Merge pull request #153 from scalecube/feature/SystemEnvironmentVaria…

…blesConfigSource

Added SystemEnvironmentVariablesConfigSource

config/src/main/java/io/scalecube/config/source/SystemEnvironmentVariablesConfigSource.java

@@ -0,0 +1,61 @@
+package io.scalecube.config.source;
+
+import io.scalecube.config.ConfigProperty;
+import java.util.Map;
+import java.util.Objects;
+import java.util.TreeMap;
+import java.util.function.Consumer;
+
+public final class SystemEnvironmentVariablesConfigSource implements ConfigSource {
+
+ private Map<String, ConfigProperty> loadedConfig;
+
+ // from-to environment variables mappings
+ private final Map<String, String> mappings = new TreeMap<>();
+
+ public SystemEnvironmentVariablesConfigSource(Consumer<Mapper> consumer) {
+ consumer.accept(new MapperImpl());
+ }
+
+ @Override
+ public Map<String, ConfigProperty> loadConfig() {
+ if (loadedConfig != null) {
+ return loadedConfig;
+ }
+
+ Map<String, ConfigProperty> result = new TreeMap<>();
+
+ System.getenv()
+ .forEach(
+ (propName, propValue) -> {
+ String dst = mappings.get(propName);
+ if (dst != null) {
+ // store value as system property under mapped name
+ System.setProperty(dst, propValue);
+ result.put(dst, LoadedConfigProperty.forNameAndValue(dst, propValue));
+ } else {
+ result.put(propName, LoadedConfigProperty.forNameAndValue(propName, propValue));
+ }
+ });
+
+ return loadedConfig = result;
+ }
+
+ // Stores mapping between environemnt variable name and corresponding system property name.
+ interface Mapper {
+
+ Mapper map(String src, String dst);
+ }
+
+ // Inner implementation class
+ private class MapperImpl implements Mapper {
+
+ @Override
+ public Mapper map(String src, String dst) {
+ Objects.requireNonNull(src);
+ Objects.requireNonNull(dst);
+ mappings.put(src, dst);
+ return this;
+ }
+ }
+}