I’m encountering an issue while building a Maven project using Docker. Despite trying various solutions, I haven’t been able to resolve it. Here’s the relevant information:

POM.xml file:

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/POM/4.0.0">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.tericcabrel</groupId>
    <artifactId>bmi</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <java.version>21</java.version>
        <spring.boot.version>3.3.0</spring.boot.version>
        <lombok.version>1.18.26</lombok.version>
    </properties>

    <dependencies>
        <!-- Spring Boot Dependencies -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>${spring.boot.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
            <version>${spring.boot.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
            <version>${spring.boot.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <version>${spring.boot.version}</version>
        </dependency>
        <!-- Lombok Dependency -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>${lombok.version}</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <!-- Maven Compiler Plugin -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.12.0</version>
                <configuration>
                    <source>21</source>
                    <target>21</target>
                </configuration>
            </plugin>
            <!-- Spring Boot Maven Plugin -->
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring.boot.version}</version>
            </plugin>
        </plugins>
    </build>
</project>

Dockerfile:

# Use an official Maven image as the base image
FROM maven:3.8.4-openjdk-11
# Create a working directory inside the container
WORKDIR /app
# Copy the pom.xml file to the container
COPY pom.xml .
# Download the project dependencies
RUN mvn dependency:go-offline
# Copy the rest of the application source code to the container
COPY src ./src
# Build the application
RUN mvn package -X
# Define the command to run your application
CMD ["java", "-jar", "target/bmi-1.0-SNAPSHOT.jar"]
# EXPOSE port
EXPOSE 8000

Error:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.12.0:compile (default-compile) on project bmi: Fatal error compiling: error: invalid target release: 21 -> [Help 1]

Steps Taken:

Tried changing the maven-compiler-plugin version to 11 and 20.
Attempted to compile from the src folder directly.
Tried different versions and made various configuration changes.

Questions:

Why is Maven failing with the error invalid target release: 21?
How can I fix this issue while using Docker?
Thank you for your help!