Interceptors in Struts 2
Interceptors are conceptually analogous to Servlet Filters and are an important part of Struts 2 as it provides Struts 2 with a powerful mechanism to control any request. Interceptors can be integrated for complete process, groups of Struts 2 actions or for any combination of actions. In Struts 2 interceptors perform multiple tasks including Logging, Validation, File Upload, Double-submit guard, exception handling, internationalization, displaying intermediate result etc.
Interceptor plays an important role in Struts 2 process as they are called by the controller both before (preprocessing) as well as after invoking action (post processing) and thus lies between the controller and action.
Advantage of Interceptors
With the introduction of interceptors in Struts 2, it has helped overcome many loopholes of earlier version of Struts making it more users friendly and efficient. Though, Struts2 comprises of default number of Interceptors already configured in the application in struts-default.xml file, but if we need some customized Interceptors, it can be created into a Struts2 based web application. Moreover, if you need to remove any action of interceptor in Struts 2 application like validation, exception handling, logging etc. it does not requite reestablish the allocation but this can be done simply by removing the entry from the struts.xml file.
Struts 2 default interceptors stack
As such, there are many interceptors that comes by default in Struts 2 but custom interceptors can also be integrated. Lets discuss about the Struts 2 Interceptors in detail. We have also give Struts 2 Interceptors list here, which will be useful for you in understanding the different functionalities of Struts 2 framework.
There are many interceptors provided by struts 2 framework. We have option to create our own interceptors. The struts 2 default interceptors are as follows:
- alias: As the name suggests this interceptor allows parameters to have different name between requests.
- autowiring: The autowiring interceptor is very useful as it auto wires action classes to Spring beans in your application.
- chain: This Interceptor is used to make the properties of previous action available in the current action.
- checkbox: This helps to add automatic checkbox handling code that detect an unchecked checkbox.
- cookie: This is used to add a cookie to the current action with a certain configurable name or value into action.
- conversionError: It adds conversion errors from ActionContext to the action's field errors.
- createSession: Automatically creates an HttpSession object if it doesn't exists.
- clearSession: This interceptor is used to unbinds the HttpSession object.
- debugging: Supports debugging by providing different debugging screens.
- externalRef: The externalRef interceptor resolves external references using the ExternalReferenceResolver which is configured on the package.
- execAndWait: Used to send an intermediate waiting page for the result.
- exception: Maps exception to a result.
- fileUpload: This interceptor provides support to file upload in struts 2.
- i18n: Remembers the locale selected for a user's session and It provides support to internationalization and localization.
- jsonValidation: Used for supporting asynchronous validation.
- logger: It outputs the name of the action.
- store: It Store and retrieve action messages / errors / field errors for action that implements ValidationAware interface.
- modelDriven: Used to makes other model object, which pushes the getModel Result onto the Value Stack.
- scopedModelDriven: However, it is very similar to ModelDriven but works for action that implements ScopedModelDriven.
- params: It is used to set the request parameters into the Action.
- actionMappingParams: This interceptor performs an important work of seting all parameters from the action mapping on the value stack for a request.
- prepare: If the Action implements Preparable, then it performs preparation logic.
- profiling: Supports action profiling.
- roles: It supports action based on role.
- scope: Used for storing Action state in the session or application scope.
- servletConfig: Provide access to Maps representing HttpServletRequest and HttpServletResponse.
- sessionAutowiring: It is already configured as default interceptor.
- staticParams: Used to map the static properties to action properties.
- timer: Outputs the time required to execute an action.
- token: Prevents duplicate request form submission
- tokenSession: It prevents duplication submission of request, but stores the submitted data in session when handed an invalid token.
- validation: Provides support to input validation.
- workflow: Invokes the validate method of action class and if Action errors are created then it returns the INPUT view.
- annotationWorkflow: This interceptor is responsible for invoking any annotated methods on the action class which is being executed. It supports specially @Before, @BeforeResult and @After annotations.
- multiselect: The org.apache.struts2.interceptor.MultiselectInterceptor is configured as default interceptor. The responsibility of this interceptor is to check each form parameter submitted to the action. If it finds one with a prefix of __multiselect_ it inserts a value for a parameter whose name is derived from the suffix to __multiselect_ if it does not exist. The default value inserted is an empty String array.
Here is the code of struts-default.xml file from Struts 2.3.15.1 distribution.
<?xml version="1.0" encoding="UTF-8" ?>
<!--
/*
* $Id: struts-default.xml 1485719 2013-05-23 14:12:24Z lukaszlenart $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
-->
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
"http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
<bean class="com.opensymphony.xwork2.ObjectFactory" name="xwork" />
<bean type="com.opensymphony.xwork2.ObjectFactory" name="struts" class="org.apache.struts2.impl.StrutsObjectFactory" />
<bean type="com.opensymphony.xwork2.FileManager" class="com.opensymphony.xwork2.util.fs.DefaultFileManager" name="system" scope="singleton"/>
<bean type="com.opensymphony.xwork2.FileManagerFactory" class="com.opensymphony.xwork2.util.fs.DefaultFileManagerFactory" name="xwork" scope="singleton"/>
<bean type="com.opensymphony.xwork2.FileManagerFactory" class="com.opensymphony.xwork2.util.fs.DefaultFileManagerFactory" name="struts" scope="singleton"/>
<bean type="com.opensymphony.xwork2.ActionProxyFactory" name="xwork" class="com.opensymphony.xwork2.DefaultActionProxyFactory"/>
<bean type="com.opensymphony.xwork2.ActionProxyFactory" name="struts" class="org.apache.struts2.impl.StrutsActionProxyFactory"/>
<bean type="com.opensymphony.xwork2.conversion.ObjectTypeDeterminer" name="tiger" class="com.opensymphony.xwork2.conversion.impl.DefaultObjectTypeDeterminer"/>
<bean type="com.opensymphony.xwork2.conversion.ObjectTypeDeterminer" name="notiger" class="com.opensymphony.xwork2.conversion.impl.DefaultObjectTypeDeterminer"/>
<bean type="com.opensymphony.xwork2.conversion.ObjectTypeDeterminer" name="struts" class="com.opensymphony.xwork2.conversion.impl.DefaultObjectTypeDeterminer"/>
<bean type="com.opensymphony.xwork2.util.PatternMatcher" name="struts" class="com.opensymphony.xwork2.util.WildcardHelper" />
<bean type="com.opensymphony.xwork2.util.PatternMatcher" name="namedVariable" class="com.opensymphony.xwork2.util.NamedVariablePatternMatcher"/>
<bean type="com.opensymphony.xwork2.util.PatternMatcher" name="regex" class="org.apache.struts2.util.RegexPatternMatcher"/>
<bean type="org.apache.struts2.dispatcher.mapper.ActionMapper" name="struts" class="org.apache.struts2.dispatcher.mapper.DefaultActionMapper" />
<bean type="org.apache.struts2.dispatcher.mapper.ActionMapper" name="composite" class="org.apache.struts2.dispatcher.mapper.CompositeActionMapper" />
<bean type="org.apache.struts2.dispatcher.mapper.ActionMapper" name="restful" class="org.apache.struts2.dispatcher.mapper.RestfulActionMapper" />
<bean type="org.apache.struts2.dispatcher.mapper.ActionMapper" name="restful2" class="org.apache.struts2.dispatcher.mapper.Restful2ActionMapper" />
<bean type="org.apache.struts2.dispatcher.multipart.MultiPartRequest" name="struts" class="org.apache.struts2.dispatcher.multipart.JakartaMultiPartRequest" scope="default"/>
<bean type="org.apache.struts2.dispatcher.multipart.MultiPartRequest" name="jakarta" class="org.apache.struts2.dispatcher.multipart.JakartaMultiPartRequest" scope="default" />
<constant name="struts.multipart.parser" value="jakarta" />
<bean type="org.apache.struts2.views.TagLibrary" name="s" class="org.apache.struts2.views.DefaultTagLibrary" />
<bean class="org.apache.struts2.views.freemarker.FreemarkerManager" name="struts" />
<bean class="org.apache.struts2.views.velocity.VelocityManager" name="struts" optional="true" />
<bean class="org.apache.struts2.components.template.TemplateEngineManager" />
<bean type="org.apache.struts2.components.template.TemplateEngine" name="ftl" class="org.apache.struts2.components.template.FreemarkerTemplateEngine" />
<bean type="org.apache.struts2.components.template.TemplateEngine" name="vm" class="org.apache.struts2.components.template.VelocityTemplateEngine" />
<bean type="org.apache.struts2.components.template.TemplateEngine" name="jsp" class="org.apache.struts2.components.template.JspTemplateEngine" />
<bean type="com.opensymphony.xwork2.conversion.impl.XWorkConverter" name="struts" class="com.opensymphony.xwork2.conversion.impl.XWorkConverter" />
<bean type="com.opensymphony.xwork2.conversion.ConversionPropertiesProcessor" name="struts" class="com.opensymphony.xwork2.conversion.impl.DefaultConversionPropertiesProcessor" />
<bean type="com.opensymphony.xwork2.conversion.ConversionFileProcessor" name="struts" class="com.opensymphony.xwork2.conversion.impl.DefaultConversionFileProcessor" />
<bean type="com.opensymphony.xwork2.conversion.ConversionAnnotationProcessor" name="struts" class="com.opensymphony.xwork2.conversion.impl.DefaultConversionAnnotationProcessor" />
<bean type="com.opensymphony.xwork2.conversion.TypeConverterCreator" name="struts" class="com.opensymphony.xwork2.conversion.impl.DefaultTypeConverterCreator" />
<bean type="com.opensymphony.xwork2.conversion.TypeConverterHolder" name="struts" class="com.opensymphony.xwork2.conversion.impl.DefaultTypeConverterHolder" />
<bean class="com.opensymphony.xwork2.conversion.impl.XWorkBasicConverter" />
<bean type="com.opensymphony.xwork2.conversion.impl.CollectionConverter" name="struts" class="com.opensymphony.xwork2.conversion.impl.CollectionConverter" scope="singleton"/>
<bean type="com.opensymphony.xwork2.conversion.impl.ArrayConverter" name="struts" class="com.opensymphony.xwork2.conversion.impl.ArrayConverter" scope="singleton"/>
<bean type="com.opensymphony.xwork2.conversion.impl.DateConverter" name="struts" class="com.opensymphony.xwork2.conversion.impl.DateConverter" scope="singleton"/>
<bean type="com.opensymphony.xwork2.conversion.impl.NumberConverter" name="struts" class="com.opensymphony.xwork2.conversion.impl.NumberConverter" scope="singleton"/>
<bean type="com.opensymphony.xwork2.conversion.impl.StringConverter" name="struts" class="com.opensymphony.xwork2.conversion.impl.StringConverter" scope="singleton"/>
<bean type="com.opensymphony.xwork2.TextProvider" name="struts" class="com.opensymphony.xwork2.TextProviderSupport" scope="default" />
<bean type="com.opensymphony.xwork2.LocaleProvider" name="struts" class="com.opensymphony.xwork2.DefaultLocaleProvider" scope="singleton" />
<bean type="org.apache.struts2.components.UrlRenderer" name="struts" class="org.apache.struts2.components.ServletUrlRenderer"/>
<bean type="org.apache.struts2.views.util.UrlHelper" name="struts" class="org.apache.struts2.views.util.DefaultUrlHelper"/>
<bean type="com.opensymphony.xwork2.util.ValueStackFactory" name="struts" class="com.opensymphony.xwork2.ognl.OgnlValueStackFactory" />
<bean type="com.opensymphony.xwork2.util.reflection.ReflectionProvider" name="struts" class="com.opensymphony.xwork2.ognl.OgnlReflectionProvider" />
<bean type="com.opensymphony.xwork2.util.reflection.ReflectionContextFactory" name="struts" class="com.opensymphony.xwork2.ognl.OgnlReflectionContextFactory" />
<bean type="com.opensymphony.xwork2.TextProvider" name="system" class="com.opensymphony.xwork2.DefaultTextProvider" />
<bean type="com.opensymphony.xwork2.conversion.NullHandler" name="java.lang.Object" class="com.opensymphony.xwork2.conversion.impl.InstantiatingNullHandler" />
<bean type="com.opensymphony.xwork2.validator.ActionValidatorManager" name="struts" class="com.opensymphony.xwork2.validator.AnnotationActionValidatorManager" />
<bean type="com.opensymphony.xwork2.validator.ActionValidatorManager" name="no-annotations" class="com.opensymphony.xwork2.validator.DefaultActionValidatorManager" />
<bean type="com.opensymphony.xwork2.validator.ValidatorFactory" class="com.opensymphony.xwork2.validator.DefaultValidatorFactory"/>
<bean type="com.opensymphony.xwork2.validator.ValidatorFileParser" class="com.opensymphony.xwork2.validator.DefaultValidatorFileParser" />
<bean class="com.opensymphony.xwork2.ognl.OgnlUtil" />
<bean type="com.opensymphony.xwork2.util.TextParser" name="struts" class="com.opensymphony.xwork2.util.OgnlTextParser" scope="singleton"/>
<bean type="ognl.PropertyAccessor" name="com.opensymphony.xwork2.util.CompoundRoot" class="com.opensymphony.xwork2.ognl.accessor.CompoundRootAccessor" />
<bean type="ognl.PropertyAccessor" name="java.lang.Object" class="com.opensymphony.xwork2.ognl.accessor.ObjectAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.Iterator" class="com.opensymphony.xwork2.ognl.accessor.XWorkIteratorPropertyAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.Enumeration" class="com.opensymphony.xwork2.ognl.accessor.XWorkEnumerationAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.List" class="com.opensymphony.xwork2.ognl.accessor.XWorkListPropertyAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.Set" class="com.opensymphony.xwork2.ognl.accessor.XWorkCollectionPropertyAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.Map" class="com.opensymphony.xwork2.ognl.accessor.XWorkMapPropertyAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.Collection" class="com.opensymphony.xwork2.ognl.accessor.XWorkCollectionPropertyAccessor" />
<bean type="ognl.PropertyAccessor" name="com.opensymphony.xwork2.ognl.ObjectProxy" class="com.opensymphony.xwork2.ognl.accessor.ObjectProxyPropertyAccessor" />
<bean type="ognl.MethodAccessor" name="java.lang.Object" class="com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor" />
<bean type="ognl.MethodAccessor" name="com.opensymphony.xwork2.util.CompoundRoot" class="com.opensymphony.xwork2.ognl.accessor.CompoundRootAccessor" />
<bean class="org.apache.struts2.views.jsp.ui.OgnlTool" />
<bean type="org.apache.struts2.dispatcher.StaticContentLoader" class="org.apache.struts2.dispatcher.DefaultStaticContentLoader" name="struts" />
<bean type="com.opensymphony.xwork2.UnknownHandlerManager" class="com.opensymphony.xwork2.DefaultUnknownHandlerManager" name="struts" />
<!-- Silly workarounds for OGNL since there is currently no way to flush its internal caches -->
<bean type="ognl.PropertyAccessor" name="java.util.ArrayList" class="com.opensymphony.xwork2.ognl.accessor.XWorkListPropertyAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.HashSet" class="com.opensymphony.xwork2.ognl.accessor.XWorkCollectionPropertyAccessor" />
<bean type="ognl.PropertyAccessor" name="java.util.HashMap" class="com.opensymphony.xwork2.ognl.accessor.XWorkMapPropertyAccessor" />
<package name="struts-default" abstract="true">
<result-types>
<result-type name="chain" class="com.opensymphony.xwork2.ActionChainResult"/>
<result-type name="dispatcher" class="org.apache.struts2.dispatcher.ServletDispatcherResult" default="true"/>
<result-type name="freemarker" class="org.apache.struts2.views.freemarker.FreemarkerResult"/>
<result-type name="httpheader" class="org.apache.struts2.dispatcher.HttpHeaderResult"/>
<result-type name="redirect" class="org.apache.struts2.dispatcher.ServletRedirectResult"/>
<result-type name="redirectAction" class="org.apache.struts2.dispatcher.ServletActionRedirectResult"/>
<result-type name="stream" class="org.apache.struts2.dispatcher.StreamResult"/>
<result-type name="velocity" class="org.apache.struts2.dispatcher.VelocityResult"/>
<result-type name="xslt" class="org.apache.struts2.views.xslt.XSLTResult"/>
<result-type name="plainText" class="org.apache.struts2.dispatcher.PlainTextResult" />
</result-types>
<interceptors>
<interceptor name="alias" class="com.opensymphony.xwork2.interceptor.AliasInterceptor"/>
<interceptor name="autowiring" class="com.opensymphony.xwork2.spring.interceptor.ActionAutowiringInterceptor"/>
<interceptor name="chain" class="com.opensymphony.xwork2.interceptor.ChainingInterceptor"/>
<interceptor name="conversionError" class="org.apache.struts2.interceptor.StrutsConversionErrorInterceptor"/>
<interceptor name="cookie" class="org.apache.struts2.interceptor.CookieInterceptor"/>
<interceptor name="cookieProvider" class="org.apache.struts2.interceptor.CookieProviderInterceptor"/>
<interceptor name="clearSession" class="org.apache.struts2.interceptor.ClearSessionInterceptor" />
<interceptor name="createSession" class="org.apache.struts2.interceptor.CreateSessionInterceptor" />
<interceptor name="debugging" class="org.apache.struts2.interceptor.debugging.DebuggingInterceptor" />
<interceptor name="execAndWait" class="org.apache.struts2.interceptor.ExecuteAndWaitInterceptor"/>
<interceptor name="exception" class="com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor"/>
<interceptor name="fileUpload" class="org.apache.struts2.interceptor.FileUploadInterceptor"/>
<interceptor name="i18n" class="com.opensymphony.xwork2.interceptor.I18nInterceptor"/>
<interceptor name="logger" class="com.opensymphony.xwork2.interceptor.LoggingInterceptor"/>
<interceptor name="modelDriven" class="com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor"/>
<interceptor name="scopedModelDriven" class="com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor"/>
<interceptor name="params" class="com.opensymphony.xwork2.interceptor.ParametersInterceptor"/>
<interceptor name="actionMappingParams" class="org.apache.struts2.interceptor.ActionMappingParametersInteceptor"/>
<interceptor name="prepare" class="com.opensymphony.xwork2.interceptor.PrepareInterceptor"/>
<interceptor name="staticParams" class="com.opensymphony.xwork2.interceptor.StaticParametersInterceptor"/>
<interceptor name="scope" class="org.apache.struts2.interceptor.ScopeInterceptor"/>
<interceptor name="servletConfig" class="org.apache.struts2.interceptor.ServletConfigInterceptor"/>
<interceptor name="timer" class="com.opensymphony.xwork2.interceptor.TimerInterceptor"/>
<interceptor name="token" class="org.apache.struts2.interceptor.TokenInterceptor"/>
<interceptor name="tokenSession" class="org.apache.struts2.interceptor.TokenSessionStoreInterceptor"/>
<interceptor name="validation" class="org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor"/>
<interceptor name="workflow" class="com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor"/>
<interceptor name="store" class="org.apache.struts2.interceptor.MessageStoreInterceptor" />
<interceptor name="checkbox" class="org.apache.struts2.interceptor.CheckboxInterceptor" />
<interceptor name="profiling" class="org.apache.struts2.interceptor.ProfilingActivationInterceptor" />
<interceptor name="roles" class="org.apache.struts2.interceptor.RolesInterceptor" />
<interceptor name="annotationWorkflow" class="com.opensymphony.xwork2.interceptor.annotations.AnnotationWorkflowInterceptor" />
<interceptor name="multiselect" class="org.apache.struts2.interceptor.MultiselectInterceptor" />
<!-- Basic stack -->
<interceptor-stack name="basicStack">
<interceptor-ref name="exception"/>
<interceptor-ref name="servletConfig"/>
<interceptor-ref name="prepare"/>
<interceptor-ref name="checkbox"/>
<interceptor-ref name="multiselect"/>
<interceptor-ref name="actionMappingParams"/>
<interceptor-ref name="params">
<param name="excludeParams">dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,parameters\...*</param>
</interceptor-ref>
<interceptor-ref name="conversionError"/>
</interceptor-stack>
<!-- Sample validation and workflow stack -->
<interceptor-stack name="validationWorkflowStack">
<interceptor-ref name="basicStack"/>
<interceptor-ref name="validation"/>
<interceptor-ref name="workflow"/>
</interceptor-stack>
<!-- Sample file upload stack -->
<interceptor-stack name="fileUploadStack">
<interceptor-ref name="fileUpload"/>
<interceptor-ref name="basicStack"/>
</interceptor-stack>
<!-- Sample model-driven stack -->
<interceptor-stack name="modelDrivenStack">
<interceptor-ref name="modelDriven"/>
<interceptor-ref name="basicStack"/>
</interceptor-stack>
<!-- Sample action chaining stack -->
<interceptor-stack name="chainStack">
<interceptor-ref name="chain"/>
<interceptor-ref name="basicStack"/>
</interceptor-stack>
<!-- Sample i18n stack -->
<interceptor-stack name="i18nStack">
<interceptor-ref name="i18n"/>
<interceptor-ref name="basicStack"/>
</interceptor-stack>
<!-- An example of the paramsPrepareParams trick. This stack
is exactly the same as the defaultStack, except that it
includes one extra interceptor before the prepare interceptor:
the params interceptor.
This is useful for when you wish to apply parameters directly
to an object that you wish to load externally (such as a DAO
or database or service layer), but can't load that object
until at least the ID parameter has been loaded. By loading
the parameters twice, you can retrieve the object in the
prepare() method, allowing the second params interceptor to
apply the values on the object. -->
<interceptor-stack name="paramsPrepareParamsStack">
<interceptor-ref name="exception"/>
<interceptor-ref name="alias"/>
<interceptor-ref name="i18n"/>
<interceptor-ref name="checkbox"/>
<interceptor-ref name="multiselect"/>
<interceptor-ref name="params">
<param name="excludeParams">dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,parameters\...*</param>
</interceptor-ref>
<interceptor-ref name="servletConfig"/>
<interceptor-ref name="prepare"/>
<interceptor-ref name="chain"/>
<interceptor-ref name="modelDriven"/>
<interceptor-ref name="fileUpload"/>
<interceptor-ref name="staticParams"/>
<interceptor-ref name="actionMappingParams"/>
<interceptor-ref name="params">
<param name="excludeParams">dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,parameters\...*</param>
</interceptor-ref>
<interceptor-ref name="conversionError"/>
<interceptor-ref name="validation">
<param name="excludeMethods">input,back,cancel,browse</param>
</interceptor-ref>
<interceptor-ref name="workflow">
<param name="excludeMethods">input,back,cancel,browse</param>
</interceptor-ref>
</interceptor-stack>
<!-- A complete stack with all the common interceptors in place.
Generally, this stack should be the one you use, though it
may do more than you need. Also, the ordering can be
switched around (ex: if you wish to have your servlet-related
objects applied before prepare() is called, you'd need to move
servletConfig interceptor up.
This stack also excludes from the normal validation and workflow
the method names input, back, and cancel. These typically are
associated with requests that should not be validated.
-->
<interceptor-stack name="defaultStack">
<interceptor-ref name="exception"/>
<interceptor-ref name="alias"/>
<interceptor-ref name="servletConfig"/>
<interceptor-ref name="i18n"/>
<interceptor-ref name="prepare"/>
<interceptor-ref name="chain"/>
<interceptor-ref name="scopedModelDriven"/>
<interceptor-ref name="modelDriven"/>
<interceptor-ref name="fileUpload"/>
<interceptor-ref name="checkbox"/>
<interceptor-ref name="multiselect"/>
<interceptor-ref name="staticParams"/>
<interceptor-ref name="actionMappingParams"/>
<interceptor-ref name="params">
<param name="excludeParams">dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,parameters\...*</param>
</interceptor-ref>
<interceptor-ref name="conversionError"/>
<interceptor-ref name="validation">
<param name="excludeMethods">input,back,cancel,browse</param>
</interceptor-ref>
<interceptor-ref name="workflow">
<param name="excludeMethods">input,back,cancel,browse</param>
</interceptor-ref>
<interceptor-ref name="debugging"/>
</interceptor-stack>
<!-- The completeStack is here for backwards compatibility for
applications that still refer to the defaultStack by the
old name -->
<interceptor-stack name="completeStack">
<interceptor-ref name="defaultStack"/>
</interceptor-stack>
<!-- Sample execute and wait stack.
Note: execAndWait should always be the *last* interceptor. -->
<interceptor-stack name="executeAndWaitStack">
<interceptor-ref name="execAndWait">
<param name="excludeMethods">input,back,cancel</param>
</interceptor-ref>
<interceptor-ref name="defaultStack"/>
<interceptor-ref name="execAndWait">
<param name="excludeMethods">input,back,cancel</param>
</interceptor-ref>
</interceptor-stack>
</interceptors>
<default-interceptor-ref name="defaultStack"/>
<default-class-ref class="com.opensymphony.xwork2.ActionSupport" />
</package>
</struts>
In the above code you can see all the interceptors which is configured in Struts 2.
You can learn Struts 2 on Rose India at the page Struts 2.3.15.1 tutorials, which is loaded with tons of Struts 2 tutorials. framework.