Compilation failed

gistfile1.txt

$ gradle compileJava
:compileJava
/Users/muga/works/workspace/embulk-plugin-s3/src/main/java/org/embulk/plugin/s3/S3FileInputPlugin.java:21: error: cannot find symbol
import org.embulk.config.ConfigDiff;
                        ^
  symbol:   class ConfigDiff
  location: package org.embulk.config
/Users/muga/works/workspace/embulk-plugin-s3/src/main/java/org/embulk/plugin/s3/S3FileInputPlugin.java:54: error: cannot find symbol
import org.embulk.config.ConfigDiff;
                        ^
  symbol:   class ConfigDiff
  location: package org.embulk.config
/Users/muga/works/workspace/embulk-plugin-s3/src/main/java/org/embulk/plugin/s3/S3FileInputPlugin.java:100: error: cannot find symbol
    public ConfigDiff transaction(ConfigSource config, FileInputPlugin.Control control)
           ^
  symbol:   class ConfigDiff
  location: class S3FileInputPlugin
/Users/muga/works/workspace/embulk-plugin-s3/src/main/java/org/embulk/plugin/s3/S3FileInputPlugin.java:112: error: cannot find symbol
    public ConfigDiff resume(TaskSource taskSource,
           ^
  symbol:   class ConfigDiff
  location: class S3FileInputPlugin
4 errors
:compileJava FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 4.688 secs