使用枚举类实现策略模式

一、类结构图

image.png

二、抽象类ExecutorRouter

public abstract class ExecutorRouter {
    protected static Logger logger = LoggerFactory.getLogger(ExecutorRouter.class);

    /**
     * route address
     *
     * @param addressList
     * @return  ReturnT.content=address
     */
    public abstract ReturnT<String> route(TriggerParam triggerParam, List<String> addressList);

}

三、具体的实现类（略）
。。。。。。。

四、枚举

public enum ExecutorRouteStrategyEnum {

    FIRST(I18nUtil.getString("jobconf_route_first"), new ExecutorRouteFirst()),
    LAST(I18nUtil.getString("jobconf_route_last"), new ExecutorRouteLast()),
    ROUND(I18nUtil.getString("jobconf_route_round"), new ExecutorRouteRound()),
    RANDOM(I18nUtil.getString("jobconf_route_random"), new ExecutorRouteRandom()),
    CONSISTENT_HASH(I18nUtil.getString("jobconf_route_consistenthash"), new ExecutorRouteConsistentHash()),
    LEAST_FREQUENTLY_USED(I18nUtil.getString("jobconf_route_lfu"), new ExecutorRouteLFU()),
    LEAST_RECENTLY_USED(I18nUtil.getString("jobconf_route_lru"), new ExecutorRouteLRU()),
    FAILOVER(I18nUtil.getString("jobconf_route_failover"), new ExecutorRouteFailover()),
    BUSYOVER(I18nUtil.getString("jobconf_route_busyover"), new ExecutorRouteBusyover()),
    SHARDING_BROADCAST(I18nUtil.getString("jobconf_route_shard"), null);

// 抽象类ExecutorRouter，具体的实现类直接new（见上），因为是枚举，保证了单实例。
    ExecutorRouteStrategyEnum(String title, ExecutorRouter router) {
        this.title = title;
        this.router = router;
    }

    private String title;
    private ExecutorRouter router;

    public String getTitle() {
        return title;
    }
    public ExecutorRouter getRouter() {
        return router;
    }

// 未匹配上，则返回默认的策略defaultItem
    public static ExecutorRouteStrategyEnum match(String name, ExecutorRouteStrategyEnum defaultItem){
        if (name != null) {
            for (ExecutorRouteStrategyEnum item: ExecutorRouteStrategyEnum.values()) {
                if (item.name().equals(name)) {
                    return item;
                }
            }
        }
        return defaultItem;
    }

}

五、具体的使用示例

        ExecutorRouteStrategyEnum executorRouteStrategyEnum = ExecutorRouteStrategyEnum.match(jobInfo.getExecutorRouteStrategy(), null);    // route strategy