How do I run a class compiled with jaotc?

问题:

I compiled a simple class using the Java 9 Ahead-Of-Time Compiler jaotc using the following command:

javac Test.java
jaotc Test.class

This produces a file named unnammed.so. How do I run the compiled program? Do I need to write a bootstrap program to link with the .so file?

回答1:

After executing an AOT compilation, you need to specify generated AOT library during application execution:

java -XX:AOTLibrary=./Test.so Test

You should also compile java.base to gain real improvement, performance wise:

jaotc --output libjava.base.so --module java.base

Note that the same java runtime configuration should be used during AOT compilation and execution.

For Example:

jaotc -J-XX:+UseParallelGC -J-XX:-UseCompressedOops --output libTest.so Test.class 
java -XX:+UseParallelGC -XX:-UseCompressedOops -XX:AOTLibrary=./libTest.so Test

Take a look at this, for more information.

回答2:

You should have a look at JEP 295, which describes AOT compilation in JDK 9, http://openjdk.java.net/jeps/295. You need to use the --XX::AOTLibrary command line flag.

To execute your app:

java -XX::AOTLibrary=./unnamed.so,./libjava.base.so Test

You will obviously have to copy the libjava.base.so file from the JDK 9 distribution or change the path to where it is.

When compiling you should also use the --output flag to jaotc so you don't get 'unnamed.so'.