把上传并下载到项目中ssm

要将上传和下载功能集成到SSM项目中，可以按照以下步骤操作：

1. 在项目中添加文件上传和下载的相关依赖包，例如commons-fileupload和commons-io。

2. 编写上传和下载的Controller层代码，可以参考以下示例代码：

上传文件：

@RequestMapping(value = "/uploadFile", method = RequestMethod.POST)
@ResponseBody
public String uploadFile(HttpServletRequest request, HttpServletResponse response) {
    String result = "";
    try {
        // 获取上传的文件
        MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        MultipartFile file = multipartRequest.getFile("file");
        // 获取文件名
        String fileName = file.getOriginalFilename();
        // 拼接文件存储的路径
        String filePath = request.getSession().getServletContext().getRealPath("/") + "upload/";
        File fileDir = new File(filePath);
        if (!fileDir.exists()) {
            fileDir.mkdirs();
        }
        // 将上传的文件保存到指定路径
        file.transferTo(new File(filePath + fileName));
        result = "success";
    } catch (Exception e) {
        result = "error";
        e.printStackTrace();
    }
    return result;
}

下载文件：

@RequestMapping(value = "/downloadFile", method = RequestMethod.GET)
public void downloadFile(HttpServletRequest request, HttpServletResponse response) {
    String fileName = "test.txt";
    String filePath = request.getSession().getServletContext().getRealPath("/") + "upload/";
    try {
        // 设置响应头
        response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));
        // 获取要下载的文件流
        InputStream inputStream = new FileInputStream(filePath + fileName);
        OutputStream outputStream = response.getOutputStream();
        byte[] buffer = new byte[1024];
        int len;
        while ((len = inputStream.read(buffer)) > 0) {
            outputStream.write(buffer, 0, len);
        }
        inputStream.close();
        outputStream.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

3. 在页面中添加上传和下载的相关代码，例如：

上传文件：

<form id="uploadForm" action="uploadFile" method="post" enctype="multipart/form-data">
    <input type="file" name="file"/>
    <input type="button" value="上传" onclick="uploadFile()"/>
</form>
<script>
    function uploadFile() {
        $.ajax({
            type: "POST",
            url: "uploadFile",
            data: new FormData($("#uploadForm")[0]),
            async: false,
            cache: false,
            contentType: false,
            processData: false,
            success: function (data) {
                alert(data);
            },
            error: function () {
                alert("上传失败！");
            }
        });
    }
</script>

下载文件：

<a href="downloadFile">下载</a>

4. 运行项目，测试上传和下载功能是否正常。