The HTTP server accepts the payload as a binary object. What the payload consists of depends on the service you wish to provide. Many services use string-based protocols (such as JSON). For these types of payload, you can use the String codec (see The String codec connectivity plug-in). For messages towards the host, the String codec takes a byte array and decodes it to a string using the UTF-8 encoding. If you are using the String codec, you should put it as the last codec before the HTTP server.

The resulting string can then be mapped directly into a field in an EPL event, or it can be further processed by other codecs (such as the JSON codec, as used in our default configuration) before the resulting fields are mapped into the Apama event.

If you need to vary your processing depending on the type of the data received, you may need to write a custom codec in order to handle this. To help with distinguishing different payload types, the HTTP server sets top-level fields to indicate the type of the payload. The HTTP header indicates the MIME type populated into metadata.http.contentType. If present, then the character set from the same HTTP header is copied into metadata.http.charset.

When using EPL-supplied responses, the mapping rules must be bidirectional to map both the request and the response.