UnsupportedClassVersionError: has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version (..)up to 52.0

Question

I'm trying to launch the jar file I've builded for my Spring Boot project. First I did:

mvn clean package spring-boot:repackage

then I've tried to launch the jar file, and I had the following error:

Exception in thread "main" java.lang.UnsupportedClassVersionError: it/sysdata/helios_backend_admin/HeliosAdminBackendApplication has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(Unknown Source) at java.security.SecureClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.defineClass(Unknown Source) at java.net.URLClassLoader.access$100(Unknown Source) at java.net.URLClassLoader$1.run(Unknown Source) at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:93) at java.lang.ClassLoader.loadClass(Unknown Source) at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:46) at org.springframework.boot.loader.Launcher.launch(Launcher.java:87) at org.springframework.boot.loader.Launcher.launch(Launcher.java:50) at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)

I've checked and java version is 11 everywhere (at least from what I saw). This is the pom:

<?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 http://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>2.1.2.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>it.sysdata</groupId>
    <artifactId>helios_backend_admin</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>helios-admin-backend</name>
        <packaging>jar</packaging>
    <description>Helios Backend for Dashboard admin</description>

    <properties>
        <java.version>11</java.version>
        <flowable.version>6.4.1</flowable.version>
        <swagger.version>2.9.2</swagger.version>
        <jwt.version>0.9.1</jwt.version>
        <cron4j.version>2.2.5</cron4j.version>  
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
        </dependency>  

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


        <!-- Flowable -->
        <dependency>
            <groupId>org.flowable</groupId>
            <artifactId>flowable-spring-boot-starter-process</artifactId>
            <version>${flowable.version}</version>
        </dependency>
        <dependency>
            <groupId>org.flowable</groupId>
            <artifactId>flowable-http</artifactId>
            <version>${flowable.version}</version>
        </dependency>  
        <!-- Swagger -->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>${swagger.version}</version>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>${swagger.version}</version>
        </dependency>
        <!-- JWT -->
        <dependency>
            <groupId>io.jsonwebtoken</groupId>
            <artifactId>jjwt</artifactId>
            <version>${jwt.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-cache</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>



        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.mongodb</groupId>
            <artifactId>mongo-java-driver</artifactId>
            <version>3.10.1</version>
        </dependency>

        <dependency>
            <groupId>it.sauronsoftware.cron4j</groupId>
            <artifactId>cron4j</artifactId>
            <version>${cron4j.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
        </dependency>
    </dependencies>
    <build>
        <finalName>${artifactId}</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                <source>11</source>
                <target>11</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

These are my settings under Project Properties -> Java Compiler -> JDK Compliance:

Then in Window-> Preferences -> Installed JREs:

UPDATE

Are these settings ok?

Answer 1

In my case, there was a wrong JAVA_HOME setup,
and for me worked the following steps:

1. Go to Environment Variables
   
2. Click Edit when JAVA_HOME is selected
   
3. Select the directory where your desired jdk is instaled

This might help to select the correct Java version:

• Java 1.2 uses major version 46
• Java 1.3 uses major version 47
• Java 1.4 uses major version 48
• Java 5 uses major version 49
• Java 6 uses major version 50
• Java 7 uses major version 51
• Java 8 uses major version 52
• Java 9 uses major version 53
• Java 10 uses major version 54
• Java 11 uses major version 55
• Java 12 uses major version 56
• Java 13 uses major version 57
• Java 14 uses major version 58
• Java 15 uses major version 59
• Java 16 uses major version 60
• Java 17 uses major version 61
• Java 18 uses major version 62
• Java 19 uses major version 63