Using the Aspectjweaver times "Agent library failed to init:instrument" "Error opening zip file or JAR manifest m

This is only a small experience, I still do not know why. Today, in Ant's build.xml to increase the monitoring of kieker, several times encountered this problem, it is very baffling:

The general error is similar to this:

Error occurred during initialization of VMS

Agent Library failed to init:instrument

Error opening zip file or JAR manifest Missing:lib/aspectjweaver-1.6.11.jar

This time the corresponding build.xml in the wording is:

<jvmarg value= "-javaagent:lib/aspectjweaver-1.6.11.jar"/>

has been baffled why it can not find this jar package, the results found to be similar to such a configuration can be:

<property name= "Main.aspectj.jar" location= "Lib/aspectjweaver-1.6.11.jar"/>...<jvmarg value= "-javaagent: ${main.aspectj.jar} "/>

these two kinds of writing in my opinion is the same, do not know why the former is not. A little experience, I believe other friends will also meet, so summarize.