自定义classloader实现JAVA热替换
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 {
//这个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);//This method is very important
if (null == clazz) {//If in this class loader If you can't find this class, you can't really find it
}
} catch (Exception e) {
e.printStackTrace();
}
return clazz;
}
/**
* Convert the CLASS file to BYTE
*
* @throws Exception
*/
private byte[] getClassFileBytes(File file) throws Exception {
//Use NIO to read
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();
}
}
Customize classloader to realize JAVA hot replacement
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