Apache POI implements excel import, read data, write data and export

Apache POI

POI Introduce

Apache POI Yes, it is Java Write free open source cross platform Java API,Apache POI Provide API to Java Program pair Microsoft Office Format file reading and writing functions , One of the most used is the use of POI operation Excel file .

maven coordinate ：

<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi</artifactId>
  <version>3.14</version>
</dependency>
<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi-ooxml</artifactId>
  <version>3.14</version>
</dependency>

POI structure ：

HSSF －  Provide reading and writing Microsoft Excel XLS The function of format file 
XSSF －  Provide reading and writing Microsoft Excel OOXML XLSX The function of format file 
HWPF －  Provide reading and writing Microsoft Word DOC The function of format file 
HSLF －  Provide reading and writing Microsoft PowerPoint The function of format file 
HDGF －  Offer to read Microsoft Visio The function of format file 
HPBF －  Offer to read Microsoft Publisher The function of format file 
HSMF －  Offer to read Microsoft Outlook The function of format file 

Introductory cases

ExcelTest .java file

from Excel File read data

package tech.niua.common.utils;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.DataFormatter;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.IOException;

public class ExcelTest {
    
    public static void main(String[] args) throws IOException {
    
        // Create Workbook 
        XSSFWorkbook workbook = new XSSFWorkbook("E:\\qcby_software\\ Test data \\test.xlsx");
        // Get worksheet , It can be obtained according to the order of the worksheet , You can also get... By the name of the worksheet 
        XSSFSheet sheet = workbook.getSheetAt(0);
        // Set cell type , Not set some number The data will report an error 
        sheet.setCellType(CellType.STRING);
        // Traverse the worksheet to get the row object 
        for (Row row : sheet) {
    
            // Traverse the row object to get the cell object 
            for (Cell cell : row) {
    
                // Get the value in the cell 
                String value = cell.getStringCellValue();
                System.out.print(value +" ");
            }
            System.out.println();
        }
        workbook.close();
    }
}

The above introductory case can be seen ,POI operation Excel The table encapsulates several core objects ：

XSSFWorkbook： workbook 
XSSFSheet： Worksheet 
Row： That's ok 
Cell： Cell 

The above case is to get rows by traversing the worksheet , Traverse rows to get cells , Finally get the value in the cell .

There is another way to get the row number of the worksheet , To get the line object according to the line number , Get the index of the last cell from the row , Thus, one cell object of each row is obtained according to the cell index , The code is as follows ：

package tech.niua.common.utils;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.DataFormatter;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.IOException;

public class ExcelTest {
    
    public static void main(String[] args) throws IOException {
    
        // Create Workbook 
        XSSFWorkbook workbook = new XSSFWorkbook("E:\\qcby_software\\ Test data \\test.xlsx");
        // Get worksheet , It can be obtained according to the order of the worksheet , You can also get... By the name of the worksheet 
        XSSFSheet sheet = workbook.getSheetAt(0);
        // Set cell type , Not set some number The data will report an error 
        sheet.setCellType(CellType.STRING);
        // Gets the line number of the last line of the current sheet , Line number from 0 Start 
        int lastRowNum = sheet.getLastRowNum();
        for(int i=0;i<=lastRowNum;i++){
    
            // Get the line object according to the line number 
            XSSFRow row = sheet.getRow(i);
            short lastCellNum = row.getLastCellNum();
            for(short j=0;j<lastCellNum;j++){
    
                String value = row.getCell(j).getStringCellValue();
                System.out.print(value +" ");
            }
            System.out.println();
        }
        workbook.close();
    }
}

Be careful ：4.1.2 Version of poi No longer in use sheet.setCellType(CellType.STRING); This is set to String This form of type , Will no longer support

<dependency>
	<groupId>org.apache.poi</groupId>
	<artifactId>poi</artifactId>
	<version>4.1.2</version>
</dependency>
<dependency>
	<groupId>org.apache.poi</groupId>
	<artifactId>poi-ooxml</artifactId>
	<version>4.1.2</version>
</dependency>

Change it to DataFormatter To modify the data format

DataFormatter formatter = new DataFormatter();
String value = formatter.formatCellValue(rowValue.getCell(j));

After modification

package tech.niua.common.utils;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.DataFormatter;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.IOException;

public class ExcelTest {
    
    public static void main(String[] args) throws IOException {
    
        // Create Workbook 
        XSSFWorkbook workbook = new XSSFWorkbook("E:\\qcby_software\\ Test data \\test.xlsx");
        // Get worksheet , It can be obtained according to the order of the worksheet , You can also get... By the name of the worksheet 
        XSSFSheet sheet = workbook.getSheetAt(0);
        // Gets the line number of the last line of the current sheet , Line number from 0 Start 
        int lastRowNum = sheet.getLastRowNum();
        for(int i=0;i<=lastRowNum;i++){
    
            // Get the line object according to the line number 
            XSSFRow row = sheet.getRow(i);
            short lastCellNum = row.getLastCellNum();
            for(short j=0;j<lastCellNum;j++){
    
                DataFormatter formatter = new DataFormatter();
                String value = formatter.formatCellValue(row.getCell(j));
                System.out.print(value +" ");
            }
            System.out.println();
        }
        workbook.close();
    }
}

Running effect

In the actual development process , You can transform this tool class , Through the excel The uploaded address is passed to the tool class for reading , The read value can be received in the form of a set , Or receive as a collection object , In this way, you can do an operation on the read data .

towards Excel File write data

Use POI You can create a... In memory Excel File and write data to this file , Finally, through the output stream, the Excel Download files to disk

package tech.niua.common.utils.uuid;

import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.FileOutputStream;
import java.io.IOException;

public class ExcelTest2 {
    
    public static void main(String[] args) throws IOException {
    
        // Create a... In memory Excel file 
        XSSFWorkbook workbook = new XSSFWorkbook();
        // Create sheet , Specify the sheet name 
        XSSFSheet sheet = workbook.createSheet("TEST surface ");
        // Create lines ,0 The first line 
        XSSFRow row = sheet.createRow(0);
        // Create cells ,0 Represents the first cell 
        row.createCell(0).setCellValue(" Number ");
        row.createCell(1).setCellValue(" name ");
        row.createCell(2).setCellValue(" Age ");

        XSSFRow row1 = sheet.createRow(1);
        row1.createCell(0).setCellValue("1");
        row1.createCell(1).setCellValue(" Xiao Ming ");
        row1.createCell(2).setCellValue("10");

        XSSFRow row2 = sheet.createRow(2);
        row2.createCell(0).setCellValue("2");
        row2.createCell(1).setCellValue(" Xiao Wang ");
        row2.createCell(2).setCellValue("20");

        // Through the output stream workbook Object to disk 
        FileOutputStream out = new FileOutputStream("E:\\qcby_software\\ Test data \\TEST surface .xlsx");
        workbook.write(out);
        out.flush();
        out.close();
        workbook.close();
    }
}

test result