Support binding environment variables to configuration (12-factor app compatible).

Spring Boot does a particularly good job at this, by mapping properties defined internally to corresponding idiomatic environment variable syntax e.g. foo.bar.baz -> FOO_BAR_BAZ. They also support some flexibility in the mapping (relaxed binding).

Cfg4j on the other hand does a poor job of this, unless its improved since the last time I looked at cfg4j.

Hello! Firstly I used an OverrideConfigProvider combining two proxy config providers based on both an environment config loader and a property config loader (from the properties file) and everything worked well. Then I decided to refactor the code to be able to load configs from the environment with an opportunity to use a secondary properties source if the config is not consistent after the 'first' load. I began with validating the loaded config structure but failed because I thought only about the reflection API possibilities. (Would appreciate a piece of advice if a one can perform the consistency validation somehow). So I managed to change the solution to a worse one - I just return 'environment provider' instead of mixed one in case of a file reading failure.

And here comes the main question. So if I try to load a config using ONLY environment variables there must be contained each 'intermediate node'. So if I have the following picture in my environment ('properties' is a prefix):

PROPERTIES_GROUPONE_KEYONE -> "VALUEONE"

I just get an Exception: com.jdiazcano.cfg4k.utils.SettingNotFound: Setting 'properties.groupone' not found. on an attempt to get the value. But if I add:

PROPERTIES_GROUPONE -> ""
PROPERTIES_GROUPONE_KEYONE -> "VALUEONE"
PROPERTIES_GROUPONE_KEYTWO -> "VALUETWO"

everything gets working. Is this behavior incorrect? I do not need to include in my properties file each 'intermediate node' though. But I do in case of working with the environment.

Thank you!

Hi, Love the concept of this library and that it appears to be actively maintained.

I'm trying to use it in a project, and running into an issue where it seems that it relies on interfaces having a $DefaultImpls which as far as I can tell will not be the case in the basic use cases listed in e.g. your examples?

I end up with a ClassNotFoundException on Config$DefaultImpls in https://github.com/jdiazcano/cfg4k/blob/master/cfg4k-core/src/main/kotlin/com/jdiazcano/cfg4k/binders/BindingInvocationHandler.kt#L63 when using the following code: Config.kt:

enum class Environment {
    DEVELOPMENT,
    STAGING,
    PRODUCTION;

    fun slug() = name.toLowerCase()
}

interface Config {
    val database: DatabaseConfig
    val server: ServerConfig
}

interface DatabaseConfig {
    val url: String
    val username: String
    val password: String
}

interface ServerConfig {
    val port: Int
    val host: String
    val environment: Environment
}

App.kt (redacted):

        val sysLoader = SystemPropertyConfigLoader()
        val envLoader = EnvironmentConfigLoader()
        val baseProvider = OverrideConfigProvider(
            DefaultConfigProvider(sysLoader),
            DefaultConfigProvider(envLoader)
        )
        val baseConfig = baseProvider.bind<Config>()

        val propsDefaultLoader = PropertyConfigLoader(ClasspathConfigSource("/app.properties"))
        val propsEnvLoader = PropertyConfigLoader(ClasspathConfigSource("/app.${baseConfig.server.environment}.properties"))
        val provider = OverrideConfigProvider(
            DefaultConfigProvider(sysLoader),
            DefaultConfigProvider(envLoader),
            DefaultConfigProvider(propsDefaultLoader),
            DefaultConfigProvider(propsEnvLoader)
        )
        val config = provider.bind<Config>()

        print(config.server.host)
        print(config.database.url)

Am I missing something obvious? If I make a stubbed default function on the objects I can get past the first error (missing $DefaultImpls) but it doesn't get me much further as it still seems to expect Kotlin to auto-stub all of these, which isn't happening for me.

Thanks in advance for your help!

When using the ByteBuddy binder, every method invocation to a config object causes a new class to be created and loaded into memory. Instead, the binder should create the class only once, with the methods in the class reading the provider every time they are executed.

This is easy to reproduce. Create any config binding with ByteBuddy. Read a method on the config in a tight loop. Start the JVM with -verbose:class to see the problem.

Describe the bug Since upgrading to com.jdiazcano.cfg4k:cfg4k-core:0.9.41 i am getting the following crash

Exception in thread "main" java.lang.IllegalArgumentException: Trying to get a key from a primitive at com.jdiazcano.cfg4k.loaders.DefaultConfigLoader.get(DefaultConfigLoader.kt:27) at com.jdiazcano.cfg4k.providers.DefaultConfigProvider.get(DefaultConfigProvider.kt:51) at com.jdiazcano.cfg4k.providers.CachedConfigProvider.get(CachedConfigProvider.kt:37) at com.abc.config.ApplicationConfig.getProperty(ApplicationConfig.kt:24) at com.abc.repository.util.DataSource.(DataSource.kt:26)

To Reproduce In order for me to reproduce this behavior I need:

1. Version of Cfg4k - com.jdiazcano.cfg4k:cfg4k-core:0.9.41
2. ConfigProvider - CachedConfigProvider
3. ConfigLoader - EnvironmentConfigLoader
4. ConfigSource - Environment Variables
5. Configuration files unless the source is a String - Environment Variables
6. Any interfaces/dataclasses used for binding/getting - nope

As example, it is easy to get an easy prototype with all the 5 points in the list: I have the following configs for a DB.

        val url = Property("db.conn", "")
        val driverName = Property("db.driver.name", "org.postgresql.Driver")
        val userName = Property("db.username", "")
        val password = Property("db.password", "")
        val connectionTimeout = Property("db.conn.timeout.sec", TimeUnit.SECONDS.toMillis(30))
        val idleTimeout = Property("db.conn.idle.timeout.sec", TimeUnit.MINUTES.toMillis(10))
        val maxLifetime = Property("db.conn.max.lifetime.sec", TimeUnit.MINUTES.toMillis(30))
        val minimumIdle = Property("db.conn.minimum.idle", 4)
        val maximumPoolSize = Property("db.conn.maximum.pool.size", 32)
        val connectionTestQuery = Property("db.conn.test.query", "SELECT 1")


data class Property<T : Any>(
    val key: String,
    val default: T
)
I use cfg4k like the following:
 override fun <T : Any> getProperty(prop: Property<T>): T {

        return configProvider.get(prop.key, prop.default.javaClass, prop.default)
    }

It seems like when i am searching for val connectionTimeout = Property("db.conn.timeout.sec", TimeUnit.SECONDS.toMillis(30)) This value does not exist in my Environment Variables, and should return the default. it may be getting confused with val url = Property("db.conn", "") Which does exist in the Environment Variables. Since it finds ConfigObject(value=jdbc:postgresql://127.0.0.1:1234/abc) as root and then fails.

This works on 0.9.3

Before the key in fun DefaultConfigLoader.get() was different key = DB_CONN_TIMEOUT_SEC - 0.9.3 key = DB.CONN.TIMEOUT.SEC - 0.9.41 Before it wasnt split and now it is.

Expected behavior Since val connectionTimeout = Property("db.conn.timeout.sec", TimeUnit.SECONDS.toMillis(30)) does not exist it should return the default value.

Additional context Let me know if i am not using this Library correctly.

Current URLConfigSource lacks authentication, so the URL can only be public to be consumed by cfg4k (unless you tweak the global java.net.Authenticator which seems not the best way).

This change makes URLConfigSource to accept an optional generic content for Authorization header to be used when fetching the config from the provided URL. A helper function for encoding basic auth credentials is provided along the way just because it's easy on one hand but not completely trivial on the other.

Is it possible to take a property with a Map<String, String>/Properties? I've tried creating parsers etc, but I couldn't get it to use my parser, and it seems the BindingInvocationHandler just throws SettingNotFound when trying to use any of the maps methods.

I even tried just creating a property that was a ConfigObject type and turn it into a map myself, but it threw a SettingNotFound: Setting 'asObject' not found.

While I know most of my config and its types beforehand and can add them to the interface, I'd like to be able to supply dynamic/unknown pairs of config through. Is this possible?

Current TimedReloadStrategy has two flaws:

• the underlying Timer terminates if any reload attempt fails with an exception. This makes this reload strategy suck when dealing with I/O, for instance, reloading from a remote URL.
• if register(ConfigProvider) is called multiple times, only the last ConfigProvider can effectively call deregister(), while all previously registered timers will be lost. This makes the reload strategy not reusable, while its API suggests that it might be reused.

This change makes TimedReloadStrategy use a scheduled executor service with error-prone reload() call to prevent subsequent reload attempts from auto-cancelling, and use a map of ConfigProviders to register and unregister them properly.

The FileChangeReloadStrategy has no exception handler. This means that if an exception is thrown when the underlying config is updated -- for example, if the config is updated with invalid syntax -- the reload thread dies and no more config reloads are handled until the ConfigProvider is constructed again.

Instead, I think I would log a warning in this situation, but continue to monitor the file for more changes. However, I also note that there is no logging in the lib now, so an alternate approach may be to trigger another listener on provider in this case e.g. addReloadErrorListener?

The FileChangeReloadStrategy watcher uses an incorrect test to check if the event corresponds to the configuration file.

The javadocs for WatchEvent.context state that the path returned is relative to the parent on which the watch is registered.

However, the current code just naively does fileName == file. The following code seems to be a pretty foolproof way of doing the correct test:

parent.resolve(fileName).toRealPath() == file.toRealPath()

There are libraries with known CVEs in the published version of cfg4k -- mainly the s3 dependency brings in older versions of jackson and httpclient, and the jgit dependency also brings in an older version of httpclient.

This is fixed on my branch here: https://github.com/rocketraman/cfg4k/tree/library-updates-security.

Description

Right now if you merge two ConfigLoaders there is no way to keep the reload. An empty reload will take its place.

One thing that could be done is that the reload is a function in the constructor or something that can also be merged/called one after the other, this needs a little bit of design!

Acceptance criteria

• Document the fix in this issue
• Code changes and tests

Minor issue with cfg4k 0.9.0: always get this WARN level message from PropertyConfigLoader at startup, using Oracle JDK 1.8:

Key (java.vendor.url.bug=Oracle Corporation) has overridden another value used as root

Maybe in some way it would be nice to have a jdbc config loader to be able to use it with all the databases.

This has the inconvenience of nested properties.

a.b could be property B from table A but... what about a.b.c ?

Another thing is that it could have a properties table (defined when creating the loader) and the key would be a.b or a.b.c

When reloading, the list of configuration changes should be listed so whomever is reloading can act to that. (Even if it shouldn't be needed because it shouldn't be used as static fields but with the binding)