home-server

Features

• Provides a RESTful API to store and query data related to a smart meter
• Provides a RESTful API to store and query data related to environmental sensor readings (temperature and humidity)
• Ability to send gas meter readings to mindergas.nl on a daily basis

Links

• home-sensors
• home-frontend

Technical notes

SSL Certificates / https

Create keystore with a self-signed certificate

keytool -genkeypair -alias home-server-localhost -dname "cn=localhost, ou=home-server, o=home-server, l=Deventer, s=Overijssel, c=NL" -keyalg RSA -keysize 2048 -storetype PKCS12 -keystore home-server-localhost-keystore.p12 -validity 3650 -ext san=dns:localhost,ip:127.0.0.1,ip:::1

When prompted for a password, supply a strong one, you could for example generate one on https://passwordsgenerator.net/.

For more information about keytool, see keytool tutorial by Oracle.

If you omit the -ext san=... part, Chrome Developer Tools complains with a message like Invalid self signed SSL cert and Subject Alternative Name Missing

Export public key

keytool -export -alias home-server-localhost -keystore home-server-localhost-keystore.p12 -rfc -file home-server-localhost.cer

This command effectively:

1. Reads from the keystore file named home-server-localhost-keystore.p12.
2. Looks in that file for the alias named home-server-localhost.
3. Exports the public key to the new file named home-server-localhost.cer.

For more information about the content of the -dname parameter, see: Certificate Attributes tutorial by Oracle.

Configure Spring Boot to use the keystore on the server

Add to application.properties:

# The format used for the keystore. It could be set to JKS in case it is a JKS file
server.ssl.key-store-type=PKCS12
# The path to the keystore containing the certificate
server.ssl.key-store=classpath:home-server-localhost-keystore.p12
# The password used to generate the certificate
server.ssl.key-store-password=<replace with password that was created in step "Create keystore with a self-signed certificate">
# The alias mapped to the certificate
server.ssl.key-alias=home-server-localhost

Futhermore:

1. Make sure to require a secure channel:

    public void configure(final HttpSecurity http) throws Exception {
        http
            .requiresChannel()
            .anyRequest().requiresSecure()
            .and()

2. Change the server port, 443 is the default port for https, example application.properties:

server.port=8443

Create a truststore to be used by java clients that make requests to the server

keytool -importcert -file home-server-localhost.cer -keystore home-sensors-truststore-localhost.p12 -alias "home-server-localhost"

When prompted for a password, supply a strong one, you could for example generate one on https://passwordsgenerator.net/. Use a different password than the one used for the keystore (see "Create keystore with a self-signed certificate").

Use truststore from client

Add VM options: -Djavax.net.ssl.trustStore=<absolute-path-to->home-sensors-truststore-rpi.p12 -Djavax.net.ssl.trustStorePassword=<password, see "Create a truststore">

When connection fails, add the following VM option and retry: -Djavax.net.debug=all. Inspect the logging for hints about what is wrong. Furthermore read the following acticle Handshake failure scenarios on Baeldung

Tools

KeyStore Explorer is an open source GUI replacement for the Java command-line utilities keytool and jarsigner. https://keystore-explorer.org/

Common development tasks

Update versions

Gradle

For this, you can use the following command: gradlew wrapper --gradle-version <new version>

Dependencies

For this, you can use the following command: gradlew dependencyUpdates. Inspect the output of the command, update build.gradle manually and test if the application still builds and executes correctly.

JDK

On the Raspberry PI, the Liberica JDK distribution is used. See the downloads page and look for "Linux" ➡️ "ARM" ➡️ ".tar.gz". On the RPI:

• download it: cd /opt, sudo wget <URL of the file to be downloaded>
• unpack it (sudo tar xvfz <name of the file>.tar.gz)
• update [./etc/script/start-home-server.sh]

Compact database file

1. Login in to the application
2. Go to the H2 console, eg:

   http://home:9090/h2-console/
   

3. Connect with the following connection string

   jdbc:h2:~/home-server/database/home-server-database;DB_CLOSE_ON_EXIT=FALSE
   

4. Execute the following SQL statement:

   SHUTDOWN COMPACT