Immutable Configuration

[MoonBow-1]

Description

Relates to #33 somewhat.

Currently the configuration has setters, which are not used, or only used in tests.
Spring Boot has support for immutable external configuration.

After quickly testing by changing the Configuration to:

@ConfigurationProperties()
public class Configuration {
    private final String sysLogHost;
    private final String sysLogProtocol;
    private final int sysLogPort;
    private final int maxAckValue;
    private final int maxAckAge;
    private final int maxSessionAge;
    private final int maxChannels;
    private final long pollTime;
    private final boolean printTimes;
    public Configuration(
            String sysLogHost,
            String sysLogProtocol,
            int sysLogPort,
            int maxAckValue,
            int maxAckAge,
            int maxSessionAge,
            int maxChannels,
            long pollTime,
            boolean printTimes
    ) {
        this.sysLogHost = sysLogHost;
        this.sysLogProtocol = sysLogProtocol;
        this.sysLogPort = sysLogPort;
        this.maxAckValue = maxAckValue;
        this.maxAckAge = maxAckAge;
        this.maxSessionAge = maxSessionAge;
        this.maxChannels = maxChannels;
        this.pollTime = pollTime;
        this.printTimes = printTimes;
    }

And wiring it in the Main class by:

@EnableConfigurationProperties(Configuration.class)
public class Cfe16Application {
...
}

The IDE is happy with all the wirings, but tests have started to fail with essentially a null Configuration, even though the tests have the @TestPropertySource annotation.

Requires more digging into the test properties

[MoonBow-1]

Seems that the problem is with the application.properties field names, where Spring looks for the field in certain way, which does not align with current property names.

So this change will require additional Configuration classes, or a major version bump if the property names are to be changed to the expected names based on the Configuration class fields.

[MoonBow-1]

After trying to implement the immutable configuration with the Spring ConfigurationProperties, I ran into a problem with the tests/compiler, where tests couldn't initialize the autowired context for the Configuration, so I think the best way forwards with this issue is to just use the CNF_01 library:

https://github.com/teragrep/cnf_01