This is a small example spring LTI webapp that does the bare minimum to handle a LTI launch and display back a web page. This uses the lti-launch library that does most of the heavy lifting of validating the LTI launch and setting up a session. The tool is a single controller with a JSP to render the output.

There are a few configuration options to setup the tool provider:

# The LTI key for the launch (default: consumer)
lti.instance=canvas
# The LTI secret for the launch, which in production must be secure (default: secret)
lti.secret=canvas
# The name of the application (default: LTI Demo)
lti.name=Example LTI Demo
# The URL of the tool consumer (default: http:https://example.com)
# This only used when checking service sending request, which is not enabled by default.
lti.url=http:https://canvas.instructure.com

To build this use maven or the maven wrapper.

mvn install

or

./mvnw install

Having built the code it can be run, you can also pass in configuration if you haven't edited the config in the source:

java -jar target/lti-demo-0.0.1-SNAPSHOT.war \
  --lti.instance=canvas \
  --lti.secret=canvas \
  --lti.name="Example LTI Demo" \
  --lti.url=http:https://canvas.instructure.com

Often the service into which an LTI tool is integrated is running with is using TLS and if the LTI tool is deployed into an iframe the browser won't display non-TLS content. One workaround is to launch the LTI tool into a new browser window, but alternatively you can enable TLS on your LTI tool. There is a tool called mkcert that makes generating a certificate easier and installs a CA so that the browsers trust it. After installing mkcert and setting it up generate a certificate for use on with localhost.

mkcert -pkcs12 -p12-file config/keystore.p12 localhost

Then start the application with the ssl profile enabled and the LTI tool should be accessible on https://localhost:8443/

To install this tool into Canvas there is a snippet of XML that can be edited to paste into the tool configuration when adding a LTI tool that makes the tool appear on the course navigation. It's in the file lti.xml, you may need to change the launch URL to the actual URL you are using.