Struts 2 params interceptor example

The params interceptor also known as parameters interceptor is used to set all parameters on the valuestack.

It is found in the default stack bydefault. So you don't need to specify it explicitely.

Internal working of params interceptor

It gets all parameters by calling the getParameters() method of ActionContext and sets it on the valuestack by calling the setValue() method of ValueStack.

Parameters of params interceptor

There are 4 parameters defined for params interceptor.

Parameter	Description
ordered	It is true bydefault but can be used to top-down the property setter behaviour.
paramNameMaxLength	specifies the maximum length for the parameter. The default length is 100 characters bydefault. The parameters length more that 100 will be ignored.
excludeParams	specifies the unallowed parameter names. You can specify multiple names separated with comma.
acceptParamNames	specifies the accepted parameter names.

Example of params interceptor

Let's see the simple example of params interceptor.

<action name="login" class="com.javatpoint.Login">
    <interceptor-ref name="params"/>
    <result name="success">login-success.jsp</result>
</action>

Note: If you specify any interceptor for the action explicitely, default interceptors will not be available for the action class.

Struts 2 defaultStack interceptors

The params interceptor is found in the default stack. You don't need to specify interceptors found in the default-stack. The defaultStack interceptors are as follows:

 <interceptor-stack name="defaultStack">
                <interceptor-ref name="exception"/>
                <interceptor-ref name="alias"/>
                <interceptor-ref name="servletConfig"/>
                <interceptor-ref name="prepare"/>
                <interceptor-ref name="i18n"/>
                <interceptor-ref name="chain"/>
                <interceptor-ref name="debugging"/>
                <interceptor-ref name="profiling"/>
                <interceptor-ref name="scopedModelDriven"/>
                <interceptor-ref name="modelDriven"/>
                <interceptor-ref name="fileUpload"/>
                <interceptor-ref name="checkbox"/>
                <interceptor-ref name="staticParams"/>
                <interceptor-ref name="actionMappingParams"/>
                <interceptor-ref name="params">
                  <param name="excludeParams">dojo\..*,^struts\..*</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>

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