POI framework learning - Import and export cases

Catalog

One POI brief introduction

Two Row limit

3、 ... and Case study （ Import and export ）

3.1 Import dependence

3.2 Import case     

3.3 Export case （ Return to file flow mode ）

3.4 Export case （ return URL The way ）

3.5 Load template export

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One POI brief introduction

        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 . It is a popular import and Export excel frame .

        Official website ：Apache POI - the Java API for Microsoft Documentshttps://poi.apache.org/

Two Row limit

        HSSFWorkbook：

                 shortcoming ： At most The reason is 65536 That's ok , Otherwise, it will throw the exception

                 advantage ： Write cache in process , Do not operate disk , Finally, inhale the disk at one time , Fast

        XSSFWorkbook： Maximum data ：1048576 That's ok ,16384 Column ,

                 shortcoming ： When writing data Very slow , Very memory intensive , Memory overflow can also occur , Such as 100 Ten thousand .
                 advantage ： Can write Large amount of data , Such as 20 Ten thousand .

        SXSSFWorkbook：

                 advantage ： Can write a very large amount of data , Such as 100 Ten thousand or more data can be written quickly , Take up less memory

         Be careful ：

1. In the process Produce temporary documents , Need to clean up temporary files
2. Default by 100 Records are stored in memory , If it's more than that , The first data is written to the temporary file
3. If you want to customize the amount of data in memory , have access to new SXSSFWorkbook（ Number ）

3、 ... and Case study （ Import and export ）

3.1 Import dependence

<dependency>
       <groupId>org.apache.poi</groupId>
       <artifactId>poi</artifactId>
       <version>3.10-FINAL</version>
</dependency>
            
<dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
      <version>3.10-FINAL</version>
</dependency>
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml-schemas</artifactId>
    <version>4.1.0</version>
</dependency>

3.2 Import case     

controller entrance ：

@PostMapping("import")
public Response importRepayReconciliate(MultipartFile file,HttpServletRequest request){
    try {
        // Determine if the file is empty
        if (!file.isEmpty()) {
            // File save path
            String message = repayService.import(file.getInputStream(),request);
            return new Response(MessageConstants.MSG_SUCCESS, null, null);
        } else {
            return new Response(MessageConstants.MSG_SYS_ERROR, null, " The file is empty , Please upload the file ！");
        }
    } catch (Exception e) {
        log.error(" operation failed , Please contact the system administrator ！",e,e.getMessage());
        return new Response(MessageConstants.MSG_SYS_ERROR, null, e.getMessage());
    }
}

service class ：

Workbook book = WorkbookFactory.create(inputStream); // Create Workbook
Sheet sheet = book.getSheetAt(0);// Get worksheet
int lastRowNum = sheet.getLastRowNum();// Get the last row of the table
if (lastRowNum < 1 ) {
    return " You have not imported any data , Please add data and import ...";
}
Row row = sheet.getRow(2);
Cell cell = row.getCell(1);
String type = cell.getStringCellValue();

row = sheet.getRow(i);
cell = row.getCell(1);
cell.setCellType(CellType.STRING);

// Get cell values （ Important for text ）
String value = new DataFormatter().formatCellValue(cell);

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3.3 Export case （ Return to file flow mode ）

Summary of key words ：

The way 1：

        HSSFWorkbook book = new HSSFWorkbook();  // There is a limit on the number of rows Not greater than 65536 That's ok
        HSSFSheet sheet = book.createSheet();

The way 2：

        XSSFWorkbook book = new XSSFWorkbook();   // There is no line limit
        XSSFSheet sheet = book.createSheet();

The way 3：

        SXSSFWorkbook book = new SXSSFWorkbook();// There is no line limit Do not occupy memory （ Universal ）
        book.setCompressTempFiles(true);  // Open the compression configuration item

        XSSFRow titleRow = sheet.createRow(0);
        // Set cell width
        sheet.setColumnWidth(i, 2000); 

        .....

        book.write(out);

        response.flushBuffer();

        book.dispose(); // Temporary files need to be explicitly deleted manually , call dispose Method that will do

        out.close();

        book.close();

Style management ：

        The style of a HSSF

                HSSFCellStyle cellStyle = book.createCellStyle();

                cellStyle.setBorderBottom(HSSFCellStyle.BORDER_THIN);// Set the following

                cellStyle.setBorderLeft(HSSFCellStyle.BORDER_THIN);// Set left

                cellStyle.setBorderRight(HSSFCellStyle.BORDER_THIN);// Set right

                cellStyle.setBorderTop(HSSFCellStyle.BORDER_THIN);// Set the top

                cellStyle.setWrapText(true); // Set auto wrap

                cellStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);// Horizontal center

                cellStyle.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);// Vertical center

         Style 2 -SXSSFWorkbook

                CellStyle cellStyle = book.createCellStyle();

                cellStyle.setBorderBottom(BorderStyle.THIN); // Under the frame

                cellStyle.setBorderLeft(BorderStyle.THIN);// The left margin

                cellStyle.setBorderTop(BorderStyle.THIN);// On the border

                cellStyle.setBorderRight(BorderStyle.THIN);// Right margin

                cellStyle.setWrapText(true); // Set auto wrap

                cellStyle.setAlignment(HorizontalAlignment.CENTER);// Set the horizontal center of the cell

                cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);// Set the vertical center of the cell

merge cell Start line End line Start column End column

        sheet.addMergedRegion(new CellRangeAddress(1, 1, 0, 3));

Set the font

        HSSFFont font = book.createFont();

        font.setBold(true);// Set bold

        font.setFontHeightInPoints((short) 18);// Set font size

        font.setFontName(" In black ");// Set the font

        font.setColor(Font.COLOR_RED);// Set font color

        cellStyle.setFont(font);// Apply fonts to styles

Clone style ：

        HSSFCellStyle cellStyle2 = book.createCellStyle();

        cellStyle2.cloneStyleFrom(cellStyle);// Clone the previous style

Bank management ：

        HSSFRow row = sheet.createRow(0);

        row.setHeightInPoints(50); // Set row height

Column management ：

        HSSFCell cell = row.createCell(0);

        cell.setCellValue(" Comprehensive test "); // Set the value of the column

        cell.setCellStyle(cellStyle); // Apply styles to each cell

controller entrance ：

@RequestMapping(params = "enterpriseBaseInfoExport")
public void export(JSONObject data,HttpServletRequest request, HttpServletResponse response) {
    try {
        String fileName = "XXX.xls";
        response.setHeader("content-disposition","attachment;filename=" + new String(fileName.getBytes(), "ISO-8859-1"));
        ServletOutputStream out = response.getOutputStream();
        dataService.export(data,out);
    } catch (Exception e) {
        logger.error(" The reason for the export error is ：" + e.getMessage());
        e.printStackTrace();
    }
}

service Common export methods ：

3.4 Export case （ return URL The way ）

String fileName = UUID.randomUUID().toString().replace("-","");
        String path = request.getSession().getServletContext().getRealPath(File.separator) + File.separator + 
"upload" + File.separator + "download" + File.separator;
        File file = new File(path);
        if (!file.exists()) {
            file.mkdir();
        }
        fileName = fileName + ".xlsx";
        String filePath = path + fileName;
        FileOutputStream out = new FileOutputStream(filePath);
        book.setCompressTempFiles(true);
        book.write(out);
        out.close();
        response.flushBuffer();
        book.dispose();  // Temporary files need to be explicitly deleted manually , call dispose Method that will do
}

3.5 Load template export

Template location ：

XSSFWorkbook wb = new XSSFWorkbook(POIUtil.getInputStream("/statistic/download_template/excel/first_loan_info.xlsx"));
SXSSFWorkbook book = new SXSSFWorkbook(wb);
Sheet sheet = book.getSheetAt(0);
book.setCompressTempFiles(true);

public static InputStream getInputStream(String filePath) throws Exception{
    ClassPathResource classPathResource = new ClassPathResource(filePath);
    if(!classPathResource.exists()){
        throw new RuntimeException(" file does not exist :{}"+filePath);
    }
    return classPathResource.getInputStream();
}

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