1、自定义ClassLoader代码如下：
package zmx.classloader.test;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.HashSet;
/*
* 实现热部署，自定义ClassLoader，加载的是.class
*/
public class CustomClassLoader extends ClassLoader {
private String basedir; // 需要该类加载器直接加载的类文件的基目录
private HashSet<String> dynaclazns; // 需要由该类加载器直接加载的类名
public CustomClassLoader(String basedir, String[] clazns) {
super(null); // 指定父类加载器为 null
this.basedir = basedir;
dynaclazns = new HashSet<>();
loadClassByMe(clazns);
}
private void loadClassByMe(String[] clazns) {
for (int i = 0; i < clazns.length; i++) {
loadDirectly(clazns[i]);
dynaclazns.add(clazns[i]);
}
}
private Class loadDirectly(String name) {
Class cls = null;
StringBuffer sb = new StringBuffer(basedir);
String classname = name.replace('.', File.separatorChar) + ".class";
sb.append(File.separator + classname);
File classF = new File(sb.toString());
try {
cls = instantiateClass(name, new FileInputStream(classF),classF.length());
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return cls;
}
private Class instantiateClass(String name, InputStream fin, long len) {
byte[] raw = new byte[(int) len];
try {
fin.read(raw);
fin.close();
} catch (IOException e) {
e.printStackTrace();
}
return defineClass(name, raw, 0, raw.length);
}
protected Class loadClass(String name, boolean resolve)
throws ClassNotFoundException {
Class cls = null;
cls = findLoadedClass(name);
if (!this.dynaclazns.contains(name) && cls == null)
cls = getSystemClassLoader().loadClass(name);
if (cls == null)
throw new ClassNotFoundException(name);
if (resolve)
resolveClass(cls);
return cls;
}
}
/*
* 每隔500ms运行一次，不断加载class
*/
class Multirun implements Runnable {
public void run() {
try {
while (true) {
// 每次都创建出一个新的类加载器
// class需要放在自己package名字的文件夹下
String url = System.getProperty("user.dir") + "/WebRoot/WEB-INF/classes"; // "D:/projects/testWeb/WebRoot/WEB-INF/classes/zmx/classloader/test/DynamicClass.class";
CustomClassLoader cl = new CustomClassLoader(url, new String[] { "zmx.classloader.test.DynamicClass" });
Class cls = cl.loadClass("zmx.classloader.test.DynamicClass");
Object foo = cls.newInstance();
// 被调用函数的参数
Method m = foo.getClass().getMethod("Output", new Class[] {});
m.invoke(foo, new Object[] {});
Thread.sleep(500);
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
package zmx.classloader
