06【SpringMVC的Restful支持】

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六、SpringMVC的Restful支持

REST（英文：Representational State Transfer，即表述性状态传递，简称REST）RESTful是一种软件架构风格、设计风格，而不是标准，只是提供了一组设计原则和约束条件。它主要用于客户端和服务器交互类的软件。基于这个风格设计的软件可以更简洁，更有层次，更易于实现缓存等机制。

6.1 RESTFUL示例：

请求方式共有其中，其中对应的就是HttpServlet中的七个方法：

Tips：目前我们的jsp、html，都只支持get、post。

6.2 基于restful风格的url

• 添加

URL：

http://localhost:8080/user
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请求体：

{"username":"zhangsan","age":20}
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提交方式： post

• 修改

http://localhost:8080/user/1
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• 请求体：

{"username":"lisi","age":30}
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提交方式：put

• 删除

http://localhost:8080/user/1
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提交方式：delete

• 查询

http://localhost:8080/user/1
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提交方式：get

6.3 基于Rest风格的方法

• 引入依赖：

<dependencies>
    
    <dependency>
        <groupId>org.springframeworkgroupId>
        <artifactId>spring-webmvcartifactId>
        <version>5.2.9.RELEASEversion>
    dependency>

    <dependency>
        <groupId>org.apache.tomcatgroupId>
        <artifactId>tomcat-apiartifactId>
        <version>8.5.71version>
    dependency>

    <dependency>
        <groupId>org.projectlombokgroupId>
        <artifactId>lombokartifactId>
        <version>1.18.18version>
    dependency>
dependencies>
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• 实体类：

package com.dfbz.entity;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author lscl
 * @version 1.0
 * @intro:
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class City {
    private Integer id;         // 城市id
    private String cityName;    // 城市名称
    private Double GDP;         // 城市GDP,单位亿元
    private Boolean capital;    // 是否省会城市
}
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• 测试代码：

package com.dfbz.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @author lscl
 * @version 1.0
 * @intro:
 */
@Controller
@RequestMapping("/city")
public class CityController {

    /**
     * 新增
     */
    @PostMapping
    public void save(HttpServletResponse response) throws IOException {
        response.getWriter().write("save...");
    }

    /**
     * 删除
     *
     * @param id
     * @param response
     * @throws IOException
     */
    @DeleteMapping("/{id}")
    public void delete(@PathVariable Integer id, HttpServletResponse response) throws IOException {
        response.getWriter().write("delete...id: " + id);
    }

    /**
     * 修改
     *
     * @param id
     * @param response
     * @throws IOException
     */
    @PutMapping("/{id}")
    public void update(@PathVariable Integer id, HttpServletResponse response) throws IOException {
        response.getWriter().write("update...id: " + id);
    }

    /**
     * 根据id查询
     *
     * @param id
     * @param response
     * @throws IOException
     */
    @GetMapping("/{id}")
    public void findById(@PathVariable Integer id, HttpServletResponse response) throws IOException {
        response.getWriter().write("findById...id: " + id);
    }
}
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注意：restful风格的请求显然与我们之前的.form后置的请求相悖，我们把拦截规则更换为：/

• 准备一个表单：
• Demo01.jsp：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    



新增

    


删除

    <%--建立一个名为_method的一个表单项--%>
    
    


修改

    
    


查询

    



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6.4 配置HiddenHttpMethodFilter

默认情况下，HTML页面中的表单并不支持提交除GET/POST之外的请求，但SpringMVC提供有对应的过滤器来帮我们解决这个问题；

在web.xml中添加配置：

<filter>
    <filter-name>methodFilterfilter-name>
    <filter-class>org.springframework.web.filter.HiddenHttpMethodFilterfilter-class>
filter>
<filter-mapping>
    <filter-name>methodFilterfilter-name>
    <url-pattern>/*url-pattern>
filter-mapping>
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相关源码：

public class HiddenHttpMethodFilter extends OncePerRequestFilter {
    private static final List<String> ALLOWED_METHODS;
    public static final String DEFAULT_METHOD_PARAM = "_method";
    private String methodParam = "_method";

    public HiddenHttpMethodFilter() {
    }

    public void setMethodParam(String methodParam) {
        Assert.hasText(methodParam, "'methodParam' must not be empty");
        this.methodParam = methodParam;
    }

    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        HttpServletRequest requestToUse = request;
        if ("POST".equals(request.getMethod()) && request.getAttribute("javax.servlet.error.exception") == null) {
            // 获取request中_method表单项的值
            String paramValue = request.getParameter(this.methodParam);
            if (StringUtils.hasLength(paramValue)) {
                
                // 全部转换为大写(delete--->DELETE)
                String method = paramValue.toUpperCase(Locale.ENGLISH);
                if (ALLOWED_METHODS.contains(method)) {
                    requestToUse = new HiddenHttpMethodFilter.HttpMethodRequestWrapper(request, method);
                }
            }
        }

        filterChain.doFilter((ServletRequest)requestToUse, response);
    }

    static {
        ALLOWED_METHODS = Collections.unmodifiableList(Arrays.asList(HttpMethod.PUT.name(), HttpMethod.DELETE.name(), HttpMethod.PATCH.name()));
    }

    private static class HttpMethodRequestWrapper extends HttpServletRequestWrapper {
        private final String method;

        public HttpMethodRequestWrapper(HttpServletRequest request, String method) {
            
            // 修改request自身的的method值
            super(request);
            this.method = method;
        }

        public String getMethod() {
            return this.method;
        }
    }
}
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6.5 Restful相关注解

• @GetMapping：接收get请求
• @PostMapping：接收post请求
• @DeleteMapping：接收delete请求
• @PutMapping：接收put请求

修改后的CityController：

package com.dfbz.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/city")
public class CityController_RestFul {

    /**
     * 新增
     */
    @PostMapping
    public void save(HttpServletResponse response) throws IOException {

        response.getWriter().write("save...");
    }

    /**
     * 删除
     *
     * @param id
     * @param response
     * @throws IOException
     */
    @DeleteMapping("/{id}")
    public void delete(@PathVariable Integer id, HttpServletResponse response) throws IOException {
        response.getWriter().write("delete...id: " + id);
    }

    /**
     * 修改
     * @param id
     * @param response
     * @throws IOException
     */
    @PutMapping("/{id}")
    public void update(@PathVariable Integer id, HttpServletResponse response) throws IOException {

        response.getWriter().write("update...id: " + id);
    }

    /**
     * 根据id查询
     *
     * @param id
     * @param response
     * @throws IOException
     */
    @GetMapping("/{id}")
    public void findById(@PathVariable Integer id, HttpServletResponse response) throws IOException {
        response.getWriter().write("findById...id: " + id);
    }
}
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