在spring boot rest api控制器中调用singleton类

Question

我是spring Framework的新手。我必须使用Spring引导和Rest控制器如下：-

@RestController
public class StatisticsController {

    private TransactionCache transactionCache;

    public StatisticsController(TransactionCache transactionCache) {
        this.transactionCache = transactionCache;
    }

    @PostMapping("/tick")
    public ResponseEntity<Object> addInstrumentTransaction(@Valid @RequestBody InstrumentTransaction instrumentTransaction) {
        transactionCache.addTransaction(instrumentTransaction);
        return new ResponseEntity<>(HttpStatus.CREATED);
    }

我有一门课必须是单人的：-

@Component
public class TransactionStatisticsCacheImpl implements TransactionCache {

    private static TransactionStatisticsCacheImpl instance;

    public static TransactionStatisticsCacheImpl getInstance(){

        if(Objects.isNull(instance)){
            synchronized (TransactionStatisticsCacheImpl.class) {
                if(Objects.isNull(instance)){
                    instance = new TransactionStatisticsCacheImpl();
                }
            }
        }

        return instance;
    }

    private TransactionStatisticsCacheImpl() {}

@RestController
public class StatisticsController {

    private TransactionCache transactionCache;

    public StatisticsController(TransactionCache transactionCache) {
        this.transactionCache = transactionCache;
    }

    @PostMapping("/tick")
    public ResponseEntity<Object> addInstrumentTransaction(@Valid @RequestBody InstrumentTransaction instrumentTransaction) {
        transactionCache.addTransaction(instrumentTransaction);
        return new ResponseEntity<>(HttpStatus.CREATED);
    }

或

我们需要使用getInstance（）方法调用它？另外，我们是否需要在TransactionStatisticsCacheImpl类中显式地使用getInstance方法？

Answer 1

容器注入的一个主要优点是，您可以获得单例语义的好处，而不需要“硬”单例的所有严重问题（如困难测试）。摆脱getInstance手工业务，让Spring负责确保创建一个实例并将其用于上下文。