Config: Refactor usage of exceptions in optional sources

[tomas-langer]

When we start Helidon SE and have logging set to "FINE", config logs a number of exceptions that should not be thrown, related to optional config sources.
When a config source is optional, there should be no exception thrown, instead we should gracefully ignore it.

Reasons:

1. Log is polluted with useless information
2. Debugging using Exception breakpoints is more complicated, as it stops on "false" positives

Environment Details

• Helidon Version: 1.0.0
• Helidon SE

---

Log output:

Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource loadDataChangedSinceLastLoad
FINE: Source ClasspathConfig[meta-config.yaml]? has changed to Optional[1970-01-01T00:00:00Z] from Optional.empty.
Mar 06, 2019 7:22:19 PM io.helidon.config.internal.ClasspathConfigSource content
FINE: Error to get ClasspathConfig[meta-config.yaml]? using java.lang.ClassLoader@1043d64e8 CONTEXT ClassLoader.
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
CONFIG: Cannot load data from optional source ClasspathConfig[meta-config.yaml]?. Will not be used to load from. ClasspathConfig[meta-config.yaml]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
FINE: Load of 'ClasspathConfig[meta-config.yaml]?' source failed with an exception.
io.helidon.config.ConfigException: ClasspathConfig[meta-config.yaml]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
        at io.helidon.config.internal.ClasspathConfigSource.content(ClasspathConfigSource.java:115)
        at io.helidon.config.spi.AbstractParsableConfigSource.loadData(AbstractParsableConfigSource.java:58)
        at io.helidon.config.RetryPolicies$JustCallRetryPolicyHolder$1.execute(RetryPolicies.java:77)
        at io.helidon.config.spi.AbstractSource.loadDataChangedSinceLastLoad(AbstractSource.java:197)
        at io.helidon.config.spi.AbstractSource.load(AbstractSource.java:177)
        at io.helidon.config.UseFirstAvailableConfigSource.load(UseFirstAvailableConfigSource.java:58)
        at io.helidon.config.ProviderImpl.newConfig(ProviderImpl.java:103)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.ConfigSources.load(ConfigSources.java:345)
        at io.helidon.config.BuilderImpl.defaultConfigSource(BuilderImpl.java:348)
        at io.helidon.config.BuilderImpl.targetConfigSource(BuilderImpl.java:309)
        at io.helidon.config.BuilderImpl.buildProvider(BuilderImpl.java:278)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.Config.create(Config.java:358)
        at io.helidon.examples.graalvm.GraalVMNativeImageMain.main(GraalVMNativeImageMain.java:76)

Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource loadDataChangedSinceLastLoad
FINE: Source ClasspathConfig[meta-config.conf]? has changed to Optional[1970-01-01T00:00:00Z] from Optional.empty.
Mar 06, 2019 7:22:19 PM io.helidon.config.internal.ClasspathConfigSource content
FINE: Error to get ClasspathConfig[meta-config.conf]? using java.lang.ClassLoader@1043d64e8 CONTEXT ClassLoader.
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
CONFIG: Cannot load data from optional source ClasspathConfig[meta-config.conf]?. Will not be used to load from. ClasspathConfig[meta-config.conf]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
FINE: Load of 'ClasspathConfig[meta-config.conf]?' source failed with an exception.
io.helidon.config.ConfigException: ClasspathConfig[meta-config.conf]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
        at io.helidon.config.internal.ClasspathConfigSource.content(ClasspathConfigSource.java:115)
        at io.helidon.config.spi.AbstractParsableConfigSource.loadData(AbstractParsableConfigSource.java:58)
        at io.helidon.config.RetryPolicies$JustCallRetryPolicyHolder$1.execute(RetryPolicies.java:77)
        at io.helidon.config.spi.AbstractSource.loadDataChangedSinceLastLoad(AbstractSource.java:197)
        at io.helidon.config.spi.AbstractSource.load(AbstractSource.java:177)
        at io.helidon.config.UseFirstAvailableConfigSource.load(UseFirstAvailableConfigSource.java:58)
        at io.helidon.config.ProviderImpl.newConfig(ProviderImpl.java:103)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.ConfigSources.load(ConfigSources.java:345)
        at io.helidon.config.BuilderImpl.defaultConfigSource(BuilderImpl.java:348)
        at io.helidon.config.BuilderImpl.targetConfigSource(BuilderImpl.java:309)
        at io.helidon.config.BuilderImpl.buildProvider(BuilderImpl.java:278)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.Config.create(Config.java:358)
        at io.helidon.examples.graalvm.GraalVMNativeImageMain.main(GraalVMNativeImageMain.java:76)

Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource loadDataChangedSinceLastLoad
FINE: Source ClasspathConfig[meta-config.json]? has changed to Optional[1970-01-01T00:00:00Z] from Optional.empty.
Mar 06, 2019 7:22:19 PM io.helidon.config.internal.ClasspathConfigSource content
FINE: Error to get ClasspathConfig[meta-config.json]? using java.lang.ClassLoader@1043d64e8 CONTEXT ClassLoader.
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
CONFIG: Cannot load data from optional source ClasspathConfig[meta-config.json]?. Will not be used to load from. ClasspathConfig[meta-config.json]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
FINE: Load of 'ClasspathConfig[meta-config.json]?' source failed with an exception.
io.helidon.config.ConfigException: ClasspathConfig[meta-config.json]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
        at io.helidon.config.internal.ClasspathConfigSource.content(ClasspathConfigSource.java:115)
        at io.helidon.config.spi.AbstractParsableConfigSource.loadData(AbstractParsableConfigSource.java:58)
        at io.helidon.config.RetryPolicies$JustCallRetryPolicyHolder$1.execute(RetryPolicies.java:77)
        at io.helidon.config.spi.AbstractSource.loadDataChangedSinceLastLoad(AbstractSource.java:197)
        at io.helidon.config.spi.AbstractSource.load(AbstractSource.java:177)
        at io.helidon.config.UseFirstAvailableConfigSource.load(UseFirstAvailableConfigSource.java:58)
        at io.helidon.config.ProviderImpl.newConfig(ProviderImpl.java:103)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.ConfigSources.load(ConfigSources.java:345)
        at io.helidon.config.BuilderImpl.defaultConfigSource(BuilderImpl.java:348)
        at io.helidon.config.BuilderImpl.targetConfigSource(BuilderImpl.java:309)
        at io.helidon.config.BuilderImpl.buildProvider(BuilderImpl.java:278)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.Config.create(Config.java:358)
        at io.helidon.examples.graalvm.GraalVMNativeImageMain.main(GraalVMNativeImageMain.java:76)

Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource loadDataChangedSinceLastLoad
FINE: Source ClasspathConfig[meta-config.properties]? has changed to Optional[1970-01-01T00:00:00Z] from Optional.empty.
Mar 06, 2019 7:22:19 PM io.helidon.config.internal.ClasspathConfigSource content
FINE: Error to get ClasspathConfig[meta-config.properties]? using java.lang.ClassLoader@1043d64e8 CONTEXT ClassLoader.
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
CONFIG: Cannot load data from optional source ClasspathConfig[meta-config.properties]?. Will not be used to load from. ClasspathConfig[meta-config.properties]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
Mar 06, 2019 7:22:19 PM io.helidon.config.spi.AbstractSource processMissingData
FINE: Load of 'ClasspathConfig[meta-config.properties]?' source failed with an exception.
io.helidon.config.ConfigException: ClasspathConfig[meta-config.properties]? does not exist. Used ClassLoader: java.lang.ClassLoader@1043d64e8
        at io.helidon.config.internal.ClasspathConfigSource.content(ClasspathConfigSource.java:115)
        at io.helidon.config.spi.AbstractParsableConfigSource.loadData(AbstractParsableConfigSource.java:58)
        at io.helidon.config.RetryPolicies$JustCallRetryPolicyHolder$1.execute(RetryPolicies.java:77)
        at io.helidon.config.spi.AbstractSource.loadDataChangedSinceLastLoad(AbstractSource.java:197)
        at io.helidon.config.spi.AbstractSource.load(AbstractSource.java:177)
        at io.helidon.config.UseFirstAvailableConfigSource.load(UseFirstAvailableConfigSource.java:58)
        at io.helidon.config.ProviderImpl.newConfig(ProviderImpl.java:103)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.ConfigSources.load(ConfigSources.java:345)
        at io.helidon.config.BuilderImpl.defaultConfigSource(BuilderImpl.java:348)
        at io.helidon.config.BuilderImpl.targetConfigSource(BuilderImpl.java:309)
        at io.helidon.config.BuilderImpl.buildProvider(BuilderImpl.java:278)
        at io.helidon.config.BuilderImpl.build(BuilderImpl.java:245)
        at io.helidon.config.Config.create(Config.java:358)
        at io.helidon.examples.graalvm.GraalVMNativeImageMain.main(GraalVMNativeImageMain.java:76)

[tomas-langer]

related to #294