超详细的文件上传和下载(Spring Boot)

灰太狼 2023-09-26 11:03 118阅读 0赞

## 超详细的文件上传和下载 ##

### 前言Ⅰ：@RequestParam和@RequestPart的区别 ###

**@RequestPart**

*  `@RequestPart`这个注解用在`multipart/form-data`表单提交请求的方法上。
 *  支持的请求方法的方式`MultipartFile`，属于Spring的`MultipartResolver`类。这个请求是通过`http协议`传输的

**@RequestParam**

*  `@RequestParam`支持`application/json`，也同样支持`multipart/form-data`请求

**代码演示**

*  测试一：使用@RequestPart接收json数据
    
    **结论**：**`@RequestPart`可以将`jsonData`的`json数据`转换为`Person对象`**
    
        /**
             * 测试 RequestParam 和 RequestPart区别2
             * @param person
             * @param file1
             * @return
             * @throws IOException
             * @throws ServletException
             */
        @RequestMapping(value = "/upload3",method = RequestMethod.POST)
        @ResponseBody
        public String readFile1(@RequestPart("person") Person person , @RequestPart("file1") MultipartFile file1)  {
              
            StringBuilder sb = new StringBuilder();
            sb.append(file1.getOriginalFilename()).append(";;;");
            return person.toString() + ":::" + sb.toString();
        }
    
    <table> 
     <thead> 
      <tr> 
       <th>参数名</th> 
       <th>参数值</th> 
       <th>参数类型</th> 
      </tr> 
     </thead> 
     <tbody> 
      <tr> 
       <td>file1</td> 
       <td>一个文件</td> 
       <td>file</td> 
      </tr> 
      <tr> 
       <td>person</td> 
       <td>{“name”:“cvzhanshi”,“age”:23}</td> 
       <td>application/json</td> 
      </tr> 
     </tbody> 
    </table>
    
    测试结果：能够用对象去接收json
    
    ![在这里插入图片描述][8f95498b21094eaca3e9298c916ba97c.png_pic_center]
 *  测试二：使用@RequestParam接收json数据
    
    **结论**：**`@RequestParam`对于`jsonData`的`json数据`只能用`String字符串`来接收**
    
        /**
             * 测试 RequestParam 和 RequestPart区别2
             * @param person
             * @param file1
             * @return
             * @throws IOException
             * @throws ServletException
             */
        @RequestMapping(value = "/upload3",method = RequestMethod.POST)
        @ResponseBody
        public String readFile1(@RequestParam("person") Person person , @RequestPart("file1") MultipartFile file1)  {
              
            StringBuilder sb = new StringBuilder();
            sb.append(file1.getOriginalFilename()).append(";;;");
            return person.toString() + ":::" + sb.toString();
        }

测试结果：报错 2022-10-08 10:19:48.434 WARN 3440 — \[nio-8888-exec-1\] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved \[org.springframework.web.method.annotation.MethodArgumentConversionNotSupportedException: **Failed to convert value of type ‘java.lang.String’ to required type ‘cn.cvzhanshi.test.entity.Person’;** nested exception is java.lang.IllegalStateException: **Cannot convert value of type ‘java.lang.String’ to required type ‘cn.cvzhanshi.test.entity.Person’:** no matching editors or conversion strategy found\]

报错说明：只能接收解析String类型的

**区别(总结)**

*  当请求为`multipart/form-data`时，**`@RequestParam`只能接收`String类型`的`name-value`值，`@RequestPart`可以接收复杂的请求域（像`json、xml`）**
 *  `@RequestParam` 依赖`Converter or PropertyEditor`进行数据解析， `@RequestPart`参考`'Content-Type' header`，依赖`HttpMessageConverters`进行数据解析
 *  **当请求头中指定Content-Type:multipart/form-data时，传递的json参数，@RequestPart注解可以用对象来接收，@RequestParam只能用字符串接收**
 *  @RequestParam适用于name-valueString类型的请求域，@RequestPart适用于复杂的请求域（像JSON，XML）；他们最大的不同是，当请求方法的请求参数类型不再是String类型的时候

### 前言Ⅱ：getParameter() 和 getPart() 区别 ###

**代码测试**

/**
         * 测试 RequestParam 和 RequestPart区别1
         * @param request
         * @param name
         * @param file1
         * @return
         * @throws IOException
         * @throws ServletException
         */
    @RequestMapping(value = "/upload1",method = RequestMethod.POST)
    @ResponseBody
    public String readFile(HttpServletRequest request,@RequestParam("name") String name ,@RequestPart("file1") MultipartFile file1) throws IOException, ServletException {
        
    
        String ageParameter = request.getParameter("age");
        Part agePart = request.getPart("age");
    
        String file2Parameter = request.getParameter("file2");
        Part file2Part = request.getPart("file2");
    
        Enumeration<String> parameterNames = request.getParameterNames();
        Collection<Part> parts = request.getParts();
        return "";
    }

**传递参数**

<table> 
 <thead> 
  <tr> 
   <th>key</th> 
   <th>value</th> 
   <th>type</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>name</td> 
   <td>cvzhanshi</td> 
   <td>text</td> 
  </tr> 
  <tr> 
   <td>age</td> 
   <td>18</td> 
   <td>text</td> 
  </tr> 
  <tr> 
   <td>file1</td> 
   <td>新建文本文档.txt</td> 
   <td>file</td> 
  </tr> 
  <tr> 
   <td>file2</td> 
   <td>美女.jpg</td> 
   <td>file</td> 
  </tr> 
 </tbody> 
</table>

**DeBug分析**：

*  **request**：可以看到request有两个 Parameter 和 两个 Part 参数
    
    ![在这里插入图片描述][b880d3ab0d644327827dba4029b99ac5.png_pic_center]
 *  **Parameter和Part**：request.getParameter获得的值以及request.getPart获得的值
    
    ![在这里插入图片描述][9e21aa66fd64400e97b7a2e0098d160c.png_pic_center]
    
    结果发现：使用 request.getParameter() 获取文件类型参数为空，使用 request.getPart() 获取非文件类型为空
 *  **ParameterNames和Parts**：getParameterNames()和getParts()获取参数名
    
    ![在这里插入图片描述][d7a8c4d834f74ea5a698ced42935f544.png]
    
    ![在这里插入图片描述][43b08543ed554f63be3e1d23235614a2.png]
    
    结果：**使用 request.getParameterNames() 只能获取非文件类型的参数名, 使用 request.getParts() 可以获取全部参数名**

**结论**

*  Part 能获取所有的请求参数的参数名，而 Parameter 只能获取非文件类型的参数名
 *  Part 不能获得非文件类型参数的参数值，Part获得二进制的输入流
 *  Parameter 只能获得非文件类型参数值
 *  使用 Part 获取文件很方便，可以获取文件大小文件类型

### Ⅰ：文件上传 ###

#### ① form-data 类型上传 ####

form-data 类型即常用的表单提交，可以通过两种方式接收前端传过来的文件

*  通过上述讲的Part 接收字节流，即@RequestPart注解以及request.getParts()
 *  通过MultipartFile类来接收前端传过来的文件

说明：两种方法差不多

> **前端接口提交**

![在这里插入图片描述][eca059c2e847450586222abf03eb9dc5.png]

> **上传文件的后端代码（接口）**

/**
         * form-data 类型(前端表单上传)
         * @param request
         * @param name
         * @param file3
         * @param photo
         * @return
         * @throws IOException
         * @throws ServletException
         */
    @RequestMapping(value = "/upload", method = RequestMethod.POST)
    @ResponseBody
    public String readFile(HttpServletRequest request,
                           @RequestParam("name") String name,
                           @RequestPart("file1") MultipartFile file3,
                           @RequestPart("photo") MultipartFile photo
                          ) throws IOException, ServletException {
        
    
    
    
        System.out.println(name);
        /*
                第一种 ： 使用 MultipartFile 封装好的 transferTo() 方法保存文件
                photo.transferTo(new File(path + photo.getOriginalFilename()));
             */
        /*
                第二种 ：  使用 MultipartFile 字节流保存文件
                fileUtil(file3, String.valueOf(path));
             */
    
    
        /*第三种 ：用 Part 接收文件字节流
                Part file2 = request.getPart("file2");
                file2.write(path + file2.getSubmittedFileName());
                request.getParts() 获取的是全部参数（name,age,file1,file2），包括文件参数和非文件参数
    		 */
        for (Part part : request.getParts()) {
        
            // 获取文件类型
            part.getContentType();
            // 获取文件大小
            part.getSize();
            // 获取文件名
            part.getSubmittedFileName();
            // 获取参数名 （name,age,file1,file2）
            part.getName();
            if(part.getContentType()!=null){
        
                part.write(path + part.getSubmittedFileName());
            }else{
        
                // 可以获取文本参数值,文本参数 part.getContentType()为 null
                System.out.println(request.getParameter(part.getName()));
            }
        }
        return "success";
    }
    
    
    /**
         * 字节流上传文件工具方法
         * @param file
         * @param path
         * @return
         */
    public String fileUtil(MultipartFile file, String path) {
        
        if (!file.isEmpty()) {
        
            try {
        
                // 转化成字节流
                byte[] bytes = file.getBytes();
                bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(
                    new File(path + file.getOriginalFilename())));
                // 写出
                bufferedOutputStream.write(bytes);
                // 关闭资源
                bufferedOutputStream.close();
                return file.getOriginalFilename() + " 上传成功";
            } catch (Exception e) {
        
                return file.getOriginalFilename() + " failed to upload ---> " + e;
            }
        } else {
        
            return file.getOriginalFilename() + "You failed to upload file was empty.";
        }
    }

> **测试**

![在这里插入图片描述][431d4412e3f7435ebe1dc9d9f908bb5c.png]

#### ② binary 类型上传 ####

binary 这一类型，指的就是一些二进制文件类型，如application/pdf，指定了特定二进制文件的MIME类型。就像对于text文件类型若没有特定的子类型

（subtype），就使用 text/plain。类似的，二进制文件没有特定或已知的 subtype，即使用 application/octet-stream，这是应用程序文件的默认值。

对于application/octet-stream，只能提交二进制，而且只能提交一个二进制，如果提交文件的话，只能提交一个文件，后台接收参数只能有一个，而且只能是流

（或者字节数组）

> **前端接口提交**

![在这里插入图片描述][1ba961750b0a4ffcb78b02fae2e1ef13.png]

> **上传文件的后端代码（接口）**

/**
         * binary 类型上传
         * @param request
         * @return
         * @throws IOException
         */
    @RequestMapping(value = "/upload2",method = RequestMethod.POST)
    public String upload2(HttpServletRequest request) throws IOException {
        
        ServletInputStream inputStream = null;
        FileOutputStream fileOutputStream = null;
        try {
        
            // 获取上传的文件流
            inputStream = request.getInputStream();
            // 定义输出流 上传到哪里
            fileOutputStream = new FileOutputStream(new File(path + "a.pdf"));
    
            int len;
            byte[] bytes = new byte[1024];
            while((len = inputStream.read(bytes))!=-1){
        
                fileOutputStream.write(bytes,0,len);
            }
        } catch (IOException e) {
        
            e.printStackTrace();
            return "上传失败";
        } finally {
        
            // 关闭资源
            if(fileOutputStream!=null){
        
                fileOutputStream.close();
            }
            if(inputStream!=null){
        
                inputStream.close();
            }
        }
        return "上传成功";
    }

> 测试

![在这里插入图片描述][Image 1]

说明：part 使用起来比较方便，接受的就是字节流，读取文件类型，文件名，文件大小也比较方便

#### ③ 配置说明 ####

如果不自定义配置的话，他会默认上传大小1M\\

SpringBoot项目的话通过配置文件配置

server:
      port: 8888
    spring:
      servlet:
        multipart:
          max-file-size: 10MB   # 最大上传大小
          max-request-size: 100MB   # 单文件最大上传大小

### Ⅱ：文件下载 ###

#### ① 补充说明 ####

> ##### Content-Disposition #####

*  在常规的 HTTP 应答中，**`Content-Disposition`** 响应头指示回复的内容该以何种形式展示，是以**内联**的形式（即网页或者页面的一部分），还是以**附件**的形式下载并保存到本地
 *  在 multipart/form-data 类型的应答消息体中，**`Content-Disposition`** 消息头可以被用在 multipart 消息体的子部分中，用来给出其对应字段的相关信息。各个子部分由在`Content-Type` 中定义的**分隔符**分隔。用在消息体自身则无实际意义。

**语法**：

*  **作为消息主体中的消息头**：在 HTTP 场景中，第一个参数或者是 `inline`（默认值，表示回复中的消息体会以页面的一部分或者整个页面的形式展示），或者是 `attachment`（意味着消息体应该被下载到本地；大多数浏览器会呈现一个“保存为”的对话框，将 `filename` 的值预填为下载后的文件名，假如它存在的话）。
    
        Content-Disposition: inline
        Content-Disposition: attachment
        Content-Disposition: attachment; filename="filename.jpg"
 *  **作为 multipart body 中的消息头**：在 HTTP 场景中。第一个参数总是固定不变的 `form-data`；附加的参数不区分大小写，并且拥有参数值，参数名与参数值用等号 (`'='`) 连接，参数值用双引号括起来。参数之间用分号 (`';'`) 分隔。
    
        Content-Disposition: form-data
        Content-Disposition: form-data; name="fieldName"
        Content-Disposition: form-data; name="fieldName"; filename="filename.jpg"

> ##### **response.setContentType()的String参数及对应类型** #####

<table> 
 <thead> 
  <tr> 
   <th align="left">文件扩展名</th> 
   <th align="left">Content-Type(Mime-Type)</th> 
   <th align="left">文件扩展名</th> 
   <th align="left">Content-Type(Mime-Type)</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left">.*（ 二进制流，不知道下载文件类型）</td> 
   <td align="left">application/octet-stream</td> 
   <td align="left">.tif</td> 
   <td align="left">image/tiff</td> 
  </tr> 
  <tr> 
   <td align="left">.001</td> 
   <td align="left">application/x-001</td> 
   <td align="left">.301</td> 
   <td align="left">application/x-301</td> 
  </tr> 
  <tr> 
   <td align="left">.323</td> 
   <td align="left">text/h323</td> 
   <td align="left">.906</td> 
   <td align="left">application/x-906</td> 
  </tr> 
  <tr> 
   <td align="left">.907</td> 
   <td align="left">drawing/907</td> 
   <td align="left">.a11</td> 
   <td align="left">application/x-a11</td> 
  </tr> 
  <tr> 
   <td align="left">.acp</td> 
   <td align="left">audio/x-mei-aac</td> 
   <td align="left">.ai</td> 
   <td align="left">application/postscript</td> 
  </tr> 
  <tr> 
   <td align="left">.aif</td> 
   <td align="left">audio/aiff</td> 
   <td align="left">.aifc</td> 
   <td align="left">audio/aiff</td> 
  </tr> 
  <tr> 
   <td align="left">.aiff</td> 
   <td align="left">audio/aiff</td> 
   <td align="left">.anv</td> 
   <td align="left">application/x-anv</td> 
  </tr> 
  <tr> 
   <td align="left">.asa</td> 
   <td align="left">text/asa</td> 
   <td align="left">.asf</td> 
   <td align="left">video/x-ms-asf</td> 
  </tr> 
  <tr> 
   <td align="left">.asp</td> 
   <td align="left">text/asp</td> 
   <td align="left">.asx</td> 
   <td align="left">video/x-ms-asf</td> 
  </tr> 
  <tr> 
   <td align="left">.au</td> 
   <td align="left">audio/basic</td> 
   <td align="left">.avi</td> 
   <td align="left">video/avi</td> 
  </tr> 
  <tr> 
   <td align="left">.awf</td> 
   <td align="left">application/vnd.adobe.workflow</td> 
   <td align="left">.biz</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.bmp</td> 
   <td align="left">application/x-bmp</td> 
   <td align="left">.bot</td> 
   <td align="left">application/x-bot</td> 
  </tr> 
  <tr> 
   <td align="left">.c4t</td> 
   <td align="left">application/x-c4t</td> 
   <td align="left">.c90</td> 
   <td align="left">application/x-c90</td> 
  </tr> 
  <tr> 
   <td align="left">.cal</td> 
   <td align="left">application/x-cals</td> 
   <td align="left">.cat</td> 
   <td align="left">application/vnd.ms-pki.seccat</td> 
  </tr> 
  <tr> 
   <td align="left">.cdf</td> 
   <td align="left">application/x-netcdf</td> 
   <td align="left">.cdr</td> 
   <td align="left">application/x-cdr</td> 
  </tr> 
  <tr> 
   <td align="left">.cel</td> 
   <td align="left">application/x-cel</td> 
   <td align="left">.cer</td> 
   <td align="left">application/x-x509-ca-cert</td> 
  </tr> 
  <tr> 
   <td align="left">.cg4</td> 
   <td align="left">application/x-g4</td> 
   <td align="left">.cgm</td> 
   <td align="left">application/x-cgm</td> 
  </tr> 
  <tr> 
   <td align="left">.cit</td> 
   <td align="left">application/x-cit</td> 
   <td align="left">.class</td> 
   <td align="left">java/*</td> 
  </tr> 
  <tr> 
   <td align="left">.cml</td> 
   <td align="left">text/xml</td> 
   <td align="left">.cmp</td> 
   <td align="left">application/x-cmp</td> 
  </tr> 
  <tr> 
   <td align="left">.cmx</td> 
   <td align="left">application/x-cmx</td> 
   <td align="left">.cot</td> 
   <td align="left">application/x-cot</td> 
  </tr> 
  <tr> 
   <td align="left">.crl</td> 
   <td align="left">application/pkix-crl</td> 
   <td align="left">.crt</td> 
   <td align="left">application/x-x509-ca-cert</td> 
  </tr> 
  <tr> 
   <td align="left">.csi</td> 
   <td align="left">application/x-csi</td> 
   <td align="left">.css</td> 
   <td align="left">text/css</td> 
  </tr> 
  <tr> 
   <td align="left">.cut</td> 
   <td align="left">application/x-cut</td> 
   <td align="left">.dbf</td> 
   <td align="left">application/x-dbf</td> 
  </tr> 
  <tr> 
   <td align="left">.dbm</td> 
   <td align="left">application/x-dbm</td> 
   <td align="left">.dbx</td> 
   <td align="left">application/x-dbx</td> 
  </tr> 
  <tr> 
   <td align="left">.dcd</td> 
   <td align="left">text/xml</td> 
   <td align="left">.dcx</td> 
   <td align="left">application/x-dcx</td> 
  </tr> 
  <tr> 
   <td align="left">.der</td> 
   <td align="left">application/x-x509-ca-cert</td> 
   <td align="left">.dgn</td> 
   <td align="left">application/x-dgn</td> 
  </tr> 
  <tr> 
   <td align="left">.dib</td> 
   <td align="left">application/x-dib</td> 
   <td align="left">.dll</td> 
   <td align="left">application/x-msdownload</td> 
  </tr> 
  <tr> 
   <td align="left">.doc</td> 
   <td align="left">application/msword</td> 
   <td align="left">.dot</td> 
   <td align="left">application/msword</td> 
  </tr> 
  <tr> 
   <td align="left">.drw</td> 
   <td align="left">application/x-drw</td> 
   <td align="left">.dtd</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.dwf</td> 
   <td align="left">Model/vnd.dwf</td> 
   <td align="left">.dwf</td> 
   <td align="left">application/x-dwf</td> 
  </tr> 
  <tr> 
   <td align="left">.dwg</td> 
   <td align="left">application/x-dwg</td> 
   <td align="left">.dxb</td> 
   <td align="left">application/x-dxb</td> 
  </tr> 
  <tr> 
   <td align="left">.dxf</td> 
   <td align="left">application/x-dxf</td> 
   <td align="left">.edn</td> 
   <td align="left">application/vnd.adobe.edn</td> 
  </tr> 
  <tr> 
   <td align="left">.emf</td> 
   <td align="left">application/x-emf</td> 
   <td align="left">.eml</td> 
   <td align="left">message/rfc822</td> 
  </tr> 
  <tr> 
   <td align="left">.ent</td> 
   <td align="left">text/xml</td> 
   <td align="left">.epi</td> 
   <td align="left">application/x-epi</td> 
  </tr> 
  <tr> 
   <td align="left">.eps</td> 
   <td align="left">application/x-ps</td> 
   <td align="left">.eps</td> 
   <td align="left">application/postscript</td> 
  </tr> 
  <tr> 
   <td align="left">.etd</td> 
   <td align="left">application/x-ebx</td> 
   <td align="left">.exe</td> 
   <td align="left">application/x-msdownload</td> 
  </tr> 
  <tr> 
   <td align="left">.fax</td> 
   <td align="left">image/fax</td> 
   <td align="left">.fdf</td> 
   <td align="left">application/vnd.fdf</td> 
  </tr> 
  <tr> 
   <td align="left">.fif</td> 
   <td align="left">application/fractals</td> 
   <td align="left">.fo</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.frm</td> 
   <td align="left">application/x-frm</td> 
   <td align="left">.g4</td> 
   <td align="left">application/x-g4</td> 
  </tr> 
  <tr> 
   <td align="left">.gbr</td> 
   <td align="left">application/x-gbr</td> 
   <td align="left">.</td> 
   <td align="left">application/x-</td> 
  </tr> 
  <tr> 
   <td align="left">.gif</td> 
   <td align="left">image/gif</td> 
   <td align="left">.gl2</td> 
   <td align="left">application/x-gl2</td> 
  </tr> 
  <tr> 
   <td align="left">.gp4</td> 
   <td align="left">application/x-gp4</td> 
   <td align="left">.hgl</td> 
   <td align="left">application/x-hgl</td> 
  </tr> 
  <tr> 
   <td align="left">.hmr</td> 
   <td align="left">application/x-hmr</td> 
   <td align="left">.hpg</td> 
   <td align="left">application/x-hpgl</td> 
  </tr> 
  <tr> 
   <td align="left">.hpl</td> 
   <td align="left">application/x-hpl</td> 
   <td align="left">.hqx</td> 
   <td align="left">application/mac-binhex40</td> 
  </tr> 
  <tr> 
   <td align="left">.hrf</td> 
   <td align="left">application/x-hrf</td> 
   <td align="left">.hta</td> 
   <td align="left">application/hta</td> 
  </tr> 
  <tr> 
   <td align="left">.htc</td> 
   <td align="left">text/x-component</td> 
   <td align="left">.htm</td> 
   <td align="left">text/html</td> 
  </tr> 
  <tr> 
   <td align="left">.html</td> 
   <td align="left">text/html</td> 
   <td align="left">.htt</td> 
   <td align="left">text/webviewhtml</td> 
  </tr> 
  <tr> 
   <td align="left">.htx</td> 
   <td align="left">text/html</td> 
   <td align="left">.icb</td> 
   <td align="left">application/x-icb</td> 
  </tr> 
  <tr> 
   <td align="left">.ico</td> 
   <td align="left">image/x-icon</td> 
   <td align="left">.ico</td> 
   <td align="left">application/x-ico</td> 
  </tr> 
  <tr> 
   <td align="left">.iff</td> 
   <td align="left">application/x-iff</td> 
   <td align="left">.ig4</td> 
   <td align="left">application/x-g4</td> 
  </tr> 
  <tr> 
   <td align="left">.igs</td> 
   <td align="left">application/x-igs</td> 
   <td align="left">.iii</td> 
   <td align="left">application/x-iphone</td> 
  </tr> 
  <tr> 
   <td align="left">.img</td> 
   <td align="left">application/x-img</td> 
   <td align="left">.ins</td> 
   <td align="left">application/x-internet-signup</td> 
  </tr> 
  <tr> 
   <td align="left">.isp</td> 
   <td align="left">application/x-internet-signup</td> 
   <td align="left">.IVF</td> 
   <td align="left">video/x-ivf</td> 
  </tr> 
  <tr> 
   <td align="left">.java</td> 
   <td align="left">java/*</td> 
   <td align="left">.jfif</td> 
   <td align="left">image/jpeg</td> 
  </tr> 
  <tr> 
   <td align="left">.jpe</td> 
   <td align="left">image/jpeg</td> 
   <td align="left">.jpe</td> 
   <td align="left">application/x-jpe</td> 
  </tr> 
  <tr> 
   <td align="left">.jpeg</td> 
   <td align="left">image/jpeg</td> 
   <td align="left">.jpg</td> 
   <td align="left">image/jpeg</td> 
  </tr> 
  <tr> 
   <td align="left">.jpg</td> 
   <td align="left">application/x-jpg</td> 
   <td align="left">.js</td> 
   <td align="left">application/x-javascript</td> 
  </tr> 
  <tr> 
   <td align="left">.jsp</td> 
   <td align="left">text/html</td> 
   <td align="left">.la1</td> 
   <td align="left">audio/x-liquid-file</td> 
  </tr> 
  <tr> 
   <td align="left">.lar</td> 
   <td align="left">application/x-laplayer-reg</td> 
   <td align="left">.latex</td> 
   <td align="left">application/x-latex</td> 
  </tr> 
  <tr> 
   <td align="left">.lavs</td> 
   <td align="left">audio/x-liquid-secure</td> 
   <td align="left">.lbm</td> 
   <td align="left">application/x-lbm</td> 
  </tr> 
  <tr> 
   <td align="left">.lmsff</td> 
   <td align="left">audio/x-la-lms</td> 
   <td align="left">.ls</td> 
   <td align="left">application/x-javascript</td> 
  </tr> 
  <tr> 
   <td align="left">.ltr</td> 
   <td align="left">application/x-ltr</td> 
   <td align="left">.m1v</td> 
   <td align="left">video/x-mpeg</td> 
  </tr> 
  <tr> 
   <td align="left">.m2v</td> 
   <td align="left">video/x-mpeg</td> 
   <td align="left">.m3u</td> 
   <td align="left">audio/mpegurl</td> 
  </tr> 
  <tr> 
   <td align="left">.m4e</td> 
   <td align="left">video/mpeg4</td> 
   <td align="left">.mac</td> 
   <td align="left">application/x-mac</td> 
  </tr> 
  <tr> 
   <td align="left">.man</td> 
   <td align="left">application/x-troff-man</td> 
   <td align="left">.math</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.mdb</td> 
   <td align="left">application/msaccess</td> 
   <td align="left">.mdb</td> 
   <td align="left">application/x-mdb</td> 
  </tr> 
  <tr> 
   <td align="left">.mfp</td> 
   <td align="left">application/x-shockwave-flash</td> 
   <td align="left">.mht</td> 
   <td align="left">message/rfc822</td> 
  </tr> 
  <tr> 
   <td align="left">.mhtml</td> 
   <td align="left">message/rfc822</td> 
   <td align="left">.mi</td> 
   <td align="left">application/x-mi</td> 
  </tr> 
  <tr> 
   <td align="left">.mid</td> 
   <td align="left">audio/mid</td> 
   <td align="left">.midi</td> 
   <td align="left">audio/mid</td> 
  </tr> 
  <tr> 
   <td align="left">.mil</td> 
   <td align="left">application/x-mil</td> 
   <td align="left">.mml</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.mnd</td> 
   <td align="left">audio/x-musicnet-download</td> 
   <td align="left">.mns</td> 
   <td align="left">audio/x-musicnet-stream</td> 
  </tr> 
  <tr> 
   <td align="left">.mocha</td> 
   <td align="left">application/x-javascript</td> 
   <td align="left">.movie</td> 
   <td align="left">video/x-sgi-movie</td> 
  </tr> 
  <tr> 
   <td align="left">.mp1</td> 
   <td align="left">audio/mp1</td> 
   <td align="left">.mp2</td> 
   <td align="left">audio/mp2</td> 
  </tr> 
  <tr> 
   <td align="left">.mp2v</td> 
   <td align="left">video/mpeg</td> 
   <td align="left">.mp3</td> 
   <td align="left">audio/mp3</td> 
  </tr> 
  <tr> 
   <td align="left">.mp4</td> 
   <td align="left">video/mpeg4</td> 
   <td align="left">.mpa</td> 
   <td align="left">video/x-mpg</td> 
  </tr> 
  <tr> 
   <td align="left">.mpd</td> 
   <td align="left">application/vnd.ms-project</td> 
   <td align="left">.mpe</td> 
   <td align="left">video/x-mpeg</td> 
  </tr> 
  <tr> 
   <td align="left">.mpeg</td> 
   <td align="left">video/mpg</td> 
   <td align="left">.mpg</td> 
   <td align="left">video/mpg</td> 
  </tr> 
  <tr> 
   <td align="left">.mpga</td> 
   <td align="left">audio/rn-mpeg</td> 
   <td align="left">.mpp</td> 
   <td align="left">application/vnd.ms-project</td> 
  </tr> 
  <tr> 
   <td align="left">.mps</td> 
   <td align="left">video/x-mpeg</td> 
   <td align="left">.mpt</td> 
   <td align="left">application/vnd.ms-project</td> 
  </tr> 
  <tr> 
   <td align="left">.mpv</td> 
   <td align="left">video/mpg</td> 
   <td align="left">.mpv2</td> 
   <td align="left">video/mpeg</td> 
  </tr> 
  <tr> 
   <td align="left">.mpw</td> 
   <td align="left">application/vnd.ms-project</td> 
   <td align="left">.mpx</td> 
   <td align="left">application/vnd.ms-project</td> 
  </tr> 
  <tr> 
   <td align="left">.mtx</td> 
   <td align="left">text/xml</td> 
   <td align="left">.mxp</td> 
   <td align="left">application/x-mmxp</td> 
  </tr> 
  <tr> 
   <td align="left">.net</td> 
   <td align="left">image/pnetvue</td> 
   <td align="left">.nrf</td> 
   <td align="left">application/x-nrf</td> 
  </tr> 
  <tr> 
   <td align="left">.nws</td> 
   <td align="left">message/rfc822</td> 
   <td align="left">.odc</td> 
   <td align="left">text/x-ms-odc</td> 
  </tr> 
  <tr> 
   <td align="left">.out</td> 
   <td align="left">application/x-out</td> 
   <td align="left">.p10</td> 
   <td align="left">application/pkcs10</td> 
  </tr> 
  <tr> 
   <td align="left">.p12</td> 
   <td align="left">application/x-pkcs12</td> 
   <td align="left">.p7b</td> 
   <td align="left">application/x-pkcs7-certificates</td> 
  </tr> 
  <tr> 
   <td align="left">.p7c</td> 
   <td align="left">application/pkcs7-mime</td> 
   <td align="left">.p7m</td> 
   <td align="left">application/pkcs7-mime</td> 
  </tr> 
  <tr> 
   <td align="left">.p7r</td> 
   <td align="left">application/x-pkcs7-certreqresp</td> 
   <td align="left">.p7s</td> 
   <td align="left">application/pkcs7-signature</td> 
  </tr> 
  <tr> 
   <td align="left">.pc5</td> 
   <td align="left">application/x-pc5</td> 
   <td align="left">.pci</td> 
   <td align="left">application/x-pci</td> 
  </tr> 
  <tr> 
   <td align="left">.pcl</td> 
   <td align="left">application/x-pcl</td> 
   <td align="left">.pcx</td> 
   <td align="left">application/x-pcx</td> 
  </tr> 
  <tr> 
   <td align="left">.pdf</td> 
   <td align="left">application/pdf</td> 
   <td align="left">.pdf</td> 
   <td align="left">application/pdf</td> 
  </tr> 
  <tr> 
   <td align="left">.pdx</td> 
   <td align="left">application/vnd.adobe.pdx</td> 
   <td align="left">.pfx</td> 
   <td align="left">application/x-pkcs12</td> 
  </tr> 
  <tr> 
   <td align="left">.pgl</td> 
   <td align="left">application/x-pgl</td> 
   <td align="left">.pic</td> 
   <td align="left">application/x-pic</td> 
  </tr> 
  <tr> 
   <td align="left">.pko</td> 
   <td align="left">application/vnd.ms-pki.pko</td> 
   <td align="left">.pl</td> 
   <td align="left">application/x-perl</td> 
  </tr> 
  <tr> 
   <td align="left">.plg</td> 
   <td align="left">text/html</td> 
   <td align="left">.pls</td> 
   <td align="left">audio/scpls</td> 
  </tr> 
  <tr> 
   <td align="left">.plt</td> 
   <td align="left">application/x-plt</td> 
   <td align="left">.png</td> 
   <td align="left">image/png</td> 
  </tr> 
  <tr> 
   <td align="left">.png</td> 
   <td align="left">application/x-png</td> 
   <td align="left">.pot</td> 
   <td align="left">application/vnd.ms-powerpoint</td> 
  </tr> 
  <tr> 
   <td align="left">.ppa</td> 
   <td align="left">application/vnd.ms-powerpoint</td> 
   <td align="left">.ppm</td> 
   <td align="left">application/x-ppm</td> 
  </tr> 
  <tr> 
   <td align="left">.pps</td> 
   <td align="left">application/vnd.ms-powerpoint</td> 
   <td align="left">.ppt</td> 
   <td align="left">application/vnd.ms-powerpoint</td> 
  </tr> 
  <tr> 
   <td align="left">.ppt</td> 
   <td align="left">application/x-ppt</td> 
   <td align="left">.pr</td> 
   <td align="left">application/x-pr</td> 
  </tr> 
  <tr> 
   <td align="left">.prf</td> 
   <td align="left">application/pics-rules</td> 
   <td align="left">.prn</td> 
   <td align="left">application/x-prn</td> 
  </tr> 
  <tr> 
   <td align="left">.prt</td> 
   <td align="left">application/x-prt</td> 
   <td align="left">.ps</td> 
   <td align="left">application/x-ps</td> 
  </tr> 
  <tr> 
   <td align="left">.ps</td> 
   <td align="left">application/postscript</td> 
   <td align="left">.ptn</td> 
   <td align="left">application/x-ptn</td> 
  </tr> 
  <tr> 
   <td align="left">.pwz</td> 
   <td align="left">application/vnd.ms-powerpoint</td> 
   <td align="left">.r3t</td> 
   <td align="left">text/vnd.rn-realtext3d</td> 
  </tr> 
  <tr> 
   <td align="left">.ra</td> 
   <td align="left">audio/vnd.rn-realaudio</td> 
   <td align="left">.ram</td> 
   <td align="left">audio/x-pn-realaudio</td> 
  </tr> 
  <tr> 
   <td align="left">.ras</td> 
   <td align="left">application/x-ras</td> 
   <td align="left">.rat</td> 
   <td align="left">application/rat-file</td> 
  </tr> 
  <tr> 
   <td align="left">.rdf</td> 
   <td align="left">text/xml</td> 
   <td align="left">.rec</td> 
   <td align="left">application/vnd.rn-recording</td> 
  </tr> 
  <tr> 
   <td align="left">.red</td> 
   <td align="left">application/x-red</td> 
   <td align="left">.rgb</td> 
   <td align="left">application/x-rgb</td> 
  </tr> 
  <tr> 
   <td align="left">.rjs</td> 
   <td align="left">application/vnd.rn-realsystem-rjs</td> 
   <td align="left">.rjt</td> 
   <td align="left">application/vnd.rn-realsystem-rjt</td> 
  </tr> 
  <tr> 
   <td align="left">.rlc</td> 
   <td align="left">application/x-rlc</td> 
   <td align="left">.rle</td> 
   <td align="left">application/x-rle</td> 
  </tr> 
  <tr> 
   <td align="left">.rm</td> 
   <td align="left">application/vnd.rn-realmedia</td> 
   <td align="left">.rmf</td> 
   <td align="left">application/vnd.adobe.rmf</td> 
  </tr> 
  <tr> 
   <td align="left">.rmi</td> 
   <td align="left">audio/mid</td> 
   <td align="left">.rmj</td> 
   <td align="left">application/vnd.rn-realsystem-rmj</td> 
  </tr> 
  <tr> 
   <td align="left">.rmm</td> 
   <td align="left">audio/x-pn-realaudio</td> 
   <td align="left">.rmp</td> 
   <td align="left">application/vnd.rn-rn_music_package</td> 
  </tr> 
  <tr> 
   <td align="left">.rms</td> 
   <td align="left">application/vnd.rn-realmedia-secure</td> 
   <td align="left">.rmvb</td> 
   <td align="left">application/vnd.rn-realmedia-vbr</td> 
  </tr> 
  <tr> 
   <td align="left">.rmx</td> 
   <td align="left">application/vnd.rn-realsystem-rmx</td> 
   <td align="left">.rnx</td> 
   <td align="left">application/vnd.rn-realplayer</td> 
  </tr> 
  <tr> 
   <td align="left">.rp</td> 
   <td align="left">image/vnd.rn-realpix</td> 
   <td align="left">.rpm</td> 
   <td align="left">audio/x-pn-realaudio-plugin</td> 
  </tr> 
  <tr> 
   <td align="left">.rsml</td> 
   <td align="left">application/vnd.rn-rsml</td> 
   <td align="left">.rt</td> 
   <td align="left">text/vnd.rn-realtext</td> 
  </tr> 
  <tr> 
   <td align="left">.rtf</td> 
   <td align="left">application/msword</td> 
   <td align="left">.rtf</td> 
   <td align="left">application/x-rtf</td> 
  </tr> 
  <tr> 
   <td align="left">.rv</td> 
   <td align="left">video/vnd.rn-realvideo</td> 
   <td align="left">.sam</td> 
   <td align="left">application/x-sam</td> 
  </tr> 
  <tr> 
   <td align="left">.sat</td> 
   <td align="left">application/x-sat</td> 
   <td align="left">.sdp</td> 
   <td align="left">application/sdp</td> 
  </tr> 
  <tr> 
   <td align="left">.sdw</td> 
   <td align="left">application/x-sdw</td> 
   <td align="left">.sit</td> 
   <td align="left">application/x-stuffit</td> 
  </tr> 
  <tr> 
   <td align="left">.slb</td> 
   <td align="left">application/x-slb</td> 
   <td align="left">.sld</td> 
   <td align="left">application/x-sld</td> 
  </tr> 
  <tr> 
   <td align="left">.slk</td> 
   <td align="left">drawing/x-slk</td> 
   <td align="left">.smi</td> 
   <td align="left">application/smil</td> 
  </tr> 
  <tr> 
   <td align="left">.smil</td> 
   <td align="left">application/smil</td> 
   <td align="left">.smk</td> 
   <td align="left">application/x-smk</td> 
  </tr> 
  <tr> 
   <td align="left">.snd</td> 
   <td align="left">audio/basic</td> 
   <td align="left">.sol</td> 
   <td align="left">text/plain</td> 
  </tr> 
  <tr> 
   <td align="left">.sor</td> 
   <td align="left">text/plain</td> 
   <td align="left">.spc</td> 
   <td align="left">application/x-pkcs7-certificates</td> 
  </tr> 
  <tr> 
   <td align="left">.spl</td> 
   <td align="left">application/futuresplash</td> 
   <td align="left">.spp</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.ssm</td> 
   <td align="left">application/streamingmedia</td> 
   <td align="left">.sst</td> 
   <td align="left">application/vnd.ms-pki.certstore</td> 
  </tr> 
  <tr> 
   <td align="left">.stl</td> 
   <td align="left">application/vnd.ms-pki.stl</td> 
   <td align="left">.stm</td> 
   <td align="left">text/html</td> 
  </tr> 
  <tr> 
   <td align="left">.sty</td> 
   <td align="left">application/x-sty</td> 
   <td align="left">.svg</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.swf</td> 
   <td align="left">application/x-shockwave-flash</td> 
   <td align="left">.tdf</td> 
   <td align="left">application/x-tdf</td> 
  </tr> 
  <tr> 
   <td align="left">.tg4</td> 
   <td align="left">application/x-tg4</td> 
   <td align="left">.tga</td> 
   <td align="left">application/x-tga</td> 
  </tr> 
  <tr> 
   <td align="left">.tif</td> 
   <td align="left">image/tiff</td> 
   <td align="left">.tif</td> 
   <td align="left">application/x-tif</td> 
  </tr> 
  <tr> 
   <td align="left">.tiff</td> 
   <td align="left">image/tiff</td> 
   <td align="left">.tld</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.top</td> 
   <td align="left">drawing/x-top</td> 
   <td align="left">.torrent</td> 
   <td align="left">application/x-bittorrent</td> 
  </tr> 
  <tr> 
   <td align="left">.tsd</td> 
   <td align="left">text/xml</td> 
   <td align="left">.txt</td> 
   <td align="left">text/plain</td> 
  </tr> 
  <tr> 
   <td align="left">.uin</td> 
   <td align="left">application/x-icq</td> 
   <td align="left">.uls</td> 
   <td align="left">text/iuls</td> 
  </tr> 
  <tr> 
   <td align="left">.vcf</td> 
   <td align="left">text/x-vcard</td> 
   <td align="left">.vda</td> 
   <td align="left">application/x-vda</td> 
  </tr> 
  <tr> 
   <td align="left">.vdx</td> 
   <td align="left">application/vnd.visio</td> 
   <td align="left">.vml</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.vpg</td> 
   <td align="left">application/x-vpeg005</td> 
   <td align="left">.vsd</td> 
   <td align="left">application/vnd.visio</td> 
  </tr> 
  <tr> 
   <td align="left">.vsd</td> 
   <td align="left">application/x-vsd</td> 
   <td align="left">.vss</td> 
   <td align="left">application/vnd.visio</td> 
  </tr> 
  <tr> 
   <td align="left">.vst</td> 
   <td align="left">application/vnd.visio</td> 
   <td align="left">.vst</td> 
   <td align="left">application/x-vst</td> 
  </tr> 
  <tr> 
   <td align="left">.vsw</td> 
   <td align="left">application/vnd.visio</td> 
   <td align="left">.vsx</td> 
   <td align="left">application/vnd.visio</td> 
  </tr> 
  <tr> 
   <td align="left">.vtx</td> 
   <td align="left">application/vnd.visio</td> 
   <td align="left">.vxml</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.wav</td> 
   <td align="left">audio/wav</td> 
   <td align="left">.wax</td> 
   <td align="left">audio/x-ms-wax</td> 
  </tr> 
  <tr> 
   <td align="left">.wb1</td> 
   <td align="left">application/x-wb1</td> 
   <td align="left">.wb2</td> 
   <td align="left">application/x-wb2</td> 
  </tr> 
  <tr> 
   <td align="left">.wb3</td> 
   <td align="left">application/x-wb3</td> 
   <td align="left">.wbmp</td> 
   <td align="left">image/vnd.wap.wbmp</td> 
  </tr> 
  <tr> 
   <td align="left">.wiz</td> 
   <td align="left">application/msword</td> 
   <td align="left">.wk3</td> 
   <td align="left">application/x-wk3</td> 
  </tr> 
  <tr> 
   <td align="left">.wk4</td> 
   <td align="left">application/x-wk4</td> 
   <td align="left">.wkq</td> 
   <td align="left">application/x-wkq</td> 
  </tr> 
  <tr> 
   <td align="left">.wks</td> 
   <td align="left">application/x-wks</td> 
   <td align="left">.wm</td> 
   <td align="left">video/x-ms-wm</td> 
  </tr> 
  <tr> 
   <td align="left">.wma</td> 
   <td align="left">audio/x-ms-wma</td> 
   <td align="left">.wmd</td> 
   <td align="left">application/x-ms-wmd</td> 
  </tr> 
  <tr> 
   <td align="left">.wmf</td> 
   <td align="left">application/x-wmf</td> 
   <td align="left">.wml</td> 
   <td align="left">text/vnd.wap.wml</td> 
  </tr> 
  <tr> 
   <td align="left">.wmv</td> 
   <td align="left">video/x-ms-wmv</td> 
   <td align="left">.wmx</td> 
   <td align="left">video/x-ms-wmx</td> 
  </tr> 
  <tr> 
   <td align="left">.wmz</td> 
   <td align="left">application/x-ms-wmz</td> 
   <td align="left">.wp6</td> 
   <td align="left">application/x-wp6</td> 
  </tr> 
  <tr> 
   <td align="left">.wpd</td> 
   <td align="left">application/x-wpd</td> 
   <td align="left">.wpg</td> 
   <td align="left">application/x-wpg</td> 
  </tr> 
  <tr> 
   <td align="left">.wpl</td> 
   <td align="left">application/vnd.ms-wpl</td> 
   <td align="left">.wq1</td> 
   <td align="left">application/x-wq1</td> 
  </tr> 
  <tr> 
   <td align="left">.wr1</td> 
   <td align="left">application/x-wr1</td> 
   <td align="left">.wri</td> 
   <td align="left">application/x-wri</td> 
  </tr> 
  <tr> 
   <td align="left">.wrk</td> 
   <td align="left">application/x-wrk</td> 
   <td align="left">.ws</td> 
   <td align="left">application/x-ws</td> 
  </tr> 
  <tr> 
   <td align="left">.ws2</td> 
   <td align="left">application/x-ws</td> 
   <td align="left">.wsc</td> 
   <td align="left">text/scriptlet</td> 
  </tr> 
  <tr> 
   <td align="left">.wsdl</td> 
   <td align="left">text/xml</td> 
   <td align="left">.wvx</td> 
   <td align="left">video/x-ms-wvx</td> 
  </tr> 
  <tr> 
   <td align="left">.xdp</td> 
   <td align="left">application/vnd.adobe.xdp</td> 
   <td align="left">.xdr</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.xfd</td> 
   <td align="left">application/vnd.adobe.xfd</td> 
   <td align="left">.xfdf</td> 
   <td align="left">application/vnd.adobe.xfdf</td> 
  </tr> 
  <tr> 
   <td align="left">.xhtml</td> 
   <td align="left">text/html</td> 
   <td align="left">.xls</td> 
   <td align="left">application/vnd.ms-excel</td> 
  </tr> 
  <tr> 
   <td align="left">.xls</td> 
   <td align="left">application/x-xls</td> 
   <td align="left">.xlw</td> 
   <td align="left">application/x-xlw</td> 
  </tr> 
  <tr> 
   <td align="left">.xml</td> 
   <td align="left">text/xml</td> 
   <td align="left">.xpl</td> 
   <td align="left">audio/scpls</td> 
  </tr> 
  <tr> 
   <td align="left">.xq</td> 
   <td align="left">text/xml</td> 
   <td align="left">.xql</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.xquery</td> 
   <td align="left">text/xml</td> 
   <td align="left">.xsd</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.xsl</td> 
   <td align="left">text/xml</td> 
   <td align="left">.xslt</td> 
   <td align="left">text/xml</td> 
  </tr> 
  <tr> 
   <td align="left">.xwd</td> 
   <td align="left">application/x-xwd</td> 
   <td align="left">.x_b</td> 
   <td align="left">application/x-x_b</td> 
  </tr> 
  <tr> 
   <td align="left">.sis</td> 
   <td align="left">application/vnd.symbian.install</td> 
   <td align="left">.sisx</td> 
   <td align="left">application/vnd.symbian.install</td> 
  </tr> 
  <tr> 
   <td align="left">.x_t</td> 
   <td align="left">application/x-x_t</td> 
   <td align="left">.ipa</td> 
   <td align="left">application/vnd.iphone</td> 
  </tr> 
  <tr> 
   <td align="left">.apk</td> 
   <td align="left">application/vnd.android.package-archive</td> 
   <td align="left">.xap</td> 
   <td align="left">application/x-silverlight-app</td> 
  </tr> 
 </tbody> 
</table>

#### ② 下载本地资源 ####

> 下载代码

/**
         * 下载本地资源
         * @param fileName  下载的文件名
         * @param response  响应头
         * @param isOnLine  是否默认下载  true浏览器中打开
         * @throws IOException
         */
    @GetMapping("/download")
    public void download(String fileName, HttpServletResponse response, boolean isOnLine) throws IOException {
        
        // 路径可以指定当前项目相对路径
        File file = new File(path + fileName);
        if (file.exists()) {
        
            // 把文件转化成流
            FileInputStream fileInputStream = new FileInputStream(file);
            ServletOutputStream outputStream = response.getOutputStream();
            // 是否立即下载
            if(!isOnLine){
        
                response.setContentType("application/octet-stream");
                // 如果文件名为中文需要设置编码
                response.setHeader("Content-Disposition", "attachment;fileName=" + URLEncoder.encode("背景.jpg", "utf8"));
            }
            byte[] bytes = new byte[1024];
            int len;
            // 把文件流写入响应头
            while ((len = fileInputStream.read(bytes)) != -1) {
        
                outputStream.write(bytes, 0, len);
            }
        }
    }

测试链接：http://localhost:8888/download?fileName=背景.jpg

或者http://localhost:8888/download?isOnLine=true&fileName=背景.jpg

#### ③ 下载网络资源 ####

> 代码演示

说明：**首先要获取到正确的url才能获取到想要的资源**

/**
         * 下载网络资源
         * @param response
         * @throws IOException
         */
    @RequestMapping("/downLoadMusic")
    public void downloadNetworkFile(HttpServletResponse response) throws IOException {
        
        // 创建url对象
        URL url = new URL("https://m701.music.126.net/20221009103058/70acd1fa2256e82ae0a90f833aec1072/jdyyaac/obj/w5rDlsOJwrLDjj7CmsOj/18195365565/53a1/ad15/9e1c/1b3457995065a152f56f61c38eda1914.m4a");
        // 建立连接
        URLConnection urlConnection = url.openConnection();
        // 获取到输入流
        InputStream inputStream = urlConnection.getInputStream();
        // 获取到响应头的输出流
        ServletOutputStream outputStream = response.getOutputStream();
        // 设置响应头
        response.setContentType("application/octet-stream");
        response.setHeader("Content-Disposition","attachment;fileName=" + URLEncoder.encode("爱似水仙.m4a", "utf8"));
        int len;
        // 通过字节流下载下来
        byte[] bytes = new byte[1024];
        while ((len = inputStream.read(bytes)) != -1){
        
            outputStream.write(bytes,0, len);
        }
        // 关闭资源
        inputStream.close();
        outputStream.close();
    }

测试链接：http://localhost:8888/downLoadMusic

> [参考文章1][1]
> 
> [参考文章2][2]

[8f95498b21094eaca3e9298c916ba97c.png_pic_center]: https://img-blog.csdnimg.cn/8f95498b21094eaca3e9298c916ba97c.png#pic_center
[b880d3ab0d644327827dba4029b99ac5.png_pic_center]: https://img-blog.csdnimg.cn/b880d3ab0d644327827dba4029b99ac5.png#pic_center
[9e21aa66fd64400e97b7a2e0098d160c.png_pic_center]: https://img-blog.csdnimg.cn/9e21aa66fd64400e97b7a2e0098d160c.png#pic_center
[d7a8c4d834f74ea5a698ced42935f544.png]: https://img-blog.csdnimg.cn/d7a8c4d834f74ea5a698ced42935f544.png#
[43b08543ed554f63be3e1d23235614a2.png]: https://img-blog.csdnimg.cn/43b08543ed554f63be3e1d23235614a2.png#
[eca059c2e847450586222abf03eb9dc5.png]: https://img-blog.csdnimg.cn/eca059c2e847450586222abf03eb9dc5.png
[431d4412e3f7435ebe1dc9d9f908bb5c.png]: https://img-blog.csdnimg.cn/431d4412e3f7435ebe1dc9d9f908bb5c.png
[1ba961750b0a4ffcb78b02fae2e1ef13.png]: https://img-blog.csdnimg.cn/1ba961750b0a4ffcb78b02fae2e1ef13.png#
[Image 1]: https://img-blog.csdnimg.cn/a31ae814ca154c129001e8c787daee2a.png#//
[1]: https://blog.csdn.net/qq_41538097/article/details/117635355?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522166452785016800184130220%2522%252C%2522scm%2522%253A%252220140713.130102334..%2522%257D&request_id=166452785016800184130220&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduend~default-2-117635355-null-null.142%5Ev51%5Econtrol,201%5Ev3%5Eadd_ask&utm_term=java%E6%96%87%E4%BB%B6%E7%9A%84%E4%B8%8A%E4%BC%A0%E5%92%8C%E4%B8%8B%E8%BD%BD&spm=1018.2226.3001.4187
[2]: https://blog.csdn.net/qq_41538097/article/details/117637372