IntelliJ IDEAを使ってSpring Bootのアプリケーションを作成する


IntelliJ IDEAを使ってSpring Bootのアプリケーションを作成し、実行するところまでの手順です。実行はIntelliJ IDEAでのデバック実行と、JARファイルにビルドして実行できることを確認します。

## 開発環境
- macOS Caralina 10.15.4
- OpenJDK 14.0.2
- maven 14.0.1
- IntelliJ IDEA


## 事前準備
Spring Bootの開発を行うために次のものを準備してください。

- OpenJDKのダウンロードとインストール https://openjdk.java.net/
- Mavenのダウンロードとインストール https://maven.apache.org/download.cgi
- IntelliJ IDEAのダウンロードとインストール https://www.jetbrains.com/ja-jp/idea/
- パスの確認
	- `java -version`
	- `mvn -v`


## IntelliJ IDEAでSpring Bootの開発

Spring BootのGetting Startedの内容にしたがってプロジェクトを作成していきます。

https://spring.pleiades.io/spring-boot/docs/current/reference/html/getting-started.html#getting-started-first-application

次の手順で行います。

- 新規プロジェクトの作成
- pom.xmlの作成
- Hello World!アプリケーションの作成
- IntelliJ IDEAを使ってプログラムの実行
- jarファイルにビルドして実行


### 新規プロジェクトの作成
IntelliJ IDEAを起動し、「New Project」を選択します。

![intelliJ_home.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/684932/e11a5774-b8e5-12f9-d5a8-94b31d759fe4.png)


「Maven」を選択して、「Project SDK」にインストールしたOpenJDKを指定して、さらに「Next」を選択します。

![intelliJ_new_project_1.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/684932/31d45ad5-5bbc-e4ff-0424-dc8f9280fc0e.png)


プロジェクトの名前を入力して、「Finish」を選択します。

![intelliJ_new_project_2.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/684932/b73dadad-6f6b-60dd-07a0-9d12b762222a.png)


### pom.xmlの編集

`pom.xml`に以下の内容を記述します。

```xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
		 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>org.example</groupId>
	<artifactId>spring-boot-demo-app</artifactId>
	<version>1.0-SNAPSHOT</version>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.3.2.RELEASE</version>
	</parent>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<version>2.3.2.RELEASE</version>
			</plugin>
		</plugins>
	</build>
</project>
```

pom.xmlを編集したら、プロジェクトをリロードしておきます。

![intelliJ_reload_module.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/684932/42de8d67-b133-b1ca-d39a-1a1a851f5072.png)


### Hello World!アプリケーションの作成

`src/main/java/Example.java`を作成します。

![intelliJ_new_file.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/684932/5fc1f2e1-83bf-7d24-9742-40e011d97288.png)

Example.javaには以下の内容を記述します。

```java
import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.web.bind.annotation.*;

@RestController
@EnableAutoConfiguration
public class Example {

	@RequestMapping("/")
	String home() {
		return "Hello World!";
	}

	public static void main(String[] args) {
		SpringApplication.run(Example.class, args);
	}

}
```

### IntelliJ IDEAを使ってプログラムの実行
作成したプログラムを実行してみます。mainクラスの左に表示されている実行ボタンを押してプログラムを実行します。

![intelliJ_run.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/684932/78ae3218-cfe1-7aef-b99b-2920df276d0a.png)

正しく実行できた場合は、コンソールに以下のメッセージが表示されます。

```sh
/Library/Java/JavaVirtualMachines/jdk-14.0.2.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=52512:/Applications/IntelliJ IDEA CE.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Users/masayuki/Documents/program/spring-boot-demo-app/target/classes:/Users/masayuki/.m2/repository/org/springframework/boot/spring-boot-starter-web/2.3.2.RELEASE/spring-boot-starter-web-2.3.2.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/boot/spring-boot-starter/2.3.2.RELEASE/spring-boot-starter-2.3.2.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/boot/spring-boot/2.3.2.RELEASE/spring-boot-2.3.2.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.3.2.RELEASE/spring-boot-autoconfigure-2.3.2.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.3.2.RELEASE/spring-boot-starter-logging-2.3.2.RELEASE.jar:/Users/masayuki/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/Users/masayuki/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/Users/masayuki/.m2/repository/org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar:/Users/masayuki/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.13.3/log4j-to-slf4j-2.13.3.jar:/Users/masayuki/.m2/repository/org/apache/logging/log4j/log4j-api/2.13.3/log4j-api-2.13.3.jar:/Users/masayuki/.m2/repository/org/slf4j/jul-to-slf4j/1.7.30/jul-to-slf4j-1.7.30.jar:/Users/masayuki/.m2/repository/jakarta/annotation/jakarta.annotation-api/1.3.5/jakarta.annotation-api-1.3.5.jar:/Users/masayuki/.m2/repository/org/springframework/spring-core/5.2.8.RELEASE/spring-core-5.2.8.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/spring-jcl/5.2.8.RELEASE/spring-jcl-5.2.8.RELEASE.jar:/Users/masayuki/.m2/repository/org/yaml/snakeyaml/1.26/snakeyaml-1.26.jar:/Users/masayuki/.m2/repository/org/springframework/boot/spring-boot-starter-json/2.3.2.RELEASE/spring-boot-starter-json-2.3.2.RELEASE.jar:/Users/masayuki/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.11.1/jackson-databind-2.11.1.jar:/Users/masayuki/.m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.11.1/jackson-annotations-2.11.1.jar:/Users/masayuki/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.11.1/jackson-core-2.11.1.jar:/Users/masayuki/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jdk8/2.11.1/jackson-datatype-jdk8-2.11.1.jar:/Users/masayuki/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jsr310/2.11.1/jackson-datatype-jsr310-2.11.1.jar:/Users/masayuki/.m2/repository/com/fasterxml/jackson/module/jackson-module-parameter-names/2.11.1/jackson-module-parameter-names-2.11.1.jar:/Users/masayuki/.m2/repository/org/springframework/boot/spring-boot-starter-tomcat/2.3.2.RELEASE/spring-boot-starter-tomcat-2.3.2.RELEASE.jar:/Users/masayuki/.m2/repository/org/apache/tomcat/embed/tomcat-embed-core/9.0.37/tomcat-embed-core-9.0.37.jar:/Users/masayuki/.m2/repository/org/glassfish/jakarta.el/3.0.3/jakarta.el-3.0.3.jar:/Users/masayuki/.m2/repository/org/apache/tomcat/embed/tomcat-embed-websocket/9.0.37/tomcat-embed-websocket-9.0.37.jar:/Users/masayuki/.m2/repository/org/springframework/spring-web/5.2.8.RELEASE/spring-web-5.2.8.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/spring-beans/5.2.8.RELEASE/spring-beans-5.2.8.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/spring-webmvc/5.2.8.RELEASE/spring-webmvc-5.2.8.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/spring-aop/5.2.8.RELEASE/spring-aop-5.2.8.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/spring-context/5.2.8.RELEASE/spring-context-5.2.8.RELEASE.jar:/Users/masayuki/.m2/repository/org/springframework/spring-expression/5.2.8.RELEASE/spring-expression-5.2.8.RELEASE.jar Example

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.2.RELEASE)

2020-08-02 14:26:02.276  INFO 35892 --- [           main] Example                                  : Starting Example on maa with PID 35892 (/Users/masayuki/Documents/program/spring-boot-demo-app/target/classes started by masayuki in /Users/masayuki/Documents/program/spring-boot-demo-app)
2020-08-02 14:26:02.280  INFO 35892 --- [           main] Example                                  : No active profile set, falling back to default profiles: default
2020-08-02 14:26:04.567  INFO 35892 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-08-02 14:26:04.624  INFO 35892 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-08-02 14:26:04.625  INFO 35892 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.37]
2020-08-02 14:26:04.847  INFO 35892 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-08-02 14:26:04.848  INFO 35892 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 2435 ms
2020-08-02 14:26:05.231  INFO 35892 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-08-02 14:26:05.676  INFO 35892 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-08-02 14:26:05.703  INFO 35892 --- [           main] Example                                  : Started Example in 4.953 seconds (JVM running for 6.18)

```

この状態でブラウザで`http://localhost:8080`へアクセスすると、Hello World!が表示されます。

### jarファイルにビルドして実行

右側の「Maven」をクリックすると表示されるツリーから、「プロジェクト名」 > 「Lifecycle」 > 「package」を右クリックし、さらに「Run Maven Build」を選択します。

![intelliJ_build.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/684932/10afb4c7-54b2-ec81-f592-0cfe2093b5b5.png)


正しくビルドできた場合は、コンソールに以下のメッセージが表示されます。

```sh
/Library/Java/JavaVirtualMachines/jdk-14.0.2.jdk/Contents/Home/bin/java -Dmaven.multiModuleProjectDirectory=/Users/masayuki/Documents/program/spring-boot-demo-app "-Dmaven.home=/Applications/IntelliJ IDEA CE.app/Contents/plugins/maven/lib/maven3" "-Dclassworlds.conf=/Applications/IntelliJ IDEA CE.app/Contents/plugins/maven/lib/maven3/bin/m2.conf" "-Dmaven.ext.class.path=/Applications/IntelliJ IDEA CE.app/Contents/plugins/maven/lib/maven-event-listener.jar" "-javaagent:/Applications/IntelliJ IDEA CE.app/Contents/lib/idea_rt.jar=52530:/Applications/IntelliJ IDEA CE.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Applications/IntelliJ IDEA CE.app/Contents/plugins/maven/lib/maven3/boot/plexus-classworlds.license:/Applications/IntelliJ IDEA CE.app/Contents/plugins/maven/lib/maven3/boot/plexus-classworlds-2.6.0.jar" org.codehaus.classworlds.Launcher -Didea.version=2020.2 package
[INFO] Scanning for projects...
[INFO] 
[INFO] ------------------< org.example:spring-boot-demo-app >------------------
[INFO] Building spring-boot-demo-app 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:3.1.0:resources (default-resources) @ spring-boot-demo-app ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 0 resource
[INFO] Copying 0 resource
[INFO] 
[INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ spring-boot-demo-app ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to /Users/masayuki/Documents/program/spring-boot-demo-app/target/classes
[INFO] 
[INFO] --- maven-resources-plugin:3.1.0:testResources (default-testResources) @ spring-boot-demo-app ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/masayuki/Documents/program/spring-boot-demo-app/src/test/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.8.1:testCompile (default-testCompile) @ spring-boot-demo-app ---
[INFO] Changes detected - recompiling the module!
[INFO] 
[INFO] --- maven-surefire-plugin:2.22.2:test (default-test) @ spring-boot-demo-app ---
[INFO] 
[INFO] --- maven-jar-plugin:3.2.0:jar (default-jar) @ spring-boot-demo-app ---
[INFO] Building jar: /Users/masayuki/Documents/program/spring-boot-demo-app/target/spring-boot-demo-app-1.0-SNAPSHOT.jar
[INFO] 
[INFO] --- spring-boot-maven-plugin:2.3.2.RELEASE:repackage (repackage) @ spring-boot-demo-app ---
[INFO] Replacing main artifact with repackaged archive
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  9.498 s
[INFO] Finished at: 2020-08-02T14:27:21+09:00
[INFO] ------------------------------------------------------------------------

```

ビルドした際のコンソールのメッセージに`[プロジェクトのルートフォルダ]/target/[プロジェクト名]-1.0-SNAPSHOT.jar`を作成したと表示されているので、JARファイルを探し`java -jar [作成されたjarファイル]`で起動します。正しく実行できた場合は、コンソールに以下のメッセージが表示されます。

```sh
$ java -jar target/spring-boot-demo-app-1.0-SNAPSHOT.jar

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.2.RELEASE)

2020-08-02 14:27:49.758  INFO 35907 --- [           main] Example                                  : Starting Example on maa with PID 35907 (/Users/masayuki/Documents/program/spring-boot-demo-app/target/spring-boot-demo-app-1.0-SNAPSHOT.jar started by masayuki in /Users/masayuki/Documents/program/spring-boot-demo-app)
2020-08-02 14:27:49.765  INFO 35907 --- [           main] Example                                  : No active profile set, falling back to default profiles: default
2020-08-02 14:27:52.252  INFO 35907 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-08-02 14:27:52.306  INFO 35907 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-08-02 14:27:52.306  INFO 35907 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.37]
2020-08-02 14:27:52.528  INFO 35907 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-08-02 14:27:52.528  INFO 35907 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 2622 ms
2020-08-02 14:27:53.043  INFO 35907 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-08-02 14:27:53.586  INFO 35907 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-08-02 14:27:53.613  INFO 35907 --- [           main] Example                                  : Started Example in 5.628 seconds (JVM running for 6.985)
```

この状態でブラウザで`http://localhost:8080`へアクセスすると、Hello World!が表示されます。

以上、IntelliJ IDEAを使ってSpring Bootアプリケーションの実行とビルドを確認しました。