Merge pull request #1336 from DeHopen/fix_null_resource

Null Resource for Checkstyle Configuration

Author: yegor256

qulice-checkstyle/src/main/java/com/qulice/checkstyle/CheckstyleValidator.java

@@ -134,17 +134,20 @@ private Configuration configuration() {
         }
         final Properties props = new Properties();
         props.setProperty("cache.file", cache.getPath());
-        final InputSource src = new InputSource(
-            this.getClass().getResourceAsStream("checks.xml")
-        );
         final Configuration config;
-        try {
+        try (java.io.InputStream stream = this.getClass().getResourceAsStream("checks.xml")) {
+            if (stream == null) {
+                throw new IllegalStateException(
+                    "Checkstyle configuration file 'checks.xml' not found in classpath."
+                );
+            }
+            final InputSource src = new InputSource(stream);
             config = ConfigurationLoader.loadConfiguration(
                 src,
                 new PropertiesExpander(props),
                 ConfigurationLoader.IgnoredModulesOptions.OMIT
             );
-        } catch (final CheckstyleException ex) {
+        } catch (final CheckstyleException | java.io.IOException ex) {
             throw new IllegalStateException("Failed to load config", ex);
         }
         return config;