TL;DR

Neocons is a feature rich idiomatic Clojure client for the Neo4J REST API.

2.0.0 is a major release that targets Neo4J 2.0. It is backwards compatible with 1.1. Note that Neo4J 2.0 contains some breaking Cypher syntax changes.

Neocons documentation has been updated to cover the new features in Neocons 2 and Neo4J.

Changes between Neocons 1.1.0 and 2.0.0

Transaction Support (Neo4J Server 2.0)

Neocons 2.0 gains support for transactions.

Higher Level API

A group of Cypher statements can be executed in a transaction that will be committed automatically upon success. Any error during the execution will trigger a rollback.

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(require '[clojurewerkz.neocons.rest.transaction :as tx])

(tx/in-transaction
  (tx/statement "CREATE (n {props}) RETURN n" {:props {:name "Node 1"}})
  (tx/statement "CREATE (n {props}) RETURN n" {:props {:name "Node 2"}}))

Lower Level API

Transactions are instantiated from a group of Cypher statements that are passed as maps to clojurewerkz.neocons.rest.transaction/begin:

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(let [t (tx/begin-tx [{:statement "CREATE (n {props}) RETURN n" {:props {:name "My node"}}}])]
  (tx/commit t))

(let [t (tx/begin-tx)]
  (tx/rollback t))

clojurewerkz.neocons.rest.transaction/commit and clojurewerkz.neocons.rest.transaction/rollback commit and roll a transaction back, respectively.

Macro for working with a transaction

If you want a more fine grained control of working in a transaction without manually committing or checking for exceptions, you can use the clojurewerkz.neocons.rest.transaction/with-transaction macro.

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(require '[clojurewerkz.neocons.rest.transaction :as tx])

(let [transaction (tx/begin-tx)]
  (tx/with-transaction
    transaction
    true
    (let [[_ result] (tx/execute transaction [(tx/statement "CREATE (n) RETURN ID(n)")])]
    (println result))))

If there any errors while processing, the transaction is rolled back.

The first argument is the variable which holds the transaction information. The second argument to the macro is commit-on-success, which commits the transaction there are no errors.

Constraints Support (Neo4J 2.0 Only)

clojurewerkz.neocons.rest.constraints is a new namespace that implements Neo4J 2.0 constraints.

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(require '[clojurewerkz.neocons.rest.constraints :as cts])

;; create a uniqueness constraint
(cts/create-unique "Person" :name)

;; get constraint info
(cts/get-unique "Person" :name)

;; drop a constraint
(cts/drop "Person" :name)

Labels Support (Neo4J 2.0 Only)

clojurewerkz.neocons.rest.labels is a new namespace that provides support for labels in Neo4J 2.0.

It is possible to add, replace, remove and retrieve labels to/from a node.

To add labels to a node, use clojurewerkz.neocons.rest.labels/add:

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(require '[clojurewerkz.neocons.rest.labels :as nl])

(nl/add node ["neo4j" "clojure"])

To add replaces all labels on a node, use clojurewerkz.neocons.rest.labels/replace:

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(require '[clojurewerkz.neocons.rest.labels :as nl])

(nl/replace node ["graph" "database"])

Deleting a label from a node is possible with clojurewerkz.neocons.rest.labels/remove:

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(require '[clojurewerkz.neocons.rest.labels :as nl])

(nl/remove node "database")

clojurewerkz.neocons.rest.labels/get-all-labels is the function that lists either all labels in the database (w/o arguments) or on a specific node (1-arity):

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(require '[clojurewerkz.neocons.rest.labels :as nl])

(nl/get-all-labels node)
;= [all labels]
(nl/get-all-labels node)
;= [labels on node]

Clojure 1.6 Compatibility Fixes

Neocons 2.0 is compatible with recent releases of Clojure 1.6 (master).

Clojure 1.3 Support Dropped

Neocons no longer supports Clojure 1.3.

Documentation Updates

Neocons documentation has been updated to cover the new features in Neocons 2 and Neo4J:

• Transactions
• Labels
• Schema and Constraints

Change Log

We encourage all users to give this version (and Neo4J 2.0!) a try.

Neocons change log is available on GitHub.

Neocons is a ClojureWerkz Project

Neocons is part of the group of libraries known as ClojureWerkz, together with

• Langohr, a Clojure client for RabbitMQ that embraces the AMQP 0.9.1 model
• Elastisch, a minimalistic Clojure client for ElasticSearch
• Monger, a Clojure MongoDB client for a more civilized age
• Cassaforte, a Cassandra client built around CQL 3
• Quartzite, a powerful scheduling library

and several others. If you like Neocons, you may also like our other projects.

Let us know what you think on Twitter or on the Clojure mailing list.

About the Author

Michael on behalf of the ClojureWerkz Team