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I'm writing a Java web app using Spring MVC. I have a background process that goes through the database and finds notifications that must be e-mailed to my users. These e-mail messages need to include hyperlinks to the application. This seems like a fairly common pattern for a web app, but I'm having trouble.
How do I derive my application's fully qualified URL, with server name and context path? I don't have access to any of the methods in HttpServletRequest because I'm running this as a background process, not in response to a web request. The best I can do is get access to ServletContext.
Currently I'm putting the base URL into a configuration file and reading it at startup, but this application is going to be licensed and deployed to customers' application servers, and if possible I'd like them not to have to configure this manually.
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public interface ServletContext. Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file. There is one context per "web application" per Java Virtual Machine.
The typical way of getting the context path is through the HttpServletRequest class. Simply you can add a HttpServletRequest parameter to your controller method and then get the context path using getContextPath() method. Now that you get the context path, you can pass it to the services that need it.
ServletContext. Context/Application scope begins when a webapp is started and ends when it is shutdown or reloaded. Parameters/attributes within the application scope will be available to all requests and sessions. The Context/Application object is available in a JSP page as an implicit object called application.
It's used to wire the configurations from Spring beans together and use them for the application. Use ApplicationContext if you want to retrieve the information of Spring beans. Use ServletContext if you want to get/set attribute those shared to all Servlet.
It is not recommended to dynamically prepare the URL at run time, especially based on ServletRequest. This is primarily because you have no idea of the URL that users would be using to access the application - the application server could be behind a web server, a firewall or a load balancer. To keep it short, one cannot predict network topologies.
Your current technique of fetching the URL from the property file is good enough to resolve the said issue. Maybe you should look at providing an administrative console to manage the URL appearing in mails, especially if there is an admin console in place, or if there are related options that should go into one.
Edit: My last point echoes what Tony has spoken of.
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