[spring] class 繼承關係的 xml 設定

當 class 有繼承關係時，像是 Bus 及 Trunk 皆為 Vehicle。

public class Vehicle {
    protected String type = "vehicle"; 
    
    public void printType() {
        System.out.println("This is a " + type + ".");
    }
}

public class Bus extends Vehicle {
     public Bus() {
         type = "bus";
     }
}

public class Trunk extends Vehicle {
    public Trunk() {
        type = "trunk";
    }
}

Spring 的 xml 寫法為

<bean id="vehicle" class="example.Vehicle" />
<bean id="bus" class="example.Bus" parent="vehicle" />
<bean id="trunk" class="example.Trunk" parent="vehicle" />