POI API Event

In this program we are going to explain about POI API Event.

The advantage of event API is that you can read an XLS with a relatively small memory.

To use Event API we construct an instance of org.apache.poi.hssf.eventmodel.HSSFRequest. To register a class we have to create listener org.apache.poi.hssf.eventmodel.HSSFListener interface and use HSSFRequest.addListener(yourlistener, recordsid) method. The record Sid should be a static reference number (such as BOFRecord.sid) contained in the classes in org.apache.poi.hssf.record. Alternatively you can call HSSFRequest.addListenerForAllRecords(mylistener).

Once we have registered our listeners in the HSSFRequest object we can construct an instance of org.apache.poi.poifs.filesystem.FileSystem and pass it your XLS file inputstream. We can either pass this, along with the request we constructed, to an instance of HSSFEventFactory via the HSSFEventFactory.processWorkbookEvents(request, Filesystem) method, or we can get an instance of DocumentInputStream from Filesystem.createDocumentInputStream("Workbook") and pass it to HSSFEventFactory.processEvents(request, inputStream). Once we make this call, the listeners that we constructed receive calls to their processRecord(Record) methods with each Record they are registered to listen for until the file has been completely read.

The code of the program is given below:


import java.io.*;

import org.apache.poi.hssf.usermodel.*;

import org.apache.poi.poifs.filesystem.*;

import org.apache.poi.hssf.usermodel.HSSFRow;

import org.apache.poi.hssf.eventusermodel.*;

import org.apache.poi.hssf.record.*;

import org.apache.poi.hssf.dev.EFHSSF;

public class EventAPIsExample implements HSSFListener

{ 

public static void main(String[] args) throws IOException

  { 

      FileInputStream fin = new FileInputStream("example.xls");

  POIFSFileSystem poifs = new POIFSFileSystem(fin);

  InputStream din = poifs.createDocumentInputStream

    ("Workbook");

  HSSFRequest req = new HSSFRequest();

  req.addListenerForAllRecords(new EventAPIsExample());

  HSSFEventFactory factory = new HSSFEventFactory();

  System.out.println("\n\nExample of Event

     API using POI3.0)\n\n");

  factory.processEvents(req, din);

  fin.close();

  din.close();

  System.out.println("\n\nIn main method ->>

    public static void main(String[] args)");

  }

  public void processRecord(Record record)

  {

  

 System.out.println("In Processs method ->>

    public void processRecord(Record record)");

  }

    }

The output of the program is given below:

C:\POI3.0\exmples\execl>javac EventAPIsExample.java

C:\POI3.0\exmples\execl>java EventAPIsExample example.xls

Example of Event API using POI3.0)

In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)
In Processs method ->>public void processRecord(Record record)

In main method ->>public static void main(String[] args)

C:\POI3.0\exmples\execl>

Download this example.

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