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Java使用poi做加自定义注解实现对象与Excel相互转换

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【字号：大中小】日期：2022-05-22 08:31:31浏览：25作者：猪猪

引入依赖

maven

<dependency> <groupId>org.apache.poi</groupId> <artifactId>poi</artifactId> <version>3.17</version></dependency>

Gradle

implementation group: ’org.apache.poi’, name: ’poi’, version: ’3.17’代码展示

1、自定义注解类

@Retention(value = RetentionPolicy.RUNTIME)@Target(value = ElementType.FIELD)public @interface Excel { String name();//列的名字 int width() default 6000;//列的宽度 int index() default -1;//决定生成的顺序 boolean isMust() default true; // 是否为必须值,默认是必须的}

2、Java的Excel对象，只展现了field，get与set方法就忽略了

public class GoodsExcelModel { @Excel(name = 'ID_禁止改动', index = 0, width = 0) private Long picId;//picId @Excel(name = '产品ID_禁止改动', index = 1, width = 0) private Long productId; @Excel(name = '型号', index = 3) private String productName;//产品型号 @Excel(name = '系列', index = 2) private String seriesName;//系列名字 @Excel(name = '库存', index = 5) private Long quantity; @Excel(name = '属性值', index = 4) private String propValue; @Excel(name = '价格', index = 6) private Double price; @Excel(name = '商品编码', index = 7, isMust = false) private String outerId; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long dbId; // 数据库自增长id private Date createTime; // 记录创建时间 }

3、Excel表格与对象转换的工具类，使用时指定泛型参数和泛型的class即可

public class ExcelUtil { private static final String GET = 'get'; private static final String SET = 'set'; private static Logger logger = LoggerFactory.getLogger(ExcelUtil.class); /** * 将对象转换成Excel * * @param objList 需要转换的对象 * @return 返回是poi中的对象 */ public static HSSFWorkbook toExcel(List objList) {if (CollectionUtils.isEmpty(objList)) throw new NullPointerException('无效的数据');Class aClass = objList.get(0).getClass();Field[] fields = aClass.getDeclaredFields();HSSFWorkbook workbook = new HSSFWorkbook();HSSFSheet sheet = workbook.createSheet();for (int i = 0; i < objList.size(); i++) { HSSFRow row = sheet.createRow(i + 1);//要从第二行开始写 HSSFRow topRow = null; if (i == 0) topRow = sheet.createRow(0); for (Field field : fields) {Excel excel = field.getAnnotation(Excel.class);//得到字段是否使用了Excel注解if (excel == null) continue;HSSFCell cell = row.createCell(excel.index());//设置当前值放到第几列String startName = field.getName().substring(0, 1);String endName = field.getName().substring(1, field.getName().length());String methodName = new StringBuffer(GET).append(startName.toUpperCase()).append(endName).toString();try { Method method = aClass.getMethod(methodName);//根据方法名获取方法,用于调用 Object invoke = method.invoke(objList.get(i)); if (invoke == null) continue; cell.setCellValue(invoke.toString());} catch (NoSuchMethodException e) { e.printStackTrace();} catch (IllegalAccessException e) { e.printStackTrace();} catch (InvocationTargetException e) { e.printStackTrace();}if (topRow == null) continue;HSSFCell topRowCell = topRow.createCell(excel.index());topRowCell.setCellValue(excel.name());sheet.setColumnWidth(excel.index(), excel.width()); }}return workbook; } /** * 将Excel文件转换为指定对象 * * @param file 传入的Excel * @param c 需要被指定的class * @return * @throws IOException * @throws IllegalAccessException * @throws InstantiationException */ public static <T> List<T> excelFileToObject(MultipartFile file, Class<T> c) throws IOException, IllegalAccessException, InstantiationException {//key为反射得到的下标,value为对于的set方法Map<Integer, String> methodMap = new HashMap<>();//保存第一列的值与对应的下标,用于验证用户是否删除了该列,key为下标,value为名字Map<Integer, String> startRowNameMap = new HashMap<>();//用来记录当前参数是否为必须的Map<Integer, Boolean> fieldIsMustMap = new HashMap<>();//得到所有的字段Field[] fields = c.getDeclaredFields();for (Field field : fields) { Excel excel = field.getAnnotation(Excel.class); if (excel == null) continue; String startName = field.getName().substring(0, 1); String endName = field.getName().substring(1, field.getName().length()); String methodName = new StringBuffer(SET).append(startName.toUpperCase()).append(endName).toString(); methodMap.put(excel.index(), methodName); startRowNameMap.put(excel.index(), excel.name()); fieldIsMustMap.put(excel.index(), excel.isMust());}String fileName = file.getOriginalFilename();Workbook wb = fileName.endsWith('.xlsx') ? new XSSFWorkbook(file.getInputStream()) : new HSSFWorkbook(file.getInputStream());Sheet sheet = wb.getSheetAt(0);Row sheetRow = sheet.getRow(0);for (Cell cell : sheetRow) { Integer columnIndex = cell.getColumnIndex(); if (cell.getCellTypeEnum() != CellType.STRING) throw new ExcelException('excel校验失败, 请勿删除文件中第一行数据 !!!'); String value = cell.getStringCellValue(); String name = startRowNameMap.get(columnIndex); if (name == null) throw new ExcelException('excel校验失败,请勿移动文件中任何列的顺序!!!'); if (!name.equals(value)) throw new ExcelException('excel校验失败,【' + name + '】列被删除,请勿删除文件中任何列 !!!');}sheet.removeRow(sheetRow);//第一行是不需要被反射赋值的List<T> models = new ArrayList<>();for (Row row : sheet) { if (row == null || !checkRow(row)) continue; T obj = c.newInstance();//创建新的实例化对象 Class excelModelClass = obj.getClass(); startRowNameMap.entrySet().forEach(x -> {Integer index = x.getKey();Cell cell = row.getCell(index);String methodName = methodMap.get(index);if (StringUtils.isEmpty(methodName)) return;List<Method> methods = Lists.newArrayList(excelModelClass.getMethods()).stream().filter(m -> m.getName().startsWith(SET)).collect(Collectors.toList());String rowName = startRowNameMap.get(index);//列的名字for (Method method : methods) { if (!method.getName().startsWith(methodName)) continue; //检测value属性 String value = valueCheck(cell, rowName, fieldIsMustMap.get(index)); //开始进行调用方法反射赋值 methodInvokeHandler(obj, method, value);} }); models.add(obj);}return models; } /** * 检测当前需要赋值的value * * @param cell 当前循环行中的列对象 * @param rowName 列的名字{@link Excel}中的name * @param isMust 是否为必须的 * @return 值 */ private static String valueCheck(Cell cell, String rowName, Boolean isMust) {//有时候删除单个数据会造成cell为空,也可能是value为空if (cell == null && isMust) { throw new ExcelException('excel校验失败,【' + rowName + '】中的数据禁止单个删除');}if (cell == null) return null;cell.setCellType(CellType.STRING);String value = cell.getStringCellValue();if ((value == null || value.trim().isEmpty()) && isMust) { throw new ExcelException('excel校验失败,【' + rowName + '】中的数据禁止单个删除');}return value; } /** * 反射赋值的处理的方法 * * @param obj 循环创建的需要赋值的对象 * @param method 当前对象期中一个set方法 * @param value 要被赋值的内容 */ private static void methodInvokeHandler(Object obj, Method method, String value) {Class<?> parameterType = method.getParameterTypes()[0];try { if (parameterType == null) {method.invoke(obj);return; } String name = parameterType.getName(); if (name.equals(String.class.getName())) {method.invoke(obj, value);return; } if (name.equals(Long.class.getName())) {method.invoke(obj, Long.valueOf(value));return; } if (name.equals(Double.class.getName())) {method.invoke(obj, Double.valueOf(value)); }} catch (IllegalAccessException e) { e.printStackTrace();} catch (InvocationTargetException e) { e.printStackTrace();} } private static boolean checkRow(Row row) {try { if (row == null) return false; short firstCellNum = row.getFirstCellNum(); short lastCellNum = row.getLastCellNum(); if (firstCellNum < 0 && lastCellNum < 0) return false; if (firstCellNum != 0) {for (short i = firstCellNum; i < lastCellNum; i++) { Cell cell = row.getCell(i); String cellValue = cell.getStringCellValue(); if (!StringUtils.isBlank(cellValue)) return true;}return false; } return true;} catch (Exception e) { return true;} }

4、导出Excel与导入Excel的示例代码