You can find all the Out of the box OSGi configurations at - http://<host>:<port>/system/console/configMgr. Apart from out of the box configurations, we can also create our custom configurations. In this post, we will be creating a custom out of the box configuration which reads the user input and gets the JSON response from a web service.
Code in Action
- To make a custom OSGi configuration, we need to first create an interface whose public methods will represent the fields in the configuration.
- Create an interface named HttpConfiguration and paste the following code in it.
package org.redquark.demo.core.services;
import org.osgi.service.metatype.annotations.AttributeDefinition;
import org.osgi.service.metatype.annotations.AttributeType;
import org.osgi.service.metatype.annotations.ObjectClassDefinition;
import org.osgi.service.metatype.annotations.Option;
/**
* @author Anirudh Sharma
*
* This interface represents an OSGi configuration which can be found at -
* ./system/console/configMgr
*/
@ObjectClassDefinition(
name = "Http Configuration",
description = "This configuration reads the values to make an HTTP call to a JSON webservice")
public @interface HttpConfiguration {
/**
* This is a checkbox property which will indicate of the configuration is
* executed or not
*
* @return {@link Boolean}
*/
@AttributeDefinition(
name = "Enable config",
description = "This property indicates whether the configuration values will taken into account or not",
type = AttributeType.BOOLEAN)
public boolean enableConfig();
/**
* This method returns the protocol that is being used
*
* @return Protocol
*/
@AttributeDefinition(
name = "Protocol",
description = "Choose Protocol",
options = {
@Option(label = "HTTP", value = "http"),
@Option(label = "HTTPS", value = "https")
})
public String getProtocol();
/**
* Returns the server
*
* @return {@link String}
*/
@AttributeDefinition(
name = "Server",
description = "Enter the server name")
public String getServer();
/**
* Returns the endpoint
*
* @return {@link String}
*/
@AttributeDefinition(
name = "Endpoint",
description = "Enter the endpoint")
public String getEndpoint();
}
- This configuration has a checkbox Enable Config, a drop-down Protocol, two text fields Server, and Endpoint.
- Now create an interface HttpService to make the http call as below
package org.redquark.demo.core.services;
/**
* @author Anirudh Sharma
*
* This interface exposes the functionality of calling a JSON Web Service
*/
public interface HttpService {
/**
* This method makes the HTTP call on the given URL
*
* @param url
* @return {@link String}
*/
public String makeHttpCall();
}
- Create an implementation class HttpServiceImpl as below.
package org.redquark.demo.core.services.impl;
import org.osgi.service.component.annotations.Activate;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.metatype.annotations.Designate;
import org.redquark.demo.core.services.HttpConfiguration;
import org.redquark.demo.core.services.HttpService;
import org.redquark.demo.core.utils.Network;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* @author Anirudh Sharma
*
* Implementation class of HttpService interface and this class reads values from the OSGi configuration as well
*/
@Component(service = HttpService.class, immediate = true)
@Designate(ocd = HttpConfiguration.class)
public class HttpServiceImpl implements HttpService {
/**
* Logger
*/
private static final Logger log = LoggerFactory.getLogger(HttpServiceImpl.class);
/**
* Instance of the OSGi configuration class
*/
private HttpConfiguration configuration;
@Activate
protected void activate(HttpConfiguration configuration) {
this.configuration = configuration;
}
/**
* Overridden method of the HttpService
*/
@Override
public String makeHttpCall() {
log.info("----------< Reading the config values >----------");
try {
/**
* Reading values from the configuration
*/
boolean enable = configuration.enableConfig();
String protocol = configuration.getProtocol();
String server = configuration.getServer();
String endpoint = configuration.getEndpoint();
/**
* Constructing the URL
*/
String url = protocol + "://" + server + "/" + endpoint;
/**
* Make HTTP call only if "enable" is true
*/
if (enable) {
/**
* Making the actual HTTP call
*/
String response = Network.readJson(url);
/**
* Printing the response in the logs
*/
log.info("----------< JSON response from the webservice is >----------");
log.info(response);
return response;
} else {
log.info("----------< Configuration is not enabled >----------");
return "Configuration not enabled";
}
} catch (Exception e) {
log.error(e.getMessage(), e);
return "Error occurred" + e.getMessage();
}
}
}
- This is an OSGi component in which we are reading values from the OSGi configuration. Notice that we are using @Designate annotation to link this class to the configuration.
- Now create a simple Sling Servlet to use this component as follows.
package org.redquark.demo.core.servlets;
import javax.servlet.Servlet;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.HttpConstants;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.osgi.framework.Constants;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;
import org.redquark.demo.core.services.HttpService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* @author Anirudh Sharma
*
* This method makes an HTTP call and read the value from the JSON webservice via an OSGi configuration
*
*/
@Component(service = Servlet.class, property = {
Constants.SERVICE_DESCRIPTION + "=HTTP servlet",
"sling.servlet.methods=" + HttpConstants.METHOD_GET,
"sling.servlet.paths=" + "/bin/demo/httpcall"
})
public class HttpServlet extends SlingSafeMethodsServlet {
/**
* Generated serialVersionUid
*/
private static final long serialVersionUID = -2014397651676211439 L;
/**
* Logger
*/
private static final Logger log = LoggerFactory.getLogger(HttpServlet.class);
@Reference
private HttpService httpService;
/**
* Overridden doGet() method
*/
@Override
protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response) {
try {
String jsonResponse = httpService.makeHttpCall();
/**
* Printing the json response on the browser
*/
response.getWriter().println(jsonResponse);
} catch (Exception e) {
log.error(e.getMessage(), e);
}
}
}
- Go to the ./system/console/configMgr and search for Http Configuration and open it and configure it accordingly. Then save.
 |
| OSGi Configuration |
- Now hit the request - http://<host>:<port>/bin/demo/httpcall and you will get the JSON response as follows
[{"userId": 1, "id": 1, "title": "delectus aut autem", "completed": false}, {"userId": 1, "id": 2, "title": "quis ut nam facilis et officia qui", "completed": false}, {"userId": 1, "id": 3, "title": "fugiat veniam minus", "completed": false}, {"userId": 1, "id": 4, "title": "et porro tempora", "completed": true}, ...]
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