可运行jar文件中的启动清单文件 META-INF/MANIFEST.MF 内容自定义生成 

清单文件中的 Main-Class:    Premain-Class:    Can-Retransform-Classes: 在maven-assembly-plugin插件中的生成配置如下, 注意命名

<archive>
    <manifest>
        <mainClass>cn.tekin.burploaderkeygen.KeygenForm</mainClass>
    </manifest>
    <manifestEntries>
        <Premain-Class>cn.tekin.burploaderkeygen.Loader</Premain-Class>
        <Can-Retransform-Classes>true</Can-Retransform-Classes>
    </manifestEntries>
</archive>

打包jar文件夹后生成的清单如下:

Main-Class: cn.tekin.burploaderkeygen.KeygenForm
Can-Retransform-Classes: true
Premain-Class: cn.tekin.burploaderkeygen.Loader

maven pom.xml 完整配置文件如下

<?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>cn.tekin</groupId>
    <artifactId>burploaderkeygen</artifactId>
    <version>1.18</version>

    <properties>
        <maven.compiler.source>20</maven.compiler.source>
        <maven.compiler.target>20</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>3.6.0</version>
                <configuration>
                    <finalName>burploaderkeygen-v${version}</finalName>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                    <archive>
                        <manifest>
                            <mainClass>cn.tekin.burploaderkeygen.KeygenForm</mainClass>
                        </manifest>
                        <manifestEntries>
                            <Premain-Class>cn.tekin.burploaderkeygen.Loader</Premain-Class>
                            <Can-Retransform-Classes>true</Can-Retransform-Classes>
                        </manifestEntries>
                    </archive>
                </configuration>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

总结: 

从上面可以得出 主入口类的定义在manifest节点,且命名为小驼峰(配置 mainClass 最后生成 Main-Class ),  其他的清单配置都定义在manifestEntries节点,命名方式为首字母大写加连接线-的方式