ClassLoaderUtils

BootstrapLoader
ExtClassLoader
AppClassLoader（SystemClassLoader） ```java package com.javabook.classloader.utils;

import java.io.IOException; import java.net.URISyntaxException; import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.List; import java.util.Stack;

/**

@author Summer Lu
@email gmluyang@gmail.com
@date 2014-8-25 / public class ClassLoaderUtils {

/**
- @return */ public static ClassLoader getBootstrapLoader() { return getExtClassLoader().getParent(); }
  
  /**
- @return */ public static ClassLoader getExtClassLoader() { return getAppClassLoader().getParent(); }
  
  /**
- @return */ public static ClassLoader getAppClassLoader() { return ClassLoader.getSystemClassLoader(); }
  
  /**
- @return */ public static ClassLoader getThreadClassLoader() {
  
  ClassLoader classLoader = null; try {
```
 classLoader = Thread.currentThread().getContextClassLoader();
```
  } catch (Exception e) {
```
 e.printStackTrace();
```
  } return classLoader; }
  
  /**
- @return */ public static ClassLoader getCurrentClassLoader() { return ClassLoaderUtils.class.getClassLoader(); }
  
  /**
- @return */ public static ClassLoader[] getHierarchyClassLoadersDesc() {
  List hierarchyClassLoaders = new ArrayList(); getHierarchyClassLoaders(hierarchyClassLoaders, getCurrentClassLoader()); Collections.reverse(hierarchyClassLoaders); return hierarchyClassLoaders.toArray(new ClassLoader[hierarchyClassLoaders.size()]); }
  
  /**
- @param classLoaders
- @param currentClassLoader
- @return */ private static void getHierarchyClassLoaders(Collection classLoaders, ClassLoader currentClassLoader) { classLoaders.add(currentClassLoader); if(currentClassLoader!=null) {
```
 ClassLoader parentClassLoader = currentClassLoader.getParent();
 getHierarchyClassLoaders(classLoaders, parentClassLoader);
```
  } }
  
  /* */ public static void printHierarchyClassLoadersDesc() { ClassLoader[] classLoaders = getHierarchyClassLoadersDesc();
  
  StringBuffer classLoaderTree = new StringBuffer(); for (int i = 0; i < classLoaders.length; i++) {
```
 ClassLoader classLoader = classLoaders[i];

 for (int j = 0; j < i+1; j++) {
     classLoaderTree.append("-");
 }

 if(classLoader==null)
     classLoaderTree.append("null").append("\n");
 else
     classLoaderTree.append(classLoader.toString()).append("\n");
```
  }
  
  System.out.println(classLoaderTree); } }


<a name="the-console-of-the-classloaderutils"></a>
# ClassLoaderUtilsMain

- ExtClassLoader

![image.png](https://cdn.nlark.com/yuque/0/2020/png/179935/1609261112631-3ff7bac5-d7cc-4699-b554-cdffbcb05544.png#align=left&display=inline&height=349&margin=%5Bobject%20Object%5D&name=image.png&originHeight=349&originWidth=642&size=39541&status=done&style=none&width=642)
```java
package com.javabook.classloader.utils;

import java.io.IOException;
import java.net.URISyntaxException;
import java.util.*;

/**
 * @author Summer Lu
 * @email gmluyang@gmail.com
 * @date 2014-8-25
 *
 */
public class ClassLoaderUtilsMain {

    /**
     * @param args
     * @throws IOException
     * @throws URISyntaxException
     */
    public static void main(String[] args) throws IOException, URISyntaxException {

        System.out.println("BootstrapLoader:"   + ClassLoaderUtils.getBootstrapLoader());
        System.out.println("ExtClassLoader:"    + ClassLoaderUtils.getExtClassLoader());
        System.out.println("AppClassLoader:"    + ClassLoaderUtils.getAppClassLoader());

        System.out.println("----------------------------------------------------------------");

        System.out.println("\nHierarchy-ClassLoadersDesc:");
        ClassLoaderUtils.printHierarchyClassLoadersDesc();

        System.out.println("----------------------------------------------------------------");

        System.out.println("java.lang.String.class.getClassLoader():" + java.lang.String.class.getClassLoader());
        System.out.println("com.sun.java.accessibility.util.AWTEventMonitor.class.getClassLoader():" + com.sun.java.accessibility.util.AWTEventMonitor.class.getClassLoader());
        System.out.println("ClassLoaderUtilsMain.class.getClassLoader():" + ClassLoaderUtilsMain.class.getClassLoader());
        System.out.println("Thread.currentThread().getContextClassLoader():" + Thread.currentThread().getContextClassLoader());
    }
}

Console

BootstrapLoader:null
ExtClassLoader:sun.misc.Launcher$ExtClassLoader@74a14482
AppClassLoader:sun.misc.Launcher$AppClassLoader@18b4aac2
----------------------------------------------------------------

Hierarchy-ClassLoadersDesc:
-null
--sun.misc.Launcher$ExtClassLoader@74a14482
---sun.misc.Launcher$AppClassLoader@18b4aac2

----------------------------------------------------------------
java.lang.String.class.getClassLoader():null
com.sun.java.accessibility.util.AWTEventMonitor.class.getClassLoader():sun.misc.Launcher$ExtClassLoader@74a14482
ClassLoaderUtilsMain.class.getClassLoader():sun.misc.Launcher$AppClassLoader@18b4aac2
Thread.currentThread().getContextClassLoader():sun.misc.Launcher$AppClassLoader@18b4aac2

Process finished with exit code 0