Understanding the lifecycle of an ActionForm... The ActionServlet handles requests for Struts, i.e., requests ending in *.do is common. The ActionServlet looks up the RequestProcessor associated with the module prefix. The RequestProcessor implements the handling of the lifecycle and uses RequestUtils as a fa�ade to Servlets scopes.
When a form gets submitted, Struts looks up the action-mappings for the current request path from the ModuleConfig. The ModuleConfig is the object manifestation of the struts-config.xml file, each module gets its own ModuleConfig. (Recall that the action attribute in the html:form specifies the path of the action to invoke.) Struts locates the form-bean mapping from the action-mapping associated with the request path. (This occurs in the processActionForm method of the RequestProcessor by calling the createActionForm method of RequestUtils.) If Struts does not find an ActionForm in the scope specified by the action-mapping, it will create an instance of the ActionForm identified form-bean mapping. Struts populates the ActionForm by mapping the request parameters from the HTML form variables to the JavaBean properties of the ActionForm instance. Before it populates the form, Struts calls the reset method of the ActionForm. (This occurs in the processPopulate method of the RequestProcessor by calling the populate method of RequestUtils.) If validation is required and is successful an instance of the Action class execute method will be invoked. Validation is required if the validate attribute of the action mapping is not false (the default is true). If validation fails, control will be returned to the submitting form (the input JSP) where the JSP form fields will be populated by the ActionForm. The ActionForm is valid if the validate method returns null or an empty ActionErrors collection. (This occurs in the processValidate method of the RequestProcessor.) The best way to understand the lifecycle is read the source code for the RequestProcessor. commnents below.... Rick Hightower Developer Struts/J2EE training -- http://www.arc-mind.com/strutsCourse.htm Struts/J2EE consulting -- http://www.arc-mind.com/consulting.htm#StrutsMentoring -----Original Message----- From: Rodney Paul [mailto:[EMAIL PROTECTED] Sent: Tuesday, January 13, 2004 2:47 AM To: Struts Users Mailing List (E-mail) Subject: ActionForm LifeCycle (Maybe a bug in Struts) Hi All, I was wondering if anyone knew what the lifecycle of an ActionForm is? The reason I ask is in regards to the display of variables with a <html:form>. I have noticed that the values displayed within a <html:form> are values after a reset() method has been called, *** The reset method gets called on each request. Your job is to populate the form either in the reset method with default values or populate the actionForm in an action and forward to the JSP page that has the html:form to populate application specific (look up in a database). and not after a validate method is called. **Validate is for form submission not a mechanism to populate a form. You are not using the validate method correctly. Can anyone tell me the reason for this, as I seem to think this is a bug within the Struts framework. ** Sorry. It is not. You need to get a good book on Struts.... I suggest Professional Struts by James Goodwill and me. ;) An example follows as to what I am talking about (based upon the following ActionForm): // Example ActionForm public class MyActionForm extends ActionForm { private String maximumDocuments = "3"; ... // More variables public MyActionForm() { super(); System.out.println("Constructor called"); } public void setMaximumDocuments(String maximumDocuments) { this.maximumDocuments = maximumDocuments; } public String getMaximumDocuments() { return maximumDocuments; } ... // More get/set methods public ActionErrors validate(ActionMapping actionMapping, HttpServletRequest httpServletRequest) { ActionErrors errors = new ActionErrors(); System.out.println("validate called"); System.out.println("before processing maximumDocuments: " + maximumDocuments); if(maximumDocuments == null) { maximumDocuments = "50"; // The supposed default value (if no value entered) } ******************************** BAD MOJO System.out.println("after processing maximumDocuments: " + maximumDocuments); ... // Say an error has been returned return errors; } public void reset(ActionMapping mapping, HttpServletRequest request) { System.out.println("reset called"); System.out.println("before processing maximumDocuments: " + this.maximumDocuments); this.maximumDocuments = "50"; System.out.println("after processign maximumDocuments: " + this.maximumDocuments); } } SCENARIOS: ---------------------------------------------------------------------------- -------------------------------------------- LIFECYCLE 1: From a previous page to a form which uses this ActionForm The following output gets displayed: Constructor called reset called before processing maximumDocuments: 3 after processing maximumDocuments: 50 RESULT: Here the value displayed in the form is 50 for maximumDocuments (Correct) ---------------------------------------------------------------------------- -------------------------------------------- ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ------------------ LIFECYCLE 2: If an error occurs within the ActionForm (and the value 1 has been entered for maximumDocuments) The following output gets displayed: Constructor called reset called before processing maximumDocuments: 3 after processing maximumDocuments: 50 validate called before processing maximumDocuments: 1 after processing maximumDocuments: 1 RESULT: Here the value displayed in the form is 50 for maximumDocuments (Incorrect as it should be 1) ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ------------------ Can anyone please tell me why this is happening, and how to correct this problem. Cheers Rodneyt Paul --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
