【愚公系列】2023年04月 Java教学课程 142-Spring MVC框架的（文件上传下载、Restful风格API）

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>

<form action="/fileupload" method="post" enctype="multipart/form-data">
    上传LOGO： <input type="file" name="file"/><br/>
    <input type="submit" value="上传"/>
</form>

<bean id="multipartResolver"
      class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
</bean>

@RequestMapping(value = "/fileupload")
public void fileupload(MultipartFile file){
    file.transferTo(new File("file.png"));
}

@RequestMapping(value = "/fileupload")
//参数中定义MultipartFile参数，用于接收页面提交的type=file类型的表单，要求表单名称与参数名相同
public String fileupload(MultipartFile file,MultipartFile file1,MultipartFile file2, HttpServletRequest request) throws IOException {
    System.out.println("file upload is running ..."+file);
    //        MultipartFile参数中封装了上传的文件的相关信息
    //        System.out.println(file.getSize());
    //        System.out.println(file.getBytes().length);
    //        System.out.println(file.getContentType());
    //        System.out.println(file.getName());
    //        System.out.println(file.getOriginalFilename());
    //        System.out.println(file.isEmpty());
    //首先判断是否是空文件，也就是存储空间占用为0的文件
    if(!file.isEmpty()){
        //如果大小在范围要求内正常处理，否则抛出自定义异常告知用户（未实现）
        //获取原始上传的文件名，可以作为当前文件的真实名称保存到数据库中备用
        String fileName = file.getOriginalFilename();
        //设置保存的路径
        String realPath = request.getServletContext().getRealPath("/images");
        //保存文件的方法，指定保存的位置和文件名即可，通常文件名使用随机生成策略产生，避免文件名冲突问题
        file.transferTo(new File(realPath,file.getOriginalFilename()));
    }
    //测试一次性上传多个文件
    if(!file1.isEmpty()){
        String fileName = file1.getOriginalFilename();
        //可以根据需要，对不同种类的文件做不同的存储路径的区分，修改对应的保存位置即可
        String realPath = request.getServletContext().getRealPath("/images");
        file1.transferTo(new File(realPath,file1.getOriginalFilename()));
    }
    if(!file2.isEmpty()){
        String fileName = file2.getOriginalFilename();
        String realPath = request.getServletContext().getRealPath("/images");
        file2.transferTo(new File(realPath,file2.getOriginalFilename()));
    }
    return "page.jsp";
}

//设置rest风格的控制器
@RestController
//设置公共访问路径，配合下方访问路径使用
@RequestMapping("/user/")
public class UserController {

    //rest风格访问路径完整书写方式
    @RequestMapping("/user/{id}")
    //使用@PathVariable注解获取路径上配置的具名变量，该配置可以使用多次
    public String restLocation(@PathVariable Integer id){
        System.out.println("restful is running ....");
        return "success.jsp";
    }

    //rest风格访问路径简化书写方式，配合类注解@RequestMapping使用
    @RequestMapping("{id}")
    public String restLocation2(@PathVariable Integer id){
        System.out.println("restful is running ....get:"+id);
        return "success.jsp";
    }

    //接收GET请求配置方式
    @RequestMapping(value = "{id}",method = RequestMethod.GET)
    //接收GET请求简化配置方式
    @GetMapping("{id}")
    public String get(@PathVariable Integer id){
        System.out.println("restful is running ....get:"+id);
        return "success.jsp";
    }

    //接收POST请求配置方式
    @RequestMapping(value = "{id}",method = RequestMethod.POST)
    //接收POST请求简化配置方式
    @PostMapping("{id}")
    public String post(@PathVariable Integer id){
        System.out.println("restful is running ....post:"+id);
        return "success.jsp";
    }

    //接收PUT请求简化配置方式
    @RequestMapping(value = "{id}",method = RequestMethod.PUT)
    //接收PUT请求简化配置方式
    @PutMapping("{id}")
    public String put(@PathVariable Integer id){
        System.out.println("restful is running ....put:"+id);
        return "success.jsp";
    }

    //接收DELETE请求简化配置方式
    @RequestMapping(value = "{id}",method = RequestMethod.DELETE)
    //接收DELETE请求简化配置方式
    @DeleteMapping("{id}")
    public String delete(@PathVariable Integer id){
        System.out.println("restful is running ....delete:"+id);
        return "success.jsp";
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <filter>
        <filter-name>characterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>characterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <!--配置拦截器，解析请求中的参数_method，否则无法发起PUT请求与DELETE请求，配合页面表单使用-->
    <filter>
        <filter-name>HiddenHttpMethodFilter</filter-name>
        <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>HiddenHttpMethodFilter</filter-name>
        <servlet-name>DispatcherServlet</servlet-name>
    </filter-mapping>

    <servlet>
        <servlet-name>DispatcherServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath*:spring-mvc.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>DispatcherServlet</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

<form action="/user/1" method="post">
    <input type="hidden" name="_method" value="PUT"/>
    <input type="submit"/>
</form>  

@RestController
public class UserController {
    @RequestMapping(value = "/user/{id}",method = RequestMethod.DELETE)
    public String restDelete(@PathVariable String id){
        System.out.println("restful is running ....delete:"+id);
        return "success.jsp";
    }
}