无法从jar文件中找到Premain-Class清单属性 [英] Failed to find Premain-Class manifest attribute from a jar file

问题描述

我从单个.class创建了一个jar，并且在清单Premain-class中提到了，该jar是按预期生成的，但是当我尝试运行一个使用该jar中的类的程序时，出现错误

I created a jar from a single .class and I mentioned in the manifest the Premain-class, the jar was generated as expected but when I try to run a program that uses the class from that jar , I get an error

MANIFEST.MD

MANIFEST.MD

Premain-Class : Agent

Agent.java

Agent.java

import java.lang.instrument.Instrumentation;
public class Agent{
    private static Instrumentation inst;
    public static void premain(String paramString, Instrumentation paramInstrumentation) 
    { 
        inst = paramInstrumentation;
    }

    public static long size(Object paramObject)
    {
        return inst.getObjectSize(paramObject);
    }
}

Test.java

Test.java

public class Test {

  public static void main (String[] args){
    System.out.println(Agent.size(Integer.valueOf(9)));
  }
}

当我获得Agent.class时，在MANIFEST.MD文件所在的同一文件夹中，我执行以下命令

When I get the Agent.class, in the same folder where MANIFEST.MD file exist I execute the following command

jar -cvfm agent.jar MANIFEST.MF *.class

，当我得到jar时，请按照以下步骤运行Test，然后对其进行编译

and when I get the the jar I run the Test, after compiling it, as follow

java -javaagent:agent.jar Test

我得到以下错误

Failed to find Premain-Class manifest attribute in agent.jar
Error occurred during initialization of VM
agent library failed to init: instrument

我想念什么吗?预先感谢

am I missing something ? thanks in advance

推荐答案

MANIFEST规范似乎不允许在键之后使用空格，而只能在值前添加空格.

The MANIFEST specification doesn't seem to allow spaces after the key, but only before the value.

header: alphanum *headerchar ":" SPACE *otherchar newline
          *continuation

所以这个

Premain-Class : Agent

应该成为

Premain-Class: Agent

另外，将您的Agent放在一个包装下，不要使用默认的包装

Also, put your Agent under a package, don't use the default one

Premain-Class: your.package.Agent

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