Format the source code

.pre-commit-config.yaml

@@ -0,0 +1,8 @@
+repos:
+- repo: https://github.com/jguttman94/pre-commit-gradle
+  rev: efaf1704425cc50df91d63920e8353d9d081a622
+  hooks:
+  - id: gradle-task
+    args: [-w, -o, spotlessApply]
+    verbose: true
+

README.md

@@ -621,3 +621,17 @@ Fluency fluency = builder.build();
 ##### Other configurations
 
 Some of other usages are same as ingestion to Fluentd. See `Ingestion to Fluentd > Usage` above.
+
+## Development
+
+### Pre-commit hook
+
+This project uses [pre-commit](https://pre-commit.com/) to automate code format and so on as much as possible. If you're interested in the development of this project, please [install pre-commit](https://pre-commit.com/#installation) and the git hook script as follows.
+
+```
+$ ls -a .pre-commit-config.yaml
+.pre-commit-config.yaml
+$ pre-commit install
+```
+
+The code formatter is automatically executed when committing files. A commit will fail and be formatted by the formatter when any invalid code format is detected. Try to commit the change again.

build.gradle.kts

@@ -14,6 +14,7 @@ plugins {
   `maven-publish`
   id("com.github.kt3k.coveralls") version "2.12.2"
   id("com.github.johnrengelman.shadow") version "8.1.1"
+  id("com.diffplug.spotless") version "6.13.0"
 }
 
 subprojects {
@@ -26,6 +27,7 @@ subprojects {
   apply(plugin = "maven-publish")
   apply(plugin = "jacoco")
   apply(plugin = "com.github.kt3k.coveralls")
+  apply(plugin = "com.diffplug.spotless")
 
   repositories {
     mavenCentral()
@@ -187,5 +189,14 @@ subprojects {
   tasks.coveralls {
     dependsOn(jacocoRootReport)
   }
+
+  spotless {
+    java {
+      target("src/*/java/**/*.java")
+      importOrder()
+      removeUnusedImports()
+      googleJavaFormat("1.7")
+    }
+  }
 }