目录
一、集合转化为Excel文件
效果如下，是将集合转化为Excel文件，Excel包含合并单元格。
实体类：
java
@Data
public class ClassGrade {
/** 年级 */
private String grade;
/** 班主任 */
private String leader;
/** 学生列表 */
private List<Student> students;
@Data
public static class Student {
/** 姓名 */
private String name;
/** 年龄 */
private Integer age;
/** 性别 */
private String sex;
/** 成绩 */
private Integer gradeResult;
}
}需求就是将ClassGrade的集合转化为Excel表格对外输出。没有针对当前类去逐个取值处理，用到了反射来处理，达到了简化代码通用的目的。这个只针对有一个合并单元格的情形，如果是合并单元格中包含合并单元格的话，还需要加代码去处理。
实现代码如下：
1.初始化表头类，参数为表头集合
java
public static SXSSFWorkbook makeExcelHead(String[] titles) {
SXSSFWorkbook workbook = new SXSSFWorkbook();
CellStyle styleTitle = getTitleStyle(workbook, (short) 16);
SXSSFSheet sheet = workbook.createSheet();
SXSSFRow rowTitle = sheet.createRow(0);
for (int i = 0; i < titles.length; i++) {
sheet.setDefaultColumnWidth(25);
SXSSFCell cellTitle = rowTitle.createCell(i);
// 为标题设置背景颜色
styleTitle.setFillPattern(FillPatternType.SOLID_FOREGROUND);
styleTitle.setFillForegroundColor(HSSFColor.HSSFColorPredefined.GREY_25_PERCENT.getIndex());
cellTitle.setCellValue(titles[i]);
cellTitle.setCellStyle(styleTitle);
}
return workbook;
}2.反射获取实体的值
java
public static <T> Object getProperty(T t, String propertyName) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException, IndexOutOfBoundsException {
Class<?> aClass = t.getClass();
propertyName = propertyName.substring(0, 1).toUpperCase() + propertyName.substring(1);
Method method = aClass.getMethod("get" + propertyName);
Object invoke = method.invoke(t);
return invoke;
}2.将集合转化为Excel
java
@Test
public void exportExcel() throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
//初始化数据
List<ClassGrade> fileList = new ArrayList<>();
for (int m = 1; m <= 1; m++) {
fileList.addAll(getGrades());
}
//表头名称
String[] title = {"班主任", "学生姓名", "学生年龄", "学生性别", "学生成绩", "班级"};
SXSSFWorkbook workbook = SXSSFWorkbookUtil.makeExcelHead(title);
//每一列表头属性，如果子类里面的，则提取子类里面对应的属性名
String[] properties = {"leader", "name", "age", "sex", "gradeResult", "grade"};
//获取当前sheet
SXSSFSheet sheet = workbook.getSheetAt(0);
int initRowNum = 0;
//遍历数据，需要根据业务逻辑去处理是否合并单元格
for (int i = 0; i < fileList.size(); i++) {
ClassGrade file = fileList.get(i);
int size = file.getStudents().size();
//创建行，以子类的集合数为准
int startRowNum = initRowNum + 1;
int lastRowNum = startRowNum + size - 1;
SXSSFRow row = sheet.getRow(startRowNum);
if (row == null) {
row = sheet.createRow(startRowNum);
}
//班主任一列，处理合并单元格
for (int m = 0; m < 1; m++) {
if (lastRowNum - startRowNum > 0) {
sheet.addMergedRegion(new CellRangeAddress(startRowNum, lastRowNum, m, m));
}
createCell(row, m, SXSSFWorkbookUtil.getProperty(file, properties[m]));
}
//处理学生姓名~学生成绩四列，非合并单元格信息
int xRowNum = startRowNum;
List<ClassGrade.Student> receiptItems = file.getStudents();
for (ClassGrade.Student student : receiptItems) {
SXSSFRow row1 = sheet.getRow(xRowNum);
if (row1 == null) {
row1 = sheet.createRow(xRowNum);
}
for (int q = 1; q <= 4; q++) {
//利用反射获取到值，并且设置到cell里面
createCell(row1, q, SXSSFWorkbookUtil.getProperty(student, properties[q]));
}
xRowNum++;
}
//处理班级信息合并单元格
for (int n = 5; n <= 5; n++) {
if (lastRowNum - startRowNum >= 1) {
sheet.addMergedRegion(new CellRangeAddress(startRowNum, lastRowNum, n, n));
}
createCell(row, n, SXSSFWorkbookUtil.getProperty(file, properties[n]));
}
initRowNum = lastRowNum;
}
//导出
try (
FileOutputStream excel = new FileOutputStream("excel.xls");
BufferedOutputStream bos = new BufferedOutputStream(excel)) {
workbook.write(bos);
System.out.println("导出完成");
} catch (
IOException e) {
System.out.println("导出失败:" + e.getMessage());
}
}
private void createCell(SXSSFRow row, int column, Object value) {
SXSSFCell cell = row.createCell(column);
if (value != null) {
cell.setCellValue(String.valueOf(value));
}
}效果
二、Excel文件转化为集合
如题，将获取到的excel文件流转化为集合进行处理。挺简单的。思路就是将一个文件流转化为一个备用类，再将备用类转化为想要的集合。
excel：
备用类代码：
java
@Data
public class ClassGrade2 {
/** 年级 */
private String grade;
/** 班主任 */
private String leader;
/** 姓名 */
private String name;
/** 年龄 */
private Integer age;
/** 性别 */
private String sex;
/** 成绩 */
private Integer gradeResult;
}转化代码：
java
@Test
public void test1() {
ExcelReader reader = ExcelUtil.getReader("excelToList.xls");
List<List<Object>> rows = reader.read();
//根据excel的结构，需要准备一个备用类接收数据
List<ClassGrade2> listBaks = new ArrayList<>();
//初始化属性，属性是备用类的属性名
String[] properties = {"leader", "name", "age", "sex", "gradeResult", "grade"};
for (int j = 1; j < rows.size(); j++) {
List<Object> cells = rows.get(j);
try {
//反射获取值，组装成备用类
ClassGrade2 file = new ClassGrade2();
Class<?> clz = file.getClass();
Method[] methods = clz.getDeclaredMethods();
for (int i = 0; i < cells.size(); i++) {
String propertyName = properties[i].substring(0, 1).toUpperCase() + properties[i].substring(1);
Method method = Arrays.stream(methods).filter(m -> Objects.equal(m.getName(), "set" + propertyName)).findFirst().orElse(null);
Object cell = cells.get(i);
if (cell == null) {
continue;
}
Field field = clz.getDeclaredField(properties[i]);
String fieldType = field.getType().getName();
if (fieldType.equals("java.lang.String")) {
method.invoke(file, String.valueOf(cell));
} else if (fieldType.equals("java.math.BigDecimal")) {
method.invoke(file, new BigDecimal(String.valueOf(cell)));
}
}
listBaks.add(file);
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} finally {
}
}
//备用类转化为想要的集合类
int i = 0;
List<ClassGrade> files = new ArrayList<>();
for (int m = 0; m < listBaks.size(); m++) {
ClassGrade2 fileBak = listBaks.get(m);
if (Strings.isNotEmpty(fileBak.getGrade())) {
ClassGrade file = BeanUtil.copyProperties(fileBak, ClassGrade.class);
files.add(file);
ClassGrade.Student item = BeanUtil.copyProperties(fileBak, ClassGrade.Student.class);
List<ClassGrade.Student> items = new ArrayList<>();
items.add(item);
file.setStudents(items);
i++;
} else {
ClassGrade.Student item = BeanUtil.copyProperties(fileBak, ClassGrade.Student.class);
ClassGrade file = files.get(i - 1);
List<ClassGrade.Student> items = CollectionUtils.isEmpty(file.getStudents()) ? new ArrayList<>() : file.getStudents();
items.add(item);
file.setStudents(items);
}
}
log.info("{}", JSONArray.toJSONString(listBaks));
log.info("{}", JSONArray.toJSONString(files));
}实现效果：
java
11:47:03.635 [main] INFO Excel3Test - [{"grade":"八年级1班","leader":"赵老师","name":"张三","sex":"女"},{"grade":"八年级1班","leader":"赵老师","name":"李四","sex":"女"},{"grade":"八年级1班","leader":"赵老师","name":"王五","sex":"女"}]
11:47:03.647 [main] INFO Excel3Test - [{"grade":"八年级1班","leader":"赵老师","students":[{"name":"张三","sex":"女"}]},{"grade":"八年级1班","leader":"赵老师","students":[{"name":"李四","sex":"女"}]},{"grade":"八年级1班","leader":"赵老师","students":[{"name":"王五","sex":"女"}]}]