Question

我有一个基于Java 10+的源代码，我希望针对较低版本的Java（例如Java 8）进行编译，而无需修改源代码本身。我希望安装了Java 8的用户能够运行可执行文件JAR。

这是否可行？如果可以，如何使用maven完成？我没有找到任何合理的指导。降低source和target编译器选项不起作用：我仍然收到版本不匹配错误。

LauncherClient.java：

import lombok.Getter;
import lombok.val;

public class LauncherClient
{
    @Getter
    private String lombok = "Lombok";

    public static void main(String[] arguments)
    {
        val launcherClient = new LauncherClient();
        var message = "Hello world, ";
        System.out.println(message + launcherClient.getLombok());
    }
}

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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>groupId</groupId>
    <artifactId>Java11Test</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>LATEST</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.0</version>
                <configuration>
                    <source>11</source>
                    <target>1.8</target>
                </configuration>
            </plugin>

            <plugin>
                <!-- Build an executable JAR -->
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.1.0</version>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <classpathPrefix>lib/</classpathPrefix>
                            <mainClass>LauncherClient</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

使用JAR通过命令行运行可执行文件Java 8时：

java -jar Java11Test-1.0-SNAPSHOT.jar
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: LauncherClient 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$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

使用Java 11运行它可以正常工作：

"C:\Program Files\Java\jdk-11.0.1\bin\java.exe" -jar Java11Test-1.0-SNAPSHOT.jar
Hello world, Lombok

为较低的JRE版本编译Java代码

0 个答案: