POI学习札记（一）

POI学习笔记（一）

项目中经常要解析和生成Excel文件，最常用的开源组件有poi与jxl。jxl是韩国人开发的，发行较早，但是更新的很慢，目前似乎还不支持excel2007。poi是apache下的一个子项目，poi应该是处理ms的office系列文档最好的组件了。poi3.6版本已经开始支持excel2007了。但是由于excel2007底层的实现似乎变成xml与excel2003底层存储发生了本质的变化，因此poi解析excel的类就存在差异了。

现在简单的介绍下poi常用的接口。

经常用的类一般都在org.apache.poi.hssf.usermodel（excel2003）或org.apache.poi.xssf.usermodel
（excel2007）。

工作薄： WorkBook是操作Excel的入口，HSSFWorkbook, XSSFWorkbook实现了该接口。
页：Sheet表示工作薄的分页。HSSFSheet， XSSFChartSheet, XSSFDialogsheet, XSSFSheet实现了该接口。
Row：表示页中的一行。HSSFRow, XSSFRow实现了该接口。
Cell：行中的一个单元格。HSSFCell, XSSFCell实现了该接口。

从上面的介绍得知：页是通过工作薄对象创建的，行是通过页对象创建的，单元格是通过行对象创建的。接下来，我们就开始发掘poi的强大功能吧。

创建一个空白的工作薄

import java.io.FileOutputStream;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

//2003版本
Workbook wb = new HSSFWorkbook();
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
 fileOut.close();

//2007版本
// Workbook wb = new XSSFWorkbook();
// FileOutputStream fileOut = new FileOutputStrea("workbook.xlsx");
// wb.write(fileOut);
// fileOut.close();

注意：Workbook 是org.apache.poi.ss.usermodel包下的一个接口，注意与以前版本的不同，HSSFWorkbook和XSSFWorkbook实现了该接口，这样就达到了面前接口编程。下面的excel工具类中要用到此点知识。

2. 创建两个空白页

Workbook wb = new HSSFWorkbook();
//Workbook wb = new XSSFWorkbook();
Sheet sheet1 = wb.createSheet("new sheet");
Sheet sheet2 = wb.createSheet("second sheet");
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();

3. 创建单元格

public void createRow() throws Exception {
		Workbook wb = new HSSFWorkbook();
		// Workbook wb = new XSSFWorkbook();
		CreationHelper createHelper = wb.getCreationHelper();
		Sheet sheet = wb.createSheet("new sheet");

		//创建一行并放一些单元格到该行中，行的索引是以0开始的
		Row row = sheet.createRow((short) 0);
		// 创建一个单元格并填充一个整数的值
		Cell cell = row.createCell(0);
		cell.setCellValue(1);

		//链式写法
		row.createCell(1).setCellValue(1.2);
		row.createCell(2).setCellValue(
				createHelper.createRichTextString("This is a string"));
		row.createCell(3).setCellValue(true);

		//输出文件
		FileOutputStream fileOut = new FileOutputStream("workbook.xls");
		wb.write(fileOut);
		fileOut.close();

	}

4. 创建日期单元格

public void createDateCell() throws Exception {
		Workbook wb = new HSSFWorkbook();
		// Workbook wb = new XSSFWorkbook();
		CreationHelper createHelper = wb.getCreationHelper();
		Sheet sheet = wb.createSheet("new sheet");

		// Create a row and put some cells in it. Rows are 0 based.
		Row row = sheet.createRow(0);

		// Create a cell and put a date value in it. The first cell is not
		// styled
		// as a date.
		Cell cell = row.createCell(0);
		cell.setCellValue(new Date());

		// we style the second cell as a date (and time). It is important to
		// create a new cell style from the workbook otherwise you can end up
		// modifying the built in style and effecting not only this cell but
		// other cells.
		CellStyle cellStyle = wb.createCellStyle();
		cellStyle.setDataFormat(createHelper.createDataFormat().getFormat(
				"yyyy/MM/dd hh:mm"));
		cell = row.createCell(1);
		// cell.setCellValue(new Date());
		Date date = new Date();

		cell.setCellValue(createHelper.createRichTextString(date.toString()));
		cell.setCellStyle(cellStyle);

		// you can also set date as java.util.Calendar
		cell = row.createCell(2);
		cell.setCellValue(Calendar.getInstance());
		cell.setCellStyle(cellStyle);

		// Write the output to a file
		FileOutputStream fileOut = new FileOutputStream("workbook.xls");
		wb.write(fileOut);
		fileOut.close();

	}

5. 创建不同的单元格样式

public void createCellType() throws Exception{
		Workbook wb = new HSSFWorkbook();
	    Sheet sheet = wb.createSheet("new sheet");
	    Row row = sheet.createRow((short)2);
	    row.createCell(0).setCellValue(1.1);
	    row.createCell(1).setCellValue(new Date());
	    row.createCell(2).setCellValue(Calendar.getInstance());
	    row.createCell(3).setCellValue("a string");
	    row.createCell(4).setCellValue(true);
	    row.createCell(5).setCellType(HSSFCell.CELL_TYPE_ERROR);

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

6. 设置单元格水平垂直对齐方式

public static void main(String[] args)  throws Exception {
        Workbook wb = new XSSFWorkbook(); //or new HSSFWorkbook();

        Sheet sheet = wb.createSheet();
        Row row = sheet.createRow((short) 2);
        row.setHeightInPoints(30);

        createCell(wb, row, (short) 0, XSSFCellStyle.ALIGN_CENTER, XSSFCellStyle.VERTICAL_BOTTOM);
        createCell(wb, row, (short) 1, XSSFCellStyle.ALIGN_CENTER_SELECTION, XSSFCellStyle.VERTICAL_BOTTOM);
        createCell(wb, row, (short) 2, XSSFCellStyle.ALIGN_FILL, XSSFCellStyle.VERTICAL_CENTER);
        createCell(wb, row, (short) 3, XSSFCellStyle.ALIGN_GENERAL, XSSFCellStyle.VERTICAL_CENTER);
        createCell(wb, row, (short) 4, XSSFCellStyle.ALIGN_JUSTIFY, XSSFCellStyle.VERTICAL_JUSTIFY);
        createCell(wb, row, (short) 5, XSSFCellStyle.ALIGN_LEFT, XSSFCellStyle.VERTICAL_TOP);
        createCell(wb, row, (short) 6, XSSFCellStyle.ALIGN_RIGHT, XSSFCellStyle.VERTICAL_TOP);

        // Write the output to a file
        FileOutputStream fileOut = new FileOutputStream("xssf-align.xlsx");
        wb.write(fileOut);
        fileOut.close();

    }

    /**
     * Creates a cell and aligns it a certain way.
     *
     * @param wb     the workbook
     * @param row    the row to create the cell in
     * @param column the column number to create the cell in
     * @param halign the horizontal alignment for the cell.
     */
    private static void createCell(Workbook wb, Row row, short column, short halign, short valign) {
        Cell cell = row.createCell(column);
        cell.setCellValue(new XSSFRichTextString("Align It"));
        CellStyle cellStyle = wb.createCellStyle();
        cellStyle.setAlignment(halign);
        cellStyle.setVerticalAlignment(valign);
        cell.setCellStyle(cellStyle);
    }

本篇写的都是poi基本的知识，POI学习笔记二将会继续学习poi一些高级的东西。

POI学习札记（一）

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