Spring MVC 菜鸟教程 6 GET，POST，PUT，DELETE

服务器交互的不同方法

GET，POST，PUT，DELETE

URL资源

HTTP中的PUT，DELETE，POST，GET就对应着对这个URL资源的增，删，改，查4个操作。
GET一般用于获取/查询资源信息，而POST一般用于更新资源信息。

MVC框架设计问题

早期的Web MVC框架设计者们并没有意识到将URL当作抽象的资源来看的重要性，导致一个的问题是传统的Web MVC框架基本上都只支持GET和POST两种HTTP方法，而不支持PUT和DELETE方法。而Spring MVC是全部支持的。

如何使用PUT/DELETE

表单

这里提交了一个_method的参数

<form action="/put" method="post">  
        <input type="hidden" name="_method" value="PUT" />  
        <input type="submit" value="submit" />  
</form>  

HiddenHttpMethodFilter

SpringMVC 在页面访问要通过此过滤器

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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;

/**
 * {@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
 * @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 {

        String paramValue = request.getParameter(this.methodParam);
        //判断method的方式为POST并且_method不为空
        if ("POST".equals(request.getMethod()) && StringUtils.hasLength(paramValue)) {
            String method = paramValue.toUpperCase(Locale.ENGLISH);
            //关键位置，再次包装HttpServletRequest,进行method转换，看下面代码
            HttpServletRequest wrapper = new HttpMethodRequestWrapper(request, method);
            filterChain.doFilter(wrapper, response);
        }
        else {
            filterChain.doFilter(request, 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;
        }
    }

}

后台打印

@RequestMapping(value="/put",method=RequestMethod.PUT)  
public String put() throws Exception{  
        System.out.println("put");  
}  

其他关联项目

• SpringMVC 菜鸟教程 1 文件上传 配置
  http://blog.csdn/je_ge/article/details/53725357

源码地址

https://github/je-ge/spring

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