Rewrote Config handling

src/main/java/de/rwu/easydrop/Main.java

@@ -1,10 +1,12 @@
 package de.rwu.easydrop;
 
+import javax.naming.ConfigurationException;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import de.rwu.easydrop.api.client.AmazonProductDataSource;
-import de.rwu.easydrop.util.ConfigUtil;
+import de.rwu.easydrop.util.Config;
 
 /**
  * Kickoff point for the service.
@@ -29,9 +31,10 @@ public final class Main {
      *
      * @param args
      */
-    public static void main(final String[] args) {
-        String amznBaseUrl = ConfigUtil.getConfig("AMAZON_API_URL");
-        String amznApiKey = ConfigUtil.getConfig("AMAZON_API_KEY");
+    public static void main(final String[] args) throws ConfigurationException {
+        Config config = Config.getInstance();
+        String amznBaseUrl = config.getProperty("AMAZON_API_URL");
+        String amznApiKey = config.getProperty("AMAZON_API_KEY");
         String testProduct = null;
 
         AmazonProductDataSource amznSrc = new AmazonProductDataSource(amznBaseUrl, amznApiKey);

src/main/java/de/rwu/easydrop/util/Config.java

@@ -0,0 +1,89 @@
+package de.rwu.easydrop.util;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.NoSuchElementException;
+import java.util.Properties;
+
+import javax.naming.ConfigurationException;
+
+/**
+ * Allows access to the config.
+ *
+ * @since 0.1.0
+ */
+public final class Config {
+    /**
+     * Config file location.
+     */
+    private static final String CONFIG_LOCATION = "config/config.properties";
+    /**
+     * Holds the config values.
+     */
+    private Properties properties = null;
+    /**
+     * Singleton instance.
+     */
+    private static Config instance = null;
+
+    /**
+     * Private constructor to prevent unwanted instantiation.
+     */
+    private Config() throws ConfigurationException {
+        loadConfig();
+    }
+
+    /**
+     * Returns current config instance.
+     *
+     * @return Config instance
+     * @throws ConfigurationException
+     */
+    public static Config getInstance() throws ConfigurationException {
+        if (instance == null) {
+            return new Config();
+        }
+
+        return instance;
+    }
+
+    /**
+     * Loads config file values into the instance.
+     *
+     * @throws ConfigurationException
+     */
+    public void loadConfig() throws ConfigurationException {
+        Properties newProps = new Properties();
+        try (FileInputStream input = new FileInputStream(CONFIG_LOCATION)) {
+            newProps.load(input);
+            properties = newProps;
+        } catch (IOException e) {
+            throw new ConfigurationException("Couldn't load required config file");
+        }
+    }
+
+    /**
+     * Returns a config property by specified key.
+     *
+     * @param key Config Key, like "API_KEY"
+     * @return Config value
+     * @throws NoSuchElementException Required key missing
+     */
+    public String getProperty(final String key) throws NoSuchElementException {
+        String value = properties.getProperty(key);
+        if (value == null) {
+            throw new NoSuchElementException("Requested config value does not exist");
+        }
+        return value;
+    }
+
+    /**
+     * Overrides a config property loaded from file for current instance.
+     *
+     * @param key   Config Key
+     * @param value Property Value
+     */
+    public void setProperty(final String key, final String value) {
+        properties.setProperty(key, value);
+    }
+}

src/main/java/de/rwu/easydrop/util/ConfigUtil.java

@@ -1,49 +0,0 @@
-package de.rwu.easydrop.util;
-
-import java.io.FileInputStream;
-import java.io.IOException;
-import java.util.NoSuchElementException;
-import java.util.Properties;
-
-/**
- * Allows access to the config.
- *
- * @since 0.1.0
- */
-public final class ConfigUtil {
-    /**
-     * Config file location.
-     */
-    private static final String CONFIG_LOCATION = "config/config.properties";
-
-    /**
-     * Private constructor to prevent unwanted instantiation.
-     *
-     * @throws UnsupportedOperationException always
-     */
-    private ConfigUtil() throws UnsupportedOperationException {
-        throw new UnsupportedOperationException("This is a utility class, don't instantiate it.");
-    }
-
-    /**
-     * Returns a config value by specified key.
-     *
-     * @param key Config Key, like "API_KEY"
-     * @return Config value
-     */
-    public static String getConfig(final String key) {
-        Properties config = new Properties();
-        try (FileInputStream input = new FileInputStream(CONFIG_LOCATION)) {
-            config.load(input);
-        } catch (IOException e) {
-            e.printStackTrace();
-        }
-
-        String value = config.getProperty(key);
-        if (value == null) {
-            throw new NoSuchElementException("Requested config value does not exist");
-        }
-
-        return value;
-    }
-}