Split out a helper method for parsing only application overrides

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

@@ -8,8 +8,10 @@
 
 import java.io.File;
 import java.io.Reader;
+import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Properties;
 import java.util.concurrent.Callable;
 
@@ -1090,6 +1092,89 @@ public static Config parseResourcesAnySyntax(String resourceBasename) {
  return parseResourcesAnySyntax(resourceBasename, ConfigParseOptions.defaults());
  }
 
+ /**
+ * Parse only any application replacement (specified by one of config.{resource,file,url}), returning
+ * an empty Config if no overrides were set.
+ *
+ * @since 1.4.1
+ *
+ * @return a {@link java.util.Optional} containing any specified replacement, or {@link Optional#empty()}
+ * if none was specified.
+ */
+ public static java.util.Optional<Config> parseApplicationReplacement() {
+ return parseApplicationReplacement(ConfigParseOptions.defaults());
+ }
+
+ /**
+ * Like {@link #parseApplicationReplacement()} but allows you to specify a class loader
+ * ti yse rather than the current context class loader.
+ *
+ * @since 1.4.1
+ *
+ * @param loader the class loader
+ * @return a {@link java.util.Optional} containing any specified replacement, or {@link Optional#empty()}
+ * if none was specified.
+ */
+ public static java.util.Optional<Config> parseApplicationReplacement(ClassLoader loader) {
+ return parseApplicationReplacement(ConfigParseOptions.defaults().setClassLoader(loader));
+ }
+
+ /**
+ * Like {@link #parseApplicationReplacement()} but allows you to specify parse options.
+ *
+ * @since 1.4.1
+ *
+ * @param parseOptions parse options
+ * @return a {@link java.util.Optional} containing any specified replacement, or {@link Optional#empty()}
+ * if none was specified.
+ */
+ public static java.util.Optional<Config> parseApplicationReplacement(ConfigParseOptions parseOptions) {
+ ensureClassLoader(parseOptions, "parseApplicationReplacement");
+ ClassLoader loader = parseOptions.getClassLoader();
+
+ 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 java.util.Optional.empty();
+ } 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 java.util.Optional.of(ConfigFactory.parseResources(loader, resource, overrideOptions));
+ } else if (file != null) {
+ return java.util.Optional.of(ConfigFactory.parseFile(new File(file), overrideOptions));
+ } else {
+ try {
+ return java.util.Optional.of(ConfigFactory.parseURL(new URL(url), overrideOptions));
+ } catch (MalformedURLException e) {
+ throw new ConfigException.Generic("Bad URL in config.url system property: '"
+ + url + "': " + e.getMessage(), e);
+ }
+ }
+ }
+
+ }
+
  /**
  * Parses a string (which should be valid HOCON or JSON by default, or
  * the syntax specified in the options otherwise).

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

@@ -1,9 +1,5 @@
 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
@@ -12,51 +8,7 @@
 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);
- }
- }
- }
+ return ConfigFactory.parseApplicationReplacement(parseOptions)
+ .orElseGet(() -> ConfigFactory.parseResourcesAnySyntax("application", parseOptions));
  }
 }