Spring中的@ControllerAdvice注解配合@ExceptionHandler使用实现异常处理

@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的实现：

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

}

没什么特别之处，该注解使用@Component注解，这样的话当我们使用<context:component-scan>扫描时也能扫描到

/**
* 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
*/

即把@ControllerAdvice注解内部使用@ExceptionHandler、@InitBinder、@ModelAttribute注解的方法应用到所有的 @RequestMapping注解的方法。非常简单，不过只有当使用@ExceptionHandler最有用，另外两个用处不大。

  

接下来看段代码：

@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
    }
}

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.sishuok.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.sishuok.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>

该注解非常简单，大多数时候其实只@ExceptionHandler比较有用，其他两个用到的场景非常少，这样可以把异常处理器应用到所有控制器，而不是@Controller注解的单个控制器。

以下为一个实例

package com.zjr.common.web;

//import ...

@ControllerAdvice
public class WebExceptionHandler {

	Logger logger = LoggerFactory.getLogger(this.getClass());

	@ExceptionHandler({ ServletException.class })
	public void http404(HttpServletRequest request, HttpServletResponse response, ServletException e)
			throws IOException {
		logger.error("HttpRequest error:{}", request.getRequestURL());
        logger.error("HttpRequest error stack :" ,e );
		outputMessage(response, ErrorType.HTTP404_ERROR.getErrCode(), ErrorType.HTTP404_ERROR.getErrMsg());
	}

	@ExceptionHandler(BizException.class)
	public void handleBizException(HttpServletRequest request, HttpServletResponse response, BizException e)
			throws IOException {
		logger.error("Biz error occurs during :{}",request.getRequestURI());
		logger.error("Biz error stack :",e);
		outputMessage(response, e.getErrCode(), e.getMessage());
	}

	@ExceptionHandler({ Error.class, Exception.class, Throwable.class })
	public void exception(HttpServletRequest request, HttpServletResponse response, Throwable e) throws IOException {
		logger.error("Unknown error occurs during :{}",request.getRequestURI());
		logger.error("Unknown system error stack:", e);
		outputMessage(response, ErrorType.UNKNOWN_ERROR.getErrCode(),ErrorType.UNKNOWN_ERROR.getErrMsg());
	}

	private void outputMessage(HttpServletResponse response, long errCode, String errMsg) throws IOException {
		BasicResult result = BasicResult.createFailResult(errCode, errMsg);
		String json = new JsonMapper().toJson(result);
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/json");
		ServletOutputStream os = response.getOutputStream();
		os.write(json.getBytes("utf-8"));
	}
}