SpringBoot2（十四）全局异常切面

常规的写法，就是使用@ControllerAdvice，这个Spring与SpringBoot通用。

@ControllerAdvice实际上是有参数的，可以选择指定的包名，或许，你希望异常切面直接作用于全局，那么，你也可以尝试使用HandlerExceptionResolver。

/**
 * Controller异常切面
 *
 * @author postm
 */
@ControllerAdvice(basePackages = "cn.seaboot.admin")
public class ControllerExceptionHandler {
    private Logger logger = LoggerFactory.getLogger(ControllerExceptionHandler.class);

    /**
     * Handler ServiceException
     *
     * @param request  -
     * @param response -
     * @param ex       ServiceException
     * @return ModelAndView
     * @throws IOException If an input or output exception occurs
     * @see BindException
     */
    @ExceptionHandler
    public ModelAndView exceptionHandler(HttpServletRequest request, HttpServletResponse response, ServiceException ex)
        throws IOException {
        loggerError(request, ex);
        if (CommonUtils.isAjax(request)) {
            return new Result(0, ex.getMessage()).toView();
        } else {
            response.sendRedirect(request.getContextPath() + "/error/500.html");
            return null;
        }
    }
}

在一些不成熟的框架中开发，你有可能会遇到这种情况，访问后端的接口后，响应状态为400，然后返回一个错误页面（如下）。

这个问题主要是DefaultHandlerExceptionResolver引起的，在SpringBoot中，HandlerExceptionResolver默认的实现类是DefaultHandlerExceptionResolver，如果我们并未处理代码中的异常，就会默认返回400页面，

对异常的处理，也可以通过改写其中的代码实现。我们不需要完整地实现HandlerExceptionResolver，继承DefaultHandlerExceptionResolver，重写我们需要的代码即可。

import cn.seaboot.admin.others.Jackson.Result;
import org.springframework.lang.Nullable;
import org.springframework.validation.BindException;
import org.springframework.validation.BindingResult;
import org.springframework.validation.ObjectError;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ApplicationHandlerExceptionResolver extends DefaultHandlerExceptionResolver {

    /**
     * {{@link DefaultHandlerExceptionResolver#handleBindException}}
     * Override this method, a error json is sent back to the client.
     *
     * @param request  current HTTP request
     * @param response current HTTP response
     * @param handler  the executed handler
     * @return an empty ModelAndView indicating the exception was handled
     * @throws IOException potentially thrown from {@link HttpServletResponse#sendError}
     * @author Mr.css
     */
    @Override
    protected ModelAndView handleBindException(BindException ex, HttpServletRequest request,
                                               HttpServletResponse response, @Nullable Object handler) throws IOException {
        BindingResult result = ex.getBindingResult();
        if (result.hasErrors()) {
            List<ObjectError> errors = result.getAllErrors();
            Map<String, Object> object = new HashMap<>(errors.size());
            for (ObjectError error : errors) {
                object.put(error.getObjectName(), error.getDefaultMessage());
            }
            return new Result(3, object).toView();
        } else {
            return Result.failed("数据验证中发生了未知的异常!").toView();
        }
    }
}

在SpringBoot中的注册方式如下

    /**
     * 异常处理机制
     *
     * @param resolvers -
     */
    @Override
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
        if (!resolvers.isEmpty()) {
            resolvers.removeIf(resolver -> resolver instanceof DefaultHandlerExceptionResolver);
        }
        resolvers.add(0, new ApplicationHandlerExceptionResolver());
    }