Apache POI - the Java API for Microsoft Documents，顾名思义，Apache的三方包，用来操作微软office文档的，多数时候用来操作excel，所以这里就以excel方面来说明。
需要引入两个包，maven地址如下（version 3.9）：
<dependency> <groupId>org.apache.poi</groupId> <artifactId>poi</artifactId> <version>3.9</version></dependency><dependency> <groupId>org.apache.poi</groupId> <artifactId>poi-ooxml</artifactId> <version>3.9</version></dependency>
POI的组件列表中，针对excel的主要是HSSF和XSSF组件，前者针对97-2007的通用版excel，即后缀xls；后者针对2007或更高版的excel，即后缀xlsx。官方概要如下：
HSSF is the POI Project's pure Java implementation of the Excel '97(-2007) file format. XSSF is the POI Project's pure Java implementation of the Excel 2007 OOXML (.xlsx) file format.
面向对象面向对象，既然如此，自然去找找一些能表示excel中内容的类。
创建或维护Excel工作簿的所有类的超接口，Workbook，属于org.apache.poi.ss.usermodel包。其下有两个实现类：
HSSFWorkbook : 有读取.xls 格式和写入Microsoft Excel文件的方法。它与微软Office97-2003版本兼容
XSSFWorkbook : 有读写Microsoft Excel和OpenOffice的XML文件的格式.xls或.xlsx的方法。它与MS-Office版本2007或更高版本兼容
所以在针对不同版本的excel时，需要对应以上使用不同的Workbook。构造函数中，常用的：
HSSFWorkbook
HSSFWorkbook()HSSFWorkbook(java.io.InputStream s)
XSSFWorkbook
XSSFWorkbook()XSSFWorkbook(java.io.File file)XSSFWorkbook(java.io.InputStream is)
HSSFSheet 和 XSSFSheet 都是Sheet接口的实现类，Sheet可以使用Workbook的两个方法获得：
workbook.createSheet();workbook.createSheet(String sheetName);
同理，Row是 HSSFRow 和 XSSFRow 的接口，通过Sheet获取：
sheet.createRow(int rownum);
同理，Cell是 HSSFCell 和 XSSFCell 的接口，通过Row获取：
row.createCell(int column);row.createCell(int column, int type);
其实如果能理解面向对象，就很简单了，另外包括字体，公式，超链接等，都有对应的封装类，此处只提出了核心的几个，需要了解更多的需要自行展开。
例子的话，直接从别人教程里摘出来吧，另，读取的workbook，可以debug瞅瞅内容。
import java.io.*;import org.apache.poi.xssf.usermodel.*;public class CreateWorkBook { public static void main(String[] args)throws Exception { XSSFWorkbook workbook = new XSSFWorkbook(); FileOutputStream out = new FileOutputStream( new File("createworkbook.xlsx")); workbook.write(out); out.close(); System.out.println(" createworkbook.xlsx written successfully"); }}import java.io.*;import org.apache.poi.xssf.usermodel.*;public class OpenWorkBook{ public static void main(String args[])throws Exception { File file = new File("openworkbook.xlsx"); FileInputStream fIP = new FileInputStream(file); XSSFWorkbook workbook = new XSSFWorkbook(fIP); if(file.isFile() && file.exists()) { System.out.println( "openworkbook.xlsx file open successfully."); } else { System.out.println( "Error to open openworkbook.xlsx file."); } }}可用注解定义标签名和列名，写了个方法，可以将某个类的List转换为对应的Excel文档，列名如果在不使用注解的情况下默认为属性名：
类：
@Excel(name = "学生标签页")public class Student { @Excel(name = "姓名") private String name; private boolean male; @Excel(name = "身高") private int height; public String getName() { return name; } public void setName(String name) { this.name = name; } public boolean isMale() { return male; } public void setMale(boolean male) { this.male = male; } public int getHeight() { return height; } public void setHeight(int height) { this.height = height; }}测试方法：
public static void main(String[] args) { List<Student> list = new ArrayList<Student>(); Student student1 = new Student(); student1.setName("小红"); student1.setMale(false); student1.setHeight(167); Student student2 = new Student(); student2.setName("小明"); student2.setMale(true); student2.setHeight(185); list.add(student1); list.add(student2); File file = new File("C:/Users/Dulk/Desktop/1314.xls"); createExcel(list, file);}输出结果：
注解：
import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;@Retention(RetentionPolicy.RUNTIME)public @interface Excel { public String name() default "";}方法：
import org.apache.log4j.Logger;import org.apache.poi.hssf.usermodel.HSSFWorkbook;import org.apache.poi.ss.usermodel.Cell;import org.apache.poi.ss.usermodel.Row;import org.apache.poi.ss.usermodel.Sheet;import org.apache.poi.ss.usermodel.Workbook;import org.apache.poi.xssf.usermodel.XSSFWorkbook;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.ArrayList;import java.util.List;public class ExcelUtil { private static Logger log = Logger.getLogger(ExcelUtil.class); public static Workbook gainWorkbook(File file) throws ExcelException { if (!isExcel(file)) { throw new ExcelException("文件不是Excel类型"); } if (!file.exists()) { try { OutputStream os = new FileOutputStream(file); Workbook workbook = isOlderEdition(file) ? new HSSFWorkbook() : new XSSFWorkbook(); workbook.write(os); log.debug("文件不存在，新建该Excel文件"); os.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } try { InputStream is = new FileInputStream(file); return isOlderEdition(file) ? new HSSFWorkbook(is) : new XSSFWorkbook(is); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return null; } private static boolean isOlderEdition(File file) { return file.getName().matches(".+\\.(?i)xls"); } private static boolean isExcel(File file) { String fileName = file.getName(); String regXls = ".+\\.(?i)xls"; String regXlsx = ".+\\.(?i)xlsx"; return fileName.matches(regXls) || fileName.matches(regXlsx); } public static <E> Workbook createExcel(List<E> list, File file) { String sheetName = "default"; if (list.size() == 0) { return null; } Workbook workbook = null; try { Class clazz = list.get(0).getClass(); Field[] fields = clazz.getDeclaredFields(); if (clazz.isAnnotationPresent(Excel.class)) { Excel excel = (Excel) clazz.getAnnotation(Excel.class); sheetName = excel.name(); } workbook = gainWorkbook(file); Sheet sheet = workbook.createSheet(sheetName); Row line = sheet.createRow(0); for (int k = 0; k < fields.length; k++) { Cell cell = line.createCell(k); String columnName = fields[k].getName(); if (fields[k].isAnnotationPresent(Excel.class)) { Excel excel = fields[k].getAnnotation(Excel.class); columnName = excel.name(); } cell.setCellValue(columnName); } for (int i = 1; i <= list.size(); i++) { Row row = sheet.createRow(i); for (int j = 1; j <= fields.length; j++) { Cell cell = row.createCell(j - 1); String fieldName = fields[j - 1].getName(); String fieldFirstLetterUpper = fieldName.substring(0, 1).toUpperCase(); String prefix = "get"; if ("boolean".equals(fields[j - 1].getType().getName())) { prefix = "is"; } String methodName = prefix + fieldFirstLetterUpper + fieldName.substring(1); Method method = clazz.getMethod(methodName); cell.setCellValue(String.valueOf(method.invoke(list.get(i - 1)))); } } log.debug("List读入完毕"); OutputStream os = new FileOutputStream(file); workbook.write(os); os.close(); } catch (ExcelException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } catch (NoSuchMethodException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return workbook; }}参考链接：http://www.yiibai.com/apache_poi/apache_poi_core_classes.html
作者：Dulk
来源：www.cnblogs.com/deng-cc/p/7443192.html
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