Thursday, May 7, 2015

Embedded Jetty in Spring MVC, IoC/DI


I was trying to configure embedded jetty in a 
spring application that implements MVC(Model View Controller). I want to utilize single spring applicationContext xml file for IoC(Inversion of Control) and DI(Dependency Injection) on dispatcher servlets.

The goal is to be able to use or reference beans configured/located on already been loaded spring application context. Read and understand my resolution below.

This is what my main method look like:
LOG.info("Application starting");
_applicationContext = new ClassPathXmlApplicationContext(_resourceLocations);

_webServer = new Server();
SelectChannelConnector connector = new SelectChannelConnector();
connector.setHost("localhost");
connector.setPort(8080);
_webServer.addConnector(connector);

WebAppContext webAppContext = new WebAppContext(_webServer, "path to web app folder", "/");

GenericWebApplicationContext webApplicationContext = new GenericWebApplicationContext();
webApplicationContext.setServletContext(webAppContext.getServletContext());
webApplicationContext.setParent(_applicationContext);

webAppContext.getServletContext().setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, webApplicationContext);
webApplicationContext.refresh();

ServletHandler servletHandler = new ServletHandler();

ServletHolder servletHolder = new ServletHolder(new DispatcherServlet());
servletHolder.setName("dispatcher");
servletHandler.addServlet(servletHolder);

ServletMapping servletMapping = new ServletMapping();
servletMapping.setServletName(servletHolder.getName());
servletMapping.setPathSpec("*.htm");
servletHandler.addServletMapping(servletMapping);

webAppContext.setServletHandler(servletHandler);
_webServer.addHandler(webAppContext);

RequestLogHandler logHandler = new RequestLogHandler();
NCSARequestLog ncsaLog = new NCSARequestLog();
ncsaLog.setExtended(true);
ncsaLog.setFilename("logs/jetty-yyyy_mm_dd.log");
logHandler.setRequestLog(ncsaLog);
_webServer.addHandler(logHandler);

LOG.info("Starting main application context");
_applicationContext.start();

LOG.info("Starting Jetty Server");

try {
_webServer.start();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

LOG.info("Application started");
return null;

 The idea is that DispatcherServlet's context is child context of  GenericWebApplicationContext which in turn is a child of ClassPathXmlApplicationContext. Explicitly invoking setParent() gives you the access to all beans from the web application context.

Hope this helps. Feel free to leave your comment or suggestions.

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