java – 从像pojo或singleton这样的非组件类中读取application.properties

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我正在使用弹簧靴和对于属性我已将application.properties放在src / main / resources中

来自@Controllers& @Services,我能够读取属性,但是从我的模型pojo&单身类,我无法读取值.

我的@SpringBootApplication在com.vehicle&我没有覆盖@ComponentScan,所以我相信它应该读取所??有底层包.

以下是代码：

application.properties

vehicle.lift.maxWeight=10
vehicle.lift.error.overWeight=Overweight

vehicle.battery.default=5.0
vehicle.battery.critical.limit=15
vehicle.walk.distance.error=Not able to move

WalkServiceImpl.java(能从这里读取)

package com.vehicle.prototype.service.impl;

@Service
public class WalkServiceImpl implements CapabilityService {

    @Value("${vehicle.walk.distance.error}")
    private String mDistanceError;

    @Override
    public void performTask(VehicleData vehicleData) {
        double distance = vehicleData.getWalkingDistance();
        double remainingBattery = vehicleData.getRemainingBattery();

        if (remainingBattery < distance) {
            vehicleData.setErrorMessage(mDistanceError);
            System.out.println(mDistanceError);
        } else {
            vehicleData.setRemainingBattery(remainingBattery - distance);
        }

        VehicleUtil.checkBatteryStatus(vehicleData);

    }

}

VehicleData.java(Pojo – 无法从这里读取)

package com.vehicle.prototype.model;

public class VehicleData {

    private double walkingDistance;
    private double liftWeight;

    @Value("${vehicle.battery.default}")
    private double remainingBattery;

    // setters & getters ....

}

VehicleUtil.java(Singleton – 无法从这里读取)

package com.vehicle.prototype.utils;

public class VehicleUtil {

    private static VehicleUtil mInstance = null;
    private static Object mLock = new Object();

    @Value("${vehicle.battery.critical.limit}")
    private static double mCriticalLimit;

    @Value("${vehicle.battery.default}")
    private static double mTotalPower;

    @Value("${vehicle.battery.critical.warning}")
    private static String powerWarning;


    private VehicleUtil() {
        // empty private constructor.
    }

    public static VehicleUtil getInstance() {
        if (mInstance == null) {
            synchronized (mLock) {
                if (mInstance == null)
                    mInstance = new VehicleUtil();
            }
        }
        return mInstance;
    }

    public static void checkBatteryStatus(VehicleData vehicleData) {
        double criticalMark = (mCriticalLimit * 100.0f) / mTotalPower;
        if (vehicleData.getRemainingBattery() < criticalMark) {
            vehicleData.setBatteryCritical(Boolean.TRUE);
            System.out.println(powerWarning);
        } else {
            vehicleData.setBatteryCritical(Boolean.FALSE);
        }
    }

}

请让我知道如何解决这个问题.

谢谢

解决方法:

您需要将属性注入spring-managed bean.
你可以做的是将属性捆绑在这样的bean中(see documentation)

@ConfigurationProperties(prefix="vehicle")
public class VehicleProperties {
    @Value("${battery.critical.limit}")
    private double mCriticalLimit;

    @Value("${battery.default}")
    private double mTotalPower;

    @Value("${battery.critical.warning}")
    private String powerWarning;
}

然后,将Vehicle Properties注入您的服务并将它们传递给VehicleUtil：

public class WalkServiceImpl {
    @Autowired
    private VehicleProperties vehicleProperties;

    @Override
    public void performTask(VehicleData vehicleData) {
        ...
        VehicleUtil.checkBatteryStatus(vehicleProperties, vehicleData);
    }
}

更好的是,我会将VehicleUtil转换为托管bean

@Component
public class VehicleUtil {
    @Autowired
    private VehicleProperties vehicleProperties;
}

VehicleData

我假设VehicleData是一些业务对象,从客户端传递或者你自己创建的,它们是很多实例(不只是一个单例).在这种情况下,将VehicleData转换为托管bean是没有意义的,它的外部依赖关系可以通过它的setter提供给它：

public class VehicleData {
    private double walkingDistance;
    private double liftWeight;
    private double remainingBattery;
    // setters & getters ....
}

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