I am trying to build a REST Controller using Spring. To format the data for readability and more integration, I have used Mapstruct. Here's how I wrote Mapper.
@Mapper
public abstract class DeviceDataMapper {
@Autowired
DeviceService deviceService;
public static DeviceDataMapper INSTANCE = Mappers.getMapper(DeviceDataMapper.class);
@Mappings({
@Mapping(source = "deviceId", target = "iddevice"),
@Mapping(source = "deviceName", target = "name")
})
public abstract TODevice deviceToTODevice(DeviceData device);
public DeviceData toDeviceToDeviceData(TODevice toDevice){
DeviceData deviceData = new DeviceData();
deviceData.setDeviceId(toDevice.getIddevice());
deviceData.setDeviceName(toDevice.getName());
deviceData.setDeviceTemplateId(toDevice.getDeviceTemplateId());
try {
deviceData.setDeviceTemplateName(deviceService.findDeviceTemplateById(toDevice.getDeviceTemplateId()).getName());
} catch (Exception e) {
e.printStackTrace();
}
return deviceData;
}}
The API Controller function looks like this
@RequestMapping(value = "/{deviceId}",method = RequestMethod.GET)
public @ResponseBody DeviceData get(@PathVariable int deviceId) {
DeviceData deviceData=new DeviceData();
try {
deviceData = DeviceDataMapper.INSTANCE.toDeviceToDevice(deviceService.findOne(deviceId));
} catch (Exception e) {
e.printStackTrace();
}
return deviceData;
}
The output deviceData returns fine except for one detail. I couldn't get to this function deviceService.findDeviceTemplateById(toDevice.getDeviceTemplateId()
(where deviceService is autowired). The error stack trace shows me NullPointerException. So I am wondering whether is there any general rule about the accessibility of the autowired resources in abstract class? Or is the way I am instantiating that makes this function inaccessible? What should I change to make it work? I have also tried with @Inject
from javax.inject
with same result.
You could use Spring as the component model for the mapper:
@Mapper(componentModel="spring")
public abstract class DeviceDataMapper {
...
}
That way you can inject dependencies into it (e.g. other hand-written it uses) as well as inject the mapper into other classes instead of resorting to the INSTANCE
pattern.