解决当FORM的ENCTYPE=multipartform-data 时取不到值

在开发一个MIS系统中,部分页面中有需要上传文件的字段,相信大家在开发中也经常遇到这样的情况.因为要上传文件，所以FORM标记中的ENCTYPE="multipart/form-data",可是这样的话，当你在servlet里面用request.getParameter()方法无论如何都只是获得null值，没有办法只好在网上搜索一下,其中收集到了不同的方法,贴出来以备查询.
方法一
   用jspsmartupload组件实现文件上传的
   这个方法是我使用的方法,所以把主要代码贴了出来
Java代码
SmartUpload upload = new SmartUpload();  
     try{  
    upload.initialize(config, request, response);  
    // 允许上传的文件类型  
    upload.setAllowedFilesList("doc,xls,");  
    // 拒绝上传的文件类型  
    upload.setDeniedFilesList("exe,bat,jsp");  
    // 允许上传文件的单个最大大小  
    upload.setMaxFileSize(1024 * 1024 * 20);  
    // 允许上传文件的最大大小总和  
    // upload.setTotalMaxFileSize(1024*1024*10);  
    //上传数据  
    upload.upload();  
    }  
    catch (SmartUploadException e){  
        e.printStackTrace();  
        return;  
    }  
  
    Request req = upload.getRequest();  
    String spid=(String)req.getParameter("teacherId");  
         //.....  
         //To do something  

SmartUpload upload = new SmartUpload();
     try{
    upload.initialize(config, request, response);
    // 允许上传的文件类型
    upload.setAllowedFilesList("doc,xls,");
    // 拒绝上传的文件类型
    upload.setDeniedFilesList("exe,bat,jsp");
    // 允许上传文件的单个最大大小
    upload.setMaxFileSize(1024 * 1024 * 20);
    // 允许上传文件的最大大小总和
    // upload.setTotalMaxFileSize(1024*1024*10);
    //上传数据
    upload.upload();
    }
    catch (SmartUploadException e){
        e.printStackTrace();
        return;
    }

    Request req = upload.getRequest();
    String spid=(String)req.getParameter("teacherId");
         //.....
         //To do something

这样就可以取得对应的值了.
方法二
   这个是在Google中搜索的
I cannot read the submitter using request.getParameter("submitter") (it returns null). ]

Situation:

javax.servlet.HttpServletRequest.getParameter(String) returns null when the ContentType is multipart/form-data

Solutions:

Solution A:

1. download http://www.servlets.com/cos/index.html
2. invoke getParameters() on com.oreilly.servlet.MultipartRequest

Solution B:

1. download http://jakarta.apache.org/commons/sandbox/fileupload/
2. invoke readHeaders() in
org.apache.commons.fileupload.MultipartStream

Solution C:

1. download http://users.boone.net/wbrameld/multipartformdata/
2. invoke getParameter on
com.bigfoot.bugar.servlet.http.MultipartFormData

Solution D:

Use Struts. Struts 1.1 handles this automatically.

Solution B:
1. download > http://jakarta.apache.org/commons/sandbox/fileupload/ 2. invoke readHeaders()
   in > org.apache.commons.fileupload.MultipartStream
The Solution B as given by my dear friend is a bit hectic and
a bit complex :
(We can try the following solution which I found much simpler (at least in usage).
1.Download one of the versions of UploadFile from
http://jakarta.apache.org/commons/fileupload/
2. Invoke parseRequest(request)
on org.apache.commons.fileupload.FileUploadBase which returns
list of
org.apache.commons.fileupload.FileItem objects.
3. Invoke isFormField() on each of the FileItem objects.
This determines whether the file item is a form paramater or stream of uploaded file.
4. Invoke getFieldName() to get parameter name and getString() to get parameter value on FileItem if it's a form parameter.
Invoke write(java.io.File) on FileItem to save the uploaded file stream to a file if the FileItem is not a form parameter.
主要是getFieldName和getString，判断加工一下，还是可以获取到的.

方法三
    使用jspsmartupload组件的
只需要在servlet中添加
Java代码
//中文和日文时使用  
    request.setCharacterEncoding("UTF-8");      
//***************************************************************  
          JspFactory _jspxFactory = null;  
          PageContext pageContext = null;  
          JspWriter out = null;  
             _jspxFactory = JspFactory.getDefaultFactory();  
             pageContext = _jspxFactory.getPageContext(this,    
                         request, response,"", true, 8192, true);  
             out = pageContext.getOut();    
    //smartupload      
    SmartUpload su = new SmartUpload();  
    su.initialize(pageContext);      
    su.upload();      
    Request requestSu = su.getRequest();  
  
    //getParameter  
    //普通的  
              int id = Integer.parseInt(  
                      requestSu.getParameter("id"));              
            String languages = requestSu.getParameter("languages");  
            String flag = requestSu.getParameter("flag");  
//*******************************************************  
//中文和日文时使用  
     Description = request.getParameter("Description");    
//******************************************************  
另外在jsp中要传中文和日文得使用  
    document.form_SuccessfulCase.action=  
           "/homepage/SuccessfulCase?title=" +    
           encodeURI(document.form_SuccessfulCase.title.value)+  
           "&Description="+  
           encodeURI(document.form_SuccessfulCase.

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Tags: multipartform-datamultipartform-data
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