簡介
REST 即Representational State Transfer。 （資源）表現層狀態轉化。是目前最流行的一種互聯網軟件架構。它結構清晰、符合標準、易於理解、擴展方便，所以正得到越來越多網站的採用，POST, DELETE, PUT, GET 分別對應CRUD。 Spring3.0 開始支持REST 風格的請求，是通過org.springframework.web.filter.HiddenHttpMethodFilter 把POST 請求轉化為PUT 和DELETE 請求。本次實驗採用的是Spring4.0 。
HiddenHttpMethodFilter 源碼
public static final String DEFAULT_METHOD_PARAM = "_method";@Override protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {String paramValue = request.getParameter(this.methodParam);if ("POST".equals(request.getMethod()) && StringUtils.hasLength(paramValue)) {String method = paramValue.toUpperCase(Locale.ENGLISH);HttpServletRequest wrapper = new HttpMethodRequestWrapper(request, method);filterChain.doFilter(wrapper, response);} else {filterChain.doFilter(request, response);}}從HiddenHttpMethodFilter 的源碼可以看出，Spring 根據請求中的_method 參數進行轉化，因此如果想發起REST 風格的DELETE 或者PUT 請求，只需要在表單中帶上_method 參數，並且把_method 的值設置為DELETE 或者PUT（大寫） 即可。詳細例子如下：
在web.xml 中配置HiddenHttpMethodFilter
編寫handler 代碼編寫頁面
<!-- 配置org.springframework.web.filter.HiddenHttpMethodFilter ，可以把POST 請求轉化為PUT 或者DELETE 請求--> <filter> <filter-name>HiddenHttpMethodFilter</filter-name> <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class> </filter> <filter-mapping> <filter-name>HiddenHttpMethodFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
package rex.springmvc.handlers;import org.apache.log4j.Logger;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.RequestParam;@RequestMapping(value="/restTest")@Controllerpublic class RestTestHandler {private static final Logger logger = Logger.getLogger(RestTestHandler.class);private static final String SUCCESS = "success";@RequestMapping(value="/restGet/{id}", method=RequestMethod.GET) public String restGet(@RequestParam(value="id", required=false) Integer id){logger.debug("restGet:" + id);return SUCCESS;}@RequestMapping(value="/restPut/{id}", method=RequestMethod.PUT) public String restPut(@RequestParam(value="id", required=false) Integer id){logger.debug("restPut:" + id);return SUCCESS;}@RequestMapping(value="/restDelete/{id}", method=RequestMethod.DELETE) public String restDelete(@RequestParam(value="id", required=false) Integer id){logger.debug("restDelete:" + id);return SUCCESS;}@RequestMapping(value="/restPost", method=RequestMethod.POST) public String restPost(){logger.debug("restPost");return SUCCESS;}}<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Rest Test</title></head><body> <br> <br> <a href="restTest/restGet/1" rel="external nofollow" >Test Rest Get</a> <br> <br> <form action="restTest/restPut/1" method="post"> <input type="hidden" name="_method" value="PUT"> <input type="submit" value="submit"> </form> <br> <br> <form action="restTest/restDelete/1" method="post"> <input type="hidden" name="_method" value="DELETE"> <input type="submit" value="submit"> </form> <br> <br> <form action="restTest/restPost" method="post"> <input type="submit" value="submit"> </form></body></html>
注：handler 中@RequestParam 註解必須加上required 參數，否則訪問頁面會出現400錯誤。
總結
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