Build an image for a Java application by using a Dockerfile with multi-stage builds

Step 1: Create a Dockerfile with multi-stage builds

# First stage: complete build environment
FROM maven:3.5.0-jdk-8-alpine AS builder

# add pom.xml and source code
ADD ./pom.xml pom.xml
ADD ./src src/

# package jar
RUN mvn clean package

# Second stage: minimal runtime environment
From openjdk:8-jre-alpine

# copy jar from the first stage
COPY --from=builder target/my-app-1.0-SNAPSHOT.jar my-app-1.0-SNAPSHOT.jar

EXPOSE 8080

CMD ["java", "-jar", "my-app-1.0-SNAPSHOT.jar"]

Step 2: Authorize Container Registry to access the source code repository

Log on to the Container Registry console and authorize Container Registry to access the source code repository. This section uses GitHub as an example of the code repository hosting service.

1. Select a region from the drop-down list at the top of the page. In the left-side navigation pane, choose Default Instance > Code Source.
2. Click Bind Account for the GitHub service. In the GitHub dialog box, click Go to the source code repository to bind account. On the page that appears, enter your username and password to log on to GitHub.
3. On the authorization page, click Authorize AliyunDeveloper.
   
   Go to the Code Source page. Check whether the status of the GitHub service appears as Bound.

Step 3: Create an image repository

1. In the left-side navigation pane, choose Default Instance > Repositories. On the Repositories page, click Create Repository.
2. Set the parameter as required.
   

   Parameter	Description
   Region	The region where the image repository resides. Container Registry supports 23 regions around the world.
   Namespaces	The namespace to which the image repository belongs. An image repository belongs to only one namespace, whereas a namespace can contain multiple image repositories.
   Repository Name	The name of the image repository.
   Repository Type	The type of the image repository. Valid values: Public and Private. You can only push images to an image repository after you log on to the image repository, regardless of the repository type. Public: You can pull images from the image repository without logging on to the image repository. Private: You can only pull images from the image repository after logging on to the image repository on the Docker client.
   Summary	The brief description of the image repository.
   Description	The detailed description of the image repository.

3. Click Next. In the Code Source step, specify the code source and build settings.
   • Code Source: the service or platform where the source code repository is hosted. Click the GitHub tab and select the source code repository that you have authorized Container Registry to access in Step 2: Authorize Container Registry to access the source code repository.
   • Build Settings: the mode in which images are built.
     1. Automatically Build Images When Code Changes: If you select this option, an image is automatically built when code is committed from a branch.
     2. Build With Servers Deployed Outside Mainland China: If you select this option, images are built in a data center outside mainland China and then pushed to the image repository.
     3. Build Without Cache: If you select this option, the system pulls the dependent base image for every image to be built. This may slow down the build time.
4. Click Create Repository.
   On the Repositories page, check whether the image repository that you have created appears.

Step 4: Build an image

1. In the left-side navigation pane, choose Default Instance > Repositories. On the Repositories page, find the target image repository and click Manage in the Actions column.
2. In the left-side navigation pane, click Build. In the Build Rules section of the page that appears, click Add Build Rule.
3. In the Add Build Rule dialog box, set the parameters as required.
   

   Parameter	Description
   Type	The type of content pushed to the source code repository that will trigger the build rule. Valid values: Branch and Tag.
   Branch/Tag	The code branch or tag that will trigger the build rule.
   Dockerfile Directory	The directory where the Dockerfile is stored. The specified directory is a relative directory, with the root directory of the code branch as its parent directory.
   Dockerfile Filename	The name of the Dockerfile. The default file name is Dockerfile.
   Tags	The tag of the image to be built.

4. Click Ok.
5. In the Build Rules section, find the created rule and click Build in the Actions column.
   After you start the build, a build record is generated in the Build Log section. When the status of the build record becomes Successful, the image is built.