Excel file parsing

In the process of application development , Need to be used frequently Excel File to import or export data . therefore , Through Java When the language implements such requirements , Often face Excel File analysis ( Import ) Or produce ( export ).

stay Java In the technological ecosystem , Can be done Excel The mainstream technologies of document processing include ：Apache POI,Alibaba EasyExcel etc. .

Today we will introduce how these two technologies can parse and generate files .

Apache POI

Apache POI It is a free and open source cross platform Java API , stay Apache POI The classes we often use to parse files in HSSF and XSSF.        

HSSF Used to parse old versions (*.xls) Excel file , Because of the old version of Excel Files can only exist 65535 Row data , Currently, it is not commonly used . So at present, it mainly adopts XSSF Make a new version （*xlsx）Excel File analysis .

 POI Technology required Jar package

 

WorkBook file (Excel file )

        Workbook The interface represents a Excel file , Used to create or load ( analysis )Excel file . The common implementation classes are XSSFWorkbook.

Sheet( workbook )

        Sheet representative Excel A workbook in a table , adopt Workbook To carry out Sheet Object acquisition or creation .

Row( data row ) 

        Row representative Sheet One row in Workbook , adopt Sheet To carry out Row Object acquisition and creation .

Cell( Cell )

        Cell Represents a cell in a data row , adopt Row To carry out Cell Object acquisition and creation .

Apache POI The creation process and parsing process

Create a process :

1, Create a Workbook , Write through the output stream Excel file

// Output stream 
FileOutputStream out = new FileOutputStream("c:\\test\\2022.xlsx");

//Excel File object 
Workbook workbook = new XSSFWorkbook();

// Write through the output stream 
workbook.write(out);

// close resource 

2, adopt Workbook Create a workbook Sheet

Sheet sheet = workbook.creatSheet();

3, adopt Sheet Create a work line Row

Row row = sheet.createRow();

4, adopt Row Create a cell Cell

// stay row Create the first cell in this row 
Cell cell = Row.createCell(0);

Analytical process

1, Create a Workbook , Load through input stream ( analysis ) Excel file

// Input stream 
FileInputStream in = new FileInputStream(c:\\test\\2022.xlsx);

//Excel File object 
Workbook workbook = new XFFSWorkbook(in)

2, adopt Workbook Get the workbooks Sheet

// Get by workbook subscript Sheet
Sheet sheet01 = workbook.getSheetAt(0);

// Get by workbook name Sheet
Sheet sheet02 = workbook.getSheet("Sheet0");

3, adopt Sheet Get row Row

// Get the first line of subscript 
int first = sheet.getFirstRowNum();

// Get the trailing subscript 
int last = sheet.getLastRowNum();

// Get the specified line according to the subscript 
Row row = sheet.getRow(0);

4, adopt Rowt Get the cell Cell

// Get cells according to the following table 
Cell cell = row.getCell(1);

// Get cell type 
CellType type = cell.getCellType();

// Set cell style 
// Create format encoding values 
DataFormat dataFormat = workbook.createDataFormat();
short dateFormatCode = dataFormat.getFormat("yyyy year MM month dd Japan  HH when mm branch ss second ");

// Create date format object 
CellStyle dataCellStyle = workbook.createCellStyle();
dataCellStyle.setDataFormat(dateFormatCode);

// Create cells , Cells are not formatted 			
Cell cell = row.createCell(2);// date 
cell.setCellStyle(dataCellStyle);
cell.setCellValue(new Date());

Part of the code is implemented as follows

public class Demo {
	public static void main(String[] args) {
		try (FileOutputStream out = new FileOutputStream("C:\\POI\\data.xlsx");
				Workbook workbook = new XSSFWorkbook()) {
			// Create Workbook 
			Sheet sheet01 = workbook.createSheet("2020 Data list ");
			Sheet sheet02 = workbook.createSheet("2021 Data list ");
			Sheet sheet03 = workbook.createSheet("2022 Data list ");
			
			// Create lines 
			Row row = sheet01.createRow(0);
			
			// Create cells 
			Cell cell0 = row.createCell(0);
			cell0.setCellValue(UUID.randomUUID().toString());
			Cell cell1 = row.createCell(1);
			cell1.setCellValue(Math.random() * 10000);
			Cell cell2 = row.createCell(2);
			cell2.setCellValue(LocalDateTime.now());
			
			// take workbook The data contained in the object , Through output stream , Write to Excel file 
			workbook.write(out);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

Alibaba EasyExcel

When we need to read or write a very large Excel When you file ,Apache POI Technology has been unable to read and write files quickly , We need to use Alibaba EasyExcel Technology operates on documents , Let's look at a group of two technologies for reading and writing large files CPU And memory occupation .

 

 

  So let's see EasyExcel Part of the code implementation of

public class Demo {
	public static void main(String[] args) {
        long begin = System.currentTimeMillis();
		//  write in 100w
        EasyExcel.write("E:\\easyExcel\\easy.xlsx", Order.class)
                 .sheet(" Order list ")
                 .doWrite(data());
        long end = System.currentTimeMillis();
        
        System.out.println(" Total time consuming " + (end - begin) + " millisecond ");
    }
    
    //  establish 100w Order data 
    private static List<Order> data() {
        List<Order> list = new ArrayList<Order>();
        for (int i = 0; i < 1000000; i++) {
            list.add(new Order());
        }
        return list;
    }
}