How to inject Spring beans into Servlets
58 September 2011 by ludovicianul
This can be achieved in 3 simple steps:
1. Implement HttpRequestHandler
First of all your servlet class must implement the org.springframework.web.HttpRequestHandlerinterface and provide an implementation for the handleRequest() method just like you would override doPost().
2. Declare the servlet as a Spring Bean
You can do this by either adding the @Component(“myServlet”) annotation to the class, or declaring a bean with a name myServlet in applicationContext.xml.
@Component("myServlet")
public class MyServlet implements HttpRequestHandler {
...
3. Declare in web.xml a servlet named exactly as the Spring Bean
The last step is to declare a new servlet in web.xml that will have the same name as the previously declared Spring bean, in our case myServlet. The servlet class must be org.springframework.web.context.support.HttpRequestHandlerServlet.
<servlet>
<display-name>MyServlet</display-name>
<servlet-name>myServlet</servlet-name>
<servlet-class>
org.springframework.web.context.support.HttpRequestHandlerServlet
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>myServlet</servlet-name>
<url-pattern>/myurl</url-pattern>
</servlet-mapping>
Now you are ready to inject any spring bean in your servlet class.
@Component("myServlet")
public class MyServlet implements HttpRequestHandler {
@Autowired
private MyService myService;
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Technically, you cannot inject Spring beans in servlets because the servlet API has no coupling with Spring API. A more correct title is: “How to define a servlet as a Spring-bean”.
A simple servlet should perform a Spring-component look-up – by using WebApplicationContextUtils.getWebApplicationContext()
Technically, yes. This is the reason why the servlet is not declard with the actual class in web.xml, but with
org.springframework.web.context.support.HttpRequestHandlerServlet.You can perform a manual lookup, but you will loose the application consistency/readability in my opinion: for some classes you use Annotations/Autowire/etc, for others you perform manual lookup…. More elegant this wayWell.. yeah. The title is not quite accurate. It’s more about perception