Java class Loader

Function: Gets the binary byte stream that describes this class by naming the permission of the class

Each class in the JVM is determined by its class loader and the class itself, and the different classloader have separate namespaces, and the same class is different in different classloader.

Classification: Can be divided into three main categories:

1. Start the class loader (Bootstrap ClassLoader)

Implemented by C + +, is part of the JVM and is used to load class libraries that can be recognized by the JVM into the JVM's memory in Java_home/lib;

2. Extension class loader (extention ClassLoader)

Used to load the class library under the Java_home/lib/ext directory, which can be used directly by the developer;

3. Application class loader (application ClassLoader)

The class library used to load the user classpath (specified by Classpath), which can be used directly by the developer and, by default, if it is not specified by its own class loader;

ClassLoader's Parent delegation Model:

If a classloader receives a class load request, ClassLoader does not load the class itself, but instead delegates the request to the parent class ClassLoader to complete.

Eventually, all class load requests are routed to Bootstrap ClassLoader. Only if the parent loader is unable to complete the load request (as found in the search scope)

Specified class), the child loader will not load itself.

Java class Loader