5 Ways to Refresh Excel Sheets with Java Code

Introduction

As the business world continues to embrace data-centric operations, Microsoft Excel remains a popular tool for data analysis and organization. However, as datasets grow larger and the demands for real-time updates increase, integrating Excel with more advanced programming capabilities becomes necessary. Java, known for its versatility and wide array of libraries, provides excellent tools for automating Excel workflows. In this blog, we’ll explore five different methods to refresh Excel sheets using Java, enhancing both productivity and data accuracy.

1. Using Apache POI

Apache POI is one of the most common libraries for working with Excel files in Java. Here’s how you can use it to refresh an Excel sheet:

• Set up: Start by adding the POI dependencies to your project.
• Reading: Use POI to read data from an Excel file.
• Writing: After refreshing data, write back to the file or create a new one.

Here is a simple example:

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import java.io.FileInputStream;
import java.io.FileOutputStream;

public class ExcelRefresh {

    public static void main(String[] args) throws Exception {
        // Open the Excel file
        FileInputStream fis = new FileInputStream("example.xlsx");
        Workbook workbook = new XSSFWorkbook(fis);
        Sheet sheet = workbook.getSheetAt(0);

        // Refresh some data (example: updating cell A1 with the current date)
        Row row = sheet.getRow(0);
        if (row == null) row = sheet.createRow(0);
        Cell cell = row.getCell(0);
        if (cell == null) cell = row.createCell(0);
        cell.setCellValue(new Date());

        // Write the output to a file
        FileOutputStream fileOut = new FileOutputStream("refreshed_example.xlsx");
        workbook.write(fileOut);
        fileOut.close();
        workbook.close();
    }
}

🗒️ Note: Apache POI is efficient for both .xls (HSSF) and .xlsx (XSSF) file formats but is not the fastest when dealing with very large files due to memory constraints.

2. Utilizing JExcelApi

JExcelApi is another Java library for Excel file manipulation, known for its simplicity and performance with older Excel files (.xls).

• Setup: Add JExcelApi to your project's dependencies.
• Processing: Read from existing Excel files, perform your refresh operations, and save changes.

Here's a basic usage example:

import jxl.*;
import jxl.write.*;

public class JExcelRefresh {

    public static void main(String[] args) throws Exception {
        Workbook workbook = Workbook.getWorkbook(new File("example.xls"));
        WritableWorkbook copy = Workbook.createWorkbook(new File("refreshed_example.xls"), workbook);
        WritableSheet sheet = copy.getSheet(0);

        // Refresh some data (example: updating cell A1 with current date)
        Label label = new Label(0, 0, new Date().toString());
        sheet.addCell(label);

        copy.write();
        copy.close();
    }
}

🗒️ Note: JExcelApi can be a good choice for legacy systems or when you need to work with older .xls files but has limitations when working with newer .xlsx formats.

3. Refresh via COM Automation

If running Java on Windows, COM automation can be used to interact with Excel directly:

• Setup: Install Jacob (Java COM Bridge).
• Automation: Use ActiveXObject to automate Excel through Java.

Here's how you can implement this:

import com.jacob.activeX.ActiveXComponent;
import com.jacob.com.Dispatch;
import com.jacob.com.Variant;

public class COMExcelRefresh {

    public static void main(String[] args) {
        ActiveXComponent excel = new ActiveXComponent("Excel.Application");
        try {
            excel.setProperty("Visible", new Variant(false));
            Dispatch workbooks = excel.getProperty("Workbooks").toDispatch();
            Dispatch workbook = Dispatch.call(workbooks, "Open", "example.xlsx").toDispatch();

            Dispatch sheets = Dispatch.get(workbook, "Sheets").toDispatch();
            Dispatch sheet = Dispatch.call(sheets, "Item", new Variant(1)).toDispatch();

            Dispatch cells = Dispatch.get(sheet, "Cells").toDispatch();
            Dispatch.call(cells, "Item", new Variant(1), new Variant(1)).toDispatch();
            Dispatch.put(cells, "Value", new Variant(new Date().toString()));

            Dispatch.call(workbook, "Save");
            Dispatch.call(workbook, "Close");
            excel.invoke("Quit");
        } finally {
            excel.invoke("Quit");
        }
    }
}

4. Using Streaming API for XSSF

For dealing with very large Excel files, SXSSF (Streaming API for XSSF) can be employed:

• Setup: Use the streaming API part of Apache POI.
• Streaming: Read and write data in a memory-efficient manner.

import org.apache.poi.xssf.streaming.SXSSFWorkbook;

public class SXSSFExcelRefresh {

    public static void main(String[] args) throws Exception {
        SXSSFWorkbook workbook = new SXSSFWorkbook(100); // Keep 100 rows in memory at a time, others are flushed to disk

        // Assuming data source is huge
        for (int i = 0; i < 1000000; i++) {
            Row row = workbook.createRow(i);
            Cell cell = row.createCell(0);
            cell.setCellValue(new Date()); // Refreshing with current date
        }

        FileOutputStream fileOut = new FileOutputStream("refreshed_example.xlsx");
        workbook.write(fileOut);
        fileOut.close();
        workbook.dispose(); // Tidy up resources
    }
}

🗒️ Note: This method is ideal for handling extremely large datasets where memory usage must be minimized.

5. Microsoft Graph API

For cloud-based solutions or when integrating with Microsoft 365:

• Setup: Register an app in Azure AD to get credentials.
• API Calls: Use Microsoft Graph API to interact with Excel files.

Here’s a basic example using the microsoft-graph library in Java:

import com.microsoft.graph.authentication.TokenCredentialAuthProvider;
import com.microsoft.graph.requests.GraphServiceClient;

public class GraphAPIExcelRefresh {

public static void main(String[] args) {
    // Setup authentication
    IAuthenticationProvider authProvider = new TokenCredentialAuthProvider(...);
    GraphServiceClient<Request> graphClient = GraphServiceClient.builder().authenticationProvider(authProvider).buildClient();

    // Refresh cell A1
    WorkbookRange range = graphClient.me().drive().items("fileItemId").workbook().worksheets("Sheet1").cells("A1").buildRequest().patch(new WorkbookRange(){{
        values = new Object[][]{{new Date()}};
    }});

    System.out.println("Cell A1 has been updated with the current date.");
}


}

In wrapping up this exploration into refreshing Excel sheets via Java, we’ve journeyed through multiple methodologies, each with its unique advantages:

• Apache POI provides comprehensive handling of Excel files, making it a versatile choice for most general Excel operations.
• JExcelApi caters well to legacy Excel systems, particularly for .xls files.
• COM Automation offers direct interaction with Excel for those running Java on Windows, leveraging the full capabilities of Excel.
• SXSSF from Apache POI is the go-to for dealing with large datasets by streaming data, minimizing memory usage.
• Microsoft Graph API opens up cloud-based interactions with Excel, ideal for modern, cloud-first environments.

Each method not only enhances productivity but also ensures data accuracy by automating what would otherwise be manual tasks. Whether it’s for updating real-time data, batch processing, or integrating with cloud services, Java’s rich ecosystem provides robust solutions. This integration of Java with Excel allows for efficient, scalable, and automated data management, propelling businesses towards greater efficiency and insight.

What are the main differences between Apache POI and JExcelApi?

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Apache POI supports both old (.xls) and new (.xlsx) Excel file formats and offers extensive features. JExcelApi, on the other hand, is specifically designed for .xls files and focuses on simplicity and performance with older Excel versions.

Can I use these methods to refresh Excel online?

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Only the Microsoft Graph API method is suited for directly interacting with Excel files stored in Microsoft 365 or OneDrive. The other methods require local file access or direct Excel application control.

Is there any risk in automating Excel via COM?

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Yes, using COM automation requires running Excel in the background, which can be resource-intensive and may lead to issues if Excel is not properly closed. This method also depends on the machine having Excel installed, limiting its use to Windows environments.