使用jdk1.6编译器API进行编译时，如何将内存中的jar文件放入类路径中？

Question

I'm doing some dynamic compilation using jdk1.6 compiler API.
For now, I just dumped all jar files needed to disk , in order to include them in classpath when compiling.
Is there some kind of trick to put jar files in memory into classpath directly?
I failed to figure out how to do this by extending javax.tools.ForwardingJavaFileManager.
Could someone give me some hints?
Thanks.

Answer 1

Read here on how to add jar files to your class path using manifest.

There should be a META-INF folder inside of your jar, the Manifest.mf file should be in that folder of the jar.

There is also an option to put the jar files in JAVA_HOME/lib/ext but this is a bad practice. The JRE can be used by many other applications than yours, and they don't need to have your classes in their classpath.

Answer 2

I wrote my own FileManager which is entirely in memory. Using this approach to can load and even write results into an in-memory "file system"

https://github.com/OpenHFT/Java-Runtime-Compiler/blob/master/compiler/src/main/java/net/openhft/compiler/MyJavaFileManager.java