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This article introduces the relevant knowledge of "what is the role of ClassLoaderFilter in dubbo". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Order

This paper mainly studies the ClassLoaderFilter of dubbo.

ClassLoaderFilter

Dubbo-2.7.2/dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/filter/ClassLoaderFilter.java

@ Activate (group = CommonConstants.PROVIDER, order =-30000) public class ClassLoaderFilter implements Filter {@ Override public Result invoke (Invoker invoker, Invocation invocation) throws RpcException {ClassLoader ocl = Thread.currentThread (). GetContextClassLoader (); Thread.currentThread (). SetContextClassLoader (invoker.getInterface (). GetClassLoader ()); try {return invoker.invoke (invocation);} finally {Thread.currentThread (). SetContextClassLoader (ocl);}

ClassLoaderFilter implements the Filter interface. Its invoke method first gets the contextClassLoader of the current thread, then sets its ContextClassLoader to invoker.getInterface (). GetClassLoader (), then executes the invoker.invoke method, and finally resets the classLoader of the current thread to the original contextClassLoader

Example

Dubbo-2.7.2/dubbo-rpc/dubbo-rpc-api/src/test/java/org/apache/dubbo/rpc/filter/ClassLoaderFilterTest.java

Public class ClassLoaderFilterTest {private ClassLoaderFilter classLoaderFilter = new ClassLoaderFilter (); @ Test public void testInvoke () throws Exception {URL url = URL.valueOf ("test://test:11/test?accesslog=true&group=dubbo&version=1.1"); String path = DemoService.class.getResource ("/") .getPath () Final URLClassLoader cl = new URLClassLoader (new java.net.URL [] {new java.net.URL ("file:" + path)}) {@ Override public Class loadClass (String name) throws ClassNotFoundException {try {return findClass (name);} catch (ClassNotFoundException e) {return super.loadClass (name) }; final Class clazz = cl.loadClass (DemoService.class.getCanonicalName ()); Invoker invoker = new MyInvoker (url) {@ Override public Class getInterface () {return clazz } @ Override public Result invoke (Invocation invocation) throws RpcException {Assertions.assertEquals (cl, Thread.currentThread (). GetContextClassLoader ()); return null;}}; Invocation invocation = Mockito.mock (Invocation.class); classLoaderFilter.invoke (invoker, invocation);}}

Here, the interface of invoker is set to DemoService.class, and then verify that Thread.currentThread (). GetContextClassLoader () in the invoke method is the URLClassLoader that loads DemoService.class

Summary

ClassLoaderFilter implements the Filter interface. Its invoke method first gets the contextClassLoader of the current thread, then sets its ContextClassLoader to invoker.getInterface (). GetClassLoader (), then executes the invoker.invoke method, and finally resets the classLoader of the current thread to the original contextClassLoader

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