Legacy code: Integrating with existing servlet

[tonylmai]

Hi all,

We have a chart library that we use to serve images for our application. To integrate with our Seam app, we wrote a simple servlet that invokes the library and return a URL of the created image. The library requires a datasource and user ID so I use dependency injection. However, during runtime, the injection objects are all null.

Here is the code for the servlet:

public class GetChart extends HttpServlet {

 @In("quoteDS")
 private ChartDatasource quoteDS;

 @In
 private WcLoginSession wcLoginSession;

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 try {
 writeChart(request, response);
 } catch (Exception e) {
 e.printStackTrace();
 }
 }

 private void writeChart(HttpServletRequest request, HttpServletResponse response) throws Exception {
 OutputStream out = response.getOutputStream();
 try {
 response.setContentType("img/png");
 ChartCriteria chartCriteria = ChartCriteria.fromRequest(request);
 if (chartCriteria != null) {
 writeChart(out, chartCriteria);
 }
 } finally {
 try {
 out.flush();
 } catch (IOException e) {
 e.printStackTrace();
 }
 out.close();
 }
 }

 private void writeChart(OutputStream out, ChartCriteria chartCriteria) {
 Chart chart = new Chart(wcLoginSession.getMyLoginId(), chartCriteria);
 try {
 chart.build(quoteDS, out);
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
}

Why would my injections not working? Is there a better way to do this?

I am running Seam 2.0.0CR2 with JBoss 4.2.1GA.

Thanks in advance for your help.

[mirko27]

You can Inject only to a seam component? And seam component is the one which declares @Name annotation. I dont see that on your servlet.

[dhinojosa]

you can also use Component.getInstance("component Name"); and remove all @In annotations.

[nickarls]

Are you using a web:context-filter as documented in 25.1.4.7?

[tonylmai]

I only enabled the servlet filter suggested in the document.

<web:context-filter url-pattern="*" />

I must be missing something. The document mentioned that I need to pass along the conversationId but I am sure how to do that.

Any suggestion?

Thanks

[tonylmai]

BTW, cid is on the URL. Is that sufficient for the servlet filter or I need to do something more?

[nickarls]

I think it's mostly using Conversation.getId() for returning new conversations, you shouldn't need to use it normally(?)

And Contexts.lookupInStatefulContexts("nameofthebean") still returns null?

[tonylmai]

Component.getInstance("component Name") threw the following exceptions:

java.lang.IllegalStateException: No application context active

:(

[nickarls]

not sure that mapping the "*" is a good idea, try to hit the URL where the servlet is mapped to...

[pmuir]

You need to map a specific prefix or suffix as nickarls
says

[tonylmai]

I have put the specific prefix but I still can't get it to work.

<web:context-filter url-pattern="http://localhost:8080/trading/getchart/" />

My servlet is as followed:

public class GetChart extends HttpServlet {
 private static final long serialVersionUID = -6087384050664740696L;

 @In("wcQuoteDS")
 private ChartDatasource quoteDS;

 protected void doGet(HttpServletRequest request, HttpServletResponse response) .....
 try {
 try {
 quoteDS = (ChartDatasource) Component.getInstance("wcQuoteDS");

 .... // Problematic

 } catch (Exception e) {
 e.printStackTrace();
 }
 }

ChartDatasourcebean is as followed:

@Scope(ScopeType.APPLICATION)
@Name("wcQuoteDS")
@Startup(depends={"wcClientMgr"})
public class QuoteDatasource implements .... {
 @In (required = true)
 private static ClientManager wcClientMgr;

...
{

I can't figure out what is wrong with it. Can someone help?

Thanks
-Tony

[dustismo]

I sincerely doubt that this is valid:

url-pattern="http://localhost:8080/trading/getchart/"

try this instead:

url-pattern="/trading/getchart/*"

also you probably want to create to create the Component if it doesnt already exist in the current convo. ala:

quoteDS = (ChartDatasource) Component.getInstance("wcQuoteDS",true);

hope that helps,
Dustin

[tonylmai]

You were right on with the URL there Dustin. With that fix, the app is up and running now.

Thank you for your advice.
-Tony