如何解决“ java.lang.NullPointerException”？

Question

我想将输出存储在变量端口s，s1中，然后在日志信息中的application.properties文件中使用它

logging.pattern.console =％d {yyyy-MM-dd HH：mm：ss.SSS} ----％msg％n

我不断收到nullpointerexception错误 @SpringBootApplication 公共类RegistrationFormApplication / *实现ApplicationListener * / {

static ServletWebServerInitializedEvent embeddedServletContainerInitializedEvent;
static {
    embeddedServletContainerInitializedEvent = null;
}

static Logger logger = LogManager.getLogger(RegistrationFormApplication.class);

public static void main(String[] args) {
    int port = embeddedServletContainerInitializedEvent.getApplicationContext().getWebServer().getPort();

// logger.info（端口）;         System.out.println（                 “ Port” + EmbeddedServletContainerInitializedEvent.getApplicationContext（）。getWebServer（）。getPort（））;

    try {
        String s = InetAddress.getLocalHost().getHostAddress();
        System.out.println("HOST Address " + InetAddress.getLocalHost().getHostAddress());
        String s1 = InetAddress.getLocalHost().getHostName();
        System.out.println("Host Name " + InetAddress.getLocalHost().getHostName());
    } catch (UnknownHostException e) {
    }
    SpringApplication.run(RegistrationFormApplication.class, args);
}

}