关于commons-fileupload组件上传文件中文名乱码问题

　　java web开发，常用到的文件上传功能，常用的commons-fileupload和commons-io两个jar包。关于如何使用这两个jar来完成文件上传的功能，这里不做详解。使用commons-fileupload来上传文件，有两种方式可以是实现。

1. 传统API

<%@page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8" language="java"%>
<%@page import="java.io.File"%>
<%@page import="java.util.List"%>
<%@page import="org.apache.commons.fileupload.*"%>
<%@page import="org.apache.commons.fileupload.disk.DiskFileItemFactory"%>
<%@page import="org.apache.commons.fileupload.servlet.ServletFileUpload"%>

<%
    request.setCharacterEncoding("UTF-8");
    // file less than 10kb will be store in memory, otherwise in file system.
    final int threshold = 10240;
    final File tmpDir = new File(getServletContext().getRealPath("/") + "fileupload" + File.separator + "tmp");
    final int maxRequestSize = 1024 * 1024 * 4;    // 4MB

    // Check that we have a file upload request
    if(ServletFileUpload.isMultipartContent(request))
    {
        // Create a factory for disk-based file items.
        FileItemFactory factory = new DiskFileItemFactory(threshold, tmpDir);
        
        // Create a new file upload handler
        ServletFileUpload upload = new ServletFileUpload(factory);

        // Set overall request size constraint.
        upload.setSizeMax(maxRequestSize);

        List<FileItem> items = upload.parseRequest(request);    // FileUploadException 
        for(FileItem item : items)
        {
            if(item.isFormField())    //regular form field
            {
                String name = item.getFieldName();
                String value = item.getString();
%>
                <h1><%=name%> --> <%=value%></h1>
<%
            }
            else
            {    //file upload
                String fieldName = item.getFieldName();
                String fileName = item.getName();
                File uploadedFile = new File(getServletContext().getRealPath("/") +
                            "fileupload" + File.separator + fieldName + "_" + fileName);
                item.write(uploadedFile);
%>
                <h1>upload file <%=uploadedFile.getName()%> done!</h1>
<%
            }
        }
    }
%>

2. Stream API

<%@page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8" language="java"%>
<%@page import="java.io.*"%>
<%@page import="java.util.List"%>
<%@page import="org.apache.commons.fileupload.*"%>
<%@page import="org.apache.commons.fileupload.util.Streams"%>
<%@page import="org.apache.commons.fileupload.servlet.ServletFileUpload"%>

<%
    request.setCharacterEncoding("UTF-8");

    // Check that we have a file upload request
    if(ServletFileUpload.isMultipartContent(request))
    {    
        // Create a new file upload handler
        ServletFileUpload upload = new ServletFileUpload();
        
        // Parse the request
        FileItemIterator iter = upload.getItemIterator(request);

        while(iter.hasNext())
        {
            FileItemStream item = iter.next();
            String fieldName = item.getFieldName();
            InputStream is = item.openStream();

            if(item.isFormField())    //regular form field
            {
%>
                <!-- read a FileItemStream's content into a string. -->
                <h1><%=fieldName%> --> <%=Streams.asString(is)%></h1>
<%
            }
            else
            {    //file upload
                String fileName = item.getName();
                File uploadedFile = new File(getServletContext().getRealPath("/") +
                            "fileupload" + File.separator + fieldName + "_" + fileName);
                OutputStream os = new FileOutputStream(uploadedFile);
                // write file to disk and close outputstream.
                Streams.copy(is, os, true);
%>
                <h1>upload file <%=uploadedFile.getName()%> done!</h1>
<%
            }
        }
    }
%>

　　Streaming API上传速度相对较快。因为它是利用内存保存上传的文件，节省了传统API将文件写入临时文件带来的开销。自然，更倾向于选用Stream API。

　　前端实现文件上传的“手段”，目前接触过的有UEditor的上传组件、jQuery的ajaxfileupload以及AngularJs的集成上传组件。发送的也都是正常的上传表单数据，而当使用Stream API，获取文件名时，“String fileName = item.getName()”，当文件名为中文名时，会出现乱码现象。

　　网上搜寻的关于设置request编码的法子都不管用，尝试了多次后，找到了解决办法，重点在于上面代码中的ServletFileUpload upload，添加upload.setHeaderEncoding("UTF-8");即可解决中文文件名的乱码问题了。