Make dockerfile robust

Dockerfile

-FROM eclipse-temurin:19-jdk-alpine
-COPY . .
-VOLUME /tmp
+# Use a specific version of the JDK image to ensure consistency
+FROM eclipse-temurin:19-jdk-alpine AS build
+
+# Set the working directory
+WORKDIR /app
+
+# Copy the pom.xml file first, and then download dependencies separately to take advantage of Docker layer caching
+COPY pom.xml .
 RUN apk add maven
+RUN mvn dependency:go-offline
+
+# Copy the source code and package the application
+COPY src ./src
 RUN mvn clean package
-ENTRYPOINT ["java","-jar","target/SmartMat-0.0.1-SNAPSHOT.jar"]
+
+# Use a new stage to reduce the final image size
+FROM eclipse-temurin:19-jre-alpine
+
+# Set the working directory
+WORKDIR /app
+
+# Copy the packaged application from the build stage
+COPY --from=build /app/target/SmartMat-0.0.1-SNAPSHOT.jar ./SmartMat.jar
+
+# Define the entrypoint and expose the application port
+ENTRYPOINT ["java","-jar","SmartMat.jar"]
 EXPOSE 8080