in web.xml:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml /WEB-INF/implementation.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>MyServlet</servlet-name>
<servlet-class>com.random.webapp.MySpringServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MyServlet</servlet-name>
<url-pattern>/myservlet/*</url-pattern>
</servlet-mapping>
</web-app>
This is the applicationContext.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<bean id="MyServlet" class="com.random.webapp.MyServlet">
<property name="Service" ref="ServiceImplementation" />
</bean>
</beans>
...and this is what implementation.xml looks like:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<bean id="ServiceImplementation" class="com.random.webapp.ServiceImplementation">
</bean>
</beans>
I've been back and forth between the web.xml, applicationContext.xml, and implementation.xml files to double and triple check my configuration, and I don't see anything wrong with any of them, but I'm obviously missing something.
Anyone have any ideas?

Answer 1

The exception you are getting
org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'MyServlet' is defined
occurs in the init() method of the HttpRequestHandlerServlet which tries to load a delegate HttpRequestHandler object from your context based on the name you give the HttpRequestHandlerServlet in your web.xml
<servlet>
<servlet-name>MyServlet</servlet-name>
<servlet-class>com.random.webapp.MySpringServlet</servlet-class>
</servlet>
In the configuration above, that would be MyServlet. Although it appears you have it correct in
<bean id="MyServlet" class="com.random.webapp.MyServlet">
<property name="Service" ref="ServiceImplementation" />
</bean>
make sure you are loading the correct context file as declared here
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml /WEB-INF/implementation.xml</param-value>
</context-param>