我正在使用 spring 实现策略模式,要加载正确的策略实现,请遵循以下示例:
public class ShippingServiceImpl implements ShippingService {
// Map of strategies
private Map<ShippingType,ShippingCostStrategy> shippingCostStrategies;
@Required
public void setShippingCostStrategies(Map<ShippingType,ShippingCostStrategy> strategies) {
this.shippingCostStrategies = strategies;
}
@Override
public BigDecimal calculateShippingCost(ShoppingCart cart) {
return shippingCostStrategies.get(cart.getShippingType()).shippingCost(cart);
}
// ...other business logic...
}
加载此策略地图的最佳方式是什么?我想要一个加载地图并传递给setShippingCostStrategies的特定方法?我可以使用弹簧注释来做到这一点吗?因为在此示例中,作者使用配置来执行此操作:
<bean id="shippingService" class="it.nicus.springstrategy.ShippingServiceImpl">
<property name="shippingCostStrategies">
<map>
<entry>
<key><util:constant static- field="it.nicus.springstrategy.ShippingType.NORMAL"/></key>
<bean class="it.nicus.springstrategy.PerItemCostStrategyImpl">
<property name="baseCost" value="5.00"/>
<property name="costPerItem" value="2.00"/>
</bean>
</entry>
<entry>
<key><util:constant static- field="it.nicus.springstrategy.ShippingType.PRIME"/></key>
<bean class="it.nicus.springstrategy.FixedCostStrategyImpl">
<property name="fixedCost" value="3.00" />
</bean>
</entry>
</map>
</property>
</bean>
您可以使用
<util:map>
标记将map
注册为 Bean,然后使用@Resource
注释自动连接该映射。
<util:map id="strategyMap">
<entry>
<key>
<util:constant static-field="it.nicus.springstrategy.ShippingType.NORMAL" />
</key>
<bean class="it.nicus.springstrategy.PerItemCostStrategyImpl">
<property name="baseCost" value="5.00" />
<property name="costPerItem" value="2.00" />
</bean>
</entry>
<entry>
<key>
<util:constant static-field="it.nicus.springstrategy.ShippingType.PRIME" />
</key>
<bean class="it.nicus.springstrategy.FixedCostStrategyImpl">
<property name="fixedCost" value="3.00" />
</bean>
</entry>
</util:map>
然后,在课堂ShippingServiceImpl
,像这样注入它:
public class ShippingServiceImpl implements ShippingService {
// Map of strategies
@Resource(name="strategyMap")
private Map<ShippingType,ShippingCostStrategy> shippingCostStrategies;
}