spring mvc/Java web 文件上传

Java web文件上传

Java 的原生文件上传其实比较简单

分为前端和后端两块

前端

<form role="form" enctype="multipart/form-data" action="">

这个enctype改成multipart/form这个是前端需要做的部分

后端

导入一些包

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.4</version>
</dependency>

配置一个servlet

public String addBook(HttpServletRequest request) throws Exception {
        String fileName = "";
        //上传的位置
        String path = request.getSession().getServletContext().getRealPath("/imgs/");
        //判断该路径是否存在
        File file = new File(path);
        if (!file.exists()) {
            file.mkdirs();
        }

        //解析request对象
        DiskFileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload upload = new ServletFileUpload(factory);
        List<FileItem> items = upload.parseRequest(request);
        //构建一个map存储变量
        Map<String,Object> map = new HashMap<>();
        //遍历
        for (FileItem item : items) {
            if (item.isFormField()) {
                //普通表单
                String fieldName = item.getFieldName();
                String string = item.getString();
                //处理编码问题
                String s = new String(string.getBytes("iso-8859-1"),"UTF-8");
                map.put(fieldName,s);
            } else {
                //上传文件项
                String filename = item.getName();
                //防止上传非图片文件
                if (filename.contains(".png")||filename.contains(".jpg")) {
                    String uuid = UUID.randomUUID().toString().replace("-", "");
                    String saveName = uuid + "_" + filename.substring(filename.lastIndexOf(File.separator) + 1);
                    fileName = saveName;
                    item.write(new File(path, saveName));
                    map.put("pic", fileName);
                    //删除临时文件
                    item.delete();
                }
            }
        }
        bookService.addBook(map);
        String view = "forward:/management/modify/"+map.get("id");
        return view;
    }

核心就是

1. DiskFileItemFactory factory = new DiskFileItemFactory();
2. ServletFileUpload upload = new ServletFileUpload(factory);
3. List<FileItem> items = upload.parseRequest(request);

然后通过io流的方式进行输出到磁盘中

通过spring mvc上传

在配置文件中配置

<!--配置MultipartResolver,用于文件上传-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!--上传文件大小上限-->
    <property name="maxInMemorySize" value="5000000"/>
    <!--请求编码格式-->
    <property name="defaultEncoding" value="UTF-8"/>
</bean>

编写Controller

@Controller
public class FileUploadController {

    private static String UPLOAD_DIRECTORY = PropertiesUtil.get("fileupload.directory", "");

    @RequestMapping(value = "uploadFile", method = RequestMethod.POST)
    public ModelAndView uploadFile(@RequestParam("file") MultipartFile file){
        // 判断文件是否为空
        if (!file.isEmpty()) {
            try {
                //判断文件目录是否存在，否则自动生成
                File directory = new File(UPLOAD_DIRECTORY);
                if (!directory.exists()){
                    directory.mkdirs();
                }

                //失败跳转视图
                if (file.getSize() > 30000)
               return new ModelAndView("uploadFail","msg",file.getOriginalFilename()+"超过了指定大小");

                // 文件保存路径
                String filePath =  FilenameUtils.concat(UPLOAD_DIRECTORY, file.getOriginalFilename());
                // 转存文件
                file.transferTo(new File(filePath));

            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        //成功跳转视图
        return new ModelAndView("uploadSuccess","msg",file.getOriginalFilename());
    }

}

还能更方便

@RequestMapping("/upload")
public String upload(@RequestParam("file") MultipartFile file, HttpServletRequest req)throws IllegalStateException, IOException {

	// 判断文件是否为空，空则返回失败页面
	if (file.isEmpty()) {
		return "failed";
	}
	// 获取文件存储路径（绝对路径）
	String path = req.getServletContext().getRealPath("/WEB-INF/file");
	// 获取原文件名
	String fileName = file.getOriginalFilename();
	// 创建文件实例
	File filePath = new File(path, fileName);
	// 如果文件目录不存在，创建目录
	if (!filePath.getParentFile().exists()) {
		filePath.getParentFile().mkdirs();
		System.out.println("创建目录" + filePath);
	}
	// 写入文件
	file.transferTo(filePath);
	return "success";
}  

使用file.transferTo(filePath);直接完成向磁盘中写入