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# Token Interceptor

Ensures that only one request per token is processed. This interceptor can make sure that back buttons and double clicks don’t cause un-intended side affects. For example, you can use this to prevent careless users who might double click on a “checkout” button at an online store. This interceptor uses a fairly primitive technique for when an invalid token is found: it returns the result `invalid.token`, which can be mapped in your action configuration. A more complex implementation, {@link TokenSessionStoreInterceptor}, can provide much better logic for when invalid tokens are found.

> Note: To set a token in your form, you should use the token tag. This tag is required and must be used in the forms that submit to actions protected by this interceptor. Any request that does not provide a token (using the token tag) will be processed as a request with an invalid token.

Internationalization Note: The following key could be used to internationalized the action errors generated by this token interceptor:

- `struts.messages.invalid.token`

> NOTE: As this method extends off MethodFilterInterceptor, it is capable of deciding if it is applicable only to selective methods in the action class. See `MethodFilterInterceptor` for more info.

## Parameters

There are no parameters for this interceptor.

## Extending the Interceptor

While not very common for users to extend, this interceptor is extended by the `TokenSessionStoreInterceptor`. The `#handleInvalidToken` and `#handleValidToken` methods are protected and available for more interesting logic, such as done with the token session interceptor.

## Examples

     <action name="someAction" class="com.examples.SomeAction">
         <interceptor-ref name="token"/>
         <interceptor-ref name="basicStack"/>
         <result name="success">good_result.ftl</result>
     </action>

     <-- In this case, myMethod of the action class will not
            get checked for invalidity of token -->
     <action name="someAction" class="com.examples.SomeAction">
         <interceptor-ref name="token">
            <param name="excludeMethods">myMethod</param>
         </interceptor-ref name="token"/>
         <interceptor-ref name="basicStack"/>
         <result name="success">good_result.ftl</result>
     </action>