Docker error while copying jar from maven target directory - spring-boot

Question

I'm building Docker image to run Spring Boot, but while building it i get error about copying jar file from target directory:
failed to solve: lstat /var/lib/docker/tmp/buildkit-mount188888512/var/www/app/target: no such file or directory
Here's the backend.Dockerfile:
FROM openjdk:17
WORKDIR /var/www/app
COPY mvnw .
COPY .mvn .mvn
COPY pom.xml .
COPY src src
RUN ./mvnw package -Dmaven.test.skip
EXPOSE 8080
COPY var/www/app/target/*.jar app.jar
CMD ["java", "-jar", "app.jar"]
Here's the part of docker-compose.yaml responsible for SpringBoot container:
app:
container_name: app
build:
dockerfile: ./docker/backend.Dockerfile
restart: on-failure
ports:
- "8080:8080"
depends_on:
- mysql
- mail-catcher
And the project structure:
.
├── docker
│   └── backend.Dockerfile
├── src
│ └──...
├── target
│ └──...
├── mvnw
├── mvnw.cmd
├── pom.xml
└── docker-compose.yaml

Answer 1

I would recommend another way of building your docker images with Spring Boot Project.
You can refer to this example by using the maven plugin during the maven build, your image will be built. The plugin comes from org.springframework.boot and it will help you build the image for the required module. You would need to use it in your pom.xml file if it is a maven project.
Then you could just run 'mvn clean install' if you have any test that you want to be run as well, or if you want your tests to be skipped you can use 'mvn clean install -DskipTests'
The image will be built in a layered format of docker, in a multistage image build format.
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<image>
<name>ms/product.service:latest</name>
</image>
</configuration>
<executions>
<execution>
<phase>install</phase>
<goals>
<goal>build-image</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>