how to change the H2 database console port number specified by Liquibase example?

Question

The Liquibase install comes with an examples directory you can use to learn about different commands. The examples use a H2 database with a web console on port 9090. Unfortunately port 9090 is not available.

I'm asking how can I change the web-conole port used with the example H2 database started by the script:

• start-h2

The port appears to be specified by the Liquibase liquibase.example.StartH2Main module itself. H2 doesn't seem influenced by changes to: $HOME/.h2.server.properties ...

java -cp h2-1.4.200.jar:liquibase.jar liquibase.example.StartH2Main
Starting Example H2 Database...
NOTE: The database does not persist data, so stopping and restarting this process will reset it back to a blank database

java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at liquibase.example.StartH2Main.startTcpServer(StartH2Main.java:74)
    at liquibase.example.StartH2Main.main(StartH2Main.java:28)
Caused by: org.h2.jdbc.JdbcSQLNonTransientConnectionException: Exception opening port "9090" (port may be in use), cause: "java.net.BindException: Address already in use" [90061-200]
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:622)
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:429)
    at org.h2.message.DbException.get(DbException.java:194)
    at org.h2.util.NetUtils.createServerSocketTry(NetUtils.java:180)
    at org.h2.util.NetUtils.createServerSocket(NetUtils.java:146)
    at org.h2.server.TcpServer.start(TcpServer.java:245)
    at org.h2.tools.Server.start(Server.java:511)

I'm hoping there's a .properties file setting or command line option that will change the web-console port number H2 to use.

Answer 1

I have answered my own question, taking the lead from @RobbyCornelissen recommendation, with the following updates.

1. It is completely possible to build the StartH2Main class.
2. Change the dbPort constant from 9090 to something 'available' like 8092.

• The StartH2Main app loads H2 and side-steps the .h2.server.properties file.

3. Build a StartH2Main.jar for yourself.

• The 9090 is hard-coded for StartH2Main.
• Port 9090 is the database port, which means that all the examples must be updated to match the new port number given.

Personally I feel that anything such as a port used for a demo or tutorial should be something I can put on the command line or in a config file. Thus, avoiding timeconsuming or inconvenient barriers to adoption. It just makes sense. Such things can always have a default, please allow them to be configured as well.