springBoot对REST支持源码解析

一、在配置类中：

@AutoConfiguration(after = { DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,ValidationAutoConfiguration.class })
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
public class WebMvcAutoConfiguration

提供了一个Filter:

	@Bean@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)@ConditionalOnProperty(prefix = "spring.mvc.hiddenmethod.filter", name = "enabled")public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {return new OrderedHiddenHttpMethodFilter();}

该Fileter通过条件注解 检查配置文件是否开启参数处理：

spring:mvc:hiddenmethod:filter:enabled: true

提供一个默认参数名称：

	/** Default method parameter: {@code _method}. */public static final String DEFAULT_METHOD_PARAM = "_method";

同时提供一个接口可以让用户自定义参数名称：

	/*** Set the parameter name to look for HTTP methods.* @see #DEFAULT_METHOD_PARAM*/public void setMethodParam(String methodParam) {Assert.hasText(methodParam, "'methodParam' must not be empty");this.methodParam = methodParam;}

通过doFileter...执行拦截器：

①：表单请求携带参数：_method。

②：进入拦截器后检查请求是否是POST请求，请求是否错误

③：获取请求参数_method。

④：判断请求是否在给定的请求集合内：private static final List<String> ALLOWED_METHODS =       Collections.unmodifiableList(Arrays.asList(HttpMethod.PUT.name(),             HttpMethod.DELETE.name(), HttpMethod.PATCH.name()));

⑤：将请求包装为：HttpMethodRequestWrapper  ，重写getmethod接口

@Overrideprotected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)throws ServletException, IOException {//获取请求HttpServletRequest requestToUse = request;//判断是否为POST请求，请求是否错误if ("POST".equals(request.getMethod()) && request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) == null) {//获取请求方式参数_methodString paramValue = request.getParameter(this.methodParam);if (StringUtils.hasLength(paramValue)) {//将请求转为大写String method = paramValue.toUpperCase(Locale.ENGLISH);//判断请求是否在给定的请求集合中if (ALLOWED_METHODS.contains(method)) {//将请求包装一下，重写了请求的getmethod方法requestToUse = new HttpMethodRequestWrapper(request, method);}}}//放行过滤器filterChain.doFilter(requestToUse, response);}

重写getmethod：

	/*** Simple {@link HttpServletRequest} wrapper that returns the supplied method for* {@link HttpServletRequest#getMethod()}.*/private static class HttpMethodRequestWrapper extends HttpServletRequestWrapper {private final String method;public HttpMethodRequestWrapper(HttpServletRequest request, String method) {super(request);this.method = method;}@Overridepublic String getMethod() {return this.method;}}

扩展：如何自定义请求方法参数名称。

自定义配置类：

@Configuration
public class MyConfiger {@Beanpublic HiddenHttpMethodFilter hiddenHttpMethodFilter(){HiddenHttpMethodFilter hiddenHttpMethodFilter =new HiddenHttpMethodFilter();//自定义请求方式参数hiddenHttpMethodFilter.setMethodParam("_m");return hiddenHttpMethodFilter;}
}