SpringBoot异常处理之ErrorPageFilter

javaspring

ErrorPageFilter 简介

ErrorPageFilter是SpringBoot在1.4.0版本提供的一个类，本质上是一个Filter。 它的作用主要有两方面：

  1. 提供应用程序注册ErrorPage的接口，此时它的角色是：ErrorPageRegistry
  2. 处理应用程序异常，根据异常的类型转发到对应的ErrorPage页, 从而不依赖部署的容器错误处理机制

ErrorPageFilter 类的工作原理

主要逻辑如下：

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@Order(Ordered.HIGHEST_PRECEDENCE)
public class ErrorPageFilter implements Filter, ErrorPageRegistr {
    private final OncePerRequestFilter delegate = new OncePerRequestFilter() {

truetrue@Override
truetrueprotected void doFilterInternal(HttpServletRequest request,
				HttpServletResponse response, FilterChain chain)
						throws ServletException, IOException {
truetruetrueErrorPageFilter.this.doFilter(request, response, chain);
truetrue}

truetrue@Override
truetrueprotected boolean shouldNotFilterAsyncDispatch() {
truetruetruereturn false;
truetrue}

true};

true@Override
truepublic void init(FilterConfig filterConfig) throws ServletException {
truetruethis.delegate.init(filterConfig);
true}

true@Override
truepublic void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
truetruethis.delegate.doFilter(request, response, chain);
true}
true/**
	* 过滤每个请求，如果请求在处理过程中发生异常则处理
	*/
trueprivate void doFilter(HttpServletRequest request, HttpServletResponse response,
			FilterChain chain) throws IOException, ServletException {
truetrueErrorWrapperResponse wrapped = new ErrorWrapperResponse(response);
truetruetry {
truetruetruechain.doFilter(request, wrapped);
truetrue}
truetruecatch (Throwable ex) {
truetruetrueThrowable exceptionToHandle = ex;
truetruetrueif (ex instanceof NestedServletException) {
truetruetruetrueexceptionToHandle = ((NestedServletException) ex).getRootCause();
truetruetrue}
truetruetruehandleException(request, response, wrapped, exceptionToHandle);
truetruetrueresponse.flushBuffer();
truetrue}
true}
trueprivate void handleException(HttpServletRequest request, HttpServletResponse response,
			ErrorWrapperResponse wrapped, Throwable ex)
					throws IOException, ServletException {
truetrueClass<?> type = ex.getClass();
truetrue//根据异常类型查询对应错误页的地址
truetrueString errorPath = getErrorPath(type);
truetrueif (errorPath == null) {
truetruetruerethrow(ex);
truetruetruereturn;
truetrue}
truetrueif (response.isCommitted()) {
truetruetruehandleCommittedResponse(request, ex);
truetruetruereturn;
truetrue}
truetrue//转发请求
truetrueforwardToErrorPage(errorPath, request, wrapped, ex);
true}
trueprivate void forwardToErrorPage(String path, HttpServletRequest request,
        		HttpServletResponse response, Throwable ex){
        setErrorAttributes(request, 500, ex.getMessage());
        request.setAttribute(ERROR_EXCEPTION, ex);
        request.setAttribute(ERROR_EXCEPTION_TYPE, ex.getClass());
        response.reset();
        response.sendError(500, ex.getMessage());
        //请求转发
        request.getRequestDispatcher(path).forward(request, response);
        request.removeAttribute(ERROR_EXCEPTION);
        request.removeAttribute(ERROR_EXCEPTION_TYPE);
true}
true/**
	* 该方法用来添加错误页信息， 是接口ErrorPageRegistry的方法
	*/
true@Override
truepublic void addErrorPages(ErrorPage... errorPages) {
truetruefor (ErrorPage errorPage : errorPages) {
truetruetrueif (errorPage.isGlobal()) {
truetruetruetruethis.global = errorPage.getPath();
truetruetrue}
truetruetrueelse if (errorPage.getStatus() != null) {
truetruetruetruethis.statuses.put(errorPage.getStatus().value(), errorPage.getPath());
truetruetrue}
truetruetrueelse {
truetruetruetruethis.exceptions.put(errorPage.getException(), errorPage.getPath());
truetruetrue}
truetrue}
true}
}

ErrorPageFilter 相关类

ErrorPageRegistry

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/**
 * Interface for a registry that holds {@link ErrorPage ErrorPages}.
 *
 * @author Phillip Webb
 * @since 1.4.0
 */
public interface ErrorPageRegistry {

true/**
	 * Adds error pages that will be used when handling exceptions.
	 * @param errorPages the error pages
	 */
truevoid addErrorPages(ErrorPage... errorPages);

}

ErrorPage

该类相当于应用部署描述符web.xml中的error-page结点的Java类表示

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/**
 * Simple container-independent abstraction for servlet error pages. Roughly equivalent to
 * the {@literal &lt;error-page&gt;} element traditionally found in web.xml.
 *
 * @author Dave Syer
 * @since 1.4.0
 */
public class ErrorPage {

trueprivate final HttpStatus status;

trueprivate final Class<? extends Throwable> exception;

trueprivate final String path;

truepublic ErrorPage(String path) {
truetruethis.status = null;
truetruethis.exception = null;
truetruethis.path = path;
true}

truepublic ErrorPage(HttpStatus status, String path) {
truetruethis.status = status;
truetruethis.exception = null;
truetruethis.path = path;
true}

truepublic ErrorPage(Class<? extends Throwable> exception, String path) {
truetruethis.status = null;
truetruethis.exception = exception;
truetruethis.path = path;
true}
}

ErrorPageRegistrar

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/**
 * Interface to be implemented by types that register {@link ErrorPage ErrorPages}.
 *
 * @author Phillip Webb
 * @since 1.4.0
 */
public interface ErrorPageRegistrar {

true/**
	 * Register pages as required with the given registry.
	 * @param registry the error page registry
	 */
truevoid registerErrorPages(ErrorPageRegistry registry);

}

容器中实现了ErrorPageRegistrar接口的类会被自动注册到ErrorPageFilter中。

SpringBoot 错误页处理原理

有了上面的原理基础，我们就可以实现自己的错误页处理类（实现接口ErrorPageRegistrar并注册到spring容器中）。熟悉spring的肯定能猜到spring已经提供了这样的类，该类就是：ErrorPageCustomizer

ErrorPageCustomizer

ErrorPageCustomizer 实现了接口 ErrorPageRegistrar，该类会在SpringBoot启动过程中被注册到ErrorPageFilter。 它是如何注册的呢？

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@Configuration
@ConditionalOnWebApplication
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class })
// Load before the main WebMvcAutoConfiguration so that the error View is available
@AutoConfigureBefore(WebMvcAutoConfiguration.class)
@EnableConfigurationProperties(ResourceProperties.class)
public class ErrorMvcAutoConfiguration {

    /**
    * 这里就实现了Bean的注册
    */
    @Bean
    public ErrorPageCustomizer errorPageCustomizer() {
        return new ErrorPageCustomizer(this.serverProperties);
    }
    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;
    		}
    }
}

ErrorPageCustomizer 默认会转发错误请求到/error， 这个可以在配置文件application.properties中进行设置：server.error.path

错误处理

当错误请求被转发到/error时， 该请求将会由SpringBoot提供的BasicErrorController进行处理：

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//${server.error.path:${error.path:/error}}
@Controller
@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController {
    @RequestMapping(produces = "text/html")
truepublic ModelAndView errorHtml(HttpServletRequest request,
			HttpServletResponse response) {
truetrueHttpStatus status = getStatus(request);
truetrueMap<String, Object> model = Collections.unmodifiableMap(getErrorAttributes(
truetruetruetruerequest, isIncludeStackTrace(request, MediaType.TEXT_HTML)));
truetrueresponse.setStatus(status.value());
truetrueModelAndView modelAndView = resolveErrorView(request, response, status, model);
truetruereturn (modelAndView == null ? new ModelAndView("error", model) : modelAndView);
true}
}

最后就是渲染出SpringBoot默认的错误页面。一般来说我们需要自己处理/error请求来渲染我们自己提供的错误页。

本文标题:SpringBoot异常处理之ErrorPageFilter

文章作者:kongwenqiang

发布时间:2017-04-07, 14:35:53

最后更新:2017-04-07, 16:09:59

原始链接:https://leokongwq.github.io/2017/04/07/spring-ErrorPageFilter.html

许可协议: "署名-非商用-相同方式共享 4.0" 转载请保留原文链接及作者。

文章目录
  1. 1. ErrorPageFilter 简介
  2. 2. ErrorPageFilter 类的工作原理
    1. 2.1. 主要逻辑如下：
  3. 3. ErrorPageFilter 相关类
    1. 3.1. ErrorPageRegistry
    2. 3.2. ErrorPage
    3. 3.3. ErrorPageRegistrar
  4. 4. SpringBoot 错误页处理原理
    1. 4.1. ErrorPageCustomizer
    2. 4.2. 错误处理
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