spring mvc为我们封装了十分简单的上传附件的方法，以下通过一个例子学习。
1.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt"%>
<!DOCTYPE>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>附件管理</title>
<!-- css文件 -->
<link rel="stylesheet" href="./static/bootstrap/css/bootstrap.min.css" />
<link rel="stylesheet"
href="./static/bootstrap/css/bootstrap-theme.min.css">
<link rel="stylesheet" href="./static/css/OtherCss/upload.css">
<!-- js文件 -->
<script type="text/javascript" src="./static/js/jquery-1.11.0.js"></script>
<script type="text/javascript"
src="./static/bootstrap/js/bootstrap.min.js"></script>
<script type="text/javascript" src="./static/js/OtherJs/upload.js"></script>
<!-- ajax form -->
<script type="text/javascript" src="./static/js/jquery.form.js"></script>
<script type="text/javascript" src="./static/js/ajaxfileupload.js"></script>
<script type="text/javascript"
src="./static/js/jquery-migrate-1.2.1.min.js"></script>
<script type="text/javascript">
var dialog = frameElement.dialog;
$(function() {
$("#submit1").click(function() {
if ($("#categoryName").val() == "") {
alert("请填写类别名称");
return false;
}
var ajax_option = {
url : "categoryAttSave",
type : "post",
dataType : "html",
success : function(data) {
if (data == 1) {
alert("成功");
} else {
alert("失败")
}
dialogClose();
}
}
$("#thisForm").ajaxSubmit(ajax_option);
});
});
//返回
function dialogClose() {
parent.g.loadData(parent.g.parms);
dialog.close();//关闭dialog
}
</script>
</head>
<body>
<form id="thisForm" method="post" action="categoryAttSave"
enctype="multipart/form-data">
<input type="hidden" name="categoryId" value="${category.categoryId}" />
<div class="container-fluid ">
<div class="col-xs-12">
<div class="panel-body ">
<div class="row">
<div class="col-xs-8 col-xs-offset-1 tipinfo"
style="padding-bottom: 10px">
<div class="input-group">
<h3>${category.categoryName}</h3>
</div>
</div>
</div>
<div class="row">
<div class="col-xs-8 col-xs-offset-1 tipinfo"
style="padding-bottom: 10px">
<div class="info_center" id="userface_x">
<div class="upload_face">
<div class="upload_btn">
<a type="button" class="upload_vl" id="upface_tt">选择您要上传的图片</a>
<p id="img_rq">仅支持JPG、GIF、PNG、JPEG、BMP格式，文件小于4M</p>
</div>
<div class="upface_img">
<c:choose>
<c:when test="${not empty category.categoryPic}">
<img id="preview" src="./${category.categoryPic}" />
</c:when>
<c:otherwise><img id="preview" src="./static/img/nopic.png" /></c:otherwise>
</c:choose>
</div>
<div class="changeimg" style="display: none">
<input id="fileimg" type="file" name="upload" />
</div>
</div>
</div>
</div>
</div>
<div class="row">
<div class="col-xs-5 col-xs-offset-5">
<button type="button" class="btn btn-default " onClick="dialogClose();">关闭</button>
<button type="button" class="btn btn-primary " id="submit1">
提交</button>
</div>
</div>
</div>
</div>
</div>
</form>
</body>
</html>
主要要注意的是form的地方必须加 enctype="multipart/form-data"这句话，还有就是<input id="fileimg" type="file" name="upload" />这句话。本实例用了一个js的上传插件。只是优化了上传的体验，不涉及到原理，所以此处不介绍相关内容。主要还是介绍如何实现上传。
2.后台代码
controller
@ResponseBody
@RequestMapping("categoryAttSave")
public String categoryAttSave(HttpServletRequest req, MultipartFile upload,
int categoryId) {
Integer result = categoryService.categoryAttSave(req, upload,
categoryId, uploadFile);
return result.toString();
}
Service
/**
* 附件上传并修改数据库
*
* @param req
* @param upload
* @param categoryId
* @param uploadFile
* @return
*/
public int categoryAttSave(HttpServletRequest req, MultipartFile upload,
int categoryId, String uploadFile) {
int result = 0;
String originalFileName = upload.getOriginalFilename();
String suffix = IOUtil.getFileSuffix(originalFileName);
String fileName = RandomUtil.getTimeStampPlusRand() + "." + suffix;
String realPath = req.getServletContext().getRealPath(uploadFile);
try {
upload.transferTo(new File(realPath + "/" + fileName));
// 数据库操作
TCategory category = baseDao.getT(
"TCategoryMapper.selectByPrimaryKey", categoryId);
String oldCategoryPic = category.getCategoryPic();
category.setCategoryPic(uploadFile + "/" + fileName);
baseDao.updateT("TCategoryMapper.updateCategoryPic", category);
// 删除原来的图片
IOUtil.deleteFile(req, oldCategoryPic);
result = 1;
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
其实主要是注意到传递过来的MultipartFile 名称，要与jsp里面的file名对应。还有就是我们需要用到request来获取附件最终存储的位置，所以传递了一个HttpServletRequest。上传就是这句话upload.transferTo(new File(realPath + "/" + fileName));很简单吧，如果我们自己写的话，就要通过输入流写入到file里了。而spring mvc只要一句简单的代码就实现了。
PS:上述代码还是有弊端的，当我们没有选定需要上传的图片而点击了上传的时候，它会报如下错误。
org.springframework.web.multipart.MultipartException: The current request is not a multipart request
大概意思就是，你这个请求并不是关于文件上传的请求。这是spring 替你检查了并直接报运行错误。
我们可以通过修改controller代码，替代spring 的检查，就可以规避这个错误了。
@ResponseBody
@RequestMapping("categoryAttSave")
public String categoryAttSave(HttpServletRequest req, int categoryId) {
MultipartFile upload = null;
if (req instanceof MultipartHttpServletRequest) {
upload = ((MultipartHttpServletRequest) req).getFile("upload");
}
Integer result = categoryService.categoryAttSave(req, upload, categoryId,
uploadFile);
return result.toString();
}
上述代码我们自己检查是不是关于文件上传的请求，就不会报错了。