Package org.springframework.webflow.action

Class FormAction

java.lang.Object
org.springframework.webflow.action.AbstractAction
org.springframework.webflow.action.MultiAction
org.springframework.webflow.action.FormAction
All Implemented Interfaces:
org.springframework.beans.factory.InitializingBean, Action
public class FormAction extends MultiAction implements org.springframework.beans.factory.InitializingBean
Multi-action that implements common logic dealing with input forms. This class uses the Spring Web data binding code to do binding and validation.

Several action execution methods are provided:

  • setupForm(RequestContext) - Prepares the form object for display on a form, creating it and an associated errors if necessary, then caching them in the configured form object scope and form errors scope, respectively. Also installs any custom property editors for formatting form object field values. This action method will return the "success" event unless an exception is thrown.
  • bindAndValidate(RequestContext) - Binds all incoming request parameters to the form object and then validates the form object using a registered validator. This action method will return the "success" event if there are no binding or validation errors, otherwise it will return the "error" event.
  • bind(RequestContext) - Binds all incoming request parameters to the form object. No additional validation is performed. This action method will return the "success" event if there are no binding errors, otherwise it will return the "error" event.
  • validate(RequestContext) - Validates the form object using a registered validator. No data binding is performed. This action method will return the "success" event if there are no validation errors, otherwise it will return the "error" event.
  • resetForm(RequestContext) - Resets the form by reloading the backing form object and reinstalling any custom property editors. Returns "success" on completion, an exception is thrown when a failure occurs.

Since this is a multi-action a subclass could add any number of additional action execution methods, e.g. "setupReferenceData(RequestContext)", or "processSubmit(RequestContext)".

Using this action, it becomes very easy to implement form preparation and submission logic in your flow. One way to do this follows:

  1. Create a view state to display the form. In a render action of that state, invoke setupForm to prepare the new form for display.
  2. On a matching "submit" transition execute an action that invokes bindAndValidate to bind incoming request parameters to the form object and validate the form object.
  3. If there are binding or validation errors, the transition will not be allowed and the view state will automatically be re-entered.
  4. If binding and validation are successful go to an action state called "processSubmit" (or any other appropriate name). This will invoke an action method called "processSubmit" you must provide on a subclass to process form submission, e.g. interacting with the business logic.
  5. If business processing is ok, continue to a view state to display the success view.

Here is an example implementation of such a form flow: 

     <view-state id="displayCriteria">
         <on-render>
             <evaluate expression="formAction.setupForm"/>
         </on-render>
         <transition on="search" to="executeSearch">
             <evaluate expression="formAction.bindAndValidate"/>
         </transition>
     </view-state>

When you need additional flexibility consider splitting the view state above acting as a single logical form state into multiple states. For example, you could have one action state handle form setup, a view state trigger form display, another action state handle data binding and validation, and another process form submission. This would be a bit more verbose but would also give you more control over how you respond to specific results of fine-grained actions that occur within the flow.

Subclassing hooks:

  • A important hook is createFormObject. You may override this to customize where the backing form object instance comes from (e.g instantiated transiently in memory or loaded from a database).
  • An optional hook method provided by this class is initBinder. This is called after a new data binder is created.
  • Another optional hook method is registerPropertyEditors(PropertyEditorRegistry). By overriding it you can register any required property editors for your form. Instead of overriding this method, consider setting an explicit PropertyEditorRegistrar strategy as a more reusable way to encapsulate custom PropertyEditor installation logic.
  • Override validationEnabled(RequestContext) to dynamically decide whether or not to do validation based on data available in the request context.

Note that this action does not provide a referenceData() hook method similar to that of Spring MVC's SimpleFormController. If you wish to expose reference data to populate form drop downs you can define a custom action method in your FormAction subclass that does just that. Simply invoke it as either a chained action as part of the setupForm state, or as a fine grained state definition itself.

For example, you might create this method in your subclass: 

 public Event setupReferenceData(RequestContext context) throws Exception {
        MutableAttributeMap requestScope = context.getRequestScope();
        requestScope.put("refData", lookupService.getSupportingFormData());
        return success();
 }
... and then invoke it like this: 
     <view-state id="displayCriteria">
         <on-render>
             <evaluate expression="formAction.setupForm"/>
             <evaluate expression="formAction.setupReferenceData"/>
         </on-render>
         ...
     </view-state>
This style of calling multiple action methods in a chain (Chain of Responsibility) is preferred to overriding a single action method. In general, action method overriding is discouraged.

When it comes to validating submitted input data using a registered Validator, this class offers the following options:

  • If you don't want validation at all, just call bind(RequestContext) instead of bindAndValidate(RequestContext) or don't register a validator.
  • If you want piecemeal validation, e.g. in a multi-page wizard, call bindAndValidate(RequestContext) or validate(RequestContext) and specify a validatorMethod action execution attribute. This will invoke the identified custom validator method on the validator. The validator method signature should follow the following pattern: 
         public void ${validateMethodName}(${formObjectClass}, Errors)
    For instance, having a action definition like this: 
         <evaluate expression="formAction.bindAndValidate">
         <attribute name="validatorMethod" value="validateSearchCriteria"/>
     </evaluate>
    Would result in the public void validateSearchCriteria(SearchCriteria, Errors) method of the registered validator being called if the form object class would be SearchCriteria.
  • If you want to do full validation using the validate method of the registered validator, call bindAndValidate(RequestContext) or validate(RequestContext) without specifying a "validatorMethod" action execution attribute.

FormAction configurable properties
name default description
formObjectName formObject The name of the form object. The form object will be set in the configured scope using this name.
formObjectClass null The form object class for this action. An instance of this class will get populated and validated. Required when using a validator.
formObjectScope flow The scope in which the form object will be put. If put in flow scope the object will be cached and reused over the life of the flow, preserving previous values. Request scope will cause a new fresh form object instance to be created on each request into the flow execution.
formErrorsScope flash The scope in which the form object errors instance will be put. If put in flash scope form errors will be cached until the next user event is signaled.
propertyEditorRegistrar null The strategy used to register custom property editors with the data binder. This is an alternative to overriding the registerPropertyEditors(PropertyEditorRegistry) hook method.
validator null The validator for this action. The validator must support the specified form object class.
messageCodesResolver null Set the strategy to use for resolving errors into message codes.
Author:
Erwin Vervaet, Keith Donald
See Also:
  • PropertyEditorRegistrar
  • DataBinder
  • ScopeType

  • Field Details

    • DEFAULT_FORM_OBJECT_NAME

      public static final String DEFAULT_FORM_OBJECT_NAME
      The default form object name ("formObject").
      See Also:

    • VALIDATOR_METHOD_ATTRIBUTE

      public static final String VALIDATOR_METHOD_ATTRIBUTE
      Optional attribute that identifies the method that should be invoked on the configured validator instance, to support piecemeal wizard page validation ("validatorMethod").
      See Also:

  • Constructor Details

    • FormAction

      public FormAction()
      Bean-style default constructor; creates a initially unconfigured FormAction instance relying on default property values. Clients invoking this constructor directly must set the formObjectClass property or override createFormObject(RequestContext).
      See Also:

    • FormAction

      public FormAction(Class<?> formObjectClass)
      Creates a new form action that manages instance(s) of the specified form object class.
      Parameters:
      formObjectClass - the class of the form object (must be instantiable)

  • Method Details

    • getFormObjectName

      public String getFormObjectName()
      Return the name of the form object in the configured scope.

    • setFormObjectName

      public void setFormObjectName(String formObjectName)
      Set the name of the form object in the configured scope. The form object will be included in the configured scope under this name.

    • getFormObjectClass

      public Class<?> getFormObjectClass()
      Return the form object class for this action.

    • setFormObjectClass

      public void setFormObjectClass(Class<?> formObjectClass)
      Set the form object class for this action. An instance of this class will get populated and validated. This is a required property if you register a validator with the form action (setValidator(Validator))!

      If no form object name is set at the moment this method is called, a form object name will be automatically generated based on the provided form object class using ClassUtils.getShortNameAsProperty(java.lang.Class).

    • getFormObjectScope

      public ScopeType getFormObjectScope()
      Get the scope in which the form object will be placed.

    • setFormObjectScope

      public void setFormObjectScope(ScopeType scopeType)
      Set the scope in which the form object will be placed. The default if not set is flow scope.

    • getFormErrorsScope

      public ScopeType getFormErrorsScope()
      Get the scope in which the Errors object will be placed.

    • setFormErrorsScope

      public void setFormErrorsScope(ScopeType errorsScope)
      Set the scope in which the Errors object will be placed. The default if not set is flash scope.

    • getPropertyEditorRegistrar

      public org.springframework.beans.PropertyEditorRegistrar getPropertyEditorRegistrar()
      Get the property editor registration strategy for this action's data binders.

    • setPropertyEditorRegistrar

      public void setPropertyEditorRegistrar(org.springframework.beans.PropertyEditorRegistrar propertyEditorRegistrar)
      Set a property editor registration strategy for this action's data binders. This is an alternative to overriding the registerPropertyEditors(PropertyEditorRegistry) method.

    • getValidator

      public org.springframework.validation.Validator getValidator()
      Returns the validator for this action.

    • setValidator

      public void setValidator(org.springframework.validation.Validator validator)
      Set the validator for this action. When setting a validator, you must also set the form object class. The validator must support the specified form object class.

    • getMessageCodesResolver

      public org.springframework.validation.MessageCodesResolver getMessageCodesResolver()
      Return the strategy to use for resolving errors into message codes.

    • setMessageCodesResolver

      public void setMessageCodesResolver(org.springframework.validation.MessageCodesResolver messageCodesResolver)
      Set the strategy to use for resolving errors into message codes. Applies the given strategy to all data binders used by this action.

      Default is null, i.e. using the default strategy of the data binder.

      See Also:

    • initAction

      protected void initAction()
      Description copied from class: AbstractAction
      Action initializing callback, may be overridden by subclasses to perform custom initialization logic.

      Keep in mind that this hook will only be invoked when this action is deployed in a Spring application context since it uses the Spring InitializingBean mechanism to trigger action initialisation.

      Overrides:
      initAction in class AbstractAction

    • setupForm

      public Event setupForm(RequestContext context) throws Exception
      Prepares a form object for display in a new form, creating it and caching it in the getFormObjectScope() if necessary. Also installs custom property editors for formatting form object values in UI controls such as text fields.

      A new form object instance will only be created (or more generally acquired) with a call to createFormObject(RequestContext), if the form object does not yet exist in the configured scope. If you want to reset the form handling machinery, including creation or loading of a fresh form object instance, call resetForm(RequestContext) instead.

      NOTE: This action method is not designed to be overridden and might become final in a future version of Spring Web Flow. If you need to execute custom form setup logic have your flow call this method along with your own custom methods as part of a single action chain.

      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      Returns:
      "success" when binding and validation is successful
      Throws:
      Exception - an unrecoverable exception occurs, either checked or unchecked
      See Also:

    • bindAndValidate

      public Event bindAndValidate(RequestContext context) throws Exception
      Bind incoming request parameters to allowed fields of the form object and then validate the bound form object if a validator is configured.

      NOTE: This action method is not designed to be overridden and might become final in a future version of Spring Web Flow. If you need to execute custom bind and validate logic have your flow call this method along with your own custom methods as part of a single action chain. Alternatively, override the doBind(RequestContext, DataBinder) or doValidate(RequestContext, Object, Errors) hooks.

      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      Returns:
      "success" when binding and validation is successful, "error" if there were binding and/or validation errors
      Throws:
      Exception - an unrecoverable exception occurred, either checked or unchecked

    • bind

      public Event bind(RequestContext context) throws Exception
      Bind incoming request parameters to allowed fields of the form object.

      NOTE: This action method is not designed to be overridden and might become final in a future version of Spring Web Flow. If you need to execute custom data binding logic have your flow call this method along with your own custom methods as part of a single action chain. Alternatively, override the doBind(RequestContext, DataBinder) hook.

      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      Returns:
      "success" if there are no binding errors, "error" otherwise
      Throws:
      Exception - an unrecoverable exception occured, either checked or unchecked

    • validate

      public Event validate(RequestContext context) throws Exception
      Validate the form object by invoking the validator if configured.

      NOTE: This action method is not designed to be overridden and might become final in a future version of Spring Web Flow. If you need to execute custom validation logic have your flow call this method along with your own custom methods as part of a single action chain. Alternatively, override the doValidate(RequestContext, Object, Errors) hook.

      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      Returns:
      "success" if there are no validation errors, "error" otherwise
      Throws:
      Exception - an unrecoverable exception occured, either checked or unchecked
      See Also:

    • resetForm

      public Event resetForm(RequestContext context) throws Exception
      Resets the form by clearing out the form object in the specified scope and recreating it.

      NOTE: This action method is not designed to be overridden and might become final in a future version of Spring Web Flow. If you need to execute custom reset logic have your flow call this method along with your own custom methods as part of a single action chain.

      Parameters:
      context - the request context
      Returns:
      "success" if the reset action completed successfully
      Throws:
      Exception - if an exception occured
      See Also:

    • getFormObject

      protected Object getFormObject(RequestContext context) throws Exception
      Convenience method that returns the form object for this form action. If not found in the configured scope, a new form object will be created by a call to createFormObject(RequestContext) and exposed in the configured scope.

      The returned form object will become the current form object.

      Parameters:
      context - the flow execution request context
      Returns:
      the form object
      Throws:
      Exception - when an unrecoverable exception occurs

    • getFormErrors

      protected org.springframework.validation.Errors getFormErrors(RequestContext context) throws Exception
      Convenience method that returns the form object errors for this form action. If not found in the configured scope, a new form object errors will be created, initialized, and exposed in the confgured scope.

      Keep in mind that an Errors instance wraps a form object, so a form object will also be created if required (see getFormObject(RequestContext)).

      Parameters:
      context - the flow request context
      Returns:
      the form errors
      Throws:
      Exception - when an unrecoverable exception occurs

    • createBinder

      protected org.springframework.validation.DataBinder createBinder(RequestContext context, Object formObject) throws Exception
      Create a new binder instance for the given form object and request context. Can be overridden to plug in custom DataBinder subclasses.

      Default implementation creates a standard WebDataBinder, and invokes initBinder(RequestContext, DataBinder) and registerPropertyEditors(PropertyEditorRegistry).

      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      formObject - the form object to bind onto
      Returns:
      the new binder instance
      Throws:
      Exception - when an unrecoverable exception occurs
      See Also:

    • doBind

      protected void doBind(RequestContext context, org.springframework.validation.DataBinder binder) throws Exception
      Bind allowed parameters in the external context request parameter map to the form object using given binder.
      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      binder - the data binder to use
      Throws:
      Exception - when an unrecoverable exception occurs

    • doValidate

      protected void doValidate(RequestContext context, Object formObject, org.springframework.validation.Errors errors) throws Exception
      Validate given form object using a registered validator. If a "validatorMethod" action property is specified for the currently executing action, the identified validator method will be invoked. When no such property is found, the defualt validate() method is invoked.
      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      formObject - the form object
      errors - the errors instance to record validation errors in
      Throws:
      Exception - when an unrecoverable exception occurs

    • getValidateMethodInvoker

      protected org.springframework.webflow.action.DispatchMethodInvoker getValidateMethodInvoker()
      Returns a dispatcher to invoke validation methods. Subclasses could override this to return a custom dispatcher.

    • getFormObjectAccessor

      protected FormObjectAccessor getFormObjectAccessor(RequestContext context)
      Factory method that returns a new form object accessor for accessing form objects in the provided request context.
      Parameters:
      context - the flow request context
      Returns:
      the accessor

    • createFormObject

      protected Object createFormObject(RequestContext context) throws Exception
      Create the backing form object instance that should be managed by this form action. By default, will attempt to instantiate a new form object instance of type getFormObjectClass() transiently in memory.

      Subclasses should override if they need to load the form object from a specific location or resource such as a database or filesystem.

      Subclasses should override if they need to customize how a transient form object is assembled during creation.

      Parameters:
      context - the action execution context for accessing flow data
      Returns:
      the form object
      Throws:
      IllegalStateException - if the getFormObjectClass() property is not set and this method has not been overridden
      Exception - when an unrecoverable exception occurs

    • initBinder

      protected void initBinder(RequestContext context, org.springframework.validation.DataBinder binder)
      Initialize a new binder instance. This hook allows customization of binder settings such as the allowed fields, required fields and direct field access. Called by createBinder(RequestContext, Object).

      Note that registration of custom property editors should be done in registerPropertyEditors(PropertyEditorRegistry), not here! This method will only be called when a new data binder is created.

      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      binder - new binder instance
      See Also:

    • registerPropertyEditors

      protected void registerPropertyEditors(RequestContext context, org.springframework.beans.PropertyEditorRegistry registry)
      Register custom editors to perform type conversion on fields of your form object during data binding and form display. This method is called on form errors initialization and data binder initialization.

      Property editors give you full control over how objects are transformed to and from a formatted String form for display on a user interface such as a HTML page.

      This default implementation will call the simpler form of the method not taking a RequestContext parameter.

      Parameters:
      context - the action execution context, for accessing and setting data in "flow scope" or "request scope"
      registry - the property editor registry to register editors in
      See Also:

    • registerPropertyEditors

      protected void registerPropertyEditors(org.springframework.beans.PropertyEditorRegistry registry)
      Register custom editors to perform type conversion on fields of your form object during data binding and form display. This method is called on form errors initialization and data binder initialization.

      Property editors give you full control over how objects are transformed to and from a formatted String form for display on a user interface such as a HTML page.

      This default implementation will simply call registerCustomEditors on the propertyEditorRegistrar object that has been set for the action, if any.

      Parameters:
      registry - the property editor registry to register editors in

    • validationEnabled

      protected boolean validationEnabled(RequestContext context)
      Return whether validation should be performed given the state of the flow request context. Default implementation always returns true.
      Parameters:
      context - the request context, for accessing and setting data in "flow scope" or "request scope"
      Returns:
      whether or not validation is enabled

    • toString

      public String toString()
      Overrides:
      toString in class Object