Merge pull request #407 from FeiWongReed/master

issue #405 fixed: config loading strategy implemented

config/src/main/java/com/typesafe/config/ConfigFactory.java

@@ -3,17 +3,16 @@
  */
 package com.typesafe.config;
 
+import com.typesafe.config.impl.ConfigImpl;
+import com.typesafe.config.impl.Parseable;
+
 import java.io.File;
 import java.io.Reader;
-import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.Map;
 import java.util.Properties;
 import java.util.concurrent.Callable;
 
-import com.typesafe.config.impl.ConfigImpl;
-import com.typesafe.config.impl.Parseable;
-
 /**
  * Contains static methods for creating {@link Config} instances.
  *
@@ -36,6 +35,8 @@ import com.typesafe.config.impl.Parseable;
  * examples.
  */
 public final class ConfigFactory {
+    private static final String STRATEGY_PROPERTY_NAME = "config.strategy";
+
     private ConfigFactory() {
     }
 
@@ -213,54 +214,7 @@ public final class ConfigFactory {
                 .resolve(resolveOptions);
     }
 
-    private static Config parseApplicationConfig(ConfigParseOptions parseOptions) {
-        ClassLoader loader = parseOptions.getClassLoader();
-        if (loader == null)
-            throw new ConfigException.BugOrBroken(
-                    "ClassLoader should have been set here; bug in ConfigFactory. "
-                            + "(You can probably work around this bug by passing in a class loader or calling currentThread().setContextClassLoader() though.)");
 
-        int specified = 0;
-
-        // override application.conf with config.file, config.resource,
-        // config.url if requested.
-        String resource = System.getProperty("config.resource");
-        if (resource != null)
-            specified += 1;
-        String file = System.getProperty("config.file");
-        if (file != null)
-            specified += 1;
-        String url = System.getProperty("config.url");
-        if (url != null)
-            specified += 1;
-
-        if (specified == 0) {
-            return ConfigFactory.parseResourcesAnySyntax("application", parseOptions);
-        } else if (specified > 1) {
-            throw new ConfigException.Generic("You set more than one of config.file='" + file
-                    + "', config.url='" + url + "', config.resource='" + resource
-                    + "'; don't know which one to use!");
-        } else {
-            // the override file/url/resource MUST be present or it's an error
-            ConfigParseOptions overrideOptions = parseOptions.setAllowMissing(false);
-            if (resource != null) {
-                if (resource.startsWith("/"))
-                    resource = resource.substring(1);
-                // this deliberately does not parseResourcesAnySyntax; if
-                // people want that they can use an include statement.
-                return parseResources(loader, resource, overrideOptions);
-            } else if (file != null) {
-                return parseFile(new File(file), overrideOptions);
-            } else {
-                try {
-                    return parseURL(new URL(url), overrideOptions);
-                } catch (MalformedURLException e) {
-                    throw new ConfigException.Generic("Bad URL in config.url system property: '"
-                            + url + "': " + e.getMessage(), e);
-                }
-            }
-        }
-    }
 
     /**
      * Loads a default configuration, equivalent to {@link #load(Config)
@@ -516,7 +470,7 @@ public final class ConfigFactory {
      * @return the default application configuration
      */
     public static Config defaultApplication(ConfigParseOptions options) {
-        return parseApplicationConfig(ensureClassLoader(options, "defaultApplication"));
+        return getConfigLoadingStrategy().parseApplicationConfig(ensureClassLoader(options, "defaultApplication"));
     }
 
     /**
@@ -1094,4 +1048,18 @@ public final class ConfigFactory {
     public static Config parseMap(Map<String, ? extends Object> values) {
         return parseMap(values, null);
     }
+
+    private static ConfigLoadingStrategy getConfigLoadingStrategy() {
+        String className = System.getProperties().getProperty(STRATEGY_PROPERTY_NAME);
+
+        if (className != null) {
+            try {
+                return ConfigLoadingStrategy.class.cast(Class.forName(className).newInstance());
+            } catch (Throwable e) {
+                throw new ConfigException.BugOrBroken("Failed to load strategy: " + className, e);
+            }
+        } else {
+            return new DefaultConfigLoadingStrategy();
+        }
+    }
 }

config/src/main/java/com/typesafe/config/ConfigLoadingStrategy.java

@@ -0,0 +1,20 @@
+package com.typesafe.config;
+
+/**
+ * This method allows you to alter default config loading strategy for all the code which
+ * calls {@link ConfigFactory#load}.
+ *
+ * Usually you don't have to implement this interface but it may be required
+ * when you fixing a improperly implemented library with unavailable source code.
+ *
+ * You have to define VM property {@code config.strategy} to replace default strategy with your own.
+ */
+public interface ConfigLoadingStrategy {
+    /**
+     * This method must load and parse application config.
+     *
+     * @param parseOptions {@link ConfigParseOptions} to use
+     * @return loaded config
+     */
+    Config parseApplicationConfig(ConfigParseOptions parseOptions);
+}

config/src/main/java/com/typesafe/config/DefaultConfigLoadingStrategy.java

@@ -0,0 +1,62 @@
+package com.typesafe.config;
+
+import java.io.File;
+import java.net.MalformedURLException;
+import java.net.URL;
+
+/**
+ * Default config loading strategy. Able to load resource, file or URL.
+ * Behavior may be altered by defining one of VM properties
+ * {@code config.resource}, {@code config.file} or {@code config.url}
+ */
+public class DefaultConfigLoadingStrategy implements ConfigLoadingStrategy {
+    @Override
+    public Config parseApplicationConfig(ConfigParseOptions parseOptions) {
+        ClassLoader loader = parseOptions.getClassLoader();
+        if (loader == null)
+            throw new ConfigException.BugOrBroken(
+                    "ClassLoader should have been set here; bug in ConfigFactory. "
+                            + "(You can probably work around this bug by passing in a class loader or calling currentThread().setContextClassLoader() though.)");
+
+        int specified = 0;
+
+        // override application.conf with config.file, config.resource,
+        // config.url if requested.
+        String resource = System.getProperty("config.resource");
+        if (resource != null)
+            specified += 1;
+        String file = System.getProperty("config.file");
+        if (file != null)
+            specified += 1;
+        String url = System.getProperty("config.url");
+        if (url != null)
+            specified += 1;
+
+        if (specified == 0) {
+            return ConfigFactory.parseResourcesAnySyntax("application", parseOptions);
+        } else if (specified > 1) {
+            throw new ConfigException.Generic("You set more than one of config.file='" + file
+                                                      + "', config.url='" + url + "', config.resource='" + resource
+                                                      + "'; don't know which one to use!");
+        } else {
+            // the override file/url/resource MUST be present or it's an error
+            ConfigParseOptions overrideOptions = parseOptions.setAllowMissing(false);
+            if (resource != null) {
+                if (resource.startsWith("/"))
+                    resource = resource.substring(1);
+                // this deliberately does not parseResourcesAnySyntax; if
+                // people want that they can use an include statement.
+                return ConfigFactory.parseResources(loader, resource, overrideOptions);
+            } else if (file != null) {
+                return ConfigFactory.parseFile(new File(file), overrideOptions);
+            } else {
+                try {
+                    return ConfigFactory.parseURL(new URL(url), overrideOptions);
+                } catch (MalformedURLException e) {
+                    throw new ConfigException.Generic("Bad URL in config.url system property: '"
+                                                              + url + "': " + e.getMessage(), e);
+                }
+            }
+        }
+    }
+}

config/src/test/scala/com/typesafe/config/impl/PublicApiTest.scala

@@ -624,6 +624,27 @@ class PublicApiTest extends TestUtils {
         assertFalse("no b", configPlain.hasPath("b"))
     }
 
+    @Test
+    def supportsConfigLoadingStrategyAlteration(): Unit = {
+        assertEquals("config.strategy is not set", null, System.getProperty("config.strategy"))
+        System.setProperty("config.strategy", classOf[TestStrategy].getCanonicalName)
+
+        try {
+            val incovationsBeforeTest = TestStrategy.getIncovations()
+            val loaderA1 = new TestClassLoader(this.getClass().getClassLoader(),
+                Map("reference.conf" -> resourceFile("a_1.conf").toURI.toURL()))
+
+            val configA1 = withContextClassLoader(loaderA1) {
+                ConfigFactory.load()
+            }
+            ConfigFactory.load()
+            assertEquals(1, configA1.getInt("a"))
+            assertEquals(2, TestStrategy.getIncovations() - incovationsBeforeTest)
+        } finally {
+            System.clearProperty("config.strategy")
+        }
+    }
+
     @Test
     def usesContextClassLoaderForApplicationConf() {
         val loaderA1 = new TestClassLoader(this.getClass().getClassLoader(),
@@ -1104,3 +1125,16 @@ include "onclasspath"
         intercept[ConfigException.Missing] { conf.getIsNull("x.c.y") }
     }
 }
+
+class TestStrategy extends DefaultConfigLoadingStrategy {
+    override def parseApplicationConfig(parseOptions: ConfigParseOptions): Config = {
+        TestStrategy.increment()
+        super.parseApplicationConfig(parseOptions)
+    }
+}
+
+object TestStrategy {
+    private var invocations = 0
+    def getIncovations() = invocations
+    def increment() = invocations += 1
+}