Default Classloader when executing ANT task
I have implemented a custom ANT task (extending org.apache.tools.ant.Task) which uses internally the context classloader from the current thread. (looks like this)
Thread.currentThread().getContextClassLoader()
If the task is executed for example via a random main method from any java class everything just works as expected. The problem is that if I build an jar, containing this task and everything it needs and define in anothers project build.xml a for my own task... then ANT seems to use its own classloader. This results in many problems, since the ANT classloader can´t know my classes.
Is there any workaround for this? Doing things like the following has not helped: (inside execute method of my task)
Thread.currentThread()
.setContextClassLoader(AnyOwnClass.class.getClassLoader());
Is it even possible to get the "real" classloader? Any help would be nice
有关详细信息，请参阅此问题，一种可能的解决方案可能是ant-classloader任务。
I also came across this class loading issue and after trying out various things for couple of days ended up creating a new class loader and setting it as the current class loader when executing my custom task.
ClassLoader currentClazzLoader = Thread.currentThread().getContextClassLoader();
try {
ClassLoader customClazzLoader = ClasspathUtils.getUniqueClassLoaderForPath(getProject(), classpath, false);
Thread.currentThread().setContextClassLoader(customClazzLoader);
Class<?> clazz = customClazzLoader.loadClass("xxx");
....
// use reflection to instantiate/call methods
....
} catch (Exception e) {
throw new BuildException(x);
} finally {
Thread.currentThread().setContextClassLoader(currentClazzLoader);
}
My custom ant task accepted a nested 'classpath' element. This was passed as the 2nd arg to ClasspathUtils.getUniqueClassLoaderForPath method. This got rid of the below class loading problems I faced with velocity when invoked via Ant.
Caused by: java.lang.ClassNotFoundException: org.apache.velocity.tools.config.Data
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
at org.apache.commons.digester.ObjectCreateRule.begin(ObjectCreateRule.java:205)
at org.apache.commons.digester.Rule.begin(Rule.java:175)
at org.apache.commons.digester.Digester.startElement(Digester.java:1453)
... 48 more
hope this helps.
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