{"id":378,"date":"2015-11-18T11:17:02","date_gmt":"2015-11-18T11:17:02","guid":{"rendered":"http:\/\/smartfoxserver.com\/blog\/?p=378"},"modified":"2022-05-17T08:11:03","modified_gmt":"2022-05-17T08:11:03","slug":"http-request-and-extensions-integration","status":"publish","type":"post","link":"https:\/\/smartfoxserver.com\/blog\/http-request-and-extensions-integration\/","title":{"rendered":"HTTP Request and Extensions integration"},"content":{"rendered":"\n

In this new recipe we’re going to take a look at how we can integrate regular HTTP calls with the SmartFoxServer runtime and specifically how to communicate with Extension code via HTTP GET\/POST requests.<\/p>\n\n\n\n

Common applications of the HTTP\/Extension interoperability are debugging interfaces and administration UIs. With this approach developers can easily build a simple web interface that reports that game state, monitors data structures, users etc… allowing to quickly debug problems while testing, triggering events and so on.<\/p>\n\n\n\n\n\n\n\n

\u00bb A working example<\/h2>\n\n\n\n

Let’s take a look at a simple use case that illustrates how to work with servlets (Jetty) and extensions (SFS2X). We will start by building our simple SFS2X Extension and implementing the handleInternalMessage(…) <\/strong>method, which is at the bridge between the two worlds.<\/p>\n\n\n

\npackage sfs2x.test.http.ext;\n\nimport com.smartfoxserver.v2.extensions.SFSExtension;\n\npublic class SimpleSumExtension extends SFSExtension\n{\n\t@Override\n\tpublic void init()\n\t{\n\t\ttrace("Simple Sum Extension -- Ready");\n\t}\n\n\t@Override\n\tpublic Object handleInternalMessage(String cmdName, Object params)\n\t{\n\t\tObject result = null;\n\n\t\ttrace(String.format("Called by: %s, CMD: %s, Params: %s", Thread.currentThread().getName(), cmdName, params));\n\n\t\tif (cmdName.equals("numbers"))\n\t\t{\n\t\t\tString[] nums = ((String) params).split("\\\\,");\n\n\t\t\tint sum = 0;\n\n\t\t\tfor (String item : nums)\n\t\t\t{\n\t\t\t\ttry\n\t\t\t\t{\n\t\t\t\t\tsum += Integer.parseInt(item);\n\t\t\t\t}\n\t\t\t\tcatch(NumberFormatException nfe)\n\t\t\t\t{\n\t\t\t\t\t\/\/ Skip and continue\n\t\t\t\t}\n\t\t\t}\n\n\t\t\tresult = sum;\n\t\t}\n\n\t\treturn result;\n\t}\n}\n<\/pre>\n\n\n\n
The handleInternalMessage(…)<\/strong> method is very generic, allowing us to send a “command” string and a parameter object. The latter could be anything from a number to an array or collection of specific objects. Similarly the return value could be any object.<\/p>\n\n\n\n
In our case we define a command called “numbers” <\/em>and expect a String containing comma separated numbers. We’ll take these numbers, sum them all together and return the result back to the servlet.<\/p>\n\n\n\n
This will allow us to use a simple url request such as<\/p>\n\n\n\n
http:\/\/localhost:8080\/servlet?numbers=1,2,3,4<\/strong><\/p>\n\n\n\n
send the data to the Extension, obtain the result back and output it to our HTML page, integrating it with other dynamic data, JSP pages, template engines etc…<\/p>\n\n\n\n
In order to build the Extension we will export a jar file from our IDE of choice and deploy it under extensions\/HTTPSumExtension\/SumExtension.jar<\/strong><\/p>\n\n\n\n
Then we open the AdminTool <\/strong>> Zone Configurator<\/strong>, select our Zone of choice (e.g. BasicExamples) and activate the Extension:<\/p>\n\n\n\n
\"SumExt\"<\/a><\/figure><\/div>\n\n\n\n
\u00bb The servlet<\/strong><\/p>\n\n\n\n
Next we proceed with the creation of the simple servlet that will act as the bridge between the browsers’s requests and the SFS2X’s Extension.<\/p>\n\n\n
\npackage sfs2x.test.http;\n\nimport java.io.IOException;\n\nimport javax.servlet.ServletException;\nimport javax.servlet.http.HttpServlet;\nimport javax.servlet.http.HttpServletRequest;\nimport javax.servlet.http.HttpServletResponse;\n\nimport com.smartfoxserver.v2.SmartFoxServer;\nimport com.smartfoxserver.v2.extensions.ISFSExtension;\n\n@SuppressWarnings("serial")\npublic class ExtensionHTTPFacade extends HttpServlet\n{\n\tprivate final static String CMD_NUMBERS = "numbers";\n\n\tprivate SmartFoxServer sfs;\n\tprivate ISFSExtension myExtension;\n\n\t@Override\n\tpublic void init() throws ServletException\n\t{\n\t\tsfs = SmartFoxServer.getInstance();\n\t\tmyExtension = sfs.getZoneManager().getZoneByName("BasicExamples").getExtension();\n\t}\n\n\t@Override\n\tprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException\n\t{\n\t\tObject result = null;\n\t\tString numbers = req.getParameter(CMD_NUMBERS);\n\n\t\tif (numbers != null)\n\t\t\tresult = "RES: " + myExtension.handleInternalMessage(CMD_NUMBERS, numbers);\n\t\telse\n\t\t\tresult = "Please pass a list of comma separated values called 'numbers'. Example ?numbers=1,2,3,4";\n\n\t\tresp.getWriter().write(result.toString());\n\t}\n}\n<\/pre>\n\n\n\n
All of the “magic” happens in the init() <\/strong>method were we obtain a reference to the SmartFoxServer instance. From there we proceed by accessing the Zone we want to work with.<\/p>\n\n\n\n
As you may already know, each Zone represents a different application running in the server so the Zone is the top level object from which we can access the user’s list, room lists, the Zone Extension, the database manager etc…<\/p>\n\n\n\n
In this case we just reference the Zone’s Extension so that we can later invoke its handleInternalMessage(…)<\/strong> method.<\/p>\n\n\n\n
The doGet(…)<\/strong> implementation simply acts as a paper-pusher by taking the “numbers<\/em>” parameter, handing it over to the Extension and finally outputting the result to the client.<\/p>\n\n\n\n
\u00bb Putting it all together<\/h2>\n\n\n\n
Before we can test the solution we need to deploy the servlet. If you’re using an IDE such as Neatbeans or Eclipse you can generate a .war file with a few clicks and deploy it under SFS2X\/www\/<\/strong>. Otherwise you can do the same manually by creating this folder structure under SFS2X\/www\/ <\/strong><\/p>\n\n\n\n
\"servlet-test-deploy\"<\/a><\/figure><\/div>\n\n\n\n
The ExtensionTest folder must contain the usual WEB-INF\/<\/strong> with the compiled classes and the deployment descriptor (web,xml), which looks like this:<\/p>\n\n\n
\n<?xml version="1.0" encoding="ISO-8859-1"?>\n<web-app\n   xmlns="http:\/\/xmlns.jcp.org\/xml\/ns\/javaee"\n   xmlns:xsi="http:\/\/www.w3.org\/2001\/XMLSchema-instance"\n   xsi:schemaLocation="http:\/\/xmlns.jcp.org\/xml\/ns\/javaee http:\/\/xmlns.jcp.org\/xml\/ns\/javaee\/web-app_3_1.xsd"\n   metadata-complete="false"\n   version="3.1">\n\n\t<display-name>SFS2X Test<\/display-name>\n\n\t<servlet>\n\t\t<servlet-name>ExtensionTest<\/servlet-name>\n\t\t<servlet-class>sfs2x.test.http.ExtensionHTTPFacade<\/servlet-class>\n\t<\/servlet>\n\t<servlet-mapping>\n\t\t<servlet-name>ExtensionTest<\/servlet-name>\n\t\t<url-pattern>\/ExtensionTest<\/url-pattern>\n\t<\/servlet-mapping>\n<\/web-app>\n<\/pre>\n\n\n\n
Time to restart the server and test locally in the browser with this url:<\/p>\n\n\n\n
http:\/\/localhost:8080\/ExtensionTest\/ExtensionTest?numbers=100,60,50,112,88<\/strong><\/p>\n\n\n\n
 which will yield this:<\/p>\n\n\n\n
\"serlvet-res\"<\/a><\/figure><\/div>\n\n\n\n
 \u00bb Class loader woes<\/h2>\n\n\n\n
The simple example shown so far uses simple objects found in the JDK such as String, Integer etc… no big deal. When working with custom data, however, you may encounter class loading issues due to the fact that classes defined in an Extension are visible only under their class loader.<\/p>\n\n\n\n
Attempting to pass these objects between servlet and Extension will not work out of the box, and depending on the specific case it will require special attention at the deployment process.<\/p>\n\n\n\n
We have already discussed in many articles various ways to deploy Extension classes that are visible at the top class loader. Here are some links to learn more:<\/p>\n\n\n\n