modify magic string to constant.
@@ -165,7 +165,7 @@ For example, `TAGS`, `DELAY`, `TRANSACTIONAL_ARG`, `KEYS`, `WAIT_STORE_MSG_OK`,
MessageBuilder builder = MessageBuilder.withPayload(msg)
.setHeader(RocketMQHeaders.TAGS, "binder")
.setHeader(RocketMQHeaders.KEYS, "my-key")
- .setHeader("DELAY", "1");
+ .setHeader(MessageConst.PROPERTY_DELAY_TIME_LEVEL, "1");
Message message = builder.build();
output().send(message);
```
