Improve Intercepting Filter Javadoc

intercepting-filter/src/main/java/com/iluwatar/intercepting/filter/App.java

@@ -1,9 +1,33 @@
 package com.iluwatar.intercepting.filter;
 
 /**
- *
- * This is an app that checks whether the order request is valid through pre-processing done via {@link Filter}.
- * Each field has its own corresponding {@link Filter}
+ * 
+ * When a request enters a Web application, it often must pass several entrance 
+ * tests prior to the main processing stage. For example,
+ * - Has the client been authenticated?
+ * - Does the client have a valid session?
+ * - Is the client's IP address from a trusted network?
+ * - Does the request path violate any constraints?
+ * - What encoding does the client use to send the data?
+ * - Do we support the browser type of the client?
+ * Some of these checks are tests, resulting in a yes or no answer that determines 
+ * whether processing will continue. Other checks manipulate the incoming data 
+ * stream into a form suitable for processing.
+ * <p>
+ * The classic solution consists of a series of conditional checks, with any failed 
+ * check aborting the request. Nested if/else statements are a standard strategy, 
+ * but this solution leads to code fragility and a copy-and-paste style of programming, 
+ * because the flow of the filtering and the action of the filters is compiled into 
+ * the application.
+ * <p>
+ * The key to solving this problem in a flexible and unobtrusive manner is to have a 
+ * simple mechanism for adding and removing processing components, in which each 
+ * component completes a specific filtering action. This is the Intercepting Filter
+ * pattern in action.
+ * <p>
+ * In this example we check whether the order request is valid through pre-processing 
+ * done via {@link Filter}. Each field has its own corresponding {@link Filter}
+ * <p>
  * @author joshzambales
  *
  */