Java class loading and custom class loader

Class loading

All class loaders are subclasses of classloader.

Class loaders always start with Class runs in the directory.

There are several ways to read files in the root directory of classpath:

1 in the Java project, you can obtain the files under classspath in the following ways:

In tomcat, Tomcat declares two class loaders:

Standardclassloaderc loading Tomcat / lib / * jar - serlvetapi. jar

Webappclassloader / load Tomcat / webapps / project / Web inf / lib / * jar && web-inf/classes/*. class

In any project, the loader that gets the class should use the following methods:

Someclass (you wrote it) class. getClassLoader(). getResource ； Get the class loader for this class

In the Java project: appclassloader

In a web project: webappclassloader

Test parent loader:

Results of operation:

Custom class loader

Class A is loaded by which class loader JDK reads the bytecode of class A.

Whether a class with the same name can be converted to each other depends on whether it is in the same class loader.

Test class custom class loader

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