Spring Boot应用程序不能实例化类，除非它用Autowired进行注释

Question

public class StrategyFactory {
    private Strategy1 strategy1;
    private Strategy2 strategy2;
    private Strategy3 strategy3;

    @Autowired
    public StrategyFactory(Strategy1 strategy1) {
        this.strategy1 = strategy1;
    }

    public StrategyFactory(Strategy2 strategy2) {
        this.strategy2 = strategy2;
    }

    public StrategyFactory(Strategy3 strategy3) {
        this.strategy3 = strategy3;
    }

    public GenericStrategy getTrailerStrategy(String strategy) {
        LOGGER.info("Retrieving Strategy Class for {}", strategy);
        if (strategy.equals("CLOSE_DETAIL")) {
            return strategy1;
        } 
        else if(strategy.equals("LOAD_TRAILER")) {
            return strategy2;
        } 
        else if(strategy.equals("CLOSE_SUMMARY")) {
            return strategy3;
        } 
        else {
            throw new InvalidStrategyTypeException("Invalid Strategy Type");
        }
    }
}

如何将其他策略实例化？

Answer 1

因为只有用@autowired注释的构造函数才会得到处理并注入依赖项。Strategy2和Strategy3的构造函数被忽略，因为其上没有@Autowired。

您有两种选择：

（1）改为使用现场注入而不是施工方注入：

public class StrategyFactory {
    @Autowired
    private Strategy1 strategy1;
    @Autowired
    private Strategy2 strategy2;
    @Autowired
    private Strategy3 strategy3;

    StrategyFactory(){}
}

public class StrategyFactory {
    private List<GenericStrategy> strategy; 

    @Autowired
    public StrategyFactory(List<GenericStrategy> strategy) {
        this.strategy = strategy1;
    }

    public GenericStrategy getTrailerStrategy(String strategy) {
        LOGGER.info("Retrieving Strategy Class for {}", strategy);
        GenericStrategy result = null; 
        if (strategy.equals("CLOSE_DETAIL")) {
            result = getStrategy(Strategy1.class);
        } 
        else if(strategy.equals("LOAD_TRAILER")) {
            result = getStrategy(Strategy2.class);
        } 
        else if(strategy.equals("CLOSE_SUMMARY")) {
           result = getStrategy(Strategy3.class);
        } 
        else {
            throw new InvalidStrategyTypeException("Invalid Strategy Type");
        }

        if(result == null){
          throw new RuntimeException("Fail to load the strategy....");
        }
    }

    private <T> GenericStrategy getStrategy(Class<T> clazz){
        for(GenericStrategy s : strategy){
          if(clazz.isInstance(s)){
            return s;
          }
        }
        return null;
    }
}