Class ScopeInterceptor

java.lang.Object
org.apache.struts2.interceptor.AbstractInterceptor
org.apache.struts2.interceptor.ScopeInterceptor
All Implemented Interfaces:
Serializable, ConditionalInterceptor, Interceptor, PreResultListener

public class ScopeInterceptor extends AbstractInterceptor implements PreResultListener

This is designed to solve a few simple issues related to wizard-like functionality in Struts. One of those issues is that some applications have a application-wide parameters commonly used, such pageLen (used for records per page). Rather than requiring that each action check if such parameters are supplied, this interceptor can look for specified parameters and pull them out of the session.

This works by setting listed properties at action start with values from session/application attributes keyed after the action's class, the action's name, or any supplied key. After action is executed all the listed properties are taken back and put in session or application context.

To make sure that each execution of the action is consistent it makes use of session-level locking. This way it guarantees that each action execution is atomic at the session level. It doesn't guarantee application level consistency however there has yet to be enough reasons to do so. Application level consistency would also be a big performance overkill.

Note that this interceptor takes a snapshot of action properties just before result is presented (using a PreResultListener), rather than after action is invoked. There is a reason for that: At this moment we know that action's state is "complete" as it's values may depend on the rest of the stack and specifically - on the values of nested interceptors.

Interceptor parameters:

  • session - a list of action properties to be bound to session scope
  • application - a list of action properties to be bound to application scope
  • key - a session/application attribute key prefix, can contain following values:
    • CLASS - that creates a unique key prefix based on action namespace and action class, it's a default value
    • ACTION - creates a unique key prefix based on action namespace and action name
    • any other value is taken literally as key prefix
  • type - with one of the following
    • start - means it's a start action of the wizard-like action sequence and all session scoped properties are reset to their defaults
    • end - means that session scoped properties are removed from session after action is run
    • any other value throws IllegalArgumentException
  • sessionReset - name of a parameter (defaults to 'session.reset') which if set, causes all session values to be reset to action's default values or application scope values, note that it is similar to type="start" and in fact it does the same, but in our team it is sometimes semantically preferred. We use session scope in two patterns - sometimes there are wizard-like action sequences that have start and end, and sometimes we just want simply reset current session values.
  • reset - boolean, defaults to false, if set, it has the same effect as setting all session values to be reset to action's default values or application.
  • autoCreateSession - boolean value, sets if the session should be automatically created.

Extending the interceptor:

There are no know extension points for this interceptor.

Example code:

 
 <!-- As the filter and orderBy parameters are common for all my browse-type actions,
      you can move control to the scope interceptor. In the session parameter you can list
      action properties that are going to be automatically managed over session. You can
      do the same for application-scoped variables-->
 <action name="someAction" class="com.examples.SomeAction">
     <interceptor-ref name="basicStack"/>
     <interceptor-ref name="hibernate"/>
     <interceptor-ref name="scope">
         <param name="session">filter,orderBy</param>
         <param name="autoCreateSession">true</param>
     </interceptor-ref>
     <result name="success">good_result.ftl</result>
 </action>
 
 
See Also:
  • Constructor Details

    • ScopeInterceptor

      public ScopeInterceptor()
      The constructor
  • Method Details

    • setApplication

      public void setApplication(String s)
      Sets a list of application scoped properties
      Parameters:
      s - A comma-delimited list
    • setSession

      public void setSession(String s)
      Sets a list of session scoped properties
      Parameters:
      s - A comma-delimited list
    • setAutoCreateSession

      public void setAutoCreateSession(String value)
      Sets if the session should be automatically created
      Parameters:
      value - True if it should be created
    • after

      protected void after(ActionInvocation invocation, String result) throws Exception
      Throws:
      Exception
    • before

      protected void before(ActionInvocation invocation) throws Exception
      Throws:
      Exception
    • setKey

      public void setKey(String key)
    • beforeResult

      public void beforeResult(ActionInvocation invocation, String resultCode)
      Description copied from interface: PreResultListener
      This callback method will be called after the Action execution and before the Result execution.
      Specified by:
      beforeResult in interface PreResultListener
      Parameters:
      invocation - the action invocation
      resultCode - the result code returned by the action (eg. success).
    • getType

      public String getType()
      Returns:
      The type of scope operation, "start" or "end"
    • setType

      public void setType(String type)
      Sets the type of scope operation
      Parameters:
      type - Either "start" or "end"
    • getSessionReset

      public String getSessionReset()
      Returns:
      Gets the session reset parameter name
    • setSessionReset

      public void setSessionReset(String sessionReset)
      Parameters:
      sessionReset - The session reset parameter name
    • intercept

      public String intercept(ActionInvocation invocation) throws Exception
      Description copied from class: AbstractInterceptor
      Override to handle interception
      Specified by:
      intercept in interface Interceptor
      Specified by:
      intercept in class AbstractInterceptor
      Parameters:
      invocation - the action invocation
      Returns:
      the return code, either returned from ActionInvocation.invoke(), or from the interceptor itself.
      Throws:
      Exception - any system-level error, as defined in Action.execute().
    • isReset

      public boolean isReset()
      Returns:
      True if the scope is reset
    • setReset

      public void setReset(boolean reset)
      Parameters:
      reset - True if the scope should be reset