能否通过WSO2 API Manager/APIs为每个请求向端点发送自定义或唯一消息？

Absolutely! You can easily send custom static messages or unique per-request identifiers to your backend endpoints using WSO2 API Manager. Below are the most practical, widely-used approaches to achieve this:

1. Use Custom Mediation Sequences (Most Flexible) #

Mediation sequences are WSO2 APIM’s go-to tool for modifying requests before they reach the backend. You can inject headers, tweak request bodies, or add unique identifiers here with full control.

Example 1: Add a Static Custom Header #

Create a custom in-sequence (via the APIM Publisher or Management Console) with this Synapse code to inject a static custom message as an HTTP header:

<sequence xmlns="http://ws.apache.org/ns/synapse" name="StaticCustomMessageSequence">
    <!-- Inject a static custom header -->
    <header name="X-Custom-Message" value="ThisIsMyStaticCustomMessage"/>
</sequence>

Example 2: Generate a Unique Per-Request ID #

To send a unique identifier with every request (like a UUID), use the built-in uuid() function:

<sequence xmlns="http://ws.apache.org/ns/synapse" name="UniqueRequestIDSequence">
    <!-- Generate a UUID and store it in a property -->
    <property name="RequestUUID" expression="uuid()"/>
    <!-- Inject it as an HTTP header -->
    <header name="X-Request-ID" expression="get-property('RequestUUID')"/>
    <!-- Optional: Add it to the request body (for JSON payloads) -->
    <payloadFactory media-type="json">
        <format>{"originalData": $1, "requestId": "$2"}</format>
        <args>
            <arg evaluator="json" expression="$body"/>
            <arg expression="get-property('RequestUUID')"/>
        </args>
    </payloadFactory>
</sequence>

To use this sequence:

• Open your API in the APIM Publisher
• Navigate to the Message Mediation tab
• Select your custom sequence under In Sequence (this runs right before the request hits the backend)

2. Leverage API-Level Custom Properties #

If you want a static custom message that’s configurable per API (no hardcoding in sequences), use API properties:

1. In the APIM Publisher, go to your API’s Properties tab
2. Add a new property, e.g., custom.backend.message with your desired value (like APIMGeneratedCustomMessage)
3. In your API’s in-sequence, reference this property to inject it into the request:

<header name="X-Custom-Message" expression="get-property('custom.backend.message')"/>

3. Custom Unique Values (Beyond UUID) #

If you need a unique value tied to request context (like client IP + timestamp), use Synapse’s context properties:

<sequence xmlns="http://ws.apache.org/ns/synapse" name="ContextBasedUniqueSequence">
    <property name="UniqueKey" expression="concat(get-property('axis2', 'REMOTE_ADDR'), '-', get-property('SYSTEM_DATE', 'yyyyMMddHHmmssSSS'))"/>
    <header name="X-Unique-Context-Key" expression="get-property('UniqueKey')"/>
</sequence>

Key Tips: #

• Headers vs. Request Body: Use HTTP headers for lightweight metadata (like unique IDs). If your backend expects the custom message in the payload, use payloadFactory or the enrich mediator to modify the body.
• SOAP APIs: For SOAP services, use the soapHeader mediator to inject custom SOAP headers instead of HTTP headers.
• Test First: Always validate the modified request using APIM’s Try It tool to ensure the custom message is correctly sent to the backend.

内容的提问来源于stack exchange，提问作者Babu