Add devcontainer config files and downgrade JDK

JDK 15 is very new, the dev container image is not updated with it yet!

Author: Ferenc Hammerl

.devcontainer/Dockerfile

@@ -0,0 +1,23 @@
+# See here for image contents: https://github.com/microsoft/vscode-dev-containers/tree/v0.137.0/containers/java/.devcontainer/base.Dockerfile
+ARG VARIANT="14"
+FROM mcr.microsoft.com/vscode/devcontainers/java:0-${VARIANT}
+
+# [Optional] Install Maven or Gradle
+ARG INSTALL_MAVEN="false"
+ARG MAVEN_VERSION=3.6.3
+ARG INSTALL_GRADLE="false"
+ARG GRADLE_VERSION=5.4.1
+RUN if [ "${INSTALL_MAVEN}" = "true" ]; then su vscode -c "source /usr/local/sdkman/bin/sdkman-init.sh && sdk install maven \"${MAVEN_VERSION}\""; fi \
+    && if [ "${INSTALL_GRADLE}" = "true" ]; then su vscode -c "source /usr/local/sdkman/bin/sdkman-init.sh && sdk install gradle \"${GRADLE_VERSION}\""; fi
+
+# [Optional] Install a version of Node.js using nvm for front end dev
+ARG INSTALL_NODE="true"
+ARG NODE_VERSION="lts/*"
+RUN if [ "${INSTALL_NODE}" = "true" ]; then su vscode -c "source /usr/local/share/nvm/nvm.sh && nvm install ${NODE_VERSION} 2>&1"; fi
+
+# [Optional] Uncomment this section to install additional OS packages.
+# RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
+#     && apt-get -y install --no-install-recommends <your-package-list-here>
+
+# [Optional] Uncomment this line to install global node packages.
+# RUN su vscode -c "source /usr/local/share/nvm/nvm.sh && npm install -g <your-package-here>" 2>&1

.devcontainer/devcontainer.json

@@ -0,0 +1,26 @@
+{
+	"name": "Java",
+	"service": "app",
+		 
+	"workspaceFolder": "/workspace",
+
+	"dockerComposeFile": "docker-compose.yml",
+	// Set *default* container specific settings.json values on container create.
+	"settings": { 
+		"terminal.integrated.shell.linux": "/bin/bash",
+		"java.home": "/docker-java-home",
+		"maven.executable.path": "/usr/local/sdkman/candidates/maven/current/bin/mvn"
+	},
+	
+	// Add the IDs of extensions you want installed when the container is created.
+	"extensions": [
+		"vscjava.vscode-java-pack"
+	],
+	 "forwardPorts": [8080],
+
+	// Use 'postCreateCommand' to run commands after the container is created.
+	// "postCreateCommand": "java -version",
+
+	// Uncomment to connect as a non-root user. See https://aka.ms/vscode-remote/containers/non-root.
+	"remoteUser": "vscode"
+}

.devcontainer/docker-compose.yml

@@ -0,0 +1,26 @@
+version: '3.8'
+
+services:
+  app:    
+    build: 
+      context: .
+      dockerfile: Dockerfile
+    volumes:
+      # This is where VS Code should expect to find your project's source code and the value of "workspaceFolder" in .devcontainer/devcontainer.json
+      - ..:/workspace:cached
+    # Overrides default command so things don't shut down after the process ends.
+    command: /bin/sh -c "while sleep 1000; do :; done"  
+    network_mode: service:db
+  db:
+    image: "postgres"
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: pwd1234
+      POSTGRES_DB: doodle
+    ports:
+      - "5432:5432"
+    volumes:
+      - pg_db:/var/lib/postgresql/data
+
+volumes:
+  pg_db:

pom.xml

@@ -15,7 +15,7 @@
 	<description>Demo project for Spring Boot</description>
 
 	<properties>
-		<java.version>15</java.version>
+		<java.version>14</java.version>
 	</properties>
 
 	<dependencies>