com.github.stefanbirkner.filtertools.filter.http.filteraction

Interface FilterAction

All Known Implementing Classes:

FilterActionSwitch

public interface FilterAction

FilterActions are components of a frequently used type of Filters. Such filters do a piece of work before or after calling the FilterChain, but never wrap the request or response. Examples are filters that set request attributes or cookies. This piece of works can be encapsulated by a FilterAction.

Build a Filter Action

execute(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) is an action's method that executes the desired piece of work. The action can be configured by init(javax.servlet.FilterConfig) which is the equivalent to Filter.init(javax.servlet.FilterConfig). The destroy() can be used to clean up resources. A simple filter action may look like this.

 public class YourAction implements FilterAction {
   private YourService service;

   public void init(FilterConfig config) throws ServletException {
       String param = config.getInitParameter("your parameter");
       service = new YourService(param);
   }

   public void execute(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
       request.setAttribute("your attribute", service.getNextValue());
   }

   public void destroy() {
       service.shutdown();
   }
 }
 

Build a Filter with Filter Actions

Filter tools provides tow filter that are executing actions. The PreFilterChainActionsFilter executes actions before it invokes the filter chain and the PostFilterChainActionsFilter executes it afterwards. You use filter actions by creating your own filter that inherits one of the two filters. Look at this example:

 public class YourFilter implements PreFilterChainActionsFilter {
   public YourFilter() {
       super(new FirstAction(), new SecondAction());
   }
 }
 

Select one of two Filter Actions

Filter tools provides a FilterActionSwitch that selects one of two actions based on a Predicate

FilterAction actionSwitch = FilterActionSwitch.execute(new DoSomething())
    .when(new APredicate())
    .otherwiseExecute(new DoSomethingElse());

Since:

1.2.0

Method Summary

Modifier and Type	Method and Description
void	destroy() Called to indicate to an action that it is being taken out of service.
void	execute(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) The execute method of the action is called by a filter before or after the FilterChain is invoked depending on the filter itself.
void	init(javax.servlet.FilterConfig filterConfig) Called to indicate to an action that it is being placed into service.

Method Detail

init

void init(javax.servlet.FilterConfig filterConfig)
   throws javax.servlet.ServletException

Called to indicate to an action that it is being placed into service. The init method is called exactly once The init method must complete successfully before the action executed.

Parameters:

filterConfig - A filter configuration object used by a servlet container to pass information to an action during initialization.

Throws:

javax.servlet.ServletException - if an exception has occurred that interferes with the action's normal operation

execute

void execute(javax.servlet.http.HttpServletRequest request,
             javax.servlet.http.HttpServletResponse response)
      throws IOException,
             javax.servlet.ServletException

The execute method of the action is called by a filter before or after the FilterChain is invoked depending on the filter itself.

Parameters:

request - an HttpServletRequest

response - an HttpServletResponse

Throws:

IOException - if an input or output exception occurs

javax.servlet.ServletException - if an exception has occurred that interferes with the action's normal operation

destroy

void destroy()

Called to indicate to an action that it is being taken out of service. This method is only called once. After this method is called, the execute method is not called again on this instance of the filter.

This method gives the action an opportunity to clean up any resources that are being held (for example, memory, file handles, threads).