SpringMVC 使用ResponseEntity实现文件下载

╰+攻爆jí腚メ 2024-02-18 21:41 30阅读 0赞

下载文件：

(1)获取要下载的文件名，注意编码；

(2)在HttpHeaders中设置以下载方式打开，设置MIME类型；

(3)用FileUtils.readFileToByteArray()读取文件数据；用ResponseEntity构建返回对象

/**
    	 * Create a new {@code HttpEntity} with the given body, headers, and status code.
    	 * @param body the entity body
    	 * @param headers the entity headers
    	 * @param status the status code
    	 */
    	public ResponseEntity(@Nullable T body, @Nullable MultiValueMap<String, String> headers, HttpStatus status) {
    		super(body, headers);
    		Assert.notNull(status, "HttpStatus must not be null");
    		this.status = status;
    	}

在`HttpEntity`类的源码中可以看到: 将header头转变成只能读取的对象，而不是写入的对象

/**
    	 * Create a new {@code HttpEntity} with the given body and headers.
    	 * @param body the entity body
    	 * @param headers the entity headers
    	 */
    	public HttpEntity(@Nullable T body, @Nullable MultiValueMap<String, String> headers) {
    		this.body = body;
    		HttpHeaders tempHeaders = new HttpHeaders();
    		if (headers != null) {
    			tempHeaders.putAll(headers);
    		}
    		this.headers = HttpHeaders.readOnlyHttpHeaders(tempHeaders);
    	}

JSP页面:

<body>
    	<c:forEach items="${list}" var="pic">
    		<img src="${pic }" />
    		<a href="down.action?fileName=${pic }">下载${fn:substringAfter(pic,'/') }</a><p/>
    	</c:forEach>
    </body>

Controller代码:

@RequestMapping("/down")
    	public ResponseEntity<byte[]> down( HttpServletRequest request,String fileName) throws Exception {
    		// D:\apache-tomcat-7.0.82\webapps\springmvc3_20180301_am
    		
    		//处理中文编码
    		String myFileName=new String(fileName.getBytes("utf-8"),"iso-8859-1");
    		
    		// 获得服务器路径
    		String path=request.getSession().getServletContext().getRealPath("");
    		
    		//获得完整的路径
    		String string=path+File.separator+fileName;
    		
    		//输出路径
    		System.out.println(string);
    		
    		
    		//设置头信息
    		HttpHeaders headers=new HttpHeaders();
    		
    		//设置下载的附件 (myFileName必须处理中文名称哦!)
    		headers.setContentDispositionFormData("attachment", myFileName);
    		
    		//设置MIME类型
    		headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
    				
    		//用FileUpload组件的FileUtils读取文件，并构建成ResponseEntity<byte[]>返回给浏览器
            //HttpStatus.CREATED是HTTP的状态码201
    		return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(new File(string)),headers,HttpStatus.CREATED);
    		
    	}

显示:

![70][]

单击下载:

![70 1][]

[70]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/4d6f7d0985ae41b5b70892eb057127e6.png
[70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/7d6e2620d0314ad788e8295afac2e72c.png