问题
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
Premain-Class : Agent
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
public class Test {
public static void main (String[] args){
System.out.println(Agent.size(Integer.valueOf(9)));
}
}
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
and when I get the the jar I run the Test, after compiling it, as follow
java -javaagent:agent.jar Test
and I get the following error
Failed to find Premain-Class manifest attribute in agent.jar
Error occurred during initialization of VM
agent library failed to init: instrument
am I missing something ? thanks in advance
回答1:
The MANIFEST
specification doesn't seem to allow spaces after the key, but only before the value.
header: alphanum *headerchar ":" SPACE *otherchar newline
*continuation
So this
Premain-Class : Agent
should become
Premain-Class: Agent
Also, put your Agent
under a package, don't use the default one
Premain-Class: your.package.Agent
来源:https://stackoverflow.com/questions/55259056/failed-to-find-premain-class-manifest-attribute-from-a-jar-file