请求映射
@xxxMapping;
@GetMapping
@PostMapping
@PutMapping
@DeleteMapping
Rest风格支持（使用HTTP请求方式动词来表示对资源的操作）
以前：
/getUser 获取用户
/deleteUser 删除用户
/editUser 修改用户
/saveUser保存用户
现在： /user
GET-获取用户
DELETE-删除用户
PUT-修改用户
POST-保存用户
核心Filter；HiddenHttpMethodFilter
用法
开启页面表单的Rest功能
页面 form的属性method=post，隐藏域 _method=put、delete等（如果直接get或post，无需隐藏域）
编写请求映射
spring:
mvc:
hiddenmethod:
filter:
enabled: true #开启页面表单的Rest功能
<form action="/user" method="get">
<input value="REST-GET提交" type="submit" />
</form>
<form action="/user" method="post">
<input value="REST-POST提交" type="submit" />
</form>
<form action="/user" method="post">
<input name="_method" type="hidden" value="DELETE"/>
<input value="REST-DELETE 提交" type="submit"/>
</form>
<form action="/user" method="post">
<input name="_method" type="hidden" value="PUT" />
<input value="REST-PUT提交"type="submit" />
<form>
@GetMapping("/user")
//@RequestMapping(value = "/user",method = RequestMethod.GET)
public String getUser(){
return "GET-张三";
}
@PostMapping("/user")
//@RequestMapping(value = "/user",method = RequestMethod.POST)
public String saveUser(){
return "POST-张三";
}
@PutMapping("/user")
//@RequestMapping(value = "/user",method = RequestMethod.PUT)
public String putUser(){
return "PUT-张三";
}
@DeleteMapping("/user")
//@RequestMapping(value = "/user",method = RequestMethod.DELETE)
public String deleteUser(){
return "DELETE-张三";
}
Rest原理
（表单提交要使用REST的时候）
表单提交会带上_method=PUT
请求过来被HiddenHttpMethodFilter拦截
请求是否正常，并且是POST
- 获取到_method的值。
- 兼容以下请求；PUT.DELETE.PATCH
- 原生request（post），包装模式requesWrapper重写了getMethod方法，返回的是传入的值。
- 过滤器链放行的时候用wrapper。以后的方法调用getMethod是调用requesWrapper的。
public class HiddenHttpMethodFilter extends OncePerRequestFilter {
private static final List<String> ALLOWED_METHODS =
Collections.unmodifiableList(Arrays.asList(HttpMethod.PUT.name(),
HttpMethod.DELETE.name(), HttpMethod.PATCH.name()));
/** Default method parameter: {@code _method}. */
public static final String DEFAULT_METHOD_PARAM = "_method";
private String methodParam = DEFAULT_METHOD_PARAM;
/**
* 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;
}
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
HttpServletRequest requestToUse = request;
if ("POST".equals(request.getMethod()) && request.getAttribute(WebUtils.ERROR_EXCEPTION_ATTRIBUTE) == null) {
String paramValue = request.getParameter(this.methodParam);
if (StringUtils.hasLength(paramValue)) {
String method = paramValue.toUpperCase(Locale.ENGLISH);
if (ALLOWED_METHODS.contains(method)) {
requestToUse = new HttpMethodRequestWrapper(request, method);
}
}
}
filterChain.doFilter(requestToUse, response);
}
/**
* 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;
}
@Override
public String getMethod() {
return this.method;
}
}
}
怎么改变默认的_method
@Configuration(proxyBeanMethods = false)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({
Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({
DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {
...
@Bean
@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
@ConditionalOnProperty(prefix = "spring.mvc.hiddenmethod.filter", name = "enabled", matchIfMissing = false)
public OrderedHiddenHttpMethodFilter hiddenHttpMethodFilter() {
return new OrderedHiddenHttpMethodFilter();
}
...
}
@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)意味着在没有HiddenHttpMethodFilter时，才执行hiddenHttpMethodFilter()。因此，我们可以自定义filter，改变默认的_method。例如：
@Configuration(proxyBeanMethods = false)
public class WebConfig{
//自定义filter
@Bean
public HiddenHttpMethodFilter hiddenHttpMethodFilter(){
HiddenHttpMethodFilter methodFilter = new HiddenHttpMethodFilter();
methodFilter.setMethodParam("_m");
return methodFilter;
}
}
将_method改成_m。
<form action="/user" method="post">
<input name="_m" type="hidden" value="DELETE"/>
<input value="REST-DELETE 提交" type="submit"/>
</form>
请求映射原理
-
SpringBoot自动配置欢迎页的 WelcomePageHandlerMapping 。访问 /能访问到index.html；
-
SpringBoot自动配置了默认的RequestMappingHandlerMapping
-
请求进来，挨个尝试所有的HandlerMapping看是否有请求信息。
-
如果有就找到这个请求对应的handler
-
如果没有就是下一个HandlerMapping
-
我们需要一些自定义的映射处理，我们也可以自己给容器中放HandlerMapping。自定义 HandlerMapping
IDEA快捷键：
- Ctrl + Alt + U : 以UML的类图展现类有哪些继承类，派生类以及实现哪些接口。
- Crtl + Alt + Shift + U : 同上，区别在于上条快捷键结果在新页展现，而本条快捷键结果在弹窗展现。
- Ctrl + H : 以树形方式展现类层次结构图。