java无法统计应用程序。从2.0.6更新SpringBoot之后。发布到2.1.0。释放

Question

我有一个基本的SpringBoot 2.0.6。发布应用程序。使用Spring初始值设定项、JPA、嵌入式Tomcat、Thymeleaf模板引擎，并将其打包为具有restful体系结构的可执行JAR 我更新了SpringBoot应用程序。从2.0.6开始。发布到2.1.0。释放

我有一个配置类：

public class DevApplicationConfig {

     @Autowired
     private ErrorAttributes errorAttributes;

     @Bean
     public AppErrorController appErrorController(){
         return new AppErrorController(errorAttributes);
     }

}

但在更改之后，我在启动应用程序时在Eclipse中遇到了以下错误：

***************************
APPLICATION FAILED TO START
***************************

Description:

The bean 'appErrorController', defined in class path resource [io/tdk/config/DevApplicationConfig.class], could not be registered. A bean with that name has already been defined in file [/Users/nunet/Documents/workspace-sts-3.9.2.RELEASE/tdk/target/classes/io/tdk/web/controllers/AppErrorController.class] and overriding is disabled. 

@Controller
public class AppErrorController  implements ErrorController {

    private static final Logger LOG = LoggerFactory.getLogger(AppErrorController.class);
    /**
     * Error Attributes in the Application
     */
    private ErrorAttributes errorAttributes;

    private final static String ERROR_PATH = "/error";

    @Autowired
    private EmailService emailService;

    @Value("${systemadmin.email}")
    private String systemAdminEmail;

    @Value("${webmaster.email}")
    private String webMasterEmail;

    /**
     * Controller for the Error Controller
     * @param errorAttributes
     */
    public AppErrorController(ErrorAttributes errorAttributes) {
        this.errorAttributes = errorAttributes;
    }

    /**
     * Supports the HTML Error View
     * @param request
     * @return
     */
    @RequestMapping(value = ERROR_PATH, produces = "text/html")
    public ModelAndView errorHtml(HttpServletRequest request, WebRequest webRequest) {

             SimpleMailMessage mailMessage = new SimpleMailMessage();
         mailMessage.setTo(systemAdminEmail);
         mailMessage.setSubject("System Error !");
         mailMessage.setText(getErrorAttributes(request, webRequest, true).toString());
         mailMessage.setFrom(webMasterEmail);

         emailService.sendGenericEmailMessage(mailMessage);



        return new ModelAndView(serverContextPath  +"/errors/error", getErrorAttributes(request, webRequest, true));
    }

    /**
     * Supports other formats like JSON, XML
     * @param request
     * @return
     */
    @RequestMapping(value = ERROR_PATH)
    @ResponseBody
    public ResponseEntity<Map<String, Object>> error(WebRequest webRequest, HttpServletRequest request) {
        Map<String, Object> body = getErrorAttributes( request, webRequest, true);
        HttpStatus status = getStatus(request);
        return new ResponseEntity<Map<String, Object>>(body, status);
    }


    /**
     * Returns the path of the error page.
     *
     * @return the error path
     * 
     */
    @Override
    public String getErrorPath() {
        return ERROR_PATH;
    }



    private Map<String, Object> getErrorAttributes(HttpServletRequest request, WebRequest webRequest,
            boolean includeStackTrace) {

            return this.errorAttributes.getErrorAttributes(webRequest, includeStackTrace);

    }

    private HttpStatus getStatus(HttpServletRequest request) {
        Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
        if (statusCode != null) {
            try {
                return HttpStatus.valueOf(statusCode);
            } catch (Exception ex) {
            }
        }
        return HttpStatus.INTERNAL_SERVER_ERROR;
    }

}

Answer 1

将此行添加到applicaton.propertie的文件中

spring.main.allow-bean-definition-overriding=true

Answer 2

Spring Boot 2.1中做了一个更改，默认情况下禁用bean重写。这样做是为了更容易识别和纠正bean的意外重写。这里似乎发生了意外的超控

AppErrorController用@Controller注释，它在@Component中生成，并且它似乎位于组件扫描覆盖的包中。当组件扫描遇到AppErrorController时，它定义了一个名为appErrorController的bean

然后处理DevApplicationConfig。它包含一个@Bean方法，该方法定义了一个名为appErrorController的bean：

 @Bean
 public AppErrorController appErrorController(){
     return new AppErrorController(errorAttributes);
 }

在Spring Boot 2.0及更早版本中，这将导致通过组件扫描定义的AppErrorControllerbean被DevApplicationConfig中定义的bean覆盖。如果在使用Spring Boot 2.0启动应用程序时仔细查看日志。x、 您应该看到，已经为被覆盖的bean记录了一条信息消息。在Spring Boot 2.1中，由于默认情况下禁用了bean重写，因此会导致失败

要解决此问题，请从DevApplicationConfig中删除@Bean方法。这允许使用组件扫描生成的定义。我建议在Spring Boot 2.0和更早的应用程序中进行同样的更改。删除不必要的覆盖会使应用程序启动更加高效，并避免应用程序日志中出现有关被覆盖bean的信息消息

如果需要在Spring Boot 2.1中重写bean，可以通过设置以下属性来恢复2.0的行为：

spring.main.allow-bean-definition-overriding=true

我只建议您在异常情况下执行此操作，在这种情况下，重写是故意的，并且没有简单的方法来修改配置以避免发生这种情况