以 DemoVo 为实体
import lombok.Data;
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.annotation.ExcelIgnoreUnannotated;
@Data
@ExcelIgnoreUnannotated
public class ExportPromoteUnitResult {
private String id;
@ExcelProperty(value = "学号")
private String stuNo;
@ExcelProperty(value = "姓名")
private String stuName;
}
- 将一个实体的属性名取出来，整合为一个 List<String[]>格式
private static List<String[]> getData() {
// new一个实体DemoVo
DemoVo demo = new DemoVo();
List<String[]> propertyNames = getPropertyNames(demo);
return propertyNames;
}
public static List<String[]> getPropertyNames(Object obj) {
List<String[]> properties = new ArrayList<>();
Class<?> clazz = obj.getClass(); // 获取对象的Class对象
Field[] fields = clazz.getDeclaredFields(); // 获取所有字段
for (Field field : fields) {
if (field.isAccessible()) { // 如果字段可访问，则添加其名称到列表中（对于私有字段可能需要设置可访问）
properties.add(new String[]{field.getName()}); // 将属性名添加到List<String[]>中，每个String[]包含一个属性名
} else {
field.setAccessible(true); // 对于私有字段，需要设置可访问才能获取其名称（注意：这可能会破坏封装性）
properties.add(new String[]{field.getName()}); // 添加属性名到List<String[]>中
}
}
return properties; // 返回包含所有属性名的List<String[]>
}
- 将一个实体的属性名整合为 List< String > 格式
// new一个实体DemoVo,取出属性名
DemoVo demo = new DemoVo();
List<String[]> propertyNames = getPropertyNames(demo.getClass());
System.out.print("propertyNames的输出结果为：" + propertyNames);
// propertyNames的输出结果为：[id,stuNo,stuName]
// 获取实体类的所有字段名
public List<String> getPropertyNames(Class<?> clazz) {
Field[] fields = clazz.getDeclaredFields(); // 获取所有字段
List<String> propertyNames = new ArrayList<>(); // 新建一个数组propertyNames
for (Field field : fields) {
propertyNames.add(field.getName()); // 将所有字段放于数组propertyNames中
}
return propertyNames;
}
- 根据属性名/字段名获取对应的值
List<Map<String, Object>> maps = combinFixedLists(stuClassId);
System.out.print("maps的输出结果为：" + maps);
// maps的输出结果为：[{id=1,stuNo="2024001",stuName="李四",stuSex="1"},{id=2,stuNo="2024002",stuName="张三",stuSex="1"}]
private List<Map<String, Object>> combinFixedLists(Long stuClassId) throws IllegalAccessException, NoSuchFieldException {
// 先根据stuClassId查询数据,此处不过多写sql语句了
List<StudentClassResult> listObjects = this.queryStuResult(stuClassId);
System.out.print("假如得出的结果为：" + listObjects);
// 假如得出的结果为：[{id:1,stuNo:"2024001",stuName:"李四",stuSex:"1"},{id:2,stuNo:"2024002",stuName:"张三",stuSex:"1"}]
List<Map<String, Object>> combinedList = new ArrayList<>();
for (StudentClassResult object : listObjects) {
Map<String, Object> fieldMap = new HashMap<>();
Field[] fields = object.getClass().getDeclaredFields();
for (Field field : fields) {
String name = field.getName();
field.setAccessible(true);
fieldMap.put(field.getName(), field.get(object));
}
combinedList.add(fieldMap);
}
return combinedList;
}
- 去掉List< String >中指定元素
removePropertyFromString(propertyNames, "id");
// 去掉指定属性名
private static void removePropertyFromString(List<String> fixList, String fixElement) {
Iterator<String> iterator = fixList.iterator();
while (iterator.hasNext()) {
String next = iterator.next();
if (next == fixElement) {
iterator.remove();
}
}
}
- 取出JSON中的某属性名对应的属性值
System.out.print(stuData)
// stuData={"stuData":{"stuId":57,"photoList":{"fileName":["照片.png"],"filePath":["/qcbucket/2024/10/22/01.照片.png"]},"stuClassId":"3","stuName":"张三"}}
Object stuId = null;
Object photoList = null;
Object stuClassId = null;
Object stuName = null;
JSONObject jsonObject = JSONObject.parseObject(stuData.toString());
stuId = jsonObject.getJSONObject("stuData").get("stuId ");
// 57
photoList = jsonObject.getJSONObject("stuData").get("photoList");
// "fileName":["照片.png"],"filePath":["/qcbucket/2024/10/22/01.照片.png"]
stuClassId = jsonObject.getJSONObject("stuData").get("stuClassId");
// "3"
stuName = jsonObject.getJSONObject("stuData").get("stuName");
// "张三"
- 保留两位数
（1）setScale
String num = "123.4567";
BigDecimal val = new BigDecimal(num);
BigDecimal roundedVal = val.setScale(2, RoundingMode.HALF_UP);
System.out.println(roundedVal); // 输出: 123.46
（2）sql语句
- 原数组 String[] originalArray，在指定元素后添加n个空字符串 “”
// 原数组
originalArray = new String[]{"apple","banana"}
// 查找指定字符串
String[] target = {"apple"}
// 在指定字符串后追加num个 空字符串
int num = 2;
String[] array = modifyArray(originalArray, target, num);
System.out("array的结果为：" + array);
// array的结果为：["apple","","","banana"]
private static String[] modifyArray(String[] originalArray, String[] target, int n) {
List<String> resultList = new ArrayList<>();
for (String element : originalArray) {
resultList.add(element);
for (String add : target) {
if (element.equals(add)) {
for (int i = 0; i < n; i++) {
resultList.add("");
}
}
}
}
return resultList.toArray(new String[0]);
}
