无法在KIE工作台（jBPM）中添加Java导入

Question

我是jBPM的新手。 我正在使用jBPM KIE工作台。 如第二图中所示，我在KIE外部数据对象部分中添加了必要的导入。 为什么会出现错误？ 我还需要对导入做其他事情吗？

我收到以下错误消息：

[KBase: defaultKieBase]: Process Compilation error URL cannot be resolved to a type
URL cannot be resolved to a type
HttpURLConnection cannot be resolved to a type
HttpURLConnection cannot be resolved to a type
BufferedReader cannot be resolved to a type
BufferedReader cannot be resolved to a type
InputStreamReader cannot be resolved to a type

Java代码：

    try {
        URL url = new URL("http://localhost:8080/users");
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("GET");
        con.setRequestProperty("Content-Type", "application/json");

        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer content = new StringBuffer();

        while ((inputLine = in.readLine()) != null) {
            content.append(inputLine);
        }

        in.close();

        System.out.println(content);
    }

    catch(Exception e){
        throw new RuntimeException(e);
    }