- 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、符合標准、易於理解、擴展方便，所以正得到越來越多網站的采用，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。本次實驗采用的是 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")
@Controller
public 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">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 注解必須加上 required 參數，否則訪問頁面會出現400錯誤。
