Some precautions and solutions for jsp form form attribute enctype

In the form tag, enctype is used to mark the MIME encoding format, multipart/form-data is the encoding format for file uploading, and the default is application/x-www-form-urlencoded, which cannot be used for file uploading.

Therefore, a form with enctype="multipart/form-data" format will report a null pointer exception when request.getParameter gets the value of the text attribute in the background.

So in an item that has both a textfield and a file upload is my workaround is:

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1. private Map<String,String> parameters =new HashMap<String,String>();</span>  

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1. Design a map property  

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1. Use an upload component of apache:  

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1. DiskFileItemFactory factory = new DiskFileItemFactory();  
2.         ServletFileUpload upload = new ServletFileUpload(factory);  
3.         try {  
4.             List items = upload.parseRequest(request);  
5.             Iterator it = items.iterator();  
6.             while (it.hasNext()) {  
7.                 FileItem item = (FileItem) it.next();  
8.                 if  (item.isFormField()) { //Determine whether it is text field information  
9.                     parameters.put(item.getFieldName(), item.getString("UTF-8"));  
10.                       
11.   
12.                 }
13.  The getFieldName in the class is  to get the name attribute value of the input, getString is to get the value value, put these two values ​​into a map and then get it through the key.
14. 
    
15. The corresponding jar packages are: commons-email - 1.5.jar , commons-fileupload - 1.3.3.jar , commons-io-2.5.jar , mail.jar