Liking cljdoc? Tell your friends :D

Neo4J Demo in Clojure

A simple demo accessing Neo4J using the gorillalabs/neo4j-clj library.

Verify you have Java, Clojure, and Leiningen set up correctly

Try the following commands, and make sure you get similar output:

> java --version
java 13 2019-09-17
Java(TM) SE Runtime Environment (build 13+33)
Java HotSpot(TM) 64-Bit Server VM (build 13+33, mixed mode, sharing)

> lein --version
Leiningen 2.9.1 on Java 13 Java HotSpot(TM) 64-Bit Server VM

Installation

This project assumes you have already installed Neo4J Desktop (Enterprise Edition). It is available for free for local use. When you download the installer, be sure to copy the Activition Code and save it. You will need the Activation Code during the installation process.

Since the Neo4J Desktop is free to use for development, I have not played around with the open source Docker version of Neo4J.

Environment

The unit tests in this repo work against a locally running instance of Neo4j Desktop. For some unknown reason, it doesn’t work right running against a basic DB in the Neo4j Aura cloud.

Configuration after installation

Note that in the Neo4j Desktop browser, there are three (3) different entities to consider:

  1. the Project

  2. the DBMS

  3. the DB

Keep in mind that a project can have multiple DBMS’s, and a DBMS can have multiple DB’s.

For our purposes, create the following configuration in Neo4j Desktop:

  • Click the top-left "project" icon, then the + New button to create a new project. Name it "Demo Project", for example.

  • In the top-right corner, click the "+ Add" button to add a "Local DBMS". Change the default name to "Unit Test DBMS", if desired. For development purposes, set the password to "secret". Then, click the blue "Create" button.

  • Click on the DBMS name under the Project name in the Neo4j Desktop window to highlight it, then click on the "Plugins" tab in the RHS panel. Select "APOC" and install to the DB.

  • Click on the DBMS name under the Project name in the Neo4j Desktop window to highlight it, then click the green "Start" button so the DB is active (not just the neo4j desktop). If you make any changes to the DB config you’ll need to click the "restart" to make then take effect.

  • The DBMS will create 2 DB’s, "system" and "neo4j". We accept the default DB name "neo4j" in the DBMS. If you click the "Details" tab on the RHS panel, you should see the Bolt protocol running on port 7687.

  • We depend on the DB name "neo4j", the password "secret", and the port 7687 being correct. These creds must be correct or the neo4j driver can’t connect to the DB (it will fail auth).

Credentials Configuration

This code uses the lein-environ plugin to access your database credentials from a file profiles.clj which you should never check into SCM/git. After using git clone to copy this repo to your local machine, execute:

> cp profiles-template.clj profiles.clj     # copy template file to actual file

Then, in profiles.clj, replace the placeholders XXXXX and YYYYY with the actual values for your username and password.

For local development & testing with Neo4j Desktop (preferred), you may also use the pre-configured profile:

> cp profiles-localhost.clj profiles.clj     # copy profile for local DB

It is setup correctly for use with the default DB name neo4j and the "starter password" of secret.

Run the Unit Tests

I do this so much I have some bash aliases:

alias lct=" time (lein do clean, test)"
alias lctr="time (lein do clean, test-refresh)"

The first one lct is generic, the 2nd one lctr is for use with the lein-test-refresh plugin.

Running Unit Tests - Plain

Just type

> lct   # or `lein clean ; lein test`

with result:

  -----------------------------------
     Clojure 1.10.3    Java 15.0.2
  -----------------------------------

  lein test tst.demo.core
  Creating session...
  Getting Neo4j version info
  Getting APOC version info
    *** APOC not installed ***

  Ran 2 tests containing 4 assertions.
  0 failures, 0 errors.
  ( lein do clean, test; )  30.19s user 0.87s system 320% cpu 9.698 total

The message "* APOC not installed *" shows that we have not installed the free APOC library of functions for Neo4J. We want to install APOC. The APOC library is free and very useful, so we normally want to have it available.

Install the APOC library

In the Neo4j Desktop window, highlight your project in the left-hand nav pane.. Then click near the green "ACTIVE" label, which will open the "Manage" screen on the RHS of the screen. Click on Plugins → APOC → Install and Restart. After the DB has restarted, re-run the tests.

  > lct

  lein test _bootstrap

  -----------------------------------
     Clojure 1.10.3    Java 15.0.2
  -----------------------------------

  lein test tst.demo.core
  2021-10-13T17:34:30.468493101 INFO Driver - Direct driver instance 1534840003 created for server address localhost:7687
  2021-10-13T17:34:31.008078467 INFO Driver - Closing driver instance 1534840003
  2021-10-13T17:34:31.01205769 INFO ConnectionPool - Closing connection pool towards localhost:7687

  lein test tst.demo.indexes
  2021-10-13T17:34:31.221594391 INFO Driver - Direct driver instance 1561991024 created for server address localhost:7687
  2021-10-13T17:34:31.662665892 WARNING ChannelErrorHandler - [0xa2f9c9e0][localhost:7687][bolt-366] Fatal error occurred in the pipeline
  2021-10-13T17:34:31.663192391 WARNING InboundMessageHandler - [0xa2f9c9e0][localhost:7687][bolt-366] Message ignored because of the previous fatal error. Channel will be closed. Message:
  b07e
  2021-10-13T17:34:32.084772962 INFO Driver - Closing driver instance 1561991024
  2021-10-13T17:34:32.085024531 INFO ConnectionPool - Closing connection pool towards localhost:7687

  lein test tst.tupelo.neo4j
  2021-10-13T17:34:32.291197101 INFO Driver - Direct driver instance 2043010680 created for server address localhost:7687
  2021-10-13T17:34:33.153643962 INFO Driver - Closing driver instance 2043010680
  2021-10-13T17:34:33.153944616 INFO ConnectionPool - Closing connection pool towards localhost:7687

  lein test tst.tupelo.neo4j-clj-core
  2021-10-13T17:34:33.358175616 INFO Driver - Direct driver instance 1334840569 created for server address localhost:7687
  2021-10-13T17:34:33.79356691 INFO Driver - Closing driver instance 1334840569
  2021-10-13T17:34:33.793860734 INFO ConnectionPool - Closing connection pool towards localhost:7687

  Ran 6 tests containing 57 assertions.
  0 failures, 0 errors.
  ( lein do clean, test; )  33.25s user 0.92s system 252% cpu 13.558 total

Notice that this time it found the APOC library.

Code Structure

All interesting code is in the NS tst.demo.core, under the test directory. I like this naming structure better then the -test suffix as it doesn’t mess with the filename, and there is no conflict between hyphens "core-test" vs underscores "core_test.clj".

Keeping Dependency Versions Up-To-Date

This project includes the lein-ancient plugin, which will tell you if any of your dependency libraries are out of date. I have an alias:

alias laca="lein ancient check :all"

which will give you a list of version updates you should make, or just

all artifacts are up-to-date.

if you are already up-to-date on everything.

License

Copyright © 2021 Alan Thompson

Distributed under the Eclipse Public License, the same as Clojure.

Can you improve this documentation?Edit on GitHub

cljdoc is a website building & hosting documentation for Clojure/Script libraries

Keyboard shortcutsReport a problemcljdoc on GitHub
× close