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javaspring-bootmavenheroku

Deploying Spring Boot App to Heroku fails with "invalid flag: --release -> [Help 1]"

When I try to deploy my code to Heroku (via git push heroku master), I'm getting a Maven error:

remote:        [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.11.0:compile (default-compile) on project heroku-demo: Fatal error compiling: invalid flag: --release -> [Help 1]
remote:        [ERROR]
remote:        [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
remote:        [ERROR] Re-run Maven using the -X switch to enable full debug logging.
remote:        [ERROR]
remote:        [ERROR] For more information about the errors and possible solutions, please read the following articles
remote:        [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
remote:
remote:  !     ERROR: Failed to build app with Maven
remote:        We're sorry this build is failing! If you can't find the issue in application code,
remote:        please submit a ticket so we can help: https://help.heroku.com/
remote:
remote:  !     Push rejected, failed to compile Java app.
remote:
remote:  !     Push failed
remote:  !
remote:  ! ## Warning - The same version of this code has already been built: 7057f2d04a587002166d4d36c0306e793c15d775
remote:  !
remote:  ! We have detected that you have triggered a build from source code with version 7057f2d04a587002166d4d36c0306e793c15d775
remote:  ! at least twice. One common cause of this behavior is attempting to deploy code from a different branch.
remote:  !
remote:  ! If you are developing on a branch and deploying via git you must run:
remote:  !
remote:  !     git push heroku <branchname>:main
remote:  !
remote:  ! This article goes into details on the behavior:
remote:  !   https://devcenter.heroku.com/articles/duplicate-build-version

My pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.0</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>heroku-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Changing Java to version 8 in the pom.xml also did not work.

Running mvn clean package locally works fine.

This build error obviously seems to be related to my Java version possibly being Java 8 or generally too old to support the --release flag. I verified it by running mvn -v, the output is:

Apache Maven 3.9.2 (c9616018c7a021c1c39be70fb2843d6f5f9b8a1c)
Maven home: C:\maven
Java version: 19.0.1, vendor: Oracle Corporation, runtime: C:\Program Files\Java\jdk-19
Default locale: en_GB, platform encoding: UTF-8
OS name: "windows 11", version: "10.0", arch: "amd64", family: "windows"

javac:

>javac -version
javac 19.0.1

javac -help:

--release <release>
        Compile for the specified Java SE release. Supported releases: 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19

Java is modern and Maven is the latest. How else could this issue be fixed? By the way, I followed this tutorial.

Solution

  • The workaround solution of using the heroku maven plugin worked by firstly specifying war deployment by adding <package>war</package> to the pom.xml (under the <version>0.0.1-SNAPSHOT</version> tag) and the plugin definition of

    <plugin>
    <groupId>com.heroku.sdk</groupId>
    <artifactId>heroku-maven-plugin</artifactId>
    <version>3.0.7</version>
</plugin>

    into the plugins tag and running the command mvn clean heroku:deploy-war.

    However, with this my application still doesn't run successfully when I execute heroku open. HTTP Status 404 – Not Found shows up. This may be a candidate for a follow-up question then (link).