Warns the user if specified mainClass is not a valid Java class.

jib-core/src/main/java/com/google/cloud/tools/jib/builder/BuildConfiguration.java

@@ -20,12 +20,14 @@
 import com.google.cloud.tools.jib.image.json.BuildableManifestTemplate;
 import com.google.cloud.tools.jib.image.json.V22ManifestTemplate;
 import com.google.cloud.tools.jib.registry.credentials.RegistryCredentials;
+import com.google.common.base.Splitter;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import javax.annotation.Nullable;
+import javax.lang.model.SourceVersion;
 
 /** Immutable configuration options for the builder process. */
 public class BuildConfiguration {
@@ -158,6 +160,18 @@ public BuildConfiguration build() {
     }
   }
 
+  /**
+   * @return {@code true} if {@code className} is a valid Java class name; {@code false} otherwise
+   */
+  public static boolean isValidJavaClass(String className) {
+    for (String part : Splitter.on('.').split(className)) {
+      if (!SourceVersion.isIdentifier(part)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
   private final BuildLogger buildLogger;
   private ImageReference baseImageReference;
   private ImageReference targetImageReference;

jib-core/src/test/java/com/google/cloud/tools/jib/builder/BuildConfigurationTest.java

@@ -153,4 +153,16 @@ public void testBuilder_missingValues() {
           ex.getMessage());
     }
   }
+
+  @Test
+  public void testValidJavaClassRegex() {
+    Assert.assertTrue(BuildConfiguration.isValidJavaClass("my.Class"));
+    Assert.assertTrue(BuildConfiguration.isValidJavaClass("my.java_Class$valid"));
+    Assert.assertTrue(BuildConfiguration.isValidJavaClass("multiple.package.items"));
+    Assert.assertTrue(BuildConfiguration.isValidJavaClass("is123.valid"));
+    Assert.assertFalse(BuildConfiguration.isValidJavaClass("${start-class}"));
+    Assert.assertFalse(BuildConfiguration.isValidJavaClass("123not.Valid"));
+    Assert.assertFalse(BuildConfiguration.isValidJavaClass("{class}"));
+    Assert.assertFalse(BuildConfiguration.isValidJavaClass("not valid"));
+  }
 }

jib-gradle-plugin/CHANGELOG.md

@@ -4,6 +4,7 @@ All notable changes to this project will be documented in this file.
 
 ### Added
 
+- Warns if specified `mainClass` is not a valid Java class ([#206](https://github.com/google/jib/issues/206))
 - Can specify registry credentials to use directly with `from.auth` and `to.auth` ([#215](https://github.com/google/jib/issues/215))
 
 ### Changed

jib-gradle-plugin/src/main/java/com/google/cloud/tools/jib/gradle/BuildImageTask.java

@@ -127,6 +127,9 @@ public void buildImage() throws InvalidImageReferenceException, IOException {
         throw new GradleException("Could not find main class specified in a 'jar' task");
       }
     }
+    if (!BuildConfiguration.isValidJavaClass(mainClass)) {
+      getLogger().warn("'mainClass' is not a valid Java class : " + mainClass);
+    }
 
     SourceFilesConfiguration sourceFilesConfiguration = getSourceFilesConfiguration();
 

jib-maven-plugin/CHANGELOG.md

@@ -11,6 +11,7 @@ All notable changes to this project will be documented in this file.
 ## 0.1.7
 ### Added
 - Better feedback for build failures ([#197](https://github.com/google/jib/pull/197))
+- Warns if specified `mainClass` is not a valid Java class ([#206](https://github.com/google/jib/issues/206))
 
 ## 0.1.6
 ### Changed

jib-maven-plugin/src/main/java/com/google/cloud/tools/jib/maven/BuildImageMojo.java

@@ -131,6 +131,9 @@ public void execute() throws MojoExecutionException, MojoFailureException {
             "add a `mainClass` configuration to jib-maven-plugin");
       }
     }
+    if (!BuildConfiguration.isValidJavaClass(mainClass)) {
+      getLog().warn("'mainClass' is not a valid Java class : " + mainClass);
+    }
 
     SourceFilesConfiguration sourceFilesConfiguration =
         projectProperties.getSourceFilesConfiguration();
@@ -293,7 +296,7 @@ private void validateParameters() throws MojoFailureException {
         throw new MojoFailureException("Invalid configuration parameters");
       }
     }
-    // Validates 'imageFormat'
+    // Validates 'imageFormat'.
     boolean validFormat = false;
     for (ImageFormat format : ImageFormat.values()) {
       if (imageFormat.equals(format.name())) {