使用ajax、servlet实现多文件的上传

搭建环境

这里使用maven导入jar包：

<dependencies>
  <!--文件上传-->
  <dependency>
      <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
      <version>1.3.2</version>
  </dependency>
  <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-io</artifactId>
      <version>1.3.2</version>
  </dependency>
  <!--json-->
  <dependency>
      <groupId>org.json</groupId>
      <artifactId>json</artifactId>
      <version>20160810</version>
  </dependency>

</dependencies>

三个主要的jar包，这里还将使用jquery以及异步提交表单，所以需要jquery和jquery.form文件

jsp页面

<%--
  Created by IntelliJ IDEA.
  User: wqh
  Date: 2017/5/26
  Time: 9:46
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
<script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery-3.1.1.min.js"></script>
<script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery.form.js"></script>

<script type="text/javascript">
    $(function () {
      $("#sub").bind("click",function () {
          var option = {
              type:"post",
              url:"${pageContext.request.contextPath}/TestServlet",
              async: true,
              enctype:"multipart/form-data",
              dataType:"json",
              error:function(data){
                  alert(data);
              },
              success:function(msg){
                  //将结果格式化为json
                  var json = eval(msg);
                  var data = "";
                  $.each(json,function (index,item) {
                       var key = json[index].file;
                       data = data +"==="+ key
                  });
                    alert(data);
              }
          };
         $("#fileForm").ajaxSubmit(option);
      })
    });

</script>
<head>
    <title>Title</title>
</head>
<body>
    <form action="#" id="fileForm" enctype="multipart/form-data" method="post" >
        <input type="file" name="file"/><br>
        <input type="file" name="file"/><br>
        <input type="file" name="file"/><br>
        <button type="submit"  name="sub" id="sub">提交</button>
    </form>
</body>
</html>

servlet代码

文件上传测试，上传文件就不保存到本地l。直接向页面返回文件名，返回json格式。

 req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");

        List<String> fileName = new ArrayList<>();
        boolean ismultipartContent = ServletFileUpload.isMultipartContent(req);
        //判断是否是文件上传
        if (ismultipartContent) {
            DiskFileItemFactory factory = new DiskFileItemFactory();
            ServletFileUpload fileUpload = new ServletFileUpload(factory);
            try {
                List<FileItem> fileItems = fileUpload.parseRequest(req);
                for (FileItem fileItem : fileItems) {
                    //判断字段的类型
                    if (fileItem.isFormField()) {
                        //处理普通字段
                    } else{
                        //文件字段,处理上传字段，这里就不把文件保存到本地了
                        fileName.add(fileItem.getName());
                    }
                }
            } catch (FileUploadException e) {
                e.printStackTrace();
            }
            //将list转化为json
            int index = 1;
            JSONArray jsonArray = new JSONArray();
            for (String s : fileName){
                JSONObject jsonObject = new JSONObject();
                jsonObject.put("file",s);
                jsonArray.put(jsonObject);
            }
            resp.getWriter().print(jsonArray);
        }