arthas/arthas-tutorials-en/command/classloader/classloader.md

The following describes the usage of the classloader{{}} command.

First visit the jsp page: visite hello jsp page

List all ClassLoaders

classloader -l{{exec}}

Statistics ClassLoader actually used URLs and unused URLs

classloader --url-stat{{exec}}

Note: Statistics are based on all classes currently loaded by the JVM. Does not mean that Unused URLs can be removed from the application. Because it may be necessary to load classes from Unused URLs in the future, or to load resources.

List all classes loaded in ClassLoader

List all classes loaded by org.apache.jasper.servlet.JasperLoader{{}} :

classloader -a --classLoaderClass org.apache.jasper.servlet.JasperLoader | grep hello{{exec}}

Check the structure of classloader

sc -d org.apache.jsp.jsp.hello_jsp{{execute T2}}

View the ClassLoader tree

classloader -t{{execute T2}}

Show the URLs of the URLClassLoader

For example, if you have found that the LaunchedURLClassLoader for Spring is org.springframework.boot.loader.LaunchedURLClassLoader{{}} , you can use the -c <hashcode>{{}} parameter to specify the class loader. Alternatively, you can use the --classLoaderClass{{}} option to specify the class name and view the actual URLs of the URLClassLoader.

classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader{{exec}}

Load the resource file in the specified ClassLoader

Load the specified resource file: classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader -r logback-spring.xml{{exec}}

Use the classloader to load .class resource

classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader -r java/lang/String.class{{exec}}