springmvc注解标签之@ControllerAdvice理解以及使用

   本文参考地址：http://blog.csdn.net/wuhenzhangxing/article/details/46459853

   @ControllerAdvice是spring3.2提供的新注解，从名字上可以看出大体意思是控制器增强。让我们先看看        @ControllerAdvice的源码实现如下：

@Target(ElementType.TYPE)  
@Retention(RetentionPolicy.RUNTIME)  
@Documented  
@Component  
public @interface ControllerAdvice {  
  
}

    注解使用@Component注解，这样的话当我们使用<context:component-scan>扫描时也能扫描到,其             javadoc定义如下：

/**
* Indicates the annotated class assists a "Controller".
*
* <p>Serves as a specialization of {@link Component @Component}, allowing for
* implementation classes to be autodetected through classpath scanning.
*
* <p>It is typically used to define {@link ExceptionHandler @ExceptionHandler},
* {@link InitBinder @InitBinder}, and {@link ModelAttribute @ModelAttribute}
* methods that apply to all {@link RequestMapping @RequestMapping} methods.
*
* @author Rossen Stoyanchev
* @since 3.2
*/

    由javadoc可以看出在@ControllerAdvice注解内部我们可以使用@ExceptionHandler、@InitBinder、             @ModelAttribute共3个注解，使用方式如下： 

@ControllerAdvice  
public class ControllerAdviceTest {  
  
    @ModelAttribute  
    public User newUser() {  
        System.out.println("============应用到所有@RequestMapping注解方法，在其执行之前把返回值放入Model");  
        return new User();  
    }  
  
    @InitBinder  
    public void initBinder(WebDataBinder binder) {  
        System.out.println("============应用到所有@RequestMapping注解方法，在其执行之前初始化数据绑定器");  
    }  
  
    @ExceptionHandler(UnauthenticatedException.class)  
    @ResponseStatus(HttpStatus.UNAUTHORIZED)  
    public String processUnauthenticatedException(NativeWebRequest request, UnauthenticatedException e) {  
        System.out.println("===========应用到所有@RequestMapping注解的方法，在其抛出UnauthenticatedException异常时执行");  
        return "viewName"; //返回一个逻辑视图名  
    }  
}  

    以上代码可以看出@ModelAttribute、@initBinder和@ExceptionHandler对所有使用@RequestMapping的方法起作用，但@ModelAttribute和@initBinder在设置全局数据时比较有用，使用较少，                               @ExceptionHandler异常处理器，当注解的方法发生定义的异常时产生作用，使用较多。例如遇    到RuntimeException时做JSON的异常处理。 

    如果你的spring-mvc配置文件使用如下方式扫描bean

<context:component-scan base-package="com.jshi.es" use-default-filters="false">  
       <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>  
   </context:component-scan> 

    需要把@ControllerAdvice包含进来，否则不起作用：

<context:component-scan base-package="com.jshi.es" use-default-filters="false">  
       <context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>  
       <context:include-filter type="annotation" expression="org.springframework.web.bind.annotation.ControllerAdvice"/>  
   </context:component-scan>

    项目中的场景应用：使用@ControllerAdvice注解做Json的异常处理，代码如下，FieldValidationError是自     定义的错误信息，RemoteResponse是自定义的返回数据结构，RespEnum是自定义的响应码

/**
 * 通用的exception的handler的定义
 * @author jshi
 * @date 2016-6-5
 */
@ControllerAdvice
public class ExceptionAdvice {
    /**
     * 数据校验失败
     * @param ex
     * @return
     */
    @ExceptionHandler(MethodArgumentNotValidException.class)
   // @ResponseStatus(value = HttpStatus.BAD_REQUEST)
    @ResponseBody
    public RemoteResponse handleMethodArgumentNotValidException(MethodArgumentNotValidException ex) {
        BindingResult bindingResult = ex.getBindingResult();
        List<FieldValidationError> errorList=new LinkedList<FieldValidationError>();

        for (FieldError fieldError : bindingResult.getFieldErrors()) {
            errorList.add(new FieldValidationError( fieldError.getField(),fieldError.getDefaultMessage()));
        }
        return new RemoteResponse(RespEnum.COM_ARGUMENT_NOT_VALID, errorList);
    }

    /**
     * 数据校验失败
     * @param ex
     * @return
     */
    @ExceptionHandler(BindException.class)
    @ResponseBody
    public RemoteResponse handleBindException(BindException ex) {
        BindingResult bindingResult = ex.getBindingResult();
        List<FieldValidationError> errorList=new LinkedList<FieldValidationError>();

        for (FieldError fieldError : bindingResult.getFieldErrors()) {
            errorList.add(new FieldValidationError( fieldError.getField(),fieldError.getDefaultMessage()));
        }
        return new RemoteResponse(RespEnum.COM_ARGUMENT_NOT_VALID, errorList);
    }



    /**
     * 400 - Bad Request
     */
   @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(HttpMessageNotReadableException.class)
    @ResponseBody
    public RemoteResponse handleHttpMessageNotReadableException(HttpMessageNotReadableException e) {
        Loggers.demoLogger.error("参数解析失败", e);
        return new RemoteResponse(RespEnum.COM_ARGUMENT_NOT_READARABLE);
    }


    /**
     * 400 - Bad Request
     */
  //  @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ExceptionHandler(JSONException.class)
    @ResponseBody
    public RemoteResponse handleJSONException(JSONException e) {
        Loggers.demoLogger.error("json读取失败", e);
        return new RemoteResponse(RespEnum.COM_ARGUMENT_NOT_READARABLE);
    }

    /**
     * 405 - Method Not Allowed
     */

    @ExceptionHandler(HttpRequestMethodNotSupportedException.class)
    @ResponseBody
    public RemoteResponse handleHttpRequestMethodNotSupportedException(HttpRequestMethodNotSupportedException e) {
        Loggers.demoLogger.error("不支持当前请求方法", e);
        return new RemoteResponse(RespEnum.COM_METHOD_NOT_SUPPORT);
    }

    /**
     * 415 - Unsupported Media Type
     */

    @ExceptionHandler(HttpMediaTypeNotSupportedException.class)
    @ResponseBody
    public RemoteResponse handleHttpMediaTypeNotSupportedException(Exception e) {
        Loggers.demoLogger.error("不支持当前媒体类型", e);
        return new RemoteResponse(RespEnum.COM_MEDIA_NOT_SUPPORT);
    }

    /**
     * 数据库操作失败
     */
    @ExceptionHandler(SQLException.class)
    @ResponseBody
    public RemoteResponse handleSQLException(SQLException e) {
        Loggers.demoLogger.error("数据库异常", e);
        return new RemoteResponse(RespEnum.COM_DB_OPERATION_FAILED);
    }

    /**
     * 数据库操作失败
     */
    @ExceptionHandler(MaxUploadSizeExceededException.class)
    @ResponseBody
    public RemoteResponse handleMaxUploadSizeExceededException(MaxUploadSizeExceededException e) {
        Loggers.demoLogger.error("上传文件过大，上传失败，最大只能上传2M", e);
        return new RemoteResponse(RespEnum.UPLOAD_FILE_EXCEEDED_MAXSIZE);
    }

    /**
     * 500 - Internal Server Error
     */
    @ExceptionHandler(Exception.class)
    @ResponseBody
    public RemoteResponse handleException(Exception e) {
        Loggers.demoLogger.error("服务运行异常", e);
        return new RemoteResponse(RespEnum.COM_INTERNAL_ERROR);
    }
}

 

/**
 * 定义在字段的数据校验不通过的情况，返回的错误信息的结构
 * @author jshi
 * @date 2016-6-5
 */
public class FieldValidationError {
    private String field;
    private String msg;
    public FieldValidationError(String field,String msg)
    {
        this.field=field;
        this.msg=msg;
    }

    public String getField() {
        return field;
    }

    public void setField(String field) {
        this.field = field;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

 

/**
 * rest接口，返回的json结构
 * @author jshi
 */
public  class RemoteResponse {


    private int code;//code =0表示成功;  code !=0 表示失败
    private String message;
    private Object data;

    public RemoteResponse(RespEnum resp)
    {
        this.code=resp.getValue();
        this.message= I18nUtil.getMessage(resp.getName());
    }
    public RemoteResponse(RespEnum resp,String...args)
    {
        this.code=resp.getValue();
        this.message= I18nUtil.getMessage(resp.getName(),args);
    }

    public RemoteResponse(RespEnum resp,String msg)
    {
        this.code=resp.getValue();
        this.message=msg;
    }


    public RemoteResponse(RespEnum resp,Object data)
    {
        this.code=resp.getValue();
        this.message= I18nUtil.getMessage(resp.getName());
        this.data=data;
    }
    public RemoteResponse(RespEnum resp,Object data,String...agrs)
    {
        this.code=resp.getValue();
        this.message= I18nUtil.getMessage(resp.getName(),agrs);
        this.data=data;
    }
    public RemoteResponse(RespInfo resp)
    {
        this.code=resp.getCode();
        this.message=resp.getMessage();
        this.data=resp.getModel();
    }

    protected void success()
    {
        code=0;
    }
    protected RemoteResponse success(String msg)
    {
        code=RespEnum.SUCCESS_RESULT.getValue();
        this.message=msg;
        return this;
    }
    protected RemoteResponse failure(String msg)
    {
        code= RespEnum.COM_ERROR.getValue();
        this.message=msg;
        return this;
    }

    public RemoteResponse failure(int code ,String msg)
    {
        this.code=code;
        this.message=msg;
        return this;
    }



    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }
    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }
}