java logstash自定义输出控件 参数问题

如下图所示 ， 我在这定义了 HOSTNAME  和 PORT 两个参数
​

@LogstashPlugin(name = "java_output_example")

public class JavaOutputExample implements Output {



    public static final PluginConfigSpec<String> PREFIX_CONFIG =

            PluginConfigSpec.stringSetting("prefix", "");



    public static final PluginConfigSpec<String> HOSTNAME =

            PluginConfigSpec.stringSetting("hostname", "192.168.43.17");



    public static final PluginConfigSpec<String> PORT =

            PluginConfigSpec.stringSetting("port", "26666");



    private final String id;

    private String prefix;

    private PrintStream printer;

    private final CountDownLatch done = new CountDownLatch(1);

    private volatile boolean stopped = false;



    // 定义转发参数

    private String hostname;

    private String port;

    private TcpClient tcpClient;





    // all plugins must provide a constructor that accepts id, Configuration, and Context

    public JavaOutputExample(final String id, final Configuration configuration, final Context context) {

        this(id, configuration, context, null);

    }



    JavaOutputExample(final String id, final Configuration config, final Context context, OutputStream targetStream) {

        // constructors should validate configuration options

        this.id = id;

        prefix = config.get(PREFIX_CONFIG);

        // 初始化相应参数

        hostname = config.get(HOSTNAME);

        port = config.get(PORT);

        tcpClient = new TcpClient(hostname, Integer.valueOf(port));

        tcpClient.connect();

    }

然后 ，我在使用控件的时候


 
但是在验证过程中，出现


 
这个是什么原因呢。。求各位大佬解答