code: public void render(Map<?, ?> data, OutputStream outputStream) {
  		ByteWriter byteWriter = env.engineConfig.writerBuffer.getByteWriter(outputStream);
  		try {
  			ast.exec(env, new Scope(data, env.engineConfig.sharedObjectMap), byteWriter);
  		} finally {
  			byteWriter.close();
  		}
  	}
docs: 渲染到 OutputStream 中去