SpringBoot错误处理

SpringBoot提供了一个/error的URI，当访问不存在地址或者处理出错时就会重定向到这个地址，返回用户一个预设的错误页面，如果你准备了404或者500等错误页面，放到合适的地方，那么SpringBoot也能找到这些页面并返回给前端。总的来说就是SpringBoot提供了一个默认的各种错误的页面。在springboot中是/error的handler是BasicErrorController这个类型，我们来看看这个类型的定义，@RequestMapping的参数比较复杂，意思就是优先使用server.error.path这个配置地址，然后是error.path这个地址，如果以上2个都没配置，就用/error，可以看到里面有两个方法使用了@RequestMapping注解，其中一个参数为produces = "text/html"，用来处理html错误请求，一个没有参数，用来处理其他情况，

@Controller
@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController {

	private final ErrorProperties errorProperties;

	/**
	 * Create a new {@link BasicErrorController} instance.
	 * @param errorAttributes the error attributes
	 * @param errorProperties configuration properties
	 */
	public BasicErrorController(ErrorAttributes errorAttributes,
			ErrorProperties errorProperties) {
		this(errorAttributes, errorProperties,
				Collections.<ErrorViewResolver>emptyList());
	}

	/**
	 * Create a new {@link BasicErrorController} instance.
	 * @param errorAttributes the error attributes
	 * @param errorProperties configuration properties
	 * @param errorViewResolvers error view resolvers
	 */
	public BasicErrorController(ErrorAttributes errorAttributes,
			ErrorProperties errorProperties, List<ErrorViewResolver> errorViewResolvers) {
		super(errorAttributes, errorViewResolvers);
		Assert.notNull(errorProperties, "ErrorProperties must not be null");
		this.errorProperties = errorProperties;
	}

	@Override
	public String getErrorPath() {
		return this.errorProperties.getPath();
	}

	@RequestMapping(produces = "text/html")
	public ModelAndView errorHtml(HttpServletRequest request,
			HttpServletResponse response) {
		HttpStatus status = getStatus(request);
		Map<String, Object> model = Collections.unmodifiableMap(getErrorAttributes(
				request, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
		response.setStatus(status.value());
		ModelAndView modelAndView = resolveErrorView(request, response, status, model);
		return (modelAndView == null ? new ModelAndView("error", model) : modelAndView);
	}

	@RequestMapping
	@ResponseBody
	public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) {
		Map<String, Object> body = getErrorAttributes(request,
				isIncludeStackTrace(request, MediaType.ALL));
		HttpStatus status = getStatus(request);
		return new ResponseEntity<Map<String, Object>>(body, status);
	}

	/**
	 * Determine if the stacktrace attribute should be included.
	 * @param request the source request
	 * @param produces the media type produced (or {@code MediaType.ALL})
	 * @return if the stacktrace attribute should be included
	 */
	protected boolean isIncludeStackTrace(HttpServletRequest request,
			MediaType produces) {
		IncludeStacktrace include = getErrorProperties().getIncludeStacktrace();
		if (include == IncludeStacktrace.ALWAYS) {
			return true;
		}
		if (include == IncludeStacktrace.ON_TRACE_PARAM) {
			return getTraceParameter(request);
		}
		return false;
	}

	/**
	 * Provide access to the error properties.
	 * @return the error properties
	 */
	protected ErrorProperties getErrorProperties() {
		return this.errorProperties;
	}

}

我们来看看错误处理是如何注册的：

private static class ErrorPageCustomizer implements ErrorPageRegistrar, Ordered {

	private final ServerProperties properties;

	protected ErrorPageCustomizer(ServerProperties properties) {
		this.properties = properties;
	}

	@Override
	public void registerErrorPages(ErrorPageRegistry errorPageRegistry) {
		ErrorPage errorPage = new ErrorPage(this.properties.getServletPrefix()
				+ this.properties.getError().getPath());
		errorPageRegistry.addErrorPages(errorPage);
	}

	@Override
	public int getOrder() {
		return 0;
	}

}

其中this.properties.getError().getPath()就是关键：

public class ErrorProperties {

	/**
	 * Path of the error controller.
	 */
	@Value("${error.path:/error}")
	private String path = "/error";
    ......
}

这样就将错误处理url注册了，

下面我们来看看如何自定义错误请求的返回，

1、实现ErrorController接口，那么默认的错误处理机制将不再生效。
2、继承BasicErrorController类，使用一部分现成的功能，自己也可以添加新的public方法，使用@RequestMapping及其produces属性指定新的地址映射。
3、自定义一个ErrorAttribute类型的bean，那么还是默认的两种响应方式，只不过改变了内容项而已。
4、继承AbstractErrorController
5、使用@ControllerAdvice注解