Get Flags (0x2) indicate non-JSON document for id ..., could not decode

Java SDK
17

I implemented the Document/Transcoder, which doesn’t validate the flags only output logs.
I get the following log:
192.168.1.106:7092 22:36:29 INFO [org.pigai.couchbase.CikuuTranscoder:31] - Flags (0x2) indicate non-JSON document for id 845d955dfec831dbcac5c5c37d677df8ba5ccef9, could not decode. content={“0”:{“w”:"^",“l”:"^",“p”:"_decl",“b”:"",“t”:2,“s”:{}},“1”:{“w”:“I”,“l”:“i”,“p”:"_r",“b”:“anim,humn”,“t”:1,“s”:{“1”:"_n"}},“2”:{“w”:“bless”,“l”:“bless”,“p”:"_v",“b”:"",“t”:2,“s”:{}},“3”:{“w”:".",“l”:".",“p”:"_h",“b”:"",“t”:3,“s”:{}}}
The meta data which get using web consol is:

meta: {
    id: "845d955dfec831dbcac5c5c37d677df8ba5ccef9",
    rev: "2-0034940b2b18b1780000000002000000",
    expiration: 0,
    flags: 33554432
},

My program uses Jetty as the web server, run in a multithreads mode. When an http request comes, it will visit the couchbase using the code:

	public static String getRawJson(Bucket bucket, String key, boolean validated) {
		try {
			if (cluster == null || bucket == null || key == null)
				return null;
			if (validated)
				key = snt_sha(key);

			CikuuJsonDocument doc = null;
			synchronized (bucket) {
				doc = bucket.get(key, CikuuJsonDocument.class,
						bucket_read_timeout, TimeUnit.SECONDS);
			}
			return doc == null ? null : doc.content();
		} catch (Exception e) {
			logger.error("getRawJson error, for :" + e.toString() + "|" + key);
		}
		return null;
	}

After process, if the data is not in couchbase, I will store the data using the following code:

	public static void upsert(Bucket bucket, String key, String json) {
		try {
			if (cluster != null && bucket != null)
				bucket.upsert(RawJsonDocument.create(snt_sha(key), json),
						bucket_write_timeout, TimeUnit.SECONDS);
		} catch (Exception e) {
			logger.error("upsert error, for :" + e.toString() + "|" + key);
		}
	}

	protected static String snt_sha(String snt) {
		return DigestUtils.shaHex(snt);
	}

My cluster has there servers, one is 3.0.2-1603 Enterprise Edition (build-1603-rel), and tow are 3.0.3-1716 Enterprise Edition (build-1716-rel)
The Java client is couchbase-java-client-2.1.2.jar