Spring Boot - access component inside a servlet - spring

Question

I have a spring boot application that serves my jersey based api. I have a requirement to have the services layer serve blob data to a client as a stream. I wrote a servlet to do that and configured it as follows.
#Bean
public ServletRegistrationBean servletRegistrationBean(){
return new ServletRegistrationBean(new BlobReaderServlet(),"/blobReader/*");
}
However, in the servlet code I can't seem to inject any components (they are all null). I need to inject a component that actually loads the blob data from the database.
#WebServlet(name = "BlobReaderServlet",
urlPatterns = {"/blobreader"})
#Component
public class BlobReaderServlet extends HttpServlet {
Logger logger = Logger.getLogger(this.getClass().getName());
#Inject
DocumentLoaderComponent blobLoader;
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
I strongly suspect the servlet isn't a spring managed component after all and dependency injection isn't working. How can I get access to a component from the context?
UPDATE
It was much simpler than I thought.
#Override
public void init() throws ServletException {
ApplicationContext ac = (ApplicationContext) getServletConfig().getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
this.documentBlob = (DocumentBlob) ac.getBean("documentBlobBean");
}

Answer 1

You are correct that your servlet isn't a Spring managed bean. That is because you are instantiating the instance directly (i.e., calling new BlobReaderServlet() in your bean method). Another solution is to change your configuration class as follows:
#Bean
public ServletRegistrationBean servletRegistrationBean(){
return new ServletRegistrationBean(blobReaderServlet(),"/blobReader/*");
}
#Bean
public BlobReaderServlet blobReaderServlet(){
return new BlobReaderServlet();
}
This will allow Spring to manage the instance and perform autowiring on it.