com
   +- APP
         +- Application.java  <--- your main class should be here, above your controller classes
         |
         +- model
         |   +- user.java
         +- controller
             +- UserController.java

票数 208

Stack Overflow用户

发布于 2017-01-19 11:18:40

当我们创建Spring应用程序时，我们用@SpringBootApplication注释对其进行注释。这个注释‘结束’了许多其他必要的注释，以使应用程序工作。其中一个这样的注释就是@ComponentScan注释。这个注释告诉Spring查找Spring组件并配置运行的应用程序。

应用程序类需要位于包层次结构的顶端，这样Spring就可以扫描子包并找到其他必需的组件。

package com.test.spring.boot;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

下面的代码片段工作，因为控制器包在com.test.spring.boot包下

package com.test.spring.boot.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HomeController {

    @RequestMapping("/")
    public String home(){
        return "Hello World!";
    }
}

下面的代码片段不工作，因为控制器包不在com.test.spring.boot包之下。

package com.test.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HomeController {

     @RequestMapping("/")
     public String home(){
         return "Hello World!";
     }
 }

来自Spring文档：

许多Spring开发人员总是使用@Configuration、@EnableAutoConfiguration和@ComponentScan注释他们的主类。由于这些注释经常一起使用(特别是如果您遵循上面的最佳实践)，Spring提供了一个方便的@SpringBootApplication替代方案。 @SpringBootApplication注释相当于使用@Configuration、@EnableAutoConfiguration和@ComponentScan的默认属性。

票数 86

Stack Overflow用户

发布于 2015-08-05 08:50:28

您可以通过在应用程序中添加一个ErrorController来解决这个问题。您可以让错误控制器返回您需要的视图。

应用程序中的错误控制器如下所示：

import org.springframework.boot.autoconfigure.web.ErrorAttributes;
import org.springframework.boot.autoconfigure.web.ErrorController;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import java.util.Map;

/**
 * Basic Controller which is called for unhandled errors
 */
@Controller
public class AppErrorController implements ErrorController{

    /**
     * Error Attributes in the Application
     */
    private ErrorAttributes errorAttributes;

    private final static String ERROR_PATH = "/error";

    /**
     * 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) {
        return new ModelAndView("/errors/error", getErrorAttributes(request, false));
    }

    /**
     * Supports other formats like JSON, XML
     * @param request
     * @return
     */
    @RequestMapping(value = ERROR_PATH)
    @ResponseBody
    public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
        Map<String, Object> body = getErrorAttributes(request, getTraceParameter(request));
        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 boolean getTraceParameter(HttpServletRequest request) {
        String parameter = request.getParameter("trace");
        if (parameter == null) {
            return false;
        }
        return !"false".equals(parameter.toLowerCase());
    }

    private Map<String, Object> getErrorAttributes(HttpServletRequest request,
                                                   boolean includeStackTrace) {
        RequestAttributes requestAttributes = new ServletRequestAttributes(request);
        return this.errorAttributes.getErrorAttributes(requestAttributes,
                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;
    }
}

以上类基于Springs BasicErrorController类。

您可以像这样在一个ErrorController文件中实例化上面的@Configuration：

 @Autowired
 private ErrorAttributes errorAttributes;

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