Java工具集-POI导入工具

		<!--poi-->
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi</artifactId>
            <version>4.0.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>4.0.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml-schemas</artifactId>
            <version>4.0.1</version>
        </dependency>

package com.simple.util.poi;

import org.apache.poi.ss.formula.functions.T;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.DateUtil;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import java.io.InputStream;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

/**
 * @program: simple_tools
 * @description: POI导入工具类
 * @author: ChenWenLong
 * @create: 2019-12-30 14:55
 **/
public class ExcelImportUtil<T> {
    private Class clazz;
    private Field fields[];

    public ExcelImportUtil(Class clazz) {
        this.clazz = clazz;
        fields = clazz.getDeclaredFields();
    }

    public Class getClazz() {
        return clazz;
    }

    public void setClazz(Class clazz) {
        this.clazz = clazz;
    }

    public Field[] getFields() {
        return fields;
    }

    public void setFields(Field[] fields) {
        this.fields = fields;
    }

    /**
     * 功能描述:
     * 〈基于注解读取Excel〉
     *
     * @params : [is, rowIndex, cellIndex]
     * @return : java.util.List<T>
     * @author : cwl
     * @date : 2019/12/30 14:59
     */
    public List<T> readExcel(InputStream is, int rowIndex, int cellIndex) {
        List<T> list = new ArrayList<T>();
        T entity = null;
        try {
            XSSFWorkbook workbook = new XSSFWorkbook(is);
            Sheet sheet = workbook.getSheetAt(0);
            // 不准确
            int rowLength = sheet.getLastRowNum();
            System.out.println(sheet.getLastRowNum());
            for (int rowNum = rowIndex; rowNum <= sheet.getLastRowNum(); rowNum++) {
                Row row = sheet.getRow(rowNum);
                entity = (T) clazz.newInstance();
                System.out.println(row.getLastCellNum());
                for (int j = cellIndex; j < row.getLastCellNum(); j++) {
                    Cell cell = row.getCell(j);
                    for (Field field : fields) {
                        if (field.isAnnotationPresent(ExcelAttribute.class)) {
                            field.setAccessible(true);
                            ExcelAttribute ea =
                                    field.getAnnotation(ExcelAttribute.class);
                            if (j == ea.sort()) {
                                field.set(entity, covertAttrType(field, cell));
                            }
                        }
                    }
                }
                list.add(entity);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }

    /**
     * 功能描述:
     * 〈类型转换 将cell 单元格格式转为 字段类型〉
     *
     * @params : [field, cell]
     * @return : java.lang.Object
     * @author : cwl
     * @date : 2019/12/30 14:59
     */
    private Object covertAttrType(Field field, Cell cell) throws Exception {
        String fieldType = field.getType().getSimpleName();
        if ("String".equals(fieldType)) {
            return getValue(cell);
        } else if ("Date".equals(fieldType)) {
            return new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").parse(getValue(cell));
        } else if ("int".equals(fieldType) || "Integer".equals(fieldType)) {
            return Integer.parseInt(getValue(cell));
        } else if ("double".equals(fieldType) || "Double".equals(fieldType)) {
            return Double.parseDouble(getValue(cell));
        } else {
            return null;
        }
    }

    /**
     * 功能描述:
     * 〈格式转为String〉
     *
     * @params : [cell]
     * @return : java.lang.String
     * @author : cwl
     * @date : 2019/12/30 14:59
     */
    public String getValue(Cell cell) {
        if (cell == null) {
            return "";
        }
        switch (cell.getCellType()) {
            case STRING:
                return cell.getRichStringCellValue().getString().trim();
            case NUMERIC:
                if (DateUtil.isCellDateFormatted(cell)) {
                    Date dt = DateUtil.getJavaDate(cell.getNumericCellValue());
                    return new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(dt);
                } else {
                    // 防止数值变成科学计数法
                    String strCell = "";
                    Double num = cell.getNumericCellValue();
                    BigDecimal bd = new BigDecimal(num.toString());
                    if (bd != null) {
                        strCell = bd.toPlainString();
                    }
                    // 去除 浮点型 自动加的 .0
                    if (strCell.endsWith(".0")) {
                        strCell = strCell.substring(0, strCell.indexOf("."));
                    }
                    return strCell;
                }
            case BOOLEAN:
                return String.valueOf(cell.getBooleanCellValue());
            default:
                return "";
        }
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.FIELD)
    public @interface ExcelAttribute {
        /**
         * 对应的列名称
         */
        String name() default "";

        /**
         * 列序号
         */
        int sort();

        /**
         * 字段类型对应的格式
         */
        String format() default "";
    }