Sensor

The Sensor interface represents sensor entities in Home Assistant. When you define a field of type Sensor in your SmartBean class and annotate it with @Entity, the framework automatically injects an object that lets you control the corresponding entity in Home Assistant.

@Entity("sensor.temperature_bathroom")
private Sensor temperature;

State

The sensor's state in Home Assistant is represented by a String. The Sensor interface provides convenience methods to retrieve the state in commonly used datatypes for easier handling. You can query the sensor's current state using these methods:

Method	Description
getState()	Get the current state of the sensor as String including unit of measurement.
getStateAsString()	Returns the original state from the Home Assistant entity.
asInteger()	Returns the state as Integer, returns null, if current state cannot be parsed to an integer, for example if it's unavailable
asInt(int)	Returns the state as int, returns the provided default value, if current state cannot be parsed to an integer, for example if it's unavailable
asDouble()	Returns the state as Double, returns null, if current state cannot be parsed to a double, for example if it's unavailable
asDouble(double)	Returns the state as double, returns the provided default value, if current state cannot be parsed to a double, for example if it's unavailable

Attributes

The following attributes of a sensor entity can be accessed through simple getter methods:

HA attribute	Method	Description
friendly_name	getFriendlyName()	Friendly name of the entity.
icon	getIcon()	Icon of the entity.
unit_of_measurement	getUnitOfMeasurement()	Unit of measurement of the sensors's value.
device_class	getDeviceClass()	Device class of the sensor.
state_class	getStateClass()	State class of the sensor.
options	getOptions()	List of available options of the sensor, provided if sensor has a enum-like state.

You can access any additional attributes that are not directly supported through the getAttributes() method.

Example

public class ASampleBean implements SmartBean {
  
  private SmartBeans sb;

  @Entity("sensor.bathroom_temperature")
  private Sensor temperature;

  public void someBeanMethod() {
    if(temperature.asInt(0) < 15) {
      sb.log("Bathroom is too cold! It's only " + temperature.getState());
    }
  }
}

Access Entities Programmatically

In addition to the annotation-based approach, you can programmatically access sensors using the getSensor() method of the SmartBeans API. You might prefer this programmatic approach over annotations for example when the entity ID is dynamically generated through business logic and cannot be determined at compile time.

public class ASampleBean implements SmartBean {

  private SmartBeans sb;

  public void someBeanMethod() {
    Sensor sensor = sb.getSensor("sensor.temperature_outside");
    if(sensor.asDouble(0d) > 20) {
      sb.log("Outside temperature is above 20" + sensor.getUnitOfMeasurement());
    }
  }
}

note

For improved efficiency, it is recommended to cache entity objects as member variables rather than retrieving them repeatedly. Since the state and attributes of entity objects are cached internally, no additional backend communication is required for multiple state retrievals. Note that initial entity object creation always requires at least one request to the Home Assistant backend.