通过JSP页面上载CSV文件并使用Servlet打印其内容。

Question

I need to design a JSP page through which user uploads a CSV file and then I need to print its contents on the screen through a Servlet.

The HTML code goes likes this

<form action="decode" enctype="multipart/form-data" method="post>
    <input type="file" name="record" />
    <input type="submit" />
</form>

Now In decode.java,

DiskFileItemFactory fi = new DiskFileItemFactory();
ServletContext sc = this.getServletConfig().getServletContext();
File file = (File) sc.getAttribute("javax.servlet.context.tempdir");
fi.setRepository(file);
ServletFileUpload upload = new ServletFileUpload(fi);
List<FileItem> items = upload.parseRequest(request);

What should I do next to read each and every word from the uploaded CSV file...? I do not want to store the CSV file anywhere. Just want to read its contents and print them.

Answer 1

You can read CSV files using Apache's CSV parser library for JAVA.

And then after importing the library in your classpath you can simply use it as

Reader in = new FileReader(file); //The file is the file which you get from the request(java.io.File)
Iterable<CSVRecord> records = CSVFormat.EXCEL.parse(in);
for (CSVRecord record : records) {
    //Do something with the records
}

For more information look into https://commons.apache.org/proper/commons-csv/index.html

Answer 2

I also had a similar requirement, where I need to upload a jsp file through jsp and process it through Servlet

So Here I used the Library called opencsv by Apache.

upload.jsp

<form action="./upload" method="post" enctype="multipart/form-data">
    <input type="text" name="description" />
    <input type="file" name="file" />
    <input type="submit" />
</form>

UploadServlet.java

import com.opencsv.CSVReader;


@WebServlet(name = "upload", urlPatterns = { "/upload" })
@MultipartConfig
public class UploadServlet extends HttpServlet {

    public UploadServlet() {
        super();
    }

   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        Part filePart = request.getPart("file"); 
        InputStream fileContent = filePart.getInputStream();

        Reader in = new InputStreamReader(fileContent);

        CSVReader reader;
        Iterator<String[]> iterator;

        try {

            reader = new CSVReader(new InputStreamReader(fileContent));
            iterator = reader.iterator();

            String[] row = iterator.next();

            Map<Object, String> map = new HashMap<>();
            for(int i = 0; i < row.length; i++){
                map.put(i, row[i]);

                //Do rest of the code

            }

        }catch(Exception e) {}

        in.close();

    }

}

Additional :

While developing the above requirement I also encountered a problem, where a exception is throw specifying ClassNotFound.... (When converting inputstream to CSVReader instance)

It's because the library is not attached to Runtime environment even though it's properly attached to Development environment.

Solution :

Copy the library files to lib folder in the server location and restart the server (shutdown first then start). By doing this I was able to solve the issue

Another better option is to use some Build tool like gradle or maven rather than going with JSP/Servlet(my personal view)