plugins/json/src/main/resources/struts-plugin.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!--
/*
 * 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 6.0//EN"
	"https://struts.apache.org/dtds/struts-6.0.dtd">

<struts>
    <bean type="org.apache.struts2.json.JSONWriter" name="struts" class="org.apache.struts2.json.DefaultJSONWriter"
          scope="prototype"/>
    <constant name="struts.json.writer" value="struts"/>
    <!-- TODO: Make DefaultJSONWriter thread-safe to remove "prototype"s -->
    <bean class="org.apache.struts2.json.JSONUtil" scope="prototype"/>

    <package name="json-default" extends="struts-default">

        <result-types>
            <result-type name="json" class="org.apache.struts2.json.JSONResult"/>
            <result-type name="jsonActionRedirect" class="org.apache.struts2.json.JSONActionRedirectResult"/>
        </result-types>

        <interceptors>
            <interceptor name="json" class="org.apache.struts2.json.JSONInterceptor"/>
            <interceptor name="jsonValidation" class="org.apache.struts2.json.JSONValidationInterceptor"/>

            <!-- Sample JSON validation stack -->
            <interceptor-stack name="jsonValidationWorkflowStack">
                <interceptor-ref name="basicStack"/>
                <interceptor-ref name="validation">
                    <param name="excludeMethods">input,back,cancel</param>
                </interceptor-ref>
                <interceptor-ref name="jsonValidation"/>
                <interceptor-ref name="workflow"/>
            </interceptor-stack>

        </interceptors>

    </package>
</struts>