Spring boot gradle project in Docker with continuous build

Question

I've created a spring starter project with gradle as dependency manager and also including spring-boot-dev-tools. My aim is to create a docker image so that there must be live reload whenever I change a java file inside docker container. This is working well with following configurations.

Dockerfile

FROM gradle:5.6.2-jdk8
WORKDIR /app
COPY . /app
RUN gradle build
EXPOSE 8080
CMD ["sh", "start.sh"]

start.sh

#!/bin/bash
gradle --version
gradle build --continuous &
gradle bootRun

This is working

One of my controller file is as follows.

@RestController
public class MainController {
    @GetMapping("/")
    String test() {
        return "Test Success";
    }
}

Getting "Test Success" in browser when navigating to localhost:8080. When the file /app/.../MainController.java inside docker container is changed to say, return "Updated";, the change is affected automatically.

This is the issue

Even if there is RUN gradle build inside Dockerfile, docker run command with this image seems to be downloading the gradle dependencies again because of the command gradle build --continuous or gradle bootRun.

I want the docker run command fast, like it's downloaded all the dependencies already. Please suggest a workaround. Live reload is needed.

Answer 1

I've used getDeps option inside the Dockerfile and skipDownload in start.sh file. This will download all the dependencies during Docker build and the live reload is now fast.

Dockerfile

FROM gradle:5.6.2-jdk8
WORKDIR /app
COPY . /app

RUN gradle --no-daemon --warning-mode all --console=plain getDeps

EXPOSE 8080
CMD ["sh", "start.sh"]

start.sh file

#!/bin/bash
gradle --version
gradle build --continuous -PskipDownload=true --console=plain &
gradle bootRun -PskipDownload=true --console=plain

build.gradle

// other configs
ext {
    skipDownload = project.hasProperty('skipDownload') ? project.getProperty('skipDownload') as boolean : false
}    
repositories {
    if (skipDownload) {
        flatDir {
            dirs 'libs'
        }
    } else {
        mavenCentral()
    }
}
dependencies {
    if (skipDownload) {
        implementation files('libs/spring-boot-starter-data-jdbc-2.3.7.RELEASE.jar')

    } else {
        implementation group: 'org.springframework.boot', name: 'spring-boot-starter-data-jdbc', version: '2.3.7.RELEASE'

    }
}
task getDeps(type: Copy) {
    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
    from configurations.compileClasspath into "libs/"
    from configurations.runtimeClasspath into "libs/"
}