使用commons-fileupload时，文件上传与表单参数同时提交时的后台代码处理

把Form表单是的enctype="multipart/form-data"是基于流的，只能获取一次，重复获取将为空,当上传文件的input控件与hidden的input字段混合时,直接用request.getParameter一般是不行的.

下面的代码进行同时表单参数获取和文件上传:

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.servlet.ServletRequestContext;

...

 Map> getFieldMap(
            HttpServletRequest request) throws UnsupportedEncodingException {

        Map> fieldsMap;
        fieldsMap = (Map>) request
                .getAttribute(ServletFileUpload.MULTIPART_FORM_DATA);
        if (fieldsMap == null) {
            fieldsMap = new HashMap>();
            request.setAttribute(ServletFileUpload.MULTIPART_FORM_DATA,
                    fieldsMap);
        } else {
            return fieldsMap;
        }

        ServletFileUpload fu = new ServletFileUpload(new DiskFileItemFactory());
        List li = null;
        try {
            li = fu.parseRequest(request);
        } catch (FileUploadException e) {
            e.printStackTrace();
        }
        int m = 0;
        if (li != null) {
            Iterator iter = li.iterator();
            while (iter.hasNext()) {
                FileItem fi = (FileItem) iter.next();
                if (fi.isFormField()) {
                    Vector vec = new Vector();
                    String fieldName = fi.getFieldName(); // 这里取得字段名称
                    // 如果已经存在此字段信息（多选列表或多个同名的隐藏域等）
                    if (fieldsMap.get(fieldName) != null) {
                        vec = (Vector) fieldsMap.get(fieldName);
                        vec.add(fi.getString(request.getCharacterEncoding()));
                    }
                    // 第一次取到这个名的字段
                    else {
                        // logger.info("name:" + fieldName + " value: "
                        // + fi.getString(request.getCharacterEncoding()));
                        vec.add(fi.getString(request.getCharacterEncoding()));
                        fieldsMap.put(fieldName, vec);
                    }
                } else {

                    List fileNames = (List) request
                            .getAttribute(UPLOADEDFILENAME_ATTRIBUTE);
                    if (fileNames == null) {
                        fileNames = new ArrayList();
                        request.setAttribute(UPLOADEDFILENAME_ATTRIBUTE,
                                fileNames);
                    }

                    String storePath = request.getSession().getServletContext()
                            .getRealPath(UPLOADEDFILEPATH);
                    try {
                        if (fi.getSize() > 0) {
                            //这里而要对文件重全名, 可能从之前的filename取得扩展名,并白名单过滤
                            fi.write(new File("somefilename"+m++)); // 写文件到服务器.
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return fieldsMap;
    }

这里用的是apache的common-fileupload模块.
如果您使用maven构建， 需要在pom.xml里添加：

    commons-fileupload
    commons-fileupload
    1.2