自定义类加载器
public class MyClassLoader extends ClassLoader {
@Override
protected Class findClass(String name) throws ClassNotFoundException {
try {
// 文件名称
String fileName = name.substring(name.lastIndexOf(".") + 1) + ".class";
// 获取文件输入流
InputStream is = this.getClass().getResourceAsStream(fileName);
// 读取字节
byte[] b = new byte[is.available()];
is.read(b);
// 将byte字节流解析成jvm能够识别的Class对象
return defineClass(name, b, 0, b.length);
} catch (Exception e) {
throw new ClassNotFoundException();
}
}
}
更新类代码
public class Hotswap {
public static void main(String[] args)
throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException,
SecurityException, IllegalArgumentException, InvocationTargetException, InterruptedException {
loadUser();
System.gc();
Thread.sleep(1000);// 等待资源回收
// 需要被热部署的class文件
File file1 = new File("F:\\test\\User.class");
// 之前编译好的class文件
File file2 = new File(
"F:\\itmayiedujiangke2018-02-24\\itmayiedu_itmayiedu_day_17\\target\\classes\\com\\itmayiedu\\User.class");
boolean isDelete = file2.delete();// 删除旧版本的class文件
if (!isDelete) {
System.out.println("热部署失败.");
return;
}
file1.renameTo(file2);
System.out.println("update success!");
loadUser();
}
public static void loadUser() throws ClassNotFoundException, InstantiationException, IllegalAccessException,
NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {
MyClassLoader myLoader = new MyClassLoader();
Class class1 = myLoader.findClass("com.itmayiedu.User");
Object obj1 = class1.newInstance();
Method method = class1.getMethod("add");
method.invoke(obj1);
System.out.println(obj1.getClass());
System.out.println(obj1.getClass().getClassLoader());
}
}
