Eclipse: export a Runnable JAR file to be executed on an older JRE

问题

Exporting a Runnable JAR file from Eclipse is by far the quickest way to launch an Eclipse project from command line on another machine. See this answer.

A problem is that if the JRE installed on the machine you want to run from is older than the JDK used by Eclipse, you get this error:

java.lang.UnsupportedClassVersionError: test_hello_world : Unsupported major.minor version 51.0

I know that on Eclipse I can build the project with a lower compliance level (e.g., 1.6 instead of 1.7), but this does not seem to affect an exported JAR file.

Any idea on how to export a Runnable JAR file to be executed on an older JRE?

回答1:

This procedure seems to work for me (I tested with Java 1.2 and Eclipse Juno):

• Create a new project.
• Set the execution environment to J2SE-1.2.
• Create a main class that prints one line to System.out.
• Run the project.
• Export the runnable jar.
• Run the jar in JRE 1.2.

回答2:

By using Maven you can specify any version of JRE. And in result you will get jar file build to specified version of JRE. For example:

<plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
</plugins>

回答3:

Changing the compliance level should work. You have to perform a rebuild of your project. When you export a Jar eclipse do not compile your project just for package it, it usees the already compiled files.

回答4:

Change your "Java Compiler" settings in eclipse. Make compiler compliance level to 1.6.

How can I build a jar for a previous Java version?

Then export the 'Runnable Jar'. It will work !!

回答5:

I changed the compliance level and then also had to do the following:

• Right click each project and open properties->Java Build Path->Libraries
• Remove the JDK you don't want, in my case JDK 8
• Add Library -> JRE System Library -> Select the version you want, in my case 7
• Java Complier -> Set compliance level to the level you want, in my case 7
• Click ok, repeat as needed.

来源：https://stackoverflow.com/questions/16730386/eclipse-export-a-runnable-jar-file-to-be-executed-on-an-older-jre