Java – Error while reading Excel sheet using Java

apache-poiexceljava

I'm working with Spring/Hibernet using NetBeans 6.9.1. I'm trying to read an Excel file (.xlsx- Office 2007). The code for reading an Excel file is as follows using a Vactor to store data from the Excel sheet.

import java.io.FileInputStream;
import java.util.Iterator;
import java.util.Vector;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import model.NewHibernateUtil;
import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.hibernate.Session;
import org.springframework.validation.BindException;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.SimpleFormController;

private Vector importExcelSheet(ModelAndView mv)
{
    Vector cellVectorHolder = new Vector();
    try
    {         
        HSSFWorkbook myWorkBook = new HSSFWorkbook(new POIFSFileSystem(new FileInputStream("E:/Project/SpringHibernet/MultiplexTicketBookingNew/web/excelSheets/Country.xlsx")));
        HSSFSheet mySheet = myWorkBook.getSheetAt(0);
        Iterator rowIter = mySheet.rowIterator();
        System.out.println(mySheet.getRow(1).getCell(0));
        while(rowIter.hasNext())
        {
            HSSFRow myRow = (HSSFRow) rowIter.next();
            Iterator cellIter = myRow.cellIterator();
            Vector cellStoreVector=new Vector();
            while(cellIter.hasNext())
            {
                HSSFCell myCell = (HSSFCell) cellIter.next();
                cellStoreVector.addElement(myCell);
            }
            cellVectorHolder.addElement(cellStoreVector);
        }
    }
    catch (Exception e)
    {
        mv.addObject("msg", e.getMessage());
    }
    return cellVectorHolder;
}

The following is a method in my Controller that calls the above method to read the specified Excel file

@Override
protected ModelAndView onSubmit(HttpServletRequest request, HttpServletResponse response, Object command, BindException errors) throws Exception
{
    ModelAndView mv=new ModelAndView();

    try
    {
        if(request.getParameter("import")!=null)
        {
            session=NewHibernateUtil.getSessionFactory().getCurrentSession();
            session.beginTransaction();

            Vector dataHolder=importExcelSheet(mv);
            for (int i=0;i<dataHolder.size(); i++)
            {
                Vector cellStoreVector=(Vector)dataHolder.elementAt(i);
                for (int j=0; j < cellStoreVector.size();j++)
                {
                    HSSFCell myCell = (HSSFCell)cellStoreVector.elementAt(j);
                    String st = myCell.toString();
                    System.out.println(st.substring(0,1)+"\t");
                }
                System.out.println();
            }

            session.flush();
            session.getTransaction().commit();
        }
    }
    catch (Exception e)
    {
        mv.addObject("msg", e.getMessage());
    }
    return mv;
}

On executing this code, the following exception is thrown.

The supplied data appears to be in the Office 2007+ XML. You are
calling the part of POI that deals with OLE2 Office Documents. You
need to call a different part of POI to process this data (eg XSSF
instead of HSSF)

Am I using a wrong source or something else is wrong with the above code? What is the solution?

The code is taken from here.

Best Answer

Your code as it stands explicitly requests HSSF, so will only work with the older .xls (binary) files.

If you want, you can ask POI to auto-detect which file type you have, and pick the appropriate one of HSSF or XSSF for your case. However, to do that you need to change your code slightly, and use interfaces rather than concrete classes (so your code works whether you get a HSSF or XSSF object)

The POI website has a guide to making these changes which should guide you through.

As an example, when you follow this, your first few lines which were:

    HSSFWorkbook myWorkBook = new HSSFWorkbook(new POIFSFileSystem(new FileInputStream("E:/Project/SpringHibernet/MultiplexTicketBookingNew/web/excelSheets/Country.xlsx")));
    HSSFSheet mySheet = myWorkBook.getSheetAt(0);
    Iterator rowIter = mySheet.rowIterator();
    System.out.println(mySheet.getRow(1).getCell(0));

Will become in the new system:

    Workbook wb = WorkbookFactory.create(new File("/path/to/your/excel/file"));
    Sheet mySheet = wb.getSheetAt(0);
    Iterator<Row> rowIter = mySheet.rowIterator();
    System.out.println(mySheet.getRow(1).getCell(0));

This will then work for both .xls and .xlsx files

Related Solutions

Java – How to avoid Java code in JSP files, using JSP 2

The use of scriptlets (those <% %> things) in JSP is indeed highly discouraged since the birth of taglibs (like JSTL) and EL (Expression Language, those ${} things) way back in 2001.

The major disadvantages of scriptlets are:

Reusability: you can't reuse scriptlets.
Replaceability: you can't make scriptlets abstract.
OO-ability: you can't make use of inheritance/composition.
Debuggability: if scriptlet throws an exception halfway, all you get is a blank page.
Testability: scriptlets are not unit-testable.
Maintainability: per saldo more time is needed to maintain mingled/cluttered/duplicated code logic.

~~Sun~~ Oracle itself also recommends in the JSP coding conventions to avoid use of scriptlets whenever the same functionality is possible by (tag) classes. Here are several cites of relevance:

From JSP 1.2 Specification, it is highly recommended that the JSP Standard Tag Library (JSTL) be used in your web application to help reduce the need for JSP scriptlets in your pages. Pages that use JSTL are, in general, easier to read and maintain.

...

Where possible, avoid JSP scriptlets whenever tag libraries provide equivalent functionality. This makes pages easier to read and maintain, helps to separate business logic from presentation logic, and will make your pages easier to evolve into JSP 2.0-style pages (JSP 2.0 Specification supports but de-emphasizes the use of scriptlets).

...

In the spirit of adopting the model-view-controller (MVC) design pattern to reduce coupling between the presentation tier from the business logic, JSP scriptlets should not be used for writing business logic. Rather, JSP scriptlets are used if necessary to transform data (also called "value objects") returned from processing the client's requests into a proper client-ready format. Even then, this would be better done with a front controller servlet or a custom tag.

How to replace scriptlets entirely depends on the sole purpose of the code/logic. More than often this code is to be placed in a fullworthy Java class:

If you want to invoke the same Java code on every request, less-or-more regardless of the requested page, e.g. checking if a user is logged in, then implement a filter and write code accordingly in doFilter() method. E.g.:

  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
      if (((HttpServletRequest) request).getSession().getAttribute("user") == null) {
          ((HttpServletResponse) response).sendRedirect("login"); // Not logged in, redirect to login page.
      } else {
          chain.doFilter(request, response); // Logged in, just continue request.
      }
  }

When mapped on an appropriate <url-pattern> covering the JSP pages of interest, then you don't need to copypaste the same piece of code overall JSP pages.

If you want to invoke some Java code to process a GET request, e.g. preloading some list from a database to display in some table, if necessary based on some query parameters, then implement a servlet and write code accordingly in doGet() method. E.g.:
```
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      try {
          List<Product> products = productService.list(); // Obtain all products.
          request.setAttribute("products", products); // Store products in request scope.
          request.getRequestDispatcher("/WEB-INF/products.jsp").forward(request, response); // Forward to JSP page to display them in a HTML table.
      } catch (SQLException e) {
          throw new ServletException("Retrieving products failed!", e);
      }
  }
```
This way dealing with exceptions is easier. The DB is not accessed in the midst of JSP rendering, but far before the JSP is been displayed. You still have the possibility to change the response whenever the DB access throws an exception. In the above example, the default error 500 page will be displayed which you can anyway customize by an <error-page> in web.xml.

If you want to invoke some Java code to process a POST request, such as gathering data from a submitted HTML form and doing some business stuff with it (conversion, validation, saving in DB, etcetera), then implement a servlet and write code accordingly in doPost() method. E.g.:

  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      String username = request.getParameter("username");
      String password = request.getParameter("password");
      User user = userService.find(username, password);

      if (user != null) {
          request.getSession().setAttribute("user", user); // Login user.
          response.sendRedirect("home"); // Redirect to home page.
      } else {
          request.setAttribute("message", "Unknown username/password. Please retry."); // Store error message in request scope.
          request.getRequestDispatcher("/WEB-INF/login.jsp").forward(request, response); // Forward to JSP page to redisplay login form with error.
      }
  }

This way dealing with different result page destinations is easier: redisplaying the form with validation errors in case of an error (in this particular example you can redisplay it using ${message} in EL), or just taking to the desired target page in case of success.

If you want to invoke some Java code to control the execution plan and/or the destination of the request and the response, then implement a servlet according to the MVC's Front Controller Pattern. E.g.:

  protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      try {
          Action action = ActionFactory.getAction(request);
          String view = action.execute(request, response);

          if (view.equals(request.getPathInfo().substring(1)) {
              request.getRequestDispatcher("/WEB-INF/" + view + ".jsp").forward(request, response);
          } else {
              response.sendRedirect(view);
          }
      } catch (Exception e) {
          throw new ServletException("Executing action failed.", e);
      }
  }

Or just adopt an MVC framework like JSF, Spring MVC, Wicket, etc so that you end up with just a JSP/Facelets page and a JavaBean class without the need for a custom servlet.

If you want to invoke some Java code to control the flow inside a JSP page, then you need to grab an (existing) flow control taglib like JSTL core. E.g. displaying List<Product> in a table:
```
  <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
  ...
  <table>
      <c:forEach items="${products}" var="product">
          <tr>
              <td>${product.name}</td>
              <td>${product.description}</td>
              <td>${product.price}</td>
          </tr>
      </c:forEach>
  </table>
```
With XML-style tags which fit nicely among all that HTML, the code is better readable (and thus better maintainable) than a bunch of scriptlets with various opening and closing braces ("Where the heck does this closing brace belong to?"). An easy aid is to configure your web application to throw an exception whenever scriptlets are still been used by adding the following piece to web.xml:
```
  <jsp-config>
      <jsp-property-group>
          <url-pattern>*.jsp</url-pattern>
          <scripting-invalid>true</scripting-invalid>
      </jsp-property-group>
  </jsp-config>
```
In Facelets, the successor of JSP, which is part of the Java EE provided MVC framework JSF, it is already not possible to use scriptlets. This way you're automatically forced to do things "the right way".
If you want to invoke some Java code to access and display "backend" data inside a JSP page, then you need to use EL (Expression Language), those ${} things. E.g. redisplaying submitted input values:
```
  <input type="text" name="foo" value="${param.foo}" />
```
The ${param.foo} displays the outcome of request.getParameter("foo").
If you want to invoke some utility Java code directly in the JSP page (typically public static methods), then you need to define them as EL functions. There's a standard functions taglib in JSTL, but you can also easily create functions yourself. Here's an example how JSTL fn:escapeXml is useful to prevent XSS attacks.
```
  <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
  ...
  <input type="text" name="foo" value="${fn:escapeXml(param.foo)}" />
```
Note that the XSS sensitivity is in no way specifically related to Java/JSP/JSTL/EL/whatever, this problem needs to be taken into account in every web application you develop. The problem of scriptlets is that it provides no way of builtin preventions, at least not using the standard Java API. JSP's successor Facelets has already implicit HTML escaping, so you don't need to worry about XSS holes in Facelets.

BufferedReader br = new BufferedReader(new FileReader("file.txt"));
try {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    }
    String everything = sb.toString();
} finally {
    br.close();
}

Some has pointed out that after Java 7 you should use try-with-resources (i.e. auto close) features:

try(BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    }
    String everything = sb.toString();
}

When I read strings like this, I usually want to do some string handling per line anyways, so then I go for this implementation.

Though if I want to actually just read a file into a String, I always use Apache Commons IO with the class IOUtils.toString() method. You can have a look at the source here:

http://www.docjar.com/html/api/org/apache/commons/io/IOUtils.java.html

FileInputStream inputStream = new FileInputStream("foo.txt");
try {
    String everything = IOUtils.toString(inputStream);
} finally {
    inputStream.close();
}

And even simpler with Java 7:

try(FileInputStream inputStream = new FileInputStream("foo.txt")) {     
    String everything = IOUtils.toString(inputStream);
    // do something with everything string
}

Best Answer

Related Solutions

Java – How to avoid Java code in JSP files, using JSP 2

See also:

Java – Reading a plain text file in Java

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