自定義classloader實現JAVA熱替換

[url=https://blog.csdn.net/puhaiyang/article/details/78165465]自定義classloader實現JAVA熱替換[/url]

public class HotClassLoader extends ClassLoader {

public HotClassLoader() {
super(ClassLoader.getSystemClassLoader());
}

private File objFile;

public File getObjFile() {
return objFile;
}

public void setObjFile(File objFile) {
this.objFile = objFile;
}

@Override
protected Class<?> findClass(String name) throws ClassNotFoundException {
//這個classLoader的主要方法
System.out.println("findClassfindClassfindClassfindClass");
Class clazz = null;
try {
byte[] data = getClassFileBytes(getObjFile());
clazz = defineClass(name, data, 0, data.length);//這個方法非常重要
if (null == clazz) {//如果在這個類加載器中都不能找到這個類的話，就真的找不到了

}
} catch (Exception e) {
e.printStackTrace();
}
return clazz;

}

/**
* 把CLASS文件轉成BYTE
*
* @throws Exception
*/
private byte[] getClassFileBytes(File file) throws Exception {
//採用NIO讀取
FileInputStream fis = new FileInputStream(file);
FileChannel fileC = fis.getChannel();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
WritableByteChannel outC = Channels.newChannel(baos);
ByteBuffer buffer = ByteBuffer.allocateDirect(1024);
while (true) {
int i = fileC.read(buffer);
if (i == 0 || i == -1) {
break;
}
buffer.flip();
outC.write(buffer);
buffer.clear();
}
fis.close();
return baos.toByteArray();
}

}