사건

dependencies {
    compile("org.springframework.boot:spring-boot-starter-web")
    testCompile('org.springframework.boot:spring-boot-starter-test')
    testCompile('com.jayway.jsonpath:json-path')
    compileOnly 'org.projectlombok:lombok:1.18.6' <--追加
    annotationProcessor 'org.projectlombok:lombok:1.18.6' <--追加
}

오류 1

Warning:<i><b>root project 'complete': Unable to resolve additional project configuration.</b>
Details: org.gradle.api.artifacts.ResolveException: Could not resolve all dependencies for configuration ':runtimeClasspath'.
Caused by: org.gradle.internal.resolve.ArtifactResolveException: Could not download spring-boot-starter-web.jar (org.springframework.boot:spring-boot-starter-web:2.1.3.RELEASE): No cached version available for offline mode</i>

대책 1

Enable annotation processing을 체크한다.
Intellij IDEA -> Preferences -> Compiler -> Annotation Processors

Enable annotation processing을 체크한다.
파일 -> 기타 설정 -> 기본 설정 -> 컴파일러 -> 주석 처리기

Lombok 플러그인 설치
Intellij IDEA -> Preferences -> Plugins -> Browse Repositories-> Search for "Lombok"-> install plugin -> Apply and restart IDEA

Work offline을 체크한다.
Intellij IDEA -> Preferences -> Build, Execution, Deployment -> Build Tools -> Gradle

오류 2

대책 2

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.jayway.jsonpath</groupId>
            <artifactId>json-path</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- ここから -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.6</version>
            <scope>provided</scope>
        </dependency>
        <!-- ここまで追加 -->
    </dependencies>