Body Parser
Body parser is a middleware handler designed for light-rest-4jonly. It will parse the body to a list or map according to the content-type in the HTTP header for POST, PUT and PATCH HTTP methods. The content-type can be parsed includes application/json, multipart/form-data and application/x-www-form-urlencoded. The application/json type is parsed into list or map depending on the first character of the body while the others is parsed into map by using FormParserFactory provided by io.undertow. After the body is parsed, it will be attached to the exchange so that subsequent handlers can use it directly.
Introduction
In order for this handler to work, the content-type in header must be started with “application/json”, “multipart/form-data” or “application/x-www-form-urlencoded”. If the content type is correct, it will parse it to List or Map and put it into REQUEST_BODY exchange attachment.
If content type is missing or if it is not started as “application/json”, “multipart/form-data” or “application/x-www-form-urlencoded”. the bodywon’t be parsed and this handler will just call next handler in the chain.
Sanitizer, Openapi Validator and Swagger Validator depend on this middleware.
Configuration
Here is an example of configuration body.yml which has a flag to enable or disable it.
# Enable body parse flag
enabled: true
Parser
Here is the parsing logic.
if (contentType != null && contentType.startsWith("application/json")) {
if (exchange.isInIoThread()) {
exchange.dispatch(this);
return;
}
exchange.startBlocking();
InputStream is = exchange.getInputStream();
try {
Object body;
String s = StringUtils.inputStreamToString(is, StandardCharsets.UTF_8);
if (s != null) {
s = s.trim();
if (s.startsWith("{")) {
body = Config.getInstance().getMapper().readValue(s, new TypeReference<HashMap<String, Object>>() {});
} else if (s.startsWith("[")) {
body = Config.getInstance().getMapper().readValue(s, new TypeReference<List<Object>>() {});
} else {
// error here. The content type in head doesn't match the body.
setExchangeStatus(exchange, CONTENT_TYPE_MISMATCH, contentType);
return;
}
exchange.putAttachment(REQUEST_BODY, body);
}
} catch (IOException e) {
logger.error("IOException: ", e);
setExchangeStatus(exchange, CONTENT_TYPE_MISMATCH, contentType);
return;
}
// parse the body to form-data if content type is multipart/form-data or application/x-www-form-urlencoded
} else if (contentType != null &&
(contentType.startsWith("multipart/form-data") || contentType.startsWith("application/x-www-form-urlencoded"))) {
if (exchange.isInIoThread()) {
exchange.dispatch(this);
return;
}
exchange.startBlocking();
try {
Object data;
FormParserFactory formParserFactory = FormParserFactory.builder().build();
FormDataParser parser = formParserFactory.createParser(exchange);
if (parser != null) {
FormData formData = parser.parseBlocking();
data = BodyConverter.convert(formData);
exchange.putAttachment(REQUEST_BODY, data);
}
} catch (Exception e) {
logger.error("IOException: ", e);
setExchangeStatus(exchange, CONTENT_TYPE_MISMATCH, contentType);
return;
}
}Example
Here is the code example that get the boby object(Map or List) from exchange.
Object body = exchange.getAttachment(BodyHandler.REQUEST_BODY);
if(body == null) {
exchange.getResponseSender().send("nobody");
} else {
if(body instanceof List) {
exchange.getResponseSender().send("list");
} else {
exchange.getResponseSender().send("map");
}
}