Body Handler

The BodyHandler is a middleware component designed primarily for light-rest-4j services. It automatically parses the incoming request body for methods like POST, PUT, and PATCH, and attaches the parsed object to the exchange for subsequent handlers to consume.

Note: This handler is not suitable for light-gateway or http-sidecar as those services typically stream the request body directly to downstream services without consuming it. For gateway scenarios, use RequestBodyInterceptor and ResponseBodyInterceptor if inspection is required.

Functionality

The handler inspects the Content-Type header and parses the body accordingly:

1. application/json:

   • Parsed into a Map (if starts with {) or List (if starts with [).
   • Attached to exchange with key BodyHandler.REQUEST_BODY.
   • Optionally caches the raw string body to BodyHandler.REQUEST_BODY_STRING if cacheRequestBody is enabled (useful for auditing).

2. text/plain:

   • Parsed into a String.
   • Attached to exchange with key BodyHandler.REQUEST_BODY.

3. multipart/form-data / application/x-www-form-urlencoded:

   • Parsed into FormData.
   • Attached to exchange with key BodyHandler.REQUEST_BODY.

4. Other / Missing Content-Type:

   • Attached as an InputStream.
   • Attached to exchange with key BodyHandler.REQUEST_BODY.

Configuration

The configuration is managed by BodyConfig and corresponds to body.yml (or body.json/body.properties).

Configuration Properties

Configuration Example (body.yml)

# Enable body parse flag
enabled: ${body.enabled:true}

# Cache request body as a string along with JSON object.
# Required for audit logging of request body.
cacheRequestBody: ${body.cacheRequestBody:false}

# Cache response body as a string.
# Required for audit logging of response body.
cacheResponseBody: ${body.cacheResponseBody:false}

# Log full bodies for debugging (use carefully)
logFullRequestBody: ${body.logFullRequestBody:false}
logFullResponseBody: ${body.logFullResponseBody:false}

Usage

Register the BodyHandler in your handler.yml chain. It should be placed early in the chain, before any validation or business logic handlers that need access to the body.

handler.handlers:
  .
  - com.networknt.body.BodyHandler@body

handler.chains.default:
  .
  - exception
  - correlation
  - body
  .

Retrieving the Body

In your business handler or subsequent middleware:

import com.networknt.body.BodyHandler;

// ...

// Get the parsed body (Map, List, String, FormData, or InputStream)
Object body = exchange.getAttachment(BodyHandler.REQUEST_BODY);

if (body instanceof List) {
    // Handle JSON List
} else if (body instanceof Map) {
    // Handle JSON Map
} else {
    // Handle other types
}

Retrieving the Cached String

If cacheRequestBody is enabled:

// Get the raw JSON string
String bodyString = exchange.getAttachment(BodyHandler.REQUEST_BODY_STRING);