java自定义字段按字段顺序导出Excel

//使用

@PostMapping(value = "/exportCustomExcel")

public JsonResult<Boolean> exportCustomExcel(@RequestBody PcmStudentReq req, HttpServletResponse response,) throws ServiceException {
    List<StudentModel> resultList = iStudentService.getContractList(req, user);
    if (CollectionUtils.isEmpty(resultList)){
        throw new ServiceException("列表为空");
    }

    CustomExcelUtils<StudentModel> util = new CustomExcelUtils<>(StudentModel.class);
    util.exportExcel(resultList,req.getFieldsName(),"proceedsContract",response);
    return JsonResult.ok(true);
}

//工具类
package com.property.util;

import com.property.proceeds.contract.annotation.CustomExcelColumn;
import lombok.extern.slf4j.Slf4j;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.streaming.SXSSFWorkbook;
import org.springframework.http.MediaType;

import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.Field;
import java.io.IOException;
import java.math.BigDecimal;
import java.net.URLEncoder;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collectors;

/**
 * 自定义导出
 * @author jiagx
 */
@Slf4j
public class CustomExcelUtils<T> {
    /**
     * 工作薄
     */
    private Workbook wb;

    /**
     * 工作表
     */
    private Sheet sheet;

    /**
     * 需要导出的数据
     */
    private List<T> exportList;

    /**
     * 对象的class对象
     */
    private Class<T> clazz;

    /**
     * 被选中需要导出的字段名称
     */
    private List<String> checkedFieldsName;

    /**
     * 被选中需要导出的字段对象
     */
    private List<Field> checkedFields;

    /**
     * 包含需要字典转换的字段对象
     */
    private List<Field> fieldsContainDict;

    /**
     * 对象中的字典值
     */
    private Map<String, Map<String, String>> dicts;

    private CustomExcelUtils(){
    }

    public CustomExcelUtils(Class<T> clazz){
        this.clazz = clazz;
    }


    /**
     * @param list  导出的集合数据
     * @param fieldsName  需要导出的字段集合
     * @param sheetName  sheet页/文件名称
     * @param response response
     */
    public void exportExcel(List<T> list, List<String> fieldsName, String sheetName,HttpServletResponse response){
        // 初始化数据
        init(list, sheetName, fieldsName);

        // 转换字典值
        try {
            convertDict();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }

        // sheet第一行加入名称数据
        createTopRow();

        // sheet其他行，添加目标数据
        try {
            createOtherRow();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }

        // 导出wb-浏览器下周excel
        buildExcelDocument(generateFileName(sheetName),wb,response);
    }

    /**
     * 浏览器下载excel
     * @param fileName 文件名称
     * @param wb wb
     * @param response HttpServletResponse
     */
    public  void  buildExcelDocument(String fileName, Workbook wb,HttpServletResponse response){
        try {
            response.setContentType(MediaType.APPLICATION_OCTET_STREAM_VALUE);
            response.setHeader("content-Type", "application/vnd.ms-excel");
            response.setHeader("Content-Disposition", "attachment;filename="+ URLEncoder.encode(fileName, "utf-8"));
            response.flushBuffer();
            wb.write(response.getOutputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                wb.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }



    /**
     * 添加导出数据
     */
    private void createOtherRow() throws IllegalAccessException {
        for (int rowNum = 1; rowNum <= exportList.size(); rowNum++) {
            Row row = sheet.createRow(rowNum);
            T t = exportList.get(rowNum - 1);
            for (int colNum = 0; colNum < checkedFields.size(); colNum++) {
                Cell cell = row.createCell(colNum);
                Field field = checkedFields.get(colNum);
                field.setAccessible(true);

                // 单元格设置值
                addCell(cell, field, t);
            }
        }
    }

    /**
     * 单元格中添加数据
     *
     * @param cell  单元格
     * @param field 字段
     * @param t     list中的一条数据
     */
    private void addCell(Cell cell, Field field, T t) throws IllegalAccessException {
        Class<?> fieldType = field.getType();

        if (String.class == fieldType) {
            cell.setCellValue((String) field.get(t));
        } else if ((Integer.TYPE == fieldType) || (Integer.class == fieldType)) {
            cell.setCellValue((Integer) field.get(t));
        } else if ((Long.TYPE == fieldType) || (Long.class == fieldType)) {
            cell.setCellValue((Long) field.get(t));
        } else if ((Double.TYPE == fieldType) || (Double.class == fieldType)) {
            cell.setCellValue((Double) field.get(t));
        } else if ((Float.TYPE == fieldType) || (Float.class == fieldType)) {
            cell.setCellValue((Float) field.get(t));
        }else if ((BigDecimal.class == fieldType)) {
           if(null!=field.get(t)){
               if (field.get(t).toString().equals("0.00000000")||field.get(t).toString().equals("0E-8")){
                   cell.setCellValue("0");
               }else{
                   cell.setCellValue(getRateStr(field.get(t).toString()));
               }
            }
        }else if (LocalDateTime.class == fieldType) {
            String dateFormat = field.getAnnotation(CustomExcelColumn.class).dateFormat();
            cell.setCellValue(dateFormat((LocalDateTime) field.get(t), dateFormat));
        }
    }

    /**
     * 截取小数点后两位
     * @param rateStr
     * @return
     */
    public String getRateStr(String rateStr) {
        if(rateStr.indexOf(".") != -1){
            //获取小数点的位置
            int num = 0;
            num = rateStr.indexOf(".");
            //获取小数点后面的数字 是否有两位 不足两位补足两位
            String dianAfter = rateStr.substring(0,num+1);
            String afterData = rateStr.replace(dianAfter, "");
            if(afterData.length() < 2){
                afterData = afterData + "0" ;
            }
            return rateStr.substring(0,num) + "." + afterData.substring(0,2);
        }else{
            return rateStr;
        }
    }


    /**
     * 时间格式转换
     * @param date 日期
     * @param dateFormat 日期格式
     * @return
     */
    private String dateFormat(LocalDateTime date, String dateFormat) {
        if (dateFormat == null || "".equals(dateFormat)) {
            dateFormat = "yyyy-MM-dd HH:mm:ss";
        }
        if (null==date){
            return "";
        }
        DateTimeFormatter df = DateTimeFormatter.ofPattern(dateFormat);
        return df.format(date);
    }

    /**
     * sheet第一行加入名称数据
     */
    private void createTopRow() {
        Row row = sheet.createRow(0);
        Map<String, CellStyle> styles = createStyles(wb);
        AtomicInteger aj = new AtomicInteger();

        for (int index = 0; index < checkedFields.size(); index++) {
            Cell cell = row.createCell(aj.getAndIncrement());
            cell.setCellStyle(styles.get("header"));

            CellStyle cellStyle = wb.createCellStyle();
            cellStyle.setFillForegroundColor(IndexedColors.WHITE.getIndex());
            cellStyle.setFillPattern(CellStyle.SOLID_FOREGROUND);
            //设置边框
            cellStyle.setAlignment(CellStyle.ALIGN_CENTER);
            Font font = wb.createFont();
            font.setBoldweight(Font.BOLDWEIGHT_NORMAL);
            cellStyle.setFont(font);
            cell.setCellStyle(cellStyle);
            cell.setCellValue(checkedFields.get(index).getAnnotation(CustomExcelColumn.class).name());
        }
    }

    /**
     * 转换字典值
     *  将数据中字典值转化为对应的值(注:字典值应为String格式)
     */
    private void convertDict() throws IllegalAccessException {
        for (Field field : fieldsContainDict) {
            CustomExcelColumn annotation = field.getAnnotation(CustomExcelColumn.class);
            String dictKey = annotation.dictKey();
            field.setAccessible(true);
            for (T t : exportList) {
                // 获取字段值
                String o = (String) field.get(t);
                field.set(t, dicts.get(dictKey).get(o));
            }
        }
    }

    /**
     * 将数据导出Excel
     * @param list 需要导出的数据
     * @param sheetName 工作表名称
     */
    public void exportExcel(List<T> list, String sheetName,HttpServletResponse response){
        exportExcel(list, null, sheetName,response);
    }

    /**
     * 将数据导出Excel
     * @param list 需要导出的数据
     */
    public void exportExcel(List<T> list,HttpServletResponse response) {
        exportExcel(list, null, "sheet",response);
    }

    /**
     * 初始化
     */
    public void init(List<T> list ,String sheetName, List<String> fieldsName){
        this.checkedFieldsName = fieldsName;

        this.exportList = list;

        // 初始化导出数据
        initExportList();

        // 初始化工作薄
        initWorkbook();

        // 初始化工作表
        initSheet(sheetName);

        // 初始化checkedFields, fieldsContainDict
        initFields();

        // 根据注解生成生成字典
        generateObjDict();
    }

    /**
     * 初始化导出数据
     */
    private void initExportList(){
        // 防止导出过程中出现空指针
        if(Objects.isNull(this.exportList)) {
            this.exportList = new ArrayList<>();
        }
    }

    /**
     * 初始化工作簿
     */
    private void initWorkbook(){
        this.wb = new SXSSFWorkbook();
    }

    /**
     * 初始化工作表
     */
    private void initSheet(String sheetName){
        this.sheet = wb.createSheet(sheetName);
    }

    /**
     * 初始化checkedFields, fieldsContainDict
     *     fieldsContainDict含有字典表达式的字段
     *     checkedFields用户选中的字段
     *        1.如果checkedFieldsName没有定义(未自定义导出字段),所有字段全部导出
     *        2.如果checkedFieldsName进行了定义,根据定义字段进行导出
     */
    private void initFields(){
        // 获取对象所有字段对象
        Field[] fields = clazz.getDeclaredFields();

        // 过滤出checkedFields
        this.checkedFields = Arrays.
                asList(fields).
                stream().
                filter(field -> {
                    if(!Objects.isNull(this.checkedFieldsName)) {
                        if (field.isAnnotationPresent(CustomExcelColumn.class)) {
                            return checkedFieldsName.contains(field.getName());
                        }
                    } else {
                        return field.isAnnotationPresent(CustomExcelColumn.class);
                    }
                    return false;
                }).sorted(Comparator.comparing(field -> {
                    return checkedFieldsName.indexOf(field.getName());
                }))
                .collect(Collectors.toList());

        // 过滤出fieldsContainDict
        for (Field declaredField : clazz.getDeclaredFields()) {
            if(declaredField.getAnnotation(CustomExcelColumn.class) != null) {
                System.out.println(declaredField.getAnnotation(CustomExcelColumn.class).dictExp());
            }
        }
        this.fieldsContainDict = Arrays
                .asList(clazz.getDeclaredFields())
                .stream()
                .filter(item -> !"".equals(item.getAnnotation(CustomExcelColumn.class) != null? item.getAnnotation(CustomExcelColumn.class).dictExp() : ""))
                .collect(Collectors.toList());
    }

    /**
     * 通过扫描字段注解生成字典数据
     */
    private void generateObjDict(){
        if(fieldsContainDict.size() == 0) {
            return;
        }

        if(dicts == null) {
            dicts = new HashMap<>(); //  Map<String, List<Map<String, String>>>
        }

        for (Field field : fieldsContainDict) {
            String dictKey = field.getAnnotation(CustomExcelColumn.class).dictKey();
            String exps = field.getAnnotation(CustomExcelColumn.class).dictExp();
            String[] exp = exps.split(",");

            Map<String, String> keyV = new HashMap<>();

            dicts.put(dictKey, keyV);

            for (String s : exp) {
                String[] out = s.split("=");
                keyV.put(out[0], out[1]);
            }

            System.out.println("字典值:"+ dicts);
        }
    }

    /**
     * 创建表格样式
     *
     * @param wb 工作薄对象
     * @return 样式列表
     */
    private Map<String, CellStyle> createStyles(Workbook wb)
    {
        Map<String, CellStyle> styles = new HashMap<String, CellStyle>();
        // 数据格式
        CellStyle style = wb.createCellStyle();
        style.setFillForegroundColor(IndexedColors.WHITE.getIndex());
        style.setFillPattern(CellStyle.SOLID_FOREGROUND);
        style.setAlignment(CellStyle.ALIGN_CENTER);
        style.setVerticalAlignment(CellStyle.ALIGN_CENTER);

        Font dataFont = wb.createFont();
        dataFont.setBoldweight(Font.BOLDWEIGHT_NORMAL);
        style.setFont(dataFont);
        styles.put("data", style);

        // 表头格式
        CellStyle cellStyle = wb.createCellStyle();
        cellStyle.setFillForegroundColor(IndexedColors.WHITE.getIndex());
        cellStyle.setFillPattern(CellStyle.SOLID_FOREGROUND);
        cellStyle.setAlignment(CellStyle.ALIGN_CENTER);

        Font font = wb.createFont();
        font.setBoldweight(Font.BOLDWEIGHT_NORMAL);
        cellStyle.setFont(font);
        styles.put("header", cellStyle);

        return styles;
    }

    /**
     * 生成随机名称,防止文件复写
     * @return
     */
    private String generateFileName(String sheetName){
        return DateUtil.LocalDateTimeStr()+sheetName+".xlsx";
    }
}