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三、Spring MVC之Restful风格的实现
先抛论点:我觉得Restful风格仅仅是一种风格,并不是什么高深的技术架构,而是一种编程的规范。在我们进行应用程序开发的过程中,我们可以发现,80%以上的操作都是增删查改式的操作,restful就是定义了CRUD的开发规范。下面把restful风格的url和传统风格的url进行一个对比。
业务操作 | 传统风格URL | 传统请求方式 | restful风格URL | restful请求方式 |
新增 | /add | GET/POST | /order | POST |
修改 | /update?id=1 | GET/POST | /order/1 | PUT |
查询 | /get?id=1 | GET/POST | /order/1 | GET |
删除 | /delete?id=1 | GET/POST | /order/1 | DELETE |
自从我们学习jsp、servlet以来,所用的请求方式一般就是post或者get,浏览器目前也只是支持post和get请求方式,那要怎么实现put和delete请求呢?不要着急,spring mvc提供了一个filter用来实现put和delete请求。下面我们来看一下这个filter的代码,简单说一下对注视的理解,水平有限,不一定准确:浏览器目前只支持post和get请求,这个过滤器呢可以实现把post请求转为put请求或者delete请求,它是怎么实现的呢?利用一个普通的post请求,再加上一个隐藏域,隐藏域的名称为_method,当它发现是一个post请求的时候,而且还有_method属性的话,它就会把该请求转换为响应的http请求。该过滤器定义在web.xml的位置也需要注意,因为这个filter需要检查post的参数,因此需要定义在文件上传得filter后面,典型的有:org.springframework.web.multipart.support.MultipartFilter。
package org.springframework.web.filter; import java.io.IOException; import java.util.Locale; import javax.servlet.FilterChain; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletRequestWrapper; import javax.servlet.http.HttpServletResponse; import org.springframework.util.Assert; import org.springframework.util.StringUtils; import org.springframework.web.util.WebUtils; /** * {@link javax.servlet.Filter} that converts posted method * parameters into HTTP methods, retrievable via * {@link HttpServletRequest#getMethod()}. Since browsers currently only * support GET and POST, a common technique - used by the Prototype * library, for instance - is to use a normal POST with an additional * hidden form field ({@code _method}) to pass the "real" HTTP method along. * This filter reads that parameter and changes * the {@link HttpServletRequestWrapper#getMethod()} return value accordingly. * * <p>The name of the request parameter defaults to {@code _method}, but can be * adapted via the {@link #setMethodParam(String) methodParam} property. * * <p><b>NOTE: This filter needs to run after multipart processing in case of * a multipart POST request, due to its inherent need for checking a POST * body parameter.</b> * So typically, put a Spring * {@link org.springframework.web.multipart.support.MultipartFilter} * <i>before</i> this HiddenHttpMethodFilter in your {@code web.xml} filter chain. * * @author Arjen Poutsma * @author Juergen Hoeller * @since 3.0 */ public class HiddenHttpMethodFilter extends OncePerRequestFilter { /** 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)) { requestToUse = new HttpMethodRequestWrapper(request, paramValue); } } 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.toUpperCase(Locale.ENGLISH); } @Override public String getMethod() { return this.method; } } }
有了上面的filter,结合前面的RequestMapping的method属性,就可以实现put或者delete请求了,下面来看两个具体的例子
1、以put请求为例
第一步需要在web.xml中配置过滤器
<!-- HiddenHttpMethodFilter可以把post请求转为delete或者put请求, 需要借助于_method属性, --> <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>
第二步:form表单的定义,它实际上就是一个post,定义了一个隐藏域
<form action="/restful/testPut/1" method="post"> <!-- POST请求转为PUT请求的关键 --> <input type="hidden" name="_method" value="http://www.mamicode.com/PUT"/> <p>put请求</p> <input type="submit" value="http://www.mamicode.com/submit" /> </form>
第三步:后台方法的定义,定义method为put,使用注解@PathVariable获取url中的参数
@RequestMapping(value = "/testPut/{id}", method = RequestMethod.PUT) public String testPut(@PathVariable("id") int id) { System.out.println("test put function" + id); return "greeting"; }
这就是实现了一个restful风格的put请求。
项目源代码:RestfulControll.java
https://git.oschina.net/acesdream/spring-mvc
本文出自 “艾斯的梦想” 博客,请务必保留此出处http://acesdream.blog.51cto.com/10029622/1905068
三、Spring MVC之Restful风格的实现