CQ5/OSGi reference a unique service implementation

You should never ever do it. If you find yourself in the need of this; there’s something extremely wrong in your code. Nevertheless I found myself in needing it for some old legacy code that was almost impossible to fix in a reasonable time.

The question is: how can I reference a specific implementation of a service/component in an OSGi (therefore CQ5 as well) environment?

In the component, where you need to reference the implementation you can specify something like the following

@Reference(target="(component.name=com.foo.BarImpl)")
Bar bar;

In the component implementing the service you’ll have something like

@Component(immediate=true, metatype=false, name="com.foo.BarImpl")
@Service
class BarImpl implements Bar{
...

By default the framework will assign the fully qualified class name as component name. I prefer to specify it for making the code more readable and no one prohibit you to specify any arbitrary string like mickey mouse or goofy as component name.

Reference:

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CQ & Sling servlets: resourceType

Last time we see how to use Sling servlets with old legacy URL. Today we’ll see how to create Sling Servlets in the Sling-way: using resourceType.

Scenario

We want a component that can be dragged into a parsys. With a form that submit data to a sling servlet. Then the servlet will do the operations required.

Process

Let’s create the component following the CQ guidelines for making it drag-droppable into a parsys (allowedParents): geometrixx/components/test003. The test003.jsp will look like the following:

<%@include file="/libs/foundation/global.jsp"%>
<form name="frm" method="post" action="<c:out value="${resource.path}" />.c">
    <input type="submit" />
</form>

This JSP will answer at a GET http call showing the form. In order to use, create a content page and drag the component into a parsys.

Now it’s time to create the servlet. As usual you’ll have to register it using some felix annotations. The following servlet will be used when posting (HTTP POST) to a resource of type geometrixx/components/test003 with an extension of “c”.

package com.samples.sling;

import java.io.IOException;
import javax.servlet.ServletException;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.SlingAllMethodsServlet;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @scr.component immediate="true" metatype="false"
 * @scr.service interface="javax.servlet.Servlet"
 * @scr.property name="sling.servlet.methods" values.0="POST"
 * @scr.property name="sling.servlet.resourceTypes" values.0="geometrixx/components/test003"
 * @scr.property name="sling.servlet.extensions" values.0="c"
 */

public class ResourceTypePostServlet extends SlingAllMethodsServlet {
   private static final long serialVersionUID = 8795673847499208743L;
   private final static Logger logger = LoggerFactory.getLogger(ResourceTypePostServlet.class);

   @Override
   protected void doPost(SlingHttpServletRequest request, SlingHttpServletResponse response) throws ServletException, IOException {
      logger.debug("ResourceTypePostServlet::doPost()");
      response.setContentType("text/plain");
      response.getOutputStream().print("Hello ResourceTypePostServlet World!");
   }
}

We used the sling.servlet.methods to specify which HTTP method the servlet listen to, the sling.servlet.resourceTypes to specify all the resource types is should listen to and the .extensions if you wish to specify an extension.

Remember that if you specify a sling.servlet.paths, resourceTypes, extensions and selectors will be ignored.

Now build the bundle and refresh the previously created content page (should not necessary actually). If you click on the “submit” button you’ll see the Hello World.

References:

weekly links 2010-48

It’s been a long time I’m not posting but just changed job and relocated abroad, so no time for the blog.

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