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neo4j

This example is only supported when using XVM (with its jni plug-in installed), SWI-Prolog, or YAP as the backend compiler.

There are two individual examples. The first is a simple example of using Neo4j based on the HelloWorldExample found at:

https://neo4j.com/docs/java-manual/current/get-started/

The second example is more elaborated and based on Neo4j example found at:

https://console.neo4j.org

After instaling Neo4j (5.x or later version), you must edit the neo4j.conf file to run this example:

Disable authentication:

dbms.security.auth_enabled=false

Configure the Bolt connector:

server.bolt.enabled=true
server.bolt.tls_level=DISABLED
server.bolt.listen_address=:7687
server.bolt.advertised_address=:7687

You may also need to disable some Neo4j system properties:

#wrapper.java.additional=-Djava.awt.headless=true
#wrapper.java.additional.4=-Dneo4j.ext.udc.source=homebrew

Or, depending on the Neo4j version:

#server.jvm.additional=-Djava.awt.headless=true-Dunsupported.dbms.udc.source=homebrew

Save the edit file and start (or restart) Neo4j:

$ neo4j start

When running this example on Windows, check first the Neo4j installation directory path used in the `set_classpath_*.ps1` scripts and adjust it if required.

For the default location of the neo4j.conf file, see:

https://neo4j.com/docs/operations-manual/current/configuration/file-locations/

Running from a terminal

When running this example from the terminal (i.e., not as a notebook), start by setting the Java CLASSPATH environment variable. Three backend Prolog systems are supported: XVM, SWI-Prolog, and YAP. There's a Bash script file that sets the CLASSPATH environment variable when sourced:

$ cd "$LOGTALKUSER/examples/document_converter"
$ . set_classpath.sh

Running as a notebook

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Set the required environment variables (edit for the location of the Neo4j JAR files in your system):

os::directory_files('/usr/local/Cellar/neo4j/5.26.1/libexec/lib', _JARs, [paths(absolute), extensions(['.jar'])]),
atomic_list_concat(_JARs, ':', _CLASSPATH),
setenv('CLASSPATH', _CLASSPATH).

Load the example:

logtalk_load(neo4j(loader)).

Print a greeting message (if not running as a notebook):

(current_object(jupyter) -> true; hello_world('bolt://localhost:7687', 'neo4j', 'password')::print_greeting('Hello world!')).

<!-- Hello world!, from node 0

true. -->

Find the people Neo knows in the Matrix:

matrix('bolt://localhost:7687', 'neo4j', 'password')::neo_knows(Who).