Dockerize Spring Boot <80MB => https://dev.to/gofabian/dockerize-spring-boot-80mb-58m9

Dockerfile

# (1) use Alpine Linux for build stage
FROM alpine:3.10.1 as build
# (2) install build dependencies
RUN apk --no-cache add openjdk11
RUN apk --no-cache add maven

# build JDK with less modules
RUN /usr/lib/jvm/default-jvm/bin/jlink \
    --compress=2 \
    --module-path /usr/lib/jvm/default-jvm/jmods \
    --add-modules java.base,java.logging,java.xml,jdk.unsupported,java.sql,java.naming,java.desktop,java.management,java.security.jgss,java.instrument \
    --output /jdk-minimal

# fetch maven dependencies
WORKDIR /build
COPY pom.xml pom.xml
RUN mvn dependency:go-offline
# build
COPY src src
RUN mvn clean package

# prepare a fresh Alpine Linux with JDK
FROM alpine:3.10.1
# get result from build stage
COPY --from=build /build/target/*.jar /app.jar
COPY --from=build /jdk-minimal /opt/jdk/
VOLUME /tmp
EXPOSE 8080
CMD /opt/jdk/bin/java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar /app.jar

pom.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>lazy</groupId>
    <artifactId>lazy</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
    </parent>

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

    <properties>
        <java.version>11</java.version>
    </properties>


    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

SpringBootApp.java

package lazy;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class SpringBootApp {

    @GetMapping("/hello")
    public String hello() {
        return "Hello World!";
    }

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

}