Null Pointer Exception with addEventListener on Spring Boot

[ierturk]

I get the message along with addEventListener

This is a bug, passed the ownership test above: NRSerialPort

java.lang.NullPointerException at gnu.io.NRSerialPort.addEventListener(NRSerialPort.java:212) at org.erturk.online.serial.milkmeter.CommMM.Init(CommMM.java:70) at org.ieee.ierturk.interfarm.CustomConfig.onApplicationEvent(CustomConfig.java:36) at org.ieee.ierturk.interfarm.CustomConfig.onApplicationEvent(CustomConfig.java:23) at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:167) at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:393) at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:347) at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:883) at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.finishRefresh(EmbeddedWebApplicationContext.java:144) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546) at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:693) at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:360) at org.springframework.boot.SpringApplication.run(SpringApplication.java:303) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1118) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1107) at org.ieee.ierturk.interfarm.InterFarmApp.main(InterFarmApp.java:26) This is a bug, passed the ownership test above: NRSerialPort

[xxxxvelocityxxxx]

I'm also getting this when I try to add an event listener. My code is

 NRSerialPort serial;                 
 port = "COM5";
 baudRate = 38400;  
 serial = new NRSerialPort(port, baudRate);
 try {
    serial.addEventListener(new SerialPortEventListener() {
    @Override
    public void serialEvent(SerialPortEvent arg0) {
        System.out.println(arg0.getEventType());
    }
    });
} catch (TooManyListenersException e) {
    e.printStackTrace();
}

and it gives me

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at gnu.io.NRSerialPort.addEventListener(NRSerialPort.java:212)
    at station12.SerialCommunicate.<init>(SerialCommunicate.java:50)
    at station12.Station12Main.<init>(Station12Main.java:65)
    at station12.Station12Main.createAndShowGui(Station12Main.java:176)
    at station12.Station12Main.lambda$0(Station12Main.java:194)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

on the addEventListener line

[MrDOS]

There's no API documentation to make it clear, but you have to call connect() on the NRSerialPort instance before you can do just about anything else with it. (NRSerialPort.java:212 tries to use the serial instance variable which is set by connect().)

Try this:

 NRSerialPort serial;
 port = "COM5";
 baudRate = 38400;
 serial = new NRSerialPort(port, baudRate);
+serial.connect();
 try {
     serial.addEventListener(new SerialPortEventListener() {
         @Override
         public void serialEvent(SerialPortEvent arg0) {
             System.out.println(arg0.getEventType());
         }
     });
 } catch (TooManyListenersException e) {
     e.printStackTrace();
 }

[xxxxvelocityxxxx]

Thanks. That fixed it. Would you happen to know how I can detect if a com port becomes unavailable? I am checking for COM5, which is my arduino, and if I start my program with it disconnected, then connect it I am able to detect it, but when I disconnect the USB cable NRSerialPort.getAvailableSerialPorts() still tells me COM5 is available and I'm not getting any events or anything really to indicate it has been disconnected.

[madhephaestus]

usage issue