解决当FORM的ENCTYPE="multipart/form-data" 时request.getParameter()获取不到值的方法

部分转载于:

http://blog.csdn.net/georgejin/article/details/1706647

http://www.cnblogs.com/loveyunk/p/6089032.html 

http://www.cnblogs.com/greenteaone/p/4186619.html

 from表单中向后台传递参数的同时要上传文件，所以ENCTYPE="multipart/form-data" 必须要加在form里面,可是这样的话，我在servlet里面用request.getParameter()方法无论如何都只是获得null值.

我这里使用的是commons fileupload的jar包(commons-fileupload-1.2.jar).

 先附录之前写的上传文件的工具类:

public class FileUploadAndDown {
    
    private Logger logger = Logger.getLogger(FileUploadAndDown.class);
    
    public String upload(ServletConfig servletconfig, HttpServletRequest request)throws FileUploadException{
        HttpSession session = request.getSession();
        String username = session.getAttribute("username").toString();
        DiskFileUpload fu = new DiskFileUpload();
        // 判断表单是否设置了mutipart/form-data
        boolean isMultipart = DiskFileUpload.isMultipartContent(request);
        if (!isMultipart){
            return null;
        }else{
            fu.setHeaderEncoding(request.getCharacterEncoding());
            // 设置允许用户上传文件大小,单位:字节
            fu.setSizeMax(10*1024*1024);
            // 设置最多只允许在内存中存储的数据,单位:字节
            fu.setSizeThreshold(4*1024*1024);
            // 设置一旦文件大小超过getSizeThreshold()的值时数据存放在硬盘的目录
            String temp = System.getProperty("user.home")+File.separator+"catalogupload";
            fu.setRepositoryPath(temp);
            File file = new File(temp);
            if (!file.exists() || !file.isDirectory()) {
                file.mkdir();
            }
            // 开始读取上传信息

            List fileItems = fu.parseRequest(request);
            // 依次处理每个上传的文件

            Iterator iter = fileItems.iterator();
            // 如果需要上传多个文件，将if改称while即可
            while(iter.hasNext()) {
                FileItem item = (FileItem) iter.next();
                // 忽略其他不是文件域的所有表单信息

                if (!item.isFormField()) {
                    String name = item.getName();
                    String time = DateUtil.getDateTime("yyyyMMddHHmmss");
                    name = username + "_" + time + FileNameUtil.extractFileExt(name);
                    try {
                        String namepath = servletconfig.getServletContext().getRealPath("poster");
                        file = new File(namepath);
                        if(!file.exists()){
                            file.mkdirs();
                        }
                        name = namepath+File.separator+name;
                        item.write(new File(name));
                        logger.info("上传海报名为:" + name);
                        return name;
                    } catch (Exception e) {
                        logger.error("上传海报保存异常" + e.getMessage());
                        return null;
                    }
                }
            }
        }
        return "";
    }
}

对应的jsp页面

        <form name="form1" action="deleteMmobject.do" method="post" enctype="multipart/form-data" target="displayprocess" >
            导入要删除列表文件 &nbsp;&nbsp;&nbsp;    
            <input type="hidden" id="deleteFlagHidden" name="deleteFlagHidden" value="" />
            <input type="hidden" name="action" value="" />
            
            <input type="file" name="filepath" />
            <input name="deleteMmobject_radio" id="selfDelete" type="radio" value="自删除" onclick="selfDeleteFun()"; checked />自删除
            <input name="deleteMmobject_radio" id="sendToBoDelete" type="radio" value="同时下发删除到下游" onclick="sendToBoDeleteFun()" />同时下发删除到下游
            <input type="button" value="确定" onclick="deleteFun()"/>
            <!-- <input type="submit"  value="确定" /> -->
        </form>

通过servlet里面用request.getParameter("id名称")方法无论如何都只是获得null值.   通过更换上传依赖的jar包(jspsmartupload.jar)

新加代码如下:

    public Map<String,String> uploadUseJspSmart(ServletConfig servletconfig, HttpServletRequest request, HttpServletResponse response)throws FileUploadException{
        Map<String,String> uploadParametersMap = new HashMap<String,String>(); 
        HttpSession session = request.getSession();
        String username = session.getAttribute("username").toString();
        
        com.jspsmart.upload.SmartUpload smartUpload = new com.jspsmart.upload.SmartUpload();
        File file = null;
        String fileName = null;
        try {
            smartUpload.initialize(servletconfig, request, response);
            smartUpload.setTotalMaxFileSize(100000000);
            smartUpload.setAllowedFilesList("txt,excel");
            smartUpload.setDeniedFilesList("exe,bat,jsp,htm,html,,");
            
            smartUpload.upload();
            // 得到上传的文件对象
            com.jspsmart.upload.File smartFile = smartUpload.getFiles().getFile(0);
            
            fileName = smartFile.getFileName();
            String time = DateUtil.getDateTime("yyyyMMddHHmmss");
            fileName = username + "_" + time + FileNameUtil.extractFileExt(fileName);
            String namepath = System.getProperty("user.home")+File.separator+"catalogupload";
            
            file = new File(namepath);
            if(!file.exists()){
                file.mkdirs();
            }
            fileName = namepath+File.separator+fileName;
            smartFile.saveAs(fileName);
            logger.info("通过JspSamrt上传文件名为:" + fileName+"成功");
            //这里可以顺利得到jsp页面form表单中对应的"deleteFlagHidden"参数
            String deleteFlagHidden = smartUpload.getRequest().getParameter("deleteFlagHidden");
            uploadParametersMap.put("fileName", fileName);
            uploadParametersMap.put("deleteFlagHidden", deleteFlagHidden);
            return uploadParametersMap;
        } catch (Exception e1) {
            e1.printStackTrace();
            logger.info("通过JspSamrt上传文件名为:" + fileName+"失败");
        }
        return null;
    }