Unsupported major.minor version 52.0 because of dependency

Question

I have a project built with Java 7 (project pom excerpt) :

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.1</version>
    <configuration>
        <source>1.7</source>
        <target>1.7</target>
    </configuration>
</plugin>

It has a dependency with a module built with Java 8 (dependency pom excerpt) :

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <configuration>
        <source>1.8</source>
        <target>1.8</target>
    </configuration>
</plugin>

I've deployed and run my application on a server running with Java 7, and I get this error :

java.lang.UnsupportedClassVersionError: com/h/i/c/u/e/TradeStatus : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:791)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2442)
at java.lang.Class.getDeclaredMethods(Class.java:1808)
at ...

How can I fix this, knowing that I can't change the JRE on the server, and that I can't change the fact that the module is built with Java 8 ?

Simple answer: you can't. You're not going to be able to run code developed for Java 8 on Java 7. You either need to upgrade the JRE on the server or downgrade the dependency to one that supports Java 7 or less. — DaveyDaveDave, May 16 '19 at 14:41

score 1 · Answer 1 · answered May 16 '19 at 14:36

UnsupportedClassVersionError ... Major Minor occurs when you have a library built in higher version of java and you want to use in your application which is running in lower version. So there are two possible solutions.

First build the library with code changes in required version of JDK
Upgrade your JDK version so that both library and your application will work.

score 0 · Answer 2 · answered May 16 '19 at 14:46

It really depends to what extent the library uses Java8 JVM features. You can try using a retrorlanslator like Retrolambda on the library. https://github.com/luontola/retrolambda

Check discussions in Can Java 8 code be compiled to run on Java 7 JVM?

New server or JVM upgrade on the existing one is much better use of your time through.

Unsupported major.minor version 52.0 because of dependency

2 Answers2