[BEAM-7730] Reuse sources overrides from previous flink versions.

runners/flink/1.7/build.gradle

@@ -22,11 +22,9 @@ def basePath = '..'
 project.ext {
   // Set the version of all Flink-related dependencies here.
   flink_version = '1.7.2'
-  // Main source directory and Flink version specific code.
-  main_source_dirs = ["$basePath/src/main/java", "./src/main/java"]
-  test_source_dirs = ["$basePath/src/test/java", "./src/test/java"]
-  main_resources_dirs = ["$basePath/src/main/resources"]
-  test_resources_dirs = ["$basePath/src/test/resources"]
+  // Version specific code overrides.
+  main_source_overrides = ['./src/main/java']
+  test_source_overrides = ['./src/test/java']
   archives_base_name = 'beam-runners-flink-1.7'
 }
 

runners/flink/1.8/build.gradle

@@ -22,11 +22,9 @@ def basePath = '..'
 project.ext {
   // Set the version of all Flink-related dependencies here.
   flink_version = '1.8.2'
-  // Main source directory and Flink version specific code.
-  main_source_dirs = ["$basePath/src/main/java", "./src/main/java"]
-  test_source_dirs = ["$basePath/src/test/java", "./src/test/java"]
-  main_resources_dirs = ["$basePath/src/main/resources"]
-  test_resources_dirs = ["$basePath/src/test/resources"]
+  // Version specific code overrides.
+  main_source_overrides = ["${basePath}/1.7/src/main/java", './src/main/java']
+  test_source_overrides = ["${basePath}/1.7/src/test/java", './src/test/java']
   archives_base_name = 'beam-runners-flink-1.8'
 }
 

runners/flink/1.9/build.gradle

@@ -17,16 +17,13 @@
  */
 
 def basePath = '..'
-
 /* All properties required for loading the Flink build script */
 project.ext {
   // Set the version of all Flink-related dependencies here.
   flink_version = '1.9.0'
-  // Main source directory and Flink version specific code.
-  main_source_dirs = ["$basePath/src/main/java", "./src/main/java"]
-  test_source_dirs = ["$basePath/src/test/java", "./src/test/java"]
-  main_resources_dirs = ["$basePath/src/main/resources"]
-  test_resources_dirs = ["$basePath/src/test/resources"]
+  // Version specific code overrides.
+  main_source_overrides = ["${basePath}/1.7/src/main/java", "${basePath}/1.8/src/main/java", './src/main/java']
+  test_source_overrides = ["${basePath}/1.7/src/test/java", "${basePath}/1.8/src/test/java", './src/test/java']
   archives_base_name = 'beam-runners-flink-1.9'
 }