创建名为 'application' 的 bean 时出错，找不到默认构造函数；嵌套异常是 java.lang.NoSuchMethodException

Question

我不太明白为什么这段代码给我 'no default constructor found' 错误。构造函数是@Autowired。一切似乎都被正确注入。有人可以帮忙吗？谢谢

@SpringBootApplication
public class Application {

    private ApplicationContext applicationContext;
    private MessagingService messagingService;
    private Parser parser;

    private static final Logger log = LoggerFactory.getLogger(Application.class);

    @Autowired
    public Application(ApplicationContext applicationContext,
                       MessagingService messagingService,
                       Parser parser)
    {
        this.applicationContext = applicationContext;
        Assert.notNull(messagingService, "MessagingService must not be null");
        this.messagingService = messagingService;
        Assert.notNull(parser, "Parser must not be null");
        this.parser = parser;
    }

    public static void main (String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public CommandLineRunner app() {
        return args -> {
            Locale defaultLocale = Locale.getDefault();
            Locale.setDefault(defaultLocale);
            log.info("Using MessagingService: " + messagingService.getMyMessageCode());

            parser.parse();
        };
    }
}

编辑： 已更新 Application.class

@SpringBootApplication
public class Application {

    @Autowired
    private MessagingService messagingService;
    @Autowired
    private Parser parser;

    private static final Logger log = LoggerFactory.getLogger(Application.class);

    public Application() {}

    public static void main (String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public CommandLineRunner app() {
        return args -> {
            Locale defaultLocale = Locale.getDefault();
            Locale.setDefault(defaultLocale);
            log.info("Using MessagingService: " + messagingService.getMyMessageCode());

            parser.parse();
        };
    }
}

Answer 1

您不能自动连接到主 Spring 引导 class。您可以注入 CommandLineRunner 所需的依赖项作为用 @Bean 注释的方法的参数，当然也可以删除 main class:

的构造函数注入

@SpringBootApplication
public class Application {
    private static final Logger log = LoggerFactory.getLogger(Application.class);

    public static void main (String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public CommandLineRunner app(ApplicationContext applicationContext,
                       MessagingService messagingService,
                       Parser parser) {
        return args -> {
            Locale defaultLocale = Locale.getDefault();
            Locale.setDefault(defaultLocale);
            log.info("Using MessagingService: " + messagingService.getMyMessageCode());

            parser.parse();
        };
    }
}

编辑：编辑后正确的上下文配置：

@SpringBootApplication
public class Application {

    private static final Logger log = LoggerFactory.getLogger(Application.class);

    public Application() {}

    public static void main (String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public CommandLineRunner app(MessagingService messagingService, Parser parser) {
        return args -> {
            Locale defaultLocale = Locale.getDefault();
            Locale.setDefault(defaultLocale);
            log.info("Using MessagingService: " + messagingService.getMyMessageCode());

            parser.parse();
        };
    }
}

Answer 2

的回答是正确的。

但是如果你真的想用Constructor Injection你可以升级你SpringBoot 版本到 1.4.0.RELEASE 将使用 Spring 4.3.2.RELEASE

来自 Spring 4.3 @Configuration[=33 支持构造函数注入 =] class

New Features and Enhancements in Spring Framework 4.3

创建名为 'application' 的 bean 时出错，找不到默认构造函数；嵌套异常是 java.lang.NoSuchMethodException

Error creating bean with name 'application', No default constructor found; nested exception is java.lang.NoSuchMethodException

java

spring

dependency-injection

spring-ioc

spring-boot