Adding a configuration object for the jmx proxy

This patch adds a configuration object to the jmx proxy that support
both the system/command line based properties and it accept a yaml
configuration file. The later options allows the jmx to read scylla
configuration file and connect to it based on this configuration.

The configuration file reader uses a yaml parser that was added to the
pom.xml

If no configuration file is found in the command line, it would look for
SCYLLA_CONF then SCYLLA_HOME then for relative 'conf' directory

Signed-off-by: Amnon Heiman <amnon@scylladb.com>

need merge apiconfig

pom.xml

@@ -15,6 +15,11 @@
     </properties>
 
     <dependencies>
+        <dependency>
+            <groupId>org.yaml</groupId>
+                <artifactId>snakeyaml</artifactId>
+                <version>1.16</version>
+            </dependency>
         <dependency>
             <groupId>org.glassfish.jersey.core</groupId>
             <artifactId>jersey-common</artifactId>

src/main/java/com/cloudius/urchin/api/APIConfig.java

@@ -0,0 +1,115 @@
+package com.cloudius.urchin.api;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.InputStream;
+import java.util.Map;
+
+import org.yaml.snakeyaml.Yaml;
+
+/*
+ * Copyright (C) 2015 ScyllaDB
+ */
+
+/*
+ * This file is part of Scylla.
+ *
+ * Scylla is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Scylla is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+public class APIConfig {
+    static String address = "localhost";
+    static String port = "10000";
+
+    public static String getAddress() {
+        return address;
+    }
+
+    public static String getPort() {
+        return port;
+    }
+
+    public static String getBaseUrl() {
+        return "http://" + address + ":"
+                + port;
+    }
+
+    public static void readFile(String name) {
+        System.out.println("Using config file: " + name);
+        InputStream input;
+        try {
+            input = new FileInputStream(new File(name));
+            Yaml yaml = new Yaml();
+            @SuppressWarnings("unchecked")
+            Map<String, Object> map = (Map<String, Object>) yaml.load(input);
+            if (map.containsKey("listen_address")) {
+                address = (String) map.get("listen_address");
+            }
+            if (map.containsKey("api_address")) {
+                address = (String) map.get("api_address");
+            }
+            if (map.containsKey("api_port")) {
+                port = (String) map.get("api_port").toString();
+            }
+        } catch (FileNotFoundException e) {
+            System.err.println("fail reading from config file: " + name);
+            System.exit(-1);
+        }
+    }
+
+    public static boolean fileExists(String name) {
+        File varTmpDir = new File(name);
+        return varTmpDir.exists();
+    }
+
+    public static boolean loadIfExists(String path, String name) {
+        if (path == null) {
+            return false;
+        }
+        if (!fileExists(path + name)) {
+            return false;
+        }
+        readFile(path + name);
+        return true;
+    }
+    /**
+     * setConfig load the JMX proxy configuration
+     * The configuration hierarchy is as follow:
+     * Command line argument takes precedence over everything
+     * Then configuration file in the command line (command line
+     * argument can replace specific values in it.
+     * Then SCYLLA_CONF/scylla.yaml
+     * Then SCYLLA_HOME/conf/scylla.yaml
+     * Then conf/scylla.yaml
+     * Then the default values
+     * With file configuration, to make it clearer what is been used, only
+     * one file will be chosen with the highest precedence
+     */
+    public static void setConfig() {
+        if (!System.getProperty("apiconfig","").equals("")) {
+            readFile(System.getProperty("apiconfig"));
+        } else if (!loadIfExists(System.getenv("SCYLLA_CONF"), "/scylla.yaml") &&
+            !loadIfExists(System.getenv("SCYLLA_HOME"), "/conf/scylla.yaml")) {
+            loadIfExists("", "conf/scylla.yaml");
+        }
+
+        if (!System.getProperty("apiaddress", "").equals("")) {
+            address = System.getProperty("apiaddress");
+        }
+        if (!System.getProperty("apiport", "").equals("")) {
+            port = System.getProperty("apiport", "10000");
+        }
+    }
+}