LodView (lodview-ng)

LodView is a Java web application based on Spring Boot and Apache Jena that provides W3C-compliant IRI dereferencing for publishing RDF data as Linked Open Data.

This fork (teamdigitale/dati-semantic-lodview) modernizes the upstream project LodLive/LodView by porting it to:

• Java 21 (Eclipse Temurin)
• Spring Boot 3.x with embedded Tomcat
• Gradle as the build system
• An executable artifact runnable with java -jar (no external Tomcat required)

Note for users of the upstream version with Tomcat: previous LodView releases required deploying a WAR file onto Apache Tomcat 9. This fork uses Spring Boot with embedded Tomcat: running java -jar lodview.war is enough. Deployment to an external application server (Tomcat, Jetty, etc.) is not supported nor recommended.

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Prerequisites

• A reachable SPARQL endpoint (e.g. Virtuoso, Fuseki, GraphDB)
• Ubuntu 22.04+ (for native installation) or Docker

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Option 1: Docker (recommended)

Official images are published on GitHub Container Registry. This is the recommended installation mode.

1.1 Install Docker

sudo apt update
sudo apt install -y docker.io
sudo systemctl enable docker
sudo systemctl start docker

1.2 Create the environment file

Create a lodview.env file and customize the values for your environment:

# === SPARQL ENDPOINT (REQUIRED) ===
# Set the URL of your SPARQL endpoint (e.g. Virtuoso, Fuseki, GraphDB)
LodViewendpoint=<PUBLIC_SPARQL_ENDPOINT_URL>
LodViewendpointInternal=<INTERNAL_SPARQL_ENDPOINT_URL>
LodViewendpointType=virtuoso

# === NAMESPACE ===
LodViewIRInamespace=<BASE_IRI_NAMESPACE>

# === HOME PAGE ===
LodViewhomeUrl=<HOME_PAGE_URL>
LodViewhomeTitle=<HOME_PAGE_TITLE>
LodViewhomeDescription=<HOME_PAGE_DESCRIPTION>
LodViewhomeContent=<HOME_PAGE_CONTENT>

# === OPTIONAL ===
LodViewhttpRedirectSuffix=
LodViewpreferredLanguage=it
LodViewpublicUrlPrefix=auto
LodViewstaticResourceURL=auto
LodViewforceIriEncoding=auto
LodViewredirectionStrategy=
LodViewdefaultInverseBehaviour=close
LodViewauthUsername=
LodViewauthPassword=
LodViewlicense=

Note on Docker networking: if the SPARQL endpoint runs on the same host as the container, you cannot use localhost from inside the container. Use host.docker.internal (Docker Desktop) or the actual host machine IP. Alternatively, start the container with --network host (in that case the -p flag is not needed).

1.3 Start the container

docker run -d \
  --name lodview \
  --restart unless-stopped \
  -p 8080:8080 \
  --env-file lodview.env \
  ghcr.io/teamdigitale/dati-semantic-lodview:latest

Verify:

docker logs lodview
# The application is available on http://localhost:8080

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Option 2: Native installation with systemd

This mode builds from source and runs the service as a system service.

2.1 Install Java 21

sudo apt update
sudo apt install -y eclipse-temurin-21-jdk

If the package is not available, add the Adoptium repository:

sudo apt install -y wget apt-transport-https gpg
wget -qO - https://packages.adoptium.net/artifactory/api/gpg/key/public | sudo gpg --dearmor -o /usr/share/keyrings/adoptium.gpg
echo "deb [signed-by=/usr/share/keyrings/adoptium.gpg] https://packages.adoptium.net/artifactory/deb $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/adoptium.list
sudo apt update
sudo apt install -y temurin-21-jdk

Verify:

java -version
# openjdk version "21.x.x" ...

2.2 Fetch the sources and build

sudo useradd -r -s /usr/sbin/nologin lodview

cd /opt
sudo git clone https://github.com/teamdigitale/dati-semantic-lodview.git
cd dati-semantic-lodview

# Build without tests
sudo ./gradlew clean build -x test

# Copy the artifact to the installation directory
sudo mkdir -p /opt/lodview
sudo cp build/libs/lodview.war /opt/lodview/lodview.war
sudo chown -R lodview:lodview /opt/lodview

(Optional) Remove the sources after the build to save space:

sudo rm -rf /opt/dati-semantic-lodview

2.3 Create the environment file

Create /opt/lodview/lodview.env and customize the values (same format as for Docker):

# === SPARQL ENDPOINT (REQUIRED) ===
# Set the URL of your SPARQL endpoint (e.g. Virtuoso, Fuseki, GraphDB)
LodViewendpoint=<PUBLIC_SPARQL_ENDPOINT_URL>
LodViewendpointInternal=<INTERNAL_SPARQL_ENDPOINT_URL>
LodViewendpointType=virtuoso

# === NAMESPACE ===
LodViewIRInamespace=<BASE_IRI_NAMESPACE>

# === HOME PAGE ===
LodViewhomeUrl=<HOME_PAGE_URL>
LodViewhomeTitle=<HOME_PAGE_TITLE>
LodViewhomeDescription=<HOME_PAGE_DESCRIPTION>
LodViewhomeContent=<HOME_PAGE_CONTENT>

# === OPTIONAL ===
LodViewhttpRedirectSuffix=
LodViewpreferredLanguage=it
LodViewpublicUrlPrefix=auto
LodViewstaticResourceURL=auto
LodViewforceIriEncoding=auto
LodViewredirectionStrategy=
LodViewdefaultInverseBehaviour=close
LodViewauthUsername=
LodViewauthPassword=
LodViewlicense=

Note: an external environment file is used instead of inline Environment= directives in the .service unit because several values (titles, descriptions) contain spaces and special characters that would require complex quoting under systemd.

2.4 Create the systemd unit file

Create /etc/systemd/system/lodview.service:

[Unit]
Description=LodView - Linked Data Browser
After=network.target

[Service]
Type=simple
User=lodview
Group=lodview
WorkingDirectory=/opt/lodview

EnvironmentFile=/opt/lodview/lodview.env
ExecStart=/usr/bin/java -jar /opt/lodview/lodview.war

Restart=on-failure
RestartSec=10

[Install]
WantedBy=multi-user.target

2.5 Start the service

sudo systemctl daemon-reload
sudo systemctl enable lodview
sudo systemctl start lodview

# Check status
sudo systemctl status lodview

# The service is available on http://localhost:8080

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Environment variables

The environment variables override the values defined in the bundled conf.ttl file. The prefix is LodView followed by the name of the configuration property.

Variable	Description	Default
LodViewendpoint	Public SPARQL endpoint URL	http://localhost:8890/sparql
LodViewendpointInternal	Internal SPARQL endpoint URL (if different from the public one)	http://localhost:8890/sparql (from conf.ttl)
LodViewendpointType	Endpoint type (virtuoso or empty)	empty
LodViewIRInamespace	Base IRI namespace	https://w3id.org/italia
LodViewhttpRedirectSuffix	HTTP 303 redirect suffix (e.g. .html)	.html
LodViewhomeUrl	Home page URL	-
LodViewhomeTitle	Home page title	-
LodViewhomeDescription	Home page description	-
LodViewhomeContent	Home page textual content	-
LodViewpreferredLanguage	Preferred language (e.g. it, en)	it
LodViewpublicUrlPrefix	Public URL prefix (auto for automatic detection)	auto
LodViewstaticResourceURL	Static resources URL (auto for automatic detection)	auto
LodViewforceIriEncoding	IRI encoding handling (auto, decode, encode)	auto
LodViewredirectionStrategy	Redirect strategy (pubby or empty)	empty
LodViewdefaultInverseBehaviour	Inverse relations: open or close	close
LodViewauthUsername	Username for SPARQL endpoint authentication	empty
LodViewauthPassword	Password for SPARQL endpoint authentication	empty
LodViewlicense	License HTML text (shown at the bottom of the page)	empty

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Note for users of Apache HTTPD as a reverse proxy

If you already have an Apache HTTPD reverse proxy configured for the previous version (external Tomcat), keep in mind that the architectural model has changed:

• Before: Apache talked to a single Tomcat process on a single port, routing requests by path (e.g. /lodview, /lode, /webvowl).
• Now: each visualizer is an autonomous Spring Boot process listening on its own local port.

All applications start on port 8080 by default. If you run multiple visualizers on the same machine you need to assign different ports via the standard Spring Boot SERVER_PORT environment variable:

Application	Suggested SERVER_PORT
LodView	8080 (default)
LODE	8081
WebVOWL	8082

Add the following to each application's .env file (both for Docker and systemd):

SERVER_PORT=8080

For Docker, map the ports accordingly: -p 8080:8080, -p 8081:8081, -p 8082:8082.

Apache can keep acting as a reverse proxy, but the backend is no longer a single shared Tomcat.

Dedicated virtual hosts

If you use a dedicated domain (or subdomain) for each visualizer, the configuration is minimal:

<VirtualHost *:443>
    ServerName lodview.example.com

    ProxyPass / http://localhost:8080/
    ProxyPassReverse / http://localhost:8080/

    RequestHeader set X-Forwarded-Proto "https"
    RequestHeader set X-Forwarded-Port "443"

    # ... SSL configuration ...
</VirtualHost>

Path-based proxy (multiple visualizers on the same domain)

If you want to expose multiple visualizers under different paths of the same domain (e.g. example.com/lodview, example.com/lode, example.com/webvowl), you need to configure for each application:

1. SERVER_PORT — a different local port for each visualizer (see table above)
2. SERVER_SERVLET_CONTEXT_PATH — the sub-path on which the application must serve

Both are standard Spring Boot properties supported by all three applications without code changes.

Example .env file for LodView in path-based mode:

SERVER_PORT=8080
SERVER_SERVLET_CONTEXT_PATH=/lodview

Full Apache configuration for all three visualizers:

<VirtualHost *:443>
    ServerName example.com

    ProxyPass /lodview http://localhost:8080/lodview
    ProxyPassReverse /lodview http://localhost:8080/lodview

    ProxyPass /lode http://localhost:8081/lode
    ProxyPassReverse /lode http://localhost:8081/lode

    ProxyPass /webvowl http://localhost:8082/webvowl
    ProxyPassReverse /webvowl http://localhost:8082/webvowl

    RequestHeader set X-Forwarded-Proto "https"
    RequestHeader set X-Forwarded-Port "443"

    # ... SSL configuration ...
</VirtualHost>

Note: without SERVER_SERVLET_CONTEXT_PATH, Spring Boot applications serve on / (root) and the path-based proxy would not work correctly. Without SERVER_PORT, all applications would try to use port 8080.

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Ports

Port	Protocol	Description
8080	HTTP	LodView web interface (default, configurable via SERVER_PORT)