Apache Struts API Documentation: Class Action

org.apache.struts.action Class Action

java.lang.Object
  |
  +--org.apache.struts.action.Action

Direct Known Subclasses:

DefinitionDispatcherAction, DispatchAction, DownloadAction, ForwardAction, IncludeAction, LocaleAction, ReloadDefinitionsAction, SwitchAction, TilesAction, ViewDefinitionsAction

public class Action

extends java.lang.Object

An Action is an adapter between the contents of an incoming HTTP request and the corresponding business logic that should be executed to process this request. The controller (RequestProcessor) will select an appropriate Action for each request, create an instance (if necessary), and call the execute method.

Actions must be programmed in a thread-safe manner, because the controller will share the same instance for multiple simultaneous requests. This means you should design with the following items in mind:

• Instance and static variables MUST NOT be used to store information related to the state of a particular request. They MAY be used to share global resources across requests for the same action.
• Access to other resources (JavaBeans, session variables, etc.) MUST be synchronized if those resources require protection. (Generally, however, resource classes should be designed to provide their own protection where necessary.

When an Action instance is first created, the controller will call setServlet with a non-null argument to identify the servlet instance to which this Action is attached. When the servlet is to be shut down (or restarted), the setServlet method will be called with a null argument, which can be used to clean up any allocated resources in use by this Action.

Version:

$Rev: 164530 $ $Date: 2005-04-25 04:11:07 +0100 (Mon, 25 Apr 2005) $

token

private static TokenProcessor token

An instance of TokenProcessor to use for token functionality.

defaultLocale

protected static java.util.Locale defaultLocale

Deprecated. Use Locale.getDefault directly. This will be removed after Struts 1.2.

The system default Locale.

servlet

protected ActionServlet servlet

The servlet to which we are attached.

Action

public Action()

getServlet

public ActionServlet getServlet()

Return the servlet instance to which we are attached.

setServlet

public void setServlet(ActionServlet servlet)

Set the servlet instance to which we are attached (if servlet is non-null), or release any allocated resources (if servlet is null).

Parameters:

servlet - The new controller servlet, if any

execute

public ActionForward execute(ActionMapping mapping,
                             ActionForm form,
                             javax.servlet.ServletRequest request,
                             javax.servlet.ServletResponse response)
                      throws java.lang.Exception

Process the specified non-HTTP request, and create the corresponding non-HTTP response (or forward to another web component that will create it), with provision for handling exceptions thrown by the business logic. Return an ActionForward instance describing where and how control should be forwarded, or null if the response has already been completed.

The default implementation attempts to forward to the HTTP version of this method.

Parameters:

mapping - The ActionMapping used to select this instance

form - The optional ActionForm bean for this request (if any)

request - The non-HTTP request we are processing

response - The non-HTTP response we are creating

Throws:

java.lang.Exception - if the application business logic throws an exception.

Since:

Struts 1.1

execute

public ActionForward execute(ActionMapping mapping,
                             ActionForm form,
                             javax.servlet.http.HttpServletRequest request,
                             javax.servlet.http.HttpServletResponse response)
                      throws java.lang.Exception

Process the specified HTTP request, and create the corresponding HTTP response (or forward to another web component that will create it), with provision for handling exceptions thrown by the business logic. Return an ActionForward instance describing where and how control should be forwarded, or null if the response has already been completed.

Parameters:

mapping - The ActionMapping used to select this instance

form - The optional ActionForm bean for this request (if any)

request - The HTTP request we are processing

response - The HTTP response we are creating

Throws:

java.lang.Exception - if the application business logic throws an exception

Since:

Struts 1.1

addMessages

protected void addMessages(javax.servlet.http.HttpServletRequest request,
                           ActionMessages messages)

Adds the specified messages keys into the appropriate request attribute for use by the <html:messages> tag (if messages="true" is set), if any messages are required. Initialize the attribute if it has not already been. Otherwise, ensure that the request attribute is not set.

Parameters:

request - The servlet request we are processing

messages - Messages object

Since:

Struts 1.2.1

addErrors

protected void addErrors(javax.servlet.http.HttpServletRequest request,
                         ActionMessages errors)

Adds the specified errors keys into the appropriate request attribute for use by the <html:errors> tag, if any messages are required. Initialize the attribute if it has not already been. Otherwise, ensure that the request attribute is not set.

Parameters:

request - The servlet request we are processing

errors - Errors object

Since:

Struts 1.2.1

generateToken

protected java.lang.String generateToken(javax.servlet.http.HttpServletRequest request)

Generate a new transaction token, to be used for enforcing a single request for a particular transaction.

Parameters:

request - The request we are processing

getDataSource

protected javax.sql.DataSource getDataSource(javax.servlet.http.HttpServletRequest request)

Return the default data source for the current module.

Parameters:

request - The servlet request we are processing

Since:

Struts 1.1

getDataSource

protected javax.sql.DataSource getDataSource(javax.servlet.http.HttpServletRequest request,
                                             java.lang.String key)

Return the specified data source for the current module.

Parameters:

request - The servlet request we are processing

key - The key specified in the <data-sources> element.

Since:

Struts 1.1

getErrors

protected ActionMessages getErrors(javax.servlet.http.HttpServletRequest request)

Retrieves any existing errors placed in the request by previous actions. This method could be called instead of creating a new ActionMessages() at the beginning of an Action This will prevent saveErrors() from wiping out any existing Errors

Parameters:

request - The servlet request we are processing

Returns:

the Errors that already exist in the request, or a new ActionMessages object if empty.

Since:

Struts 1.2.1

getLocale

protected java.util.Locale getLocale(javax.servlet.http.HttpServletRequest request)

Return the user's currently selected Locale.

Parameters:

request - The request we are processing

getMessages

protected ActionMessages getMessages(javax.servlet.http.HttpServletRequest request)

Retrieves any existing messages placed in the request by previous actions. This method could be called instead of creating a new ActionMessages() at the beginning of an Action This will prevent saveMessages() from wiping out any existing Messages

Parameters:

request - The servlet request we are processing

Returns:

the Messages that already exist in the request, or a new ActionMessages object if empty.

Since:

Struts 1.2.1

getResources

protected MessageResources getResources(javax.servlet.http.HttpServletRequest request)

Return the default message resources for the current module.

Parameters:

request - The servlet request we are processing

Since:

Struts 1.1

getResources

protected MessageResources getResources(javax.servlet.http.HttpServletRequest request,
                                        java.lang.String key)

Return the specified message resources for the current module.

Parameters:

request - The servlet request we are processing

key - The key specified in the <message-resources> element for the requested bundle

Since:

Struts 1.1

isCancelled

protected boolean isCancelled(javax.servlet.http.HttpServletRequest request)

Returns true if the current form's cancel button was pressed. This method will check if the Globals.CANCEL_KEY request attribute has been set, which normally occurs if the cancel button generated by CancelTag was pressed by the user in the current request. If true, validation performed by an ActionForm's validate() method will have been skipped by the controller servlet.

Parameters:

request - The servlet request we are processing

See Also:

CancelTag

isTokenValid

protected boolean isTokenValid(javax.servlet.http.HttpServletRequest request)

Return true if there is a transaction token stored in the user's current session, and the value submitted as a request parameter with this action matches it. Returns false under any of the following circumstances:

• No session associated with this request
• No transaction token saved in the session
• No transaction token included as a request parameter
• The included transaction token value does not match the transaction token in the user's session

Parameters:

request - The servlet request we are processing

isTokenValid

protected boolean isTokenValid(javax.servlet.http.HttpServletRequest request,
                               boolean reset)

Return true if there is a transaction token stored in the user's current session, and the value submitted as a request parameter with this action matches it. Returns false under any of the following circumstances:

• No session associated with this request
• No transaction token saved in the session
• No transaction token included as a request parameter
• The included transaction token value does not match the transaction token in the user's session

Parameters:

request - The servlet request we are processing

reset - Should we reset the token after checking it?

resetToken

protected void resetToken(javax.servlet.http.HttpServletRequest request)

Reset the saved transaction token in the user's session. This indicates that transactional token checking will not be needed on the next request that is submitted.

Parameters:

request - The servlet request we are processing

saveErrors

protected void saveErrors(javax.servlet.http.HttpServletRequest request,
                          ActionErrors errors)

Deprecated. Use saveErrors(HttpServletRequest, ActionMessages) instead. This will be removed after Struts 1.2.

Save the specified error messages keys into the appropriate request attribute for use by the <html:errors> tag, if any messages are required. Otherwise, ensure that the request attribute is not created.

Parameters:

request - The servlet request we are processing

errors - Error messages object

saveErrors

protected void saveErrors(javax.servlet.http.HttpServletRequest request,
                          ActionMessages errors)

Save the specified error messages keys into the appropriate request attribute for use by the <html:errors> tag, if any messages are required. Otherwise, ensure that the request attribute is not created.

Parameters:

request - The servlet request we are processing

errors - Error messages object

Since:

Struts 1.2

saveMessages

protected void saveMessages(javax.servlet.http.HttpServletRequest request,
                            ActionMessages messages)

Save the specified messages keys into the appropriate request attribute for use by the <html:messages> tag (if messages="true" is set), if any messages are required. Otherwise, ensure that the request attribute is not created.

Parameters:

request - The servlet request we are processing.

messages - The messages to save. null or empty messages removes any existing ActionMessages in the request.

Since:

Struts 1.1

saveMessages

protected void saveMessages(javax.servlet.http.HttpSession session,
                            ActionMessages messages)

Save the specified messages keys into the appropriate session attribute for use by the <html:messages> tag (if messages="true" is set), if any messages are required. Otherwise, ensure that the session attribute is not created.

Parameters:

session - The session to save the messages in.

messages - The messages to save. null or empty messages removes any existing ActionMessages in the session.

Since:

Struts 1.2

saveErrors

protected void saveErrors(javax.servlet.http.HttpSession session,
                          ActionMessages errors)

Save the specified error messages keys into the appropriate session attribute for use by the <html:messages> tag (if messages="false") or <html:errors>, if any error messages are required. Otherwise, ensure that the session attribute is empty.

Parameters:

session - The session to save the error messages in.

errors - The error messages to save. null or empty messages removes any existing error ActionMessages in the session.

Since:

Struts 1.2.7

saveToken

protected void saveToken(javax.servlet.http.HttpServletRequest request)

Save a new transaction token in the user's current session, creating a new session if necessary.

Parameters:

request - The servlet request we are processing

setLocale

protected void setLocale(javax.servlet.http.HttpServletRequest request,
                         java.util.Locale locale)

Set the user's currently selected Locale into their HttpSession.

Parameters:

request - The request we are processing

locale - The user's selected Locale to be set, or null to select the server's default Locale