如何在Java中从Couchbase获取json文档？

Question

I have a couchbase database that is shared between multiple applications, storing documents as json. I cannot seem to get data into my java app, since it appears to be dependent on native java binary serialization.

This code:

CouchbaseClient client = new CouchbaseClient(hosts,"bucket","");
System.out.println((String)client.get("someKey"));

results in

net.spy.memcached.transcoders.SerializingTranscoder:  Failed to decompress data
java.util.zip.ZipException: Not in GZIP format

since it is trying to deserialize by default. I notice that I can provide my own transcoder, but I really only want the raw string data so I can json parse it myself using gson or whatever. None of the available transcoders seem to give me this.

The couchbase docs have an example for setting json, but none for reading it. How are people reading json into java?

Answer 1

First off, this problem will go away soon in that the Couchbase "2.0 SDKs" implement common flags between each other so this kind of problem doesn't come up. Michael's blogs are a good read if you want to see what's happening here. The reason for the problem in the first place is that in the 1.x series, Couchbase was trying to stay compatible with existing application code and memcached. In the memcached world, the clients were all written by different people at different times.

Based on the exception, I believe you're probably trying to read an item stored by .NET. I have a sample transcoder you can use for this from a few weeks ago.

Answer 2

Make sure you are using latest CB java client:

<dependencies>
  <dependency>
    <groupId>com.couchbase.client</groupId>
    <artifactId>couchbase-client</artifactId>
    <version>1.4.4</version>
  </dependency>
</dependencies>

see: Couchbase Java Client Library 1.4

I have my service that uses CB client running just fine. Here is how I create client:

CouchbaseConnectionFactoryBuilder cfb = new CouchbaseConnectionFactoryBuilder();
cfb.setOpTimeout(10000);
cfb.setOpQueueMaxBlockTime(5000);
CouchbaseClient client = new CouchbaseClient(cfb.buildCouchbaseConnection(baseURIs, bucketName, ""));

And here is an example how I get a raw string and convert it to POJOs:

MyPOJO get(CouchbaseClient client, String key)
{
  com.google.gson.Gson gson = new com.google.gson.Gson();
  String jsonValue = (String) client.get(key);
  return gson.fromJson(jsonValue, MyPOJO.class);
}

Also, update your question with the sample JSON doc that causing this issue. Perhaps it has something to do with the format of the document itself.