Adding ability to uses lists of configs, both with resources and files

README.md

@@ -102,7 +102,7 @@ For reference on all existing options, their description and defaults you may re
 To override needed options you may use one of the following ways: 
 * put your options to the `<working dir>/config/ethereumj.conf` file
 * put `user.conf` to the root of your classpath (as a resource) 
-* put your options to any file and supply it via `-Dethereumj.conf.file=<your config>`
+* put your options to any file and supply it via `-Dethereumj.conf.file=<your config>`, accepts several configs, separated by comma applied in provided order: `-Dethereumj.conf.file=<config1>,<config2>`
 * programmatically by using `SystemProperties.CONFIG.override*()`
 * programmatically using by overriding Spring `SystemProperties` bean 
 

ethereumj-core/src/main/java/org/ethereum/config/SystemProperties.java

@@ -52,6 +52,7 @@
 import java.net.Socket;
 import java.net.URL;
 import java.util.*;
+import java.util.function.Function;
 
 import static org.ethereum.crypto.HashUtil.sha3;
 import static org.ethereum.util.ByteUtil.toHexString;
@@ -185,8 +186,8 @@ public SystemProperties(Config apiConfig, ClassLoader classLoader) {
             Config referenceConfig = ConfigFactory.parseResources("ethereumj.conf");
             logger.info("Config (" + (referenceConfig.entrySet().size() > 0 ? " yes " : " no  ") + "): default properties from resource 'ethereumj.conf'");
             String res = System.getProperty("ethereumj.conf.res");
-            Config cmdLineConfigRes = res != null ? ConfigFactory.parseResources(res) : ConfigFactory.empty();
-            logger.info("Config (" + (cmdLineConfigRes.entrySet().size() > 0 ? " yes " : " no  ") + "): user properties from -Dethereumj.conf.res resource '" + res + "'");
+            Config cmdLineConfigRes = mergeConfigs(res, ConfigFactory::parseResources);
+            logger.info("Config (" + (cmdLineConfigRes.entrySet().size() > 0 ? " yes " : " no  ") + "): user properties from -Dethereumj.conf.res resource(s) '" + res + "'");
             Config userConfig = ConfigFactory.parseResources("user.conf");
             logger.info("Config (" + (userConfig.entrySet().size() > 0 ? " yes " : " no  ") + "): user properties from resource 'user.conf'");
             File userDirFile = new File(System.getProperty("user.dir"), "/config/ethereumj.conf");
@@ -197,8 +198,8 @@ public SystemProperties(Config apiConfig, ClassLoader classLoader) {
             Config testUserConfig = ConfigFactory.parseResources("test-user.conf");
             logger.info("Config (" + (testUserConfig.entrySet().size() > 0 ? " yes " : " no  ") + "): test properties from resource 'test-user.conf'");
             String file = System.getProperty("ethereumj.conf.file");
-            Config cmdLineConfigFile = file != null ? ConfigFactory.parseFile(new File(file)) : ConfigFactory.empty();
-            logger.info("Config (" + (cmdLineConfigFile.entrySet().size() > 0 ? " yes " : " no  ") + "): user properties from -Dethereumj.conf.file file '" + file + "'");
+            Config cmdLineConfigFile = mergeConfigs(res, s -> ConfigFactory.parseFile(new File(s)));
+            logger.info("Config (" + (cmdLineConfigFile.entrySet().size() > 0 ? " yes " : " no  ") + "): user properties from -Dethereumj.conf.file file(s) '" + file + "'");
             logger.info("Config (" + (apiConfig.entrySet().size() > 0 ? " yes " : " no  ") + "): config passed via constructor");
             config = apiConfig
                     .withFallback(cmdLineConfigFile)
@@ -316,6 +317,27 @@ private void validateConfig() {
         }
     }
 
+    /**
+     * Builds config from the list of config references in string doing following actions:
+     * 1) Splits input by "," to several strings
+     * 2) Uses parserFunc to create config from each string reference
+     * 3) Merges configs, applying them in the same order as in input, so last overrides first
+     * @param input         String with list of config references separated by ",", null or one reference works fine
+     * @param parserFunc    Function to apply to each reference, produces config from it
+     * @return Merged config
+     */
+    protected Config mergeConfigs(String input, Function<String, Config> parserFunc) {
+        Config config = ConfigFactory.empty();
+        if (input != null && !input.isEmpty()) {
+            String[] list = input.split(",");
+            for (int i = list.length - 1; i >= 0; --i) {
+                config = config.withFallback(parserFunc.apply(list[i]));
+            }
+        }
+
+        return config;
+    }
+
     public <T> T getProperty(String propName, T defaultValue) {
         if (!config.hasPath(propName)) return defaultValue;
         String string = config.getString(propName);

ethereumj-core/src/test/java/org/ethereum/config/SystemPropertiesTest.java

@@ -518,6 +518,39 @@ public void testDump() {
         assertTrue(StringUtils.countOccurrencesOf(dump, "{") > 50);
     }
 
+    @Test
+    public void testMergeConfigs1() {
+        String firstConfig = "";
+        SystemProperties props = new SystemProperties();
+        Config config = props.mergeConfigs(firstConfig, ConfigFactory::parseString);
+        assertFalse(config.hasPath("peer.listen.port"));
+    }
+
+    @Test
+    public void testMergeConfigs2() {
+        String firstConfig = "peer.listen.port=30123";
+        SystemProperties props = new SystemProperties();
+        Config config = props.mergeConfigs(firstConfig, ConfigFactory::parseString);
+        assertEquals(30123, config.getInt("peer.listen.port"));
+    }
+
+    @Test
+    public void testMergeConfigs3() {
+        String firstConfig = "peer.listen.port=30123,peer.listen.port=30145";
+        SystemProperties props = new SystemProperties();
+        Config config = props.mergeConfigs(firstConfig, ConfigFactory::parseString);
+        assertEquals(30145, config.getInt("peer.listen.port"));
+    }
+
+    @Test
+    public void testMergeConfigs4() {
+        String firstConfig = "peer.listen.port=30123,sync.enabled=true";
+        SystemProperties props = new SystemProperties();
+        Config config = props.mergeConfigs(firstConfig, ConfigFactory::parseString);
+        assertEquals(30123, config.getInt("peer.listen.port"));
+        assertEquals(Boolean.TRUE, config.getBoolean("sync.enabled"));
+    }
+
     @SuppressWarnings("SameParameterValue")
     static class ActivePeer {
         boolean asEnodeUrl;