Chapter 19. CouchDB
Camel CouchDB component
Available as of Camel 2.11
The couchdb: component allows you to treat CouchDB instances as a producer or consumer of messages. Using the lightweight LightCouch API, this camel component has the following features:
- As a consumer, monitors couch changesets for inserts, updates and deletes and publishes these as messages into camel routes.
- As a producer, can save or update documents into couch.
- Can support as many endpoints as required, eg for multiple databases across multiple instances.
- Ability to have events trigger for only deletes, only inserts/updates or all (default).
- Headers set for sequenceId, document revision, document id, and HTTP method type.
Maven users will need to add the following dependency to their
pom.xml for this component:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-couchdb</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>URI format
couchdb:http://hostname[:port]/database?[options]
Where hostname is the hostname of the running couchdb instance. Port is optional and if not specified then defaults to 5984.
Options
| Property | Default | Description |
|---|---|---|
deletes
|
true
|
document deletes are published as events |
updates
|
true
|
document inserts/updates are published as events |
heartbeat
|
30000
|
how often to send an empty message to keep socket alive in millis |
createDatabase
|
true
|
create the database if it does not already exist |
username
|
null
|
username in case of authenticated databases |
password
|
null
|
password for authenticated databases |
Headers
The following headers are set on exchanges during message transport.
| Property | Value |
|---|---|
CouchDbDatabase
|
the database the message came from |
CouchDbSeq
|
the couchdb changeset sequence number of the update / delete message |
CouchDbId
|
the couchdb document id |
CouchDbRev
|
the couchdb document revision |
CouchDbMethod
|
the method (delete / update) |
Headers are set by the consumer once the message is received. The producer will also set the headers for downstream processors once the insert/update has taken place. Any headers set prior to the producer are ignored. That means for example, if you set CouchDbId as a header, it will not be used as the id for insertion, the id of the document will still be used.
Message Body
The component will use the message body as the document to be inserted. If the body is an instance of String, then it will be marshalled into a GSON object before insert. This means that the string must be valid JSON or the insert / update will fail. If the body is an instance of a com.google.gson.JsonElement then it will be inserted as is. Otherwise the producer will throw an exception of unsupported body type.
Samples
For example if you wish to consume all inserts, updates and deletes from a CouchDB instance running locally, on port 9999 then you could use the following:
from("couchdb:http://localhost:9999").process(someProcessor);
If you were only interested in deletes, then you could use the following
from("couchdb:http://localhost:9999?updates=false").process(someProcessor);
If you wanted to insert a message as a document, then the body of the exchange is used
from("someProducingEndpoint").process(someProcessor).to("couchdb:http://localhost:9999")