Merge pull request #189 from scalecube/add-new-config-source

Added new config source -- SystemEnvironmentSingleVariableConfigSource

Author: artem-v

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

@@ -0,0 +1,66 @@
+package io.scalecube.config.source;
+
+import io.scalecube.config.ConfigProperty;
+import java.util.Map;
+import java.util.TreeMap;
+
+public final class SystemEnvironmentSingleVariableConfigSource implements ConfigSource {
+
+  private static final String VAR_NAME = "SETTINGS";
+
+  private static final String DELIMITER = ";";
+  private static final String SEPARATOR = "=";
+
+  private final String varName;
+  private final String delimiter;
+  private final String separator;
+
+  private Map<String, ConfigProperty> loadedConfig;
+
+  public SystemEnvironmentSingleVariableConfigSource() {
+    this(VAR_NAME, DELIMITER, SEPARATOR);
+  }
+
+  /**
+   * Constructor.
+   *
+   * @param varName varName
+   * @param delimiter delimiter
+   * @param separator separator
+   */
+  public SystemEnvironmentSingleVariableConfigSource(
+      String varName, String delimiter, String separator) {
+    this.varName = varName;
+    this.delimiter = delimiter;
+    this.separator = separator;
+  }
+
+  @Override
+  public Map<String, ConfigProperty> loadConfig() {
+    if (loadedConfig != null) {
+      return loadedConfig;
+    }
+
+    Map<String, ConfigProperty> result = new TreeMap<>();
+
+    String settings = System.getenv(varName);
+
+    if (settings != null && !settings.isEmpty()) {
+      for (String str : settings.split(delimiter)) {
+        String[] split = str.split(separator);
+        if (split.length != 2) {
+          break;
+        }
+
+        String propName = split[0];
+        String propValue = split[1];
+
+        // store value as system property under mapped name
+        System.setProperty(propName, propValue);
+        result.put(propName, LoadedConfigProperty.forNameAndValue(propName, propValue));
+      }
+    }
+
+    return loadedConfig = result;
+  }
+}