WSO2 Conditional Redirecting Mediation Policy

README.md

This mediation policy redirects requests based on resource variable, but keeping limit and offset query params (ignore rest).

"Endpoint type" MUST be set to "Dynamic Endpoint" at "Implement" publisher tab.

redirect-example.xml

<sequence name="ConditionalRedirectExample" statistics="enable" trace="enable" xmlns="http://ws.apache.org/ns/synapse">
    <!-- URL example: https://apim-example/context/v1/2021?foo=bar&limit=10&offset=20 -->
    <!-- Process first query param (limit) -->
    <switch source="boolean($url:limit)">
        <case regex="true">
            <property name="param_limit" expression="$url:limit"/>
        </case>
        <default>
            <property name="param_limit" value="100"/>
        </default>
    </switch>
    <!-- Process second query param (offset) -->
    <switch source="boolean($url:offset)">
        <case regex="true">
            <property name="param_offset" expression="$url:offset"/>
        </case>
        <default>
            <property name="param_offset" value="0"/>
        </default>
    </switch>
    <!-- Set backend endpoint based on variable "year" (MUST be named year in publisher) -->
    <switch source="get-property('uri.var.year')">
        <case regex="2021">
            <property name="target_url" value="https://endpoint1/"/>
        </case>
        <default>
            <property name="target_url" value="https://endpoint2/"/>
        </default>
    </switch>
    <!-- Remove original path from request -->
    <property name="REST_URL_POSTFIX" action="remove" scope="axis2"/>
    <!-- Redirect request -->
    <header name="To" expression="fn:concat(get-property('target_url'), '?limit=', get-property('param_limit'), '&amp;offset=', get-property('param_offset'))"></header>
    <!-- Enable statistics -->
    <property expression="get-property('target_url')" name="ENDPOINT_ADDRESS"></property>
</sequence>