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147 lines (122 loc) · 5.48 KB
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package classloader;
import sun.misc.Launcher;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
/**
* Created by Jay on 5/4/17.
*/
public class HelloClassLoader {
public static void main(String[] args) throws ClassNotFoundException {
// URL[] urls = Launcher.getBootstrapClassPath().getURLs();
// for (int i = 0; i < urls.length; i++) {
// System.out.println(urls[i].toExternalForm());
// }
// loadExtLibClass();
// loadClass();
// mock String class
// mockStringClass();
// fileSystemClassLoader, load ~/Desktop/LocalClassCopy , print()
// loadFileSystemClass();
// different classloader will load different class
// loadClassByDifferentLoader();
// load Network class. load http://localhost/java/classloader/NetworkClass.class, it's under /Library/WebServer/Documents directory
loadNetworkClass();
}
private static void loadNetworkClass() throws ClassNotFoundException {
String className = "classloader.NetworkClass";
NetworkClassLoader networkClassLoader = new NetworkClassLoader();
Class<?> clazz = networkClassLoader.loadClass(className);
Method printMethod = null;
try {
printMethod = clazz.getDeclaredMethod("print", null);
printMethod.invoke(clazz.newInstance());
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
private static void loadFileSystemClass() throws ClassNotFoundException {
String className = "classloader.LocalClassCopy";
FileSystemClassLoader fileSystemClassLoader = new FileSystemClassLoader();
Class<?> clazz = fileSystemClassLoader.loadClass(className);
try {
Method printMethod = clazz.getDeclaredMethod("print", null);
printMethod.invoke(clazz.newInstance(), null);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
private static void loadClassByDifferentLoader() throws ClassNotFoundException {
FileSystemClassLoader classLoader1 = new FileSystemClassLoader();
FileSystemClassLoader classLoader2 = new FileSystemClassLoader();
Class clazz1 = classLoader1.loadClass("classloader.LocalClass");
Class clazz2 = classLoader2.loadClass("classloader.LocalClass");
// System.out.println(ClassLoader.getSystemClassLoader()); // AppClassLoader
System.out.println(clazz1.getClassLoader()); // FileSystemClassLoader
System.out.println(clazz2.getClassLoader()); // FileSystemClassLoader
try {
Object object1 = clazz1.newInstance();
Method printMethod = clazz1.getDeclaredMethod("print", null);
printMethod.invoke(object1);
Method setInstanceMethod = clazz1.getMethod("setInstance", Object.class);
Object object2 = clazz2.newInstance();
setInstanceMethod.invoke(object1, object2);
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
private static void mockStringClass() throws ClassNotFoundException {
Class<?> stringClass = Class.forName("java.lang.String");
try {
Method printNameMethod = stringClass.getMethod("printName", null); // NoSuchMethodException
System.out.printf("printNameMethod = %s", (printNameMethod == null));
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
}
private static void loadClass() throws ClassNotFoundException {
ClassLoader appClassLoader = ClassLoader.getSystemClassLoader();
Class<?> clazz1 = appClassLoader.loadClass("classloader.MusicPlayer");
System.out.println(clazz1.getClassLoader());
Class<?> clazz2 = Class.forName("classloader.MusicPlayer2");
ClassLoader classLoader = clazz2.getClassLoader();
System.out.println(classLoader);
Class<?> clazz3 = Class.forName("java.lang.String");
System.out.println(clazz3.getClassLoader());
Class<?> clazz4 = new NetworkClassLoader().loadClass("java.lang.String");
System.out.println(clazz4.getClassLoader());
}
private static void loadExtLibClass() {
// mv MusicPlayer.jar into jre/lib/ext/
ClassLoader classLoader = new NetworkClassLoader();
classLoader = classLoader.getParent().getParent(); // ExtClassLoader
System.out.println(classLoader);
try {
classLoader.loadClass("classloader.MusicPlayer"); // this is in jre/lib/ext/
classLoader.loadClass("classloader.MusicPlayer2");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
}