org.apache.struts2.interceptor
Class ScopeInterceptor

java.lang.Object
  com.opensymphony.xwork2.interceptor.AbstractInterceptor
      org.apache.struts2.interceptor.ScopeInterceptor

All Implemented Interfaces:

Interceptor, PreResultListener, Serializable

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 or no value means that it's in-the-middle action that is set with session properties before it's executed, and it's properties are put back to session after execution
• sessionReset - boolean value causing all session values to be reset to action's default values or application scope values, note that it is similliar 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 wizzard-like action sequences that have start and end, and sometimes we just want simply reset current session values.

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:

Serialized Form

Nested Class Summary

private static class

ScopeInterceptor.NULLClass

Field Summary

private String[]	application
private boolean	autoCreateSession
private String	key
private static Map	locks
private static Logger	LOG
private static Object	NULL
private boolean	reset
private static long	serialVersionUID
private String[]	session
private String	sessionReset
private String	type

Constructor Summary

ScopeInterceptor()
The constructor

Method Summary

protected void	after(ActionInvocation invocation, String result)
protected void	before(ActionInvocation invocation)
void	beforeResult(ActionInvocation invocation, String resultCode) This callback method will be called after the Action execution and before the Result execution.
private String	getKey(ActionInvocation invocation)
String	getSessionReset()
String	getType()
String	intercept(ActionInvocation invocation) Override to handle interception
boolean	isReset()
(package private) static void	lock(Object o, ActionInvocation invocation)
private static Object	nullConvert(Object o)
void	setApplication(String s) Sets a list of application scoped properties
void	setAutoCreateSession(String value) Sets if the session should be automatically created
void	setKey(String key)
void	setReset(boolean reset)
void	setSession(String s) Sets a list of session scoped properties
void	setSessionReset(String sessionReset)
void	setType(String type) Sets the type of scope operation
(package private) static void	unlock(Object o)

Methods inherited from class com.opensymphony.xwork2.interceptor.AbstractInterceptor

destroy, init

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

LOG

private static final Logger LOG

application

private String[] application

session

private String[] session

key

private String key

type

private String type

autoCreateSession

private boolean autoCreateSession

sessionReset

private String sessionReset

reset

private boolean reset

NULL

private static final Object NULL

locks

private static Map locks

Constructor Detail

ScopeInterceptor

public ScopeInterceptor()

The constructor

Method Detail

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

getKey

private String getKey(ActionInvocation invocation)

nullConvert

private static final Object nullConvert(Object o)

lock

static final void lock(Object o,
                       ActionInvocation invocation)
                throws Exception

Throws:

Exception

unlock

static final void unlock(Object o)

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