DEXI-2491: implemented configuration utility

pom.xml

@@ -18,11 +18,18 @@
     </properties>
 
     <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.8.2</version>
+        </dependency>
+
         <dependency>
             <groupId>com.google.guava</groupId>
             <artifactId>guava</artifactId>
             <version>20.0</version>
         </dependency>
+
         <dependency>
             <groupId>commons-codec</groupId>
             <artifactId>commons-codec</artifactId>
@@ -33,6 +40,22 @@
             <artifactId>commons-lang</artifactId>
             <version>2.6</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-configuration2</artifactId>
+            <version>2.4</version>
+        </dependency>
+        <dependency>
+            <groupId>commons-beanutils</groupId>
+            <artifactId>commons-beanutils</artifactId>
+            <version>1.9.3</version>
+        </dependency>
+        <dependency>
+            <groupId>org.yaml</groupId>
+            <artifactId>snakeyaml</artifactId>
+            <version>1.19</version>
+        </dependency>
+
         <dependency>
             <groupId>com.squareup.retrofit2</groupId>
             <artifactId>converter-jackson</artifactId>

src/main/java/io/dexi/config/Config.java

@@ -0,0 +1,187 @@
+package io.dexi.config;
+
+import org.apache.commons.configuration2.Configuration;
+import org.apache.commons.configuration2.FileBasedConfiguration;
+import org.apache.commons.configuration2.YAMLConfiguration;
+import org.apache.commons.configuration2.builder.FileBasedConfigurationBuilder;
+import org.apache.commons.configuration2.builder.ReloadingFileBasedConfigurationBuilder;
+import org.apache.commons.configuration2.builder.fluent.Parameters;
+import org.apache.commons.configuration2.builder.fluent.PropertiesBuilderParameters;
+import org.apache.commons.configuration2.ex.ConfigurationException;
+import org.apache.commons.lang.StringUtils;
+
+import java.net.MalformedURLException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Properties;
+import java.util.Set;
+
+/**
+ *  This class supports reading a "hierarchical" configuration file with sections like:
+ *
+ *  <b>YAML example</b>
+ *  <pre>
+ *  {@code
+ *     dexi:
+ *       baseUrl: http://localhost:3000/api/
+ *       apiKey: super-secret-key
+ *  }
+ *  </pre>
+ *
+ *  <b>JSON example</b>
+ *  <pre>
+ *  {@code
+ *      {
+ *          "dexi": {
+ *              "baseUrl": "http://localhost:3000/api/",
+ *              "apiKey": "super-secret-key"
+ *          }
+ *      }
+ *  }
+ *  </pre>
+ *
+ *  The file can be read from a local disk or from a URL. The class also supports reading environment variables whose
+ *  names start with "DEXI_APP_".
+ *
+ *  Configuration is read in the following order:
+ *  <ol>
+ *      <li>A local configuration file as specified by the {@code localConfigFile} parameter. The default is
+ *          {@code ~/.dexi/my-app.yml}.
+ *          <ul>
+ *              <li>Supported file formats are YAML (.yml), JSON (.json), XML (.xml) and INI (.ini).</li>
+ *          </ul>
+ *      </li>
+ *      <li>If an environment variable or system property named {@code DEXI_APP_CONFIG_URL_YML} is set, read a YAML (.yml)
+ *          file from the specified URL.</li>
+ *      <li>Read any {@code DEXI_APP_} environment variable. The format is: {@code DEXI_APP_&lt;section>_&lt;key> = &lt;value>}.</li>
+ *  </ol>
+ *
+ *  Values for duplicate keys within sections are overwritten by later keys.
+ *
+ */
+public class Config {
+
+    public static final String DEXI_APP_CONFIG_URL = "DEXI_APP_CONFIG_URL";
+
+    private static final String DEXI_APP_ENVIRONMENT_VARIABLE_PREFIX = "DEXI_APP_";
+
+    private static String localConfigFile = System.getProperty("user.home") + "/.dexi/my-app.yml";
+    private static Properties properties = new Properties();
+
+    private static void readEnvironment() {
+        Map<String, String> env = System.getenv();
+        Set<String> envKeys = env.keySet();
+        if (envKeys.size() > 0) {
+            for (String envKey : envKeys) {
+                if (envKey.startsWith(DEXI_APP_ENVIRONMENT_VARIABLE_PREFIX) && !envKey.startsWith(DEXI_APP_CONFIG_URL)) {
+                    String envKeyWithoutPrefix = envKey.substring(5).toLowerCase();
+                    if (envKeyWithoutPrefix.indexOf("_") == -1) {
+                        continue;
+                    }
+
+                    String section = envKeyWithoutPrefix.substring(0, envKeyWithoutPrefix.indexOf("_"));
+                    String key = envKeyWithoutPrefix.substring(envKeyWithoutPrefix.indexOf("_") + 1);
+                    String value = env.get(envKey);
+
+                    String keyWithSection = String.format("%s.%s", section, key);
+                    properties.setProperty(keyWithSection, value);
+                }
+            }
+        }
+    }
+
+    private static <T extends FileBasedConfiguration> Configuration getConfigurationFile(String fileLocation, Class<T> filedBasedClazz) throws ConfigurationException, URISyntaxException, MalformedURLException {
+        T configuration = null;
+
+        Parameters parameters = new Parameters();
+        PropertiesBuilderParameters properties = parameters.properties();
+        FileBasedConfigurationBuilder<T> builder = new ReloadingFileBasedConfigurationBuilder<>(filedBasedClazz);
+
+        URI uri = new URI(fileLocation);
+        String scheme = uri.getScheme();
+        if ("http".equalsIgnoreCase(scheme)) {
+            builder = builder.configure(properties.setURL(uri.toURL()));
+            configuration = builder.getConfiguration();
+        } else {
+            URL localFileURL = Config.class.getResource(fileLocation);
+            if (localFileURL != null) {
+                builder = builder.configure(properties.setFileName(localFileURL.getFile()));
+                configuration = builder.getConfiguration();
+            }
+        }
+
+        return configuration;
+    }
+
+    private static void addConfigurationToProperties(Configuration configuration) {
+        if (configuration != null) {
+            Iterator<String> keys = configuration.getKeys();
+            while (keys.hasNext()) {
+                String keyWithSection = keys.next();
+
+                String existingValue = properties.getProperty(keyWithSection);
+                if (existingValue == null) {
+                    String value = configuration.getString(keyWithSection);
+                    properties.put(keyWithSection, value);
+                }
+            }
+        }
+    }
+
+    private static void getConfigurationFromURL() throws MalformedURLException, ConfigurationException, URISyntaxException {
+        String dexiAppConfigUrl = System.getenv(DEXI_APP_CONFIG_URL);
+        if (StringUtils.isEmpty(dexiAppConfigUrl)) {
+            dexiAppConfigUrl = System.getProperty(DEXI_APP_CONFIG_URL);
+        }
+
+        if (StringUtils.isNotEmpty(dexiAppConfigUrl)) {
+            Configuration ymlConfigurationURL = getConfigurationFile(dexiAppConfigUrl, YAMLConfiguration.class);
+            addConfigurationToProperties(ymlConfigurationURL);
+        }
+    }
+
+    private static void readLocalConfiguration() throws MalformedURLException, ConfigurationException, URISyntaxException {
+        String fileExtension = localConfigFile.substring(localConfigFile.lastIndexOf(".") + 1);
+
+        Class<? extends FileBasedConfiguration> configurationClass;
+        switch (fileExtension) {
+            case "yml":
+                configurationClass = YAMLConfiguration.class;
+                break;
+            case "json":
+                configurationClass = YAMLConfiguration.class;
+                break;
+            case "xml":
+                configurationClass = YAMLConfiguration.class;
+                break;
+            case "ini":
+                configurationClass = YAMLConfiguration.class;
+                break;
+            default:
+                throw new IllegalArgumentException("Unsupported file extension " + fileExtension);
+        }
+
+        Configuration ymlConfigurationLocal = getConfigurationFile(localConfigFile, configurationClass);
+        addConfigurationToProperties(ymlConfigurationLocal);
+    }
+
+    public static void load() throws ConfigurationException, URISyntaxException, MalformedURLException {
+        readLocalConfiguration();
+
+        getConfigurationFromURL();
+
+        readEnvironment();
+    }
+
+    public static Properties getProperties() {
+        return properties;
+    }
+
+    public static void setLocalConfigFile(String localConfigFile) {
+        Config.localConfigFile = localConfigFile;
+    }
+
+}

src/test/java/io/dexi/config/ConfigTest.java

@@ -0,0 +1,52 @@
+package io.dexi.config;
+
+import org.apache.commons.configuration2.ex.ConfigurationException;
+import org.junit.After;
+import org.junit.Test;
+
+import java.net.MalformedURLException;
+import java.net.URISyntaxException;
+import java.util.Properties;
+
+import static org.junit.Assert.assertEquals;
+
+public class ConfigTest {
+
+    @After
+    public void clearProperties() {
+        Config.getProperties().clear();
+    }
+
+    @Test
+    public void testReadingLocalFiles() throws ConfigurationException, URISyntaxException, MalformedURLException {
+        Config.setLocalConfigFile("/test-app.yml");
+
+        Config.load();
+
+        Properties properties = Config.getProperties();
+        assertEquals(3, properties.keySet().size());
+    }
+
+    @Test
+    public void testReadingFileFromURL() throws ConfigurationException, URISyntaxException, MalformedURLException {
+        Config.setLocalConfigFile("/non-existing-local-config-file.json");
+        System.setProperty(Config.DEXI_APP_CONFIG_URL, "http://config.dexi.io:1080/dexi-config/test/ini/apps/app-service-s3.yml");
+
+        Config.load();
+
+        Properties properties = Config.getProperties();
+        assertEquals(3, properties.keySet().size());
+    }
+
+    @Test
+    public void testReadingLocalFilesAndFileFromURL() throws ConfigurationException, MalformedURLException, URISyntaxException {
+        Config.setLocalConfigFile("/test-app.json");
+        System.setProperty(Config.DEXI_APP_CONFIG_URL, "http://config.dexi.io:1080/dexi-config/test/ini/apps/app-service-s3.yml");
+
+        Config.load();
+
+        Properties properties = Config.getProperties();
+        assertEquals(6, properties.keySet().size());
+    }
+
+}

src/test/resources/test-app.json

@@ -0,0 +1,9 @@
+{
+  "dexi": {
+    "baseUrl": "http://localhost:3000/api/",
+    "apiKey": "super-secret-key"
+  },
+  "google": {
+    "baseUrl": "https://www.googleapis.com/storage/v1/"
+  }
+}

src/test/resources/test-app.yml

@@ -0,0 +1,6 @@
+dexi:
+  baseUrl: http://localhost:3000/api/
+  apiKey: super-secret-key
+
+google:
+  baseUrl: https://www.googleapis.com/storage/v1/