用於excel生成，下載。
1.自定義Excel註解

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 *  用於Excel生成，註明列的名稱和其他屬性
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface
 
 ExcelColumnName {
    /**
     * 列的表頭名稱
     * @return
     */
    String name() default "-";

    /**
     * 用於日期格式化的字串，預設 yyyy-MM-dd HH:mm:ss
     * @return
     */
    String dateFormat() default "yyyy-MM-dd hh:mm:ss";
}

2.Excel通用類

import com.pingan.haofang.leshan.common.utils.DateUtils;
import
 
 org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.CreationHelper;
import org.springframework.
 
http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Field;
import java.net.URLEncoder;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;


/**
 * Excel file generator
 */
public class ExcelGenerator {

    private HSSFWorkbook workbook;

    public ExcelGenerator() {
        this.workbook = new HSSFWorkbook();
    }

    private List<Field> getFieldsWithAnnotations(Class rowClass) {
        // get all fields with annotation "ExcelColumnName"
        List<Field> rowFields = Arrays.stream(rowClass.getDeclaredFields())
                .filter(f -> f.isAnnotationPresent(ExcelColumnName.class))
                .collect(Collectors.toList());
        return rowFields;
    }

    private List<String> getColumnNames(Class rowClass) {
        List<Field> rowFields = getFieldsWithAnnotations(rowClass);
        List<String> rowNames = rowFields.stream()
                .map(f -> getColumnName(f)).collect(Collectors.toList());
        return rowNames;
    }

    private String getColumnName(Field columnField) {
        return columnField.getAnnotation(ExcelColumnName.class).name();
    }

    private String getDateFormat(Field columnField) {
        return columnField.getAnnotation(ExcelColumnName.class).dateFormat();
    }

    /**
     * 通過物件列表構造Excel Sheet
     * @param sheetName 插入的sheet名稱
     * @param rowClass rowObjs的型別
     * @param rowObjs 構成表格的物件列表
     * @throws IllegalAccessException
     */
    public void addSheetFromArray(String sheetName, Class rowClass, Object[] rowObjs) throws IllegalAccessException {
        addSheetFromArray(sheetName, rowClass, rowObjs, Collections.emptyList(), Collections.emptyMap());
    }

    /**
     * 通過物件列表構造Excel Sheet
     * @param sheetName 插入的sheet名稱
     * @param rowClass rowObjs的型別
     * @param rowObjs 構成表格的物件列表
     * @param columnsToShow 要顯示的列(如不需要請留空)
     * @param columnMapping 需要重新命名的列mapping
     * @throws IllegalAccessException
     */
    public void addSheetFromArray(String sheetName, Class rowClass, Object[] rowObjs,
                                  List<String> columnsToShow, Map<String, String> columnMapping)
            throws IllegalAccessException {
        List<Field> rowFields;
        // create new sheet on workbook
        HSSFSheet sheet = this.workbook.createSheet(sheetName);
        // create header
        HSSFRow head = sheet.createRow(0);


        // filter columns to show
        if (columnsToShow != null && !columnsToShow.isEmpty()) {
            List<Field> allFields = getFieldsWithAnnotations(rowClass);
            Map<String, Field> fieldMap = new HashMap<String, Field>();
            allFields.forEach(f -> {
                String columnName = getColumnName(f);
                fieldMap.put(columnName, f);
            });
            rowFields = columnsToShow.stream().map(c -> fieldMap.get(c)).collect(Collectors.toList());
        } else  {
            // get all fields with annotation "ExcelColumnName"
            rowFields = getFieldsWithAnnotations(rowClass);
        }
        // getColumnNames
        List<String> columnNames = rowFields.stream().map(f -> getColumnName(f)).collect(Collectors.toList());
        columnNames = columnNames.stream().map(name -> columnMapping.getOrDefault(name, name))
                .collect(Collectors.toList());
        // add column names to header
        for (int i = 0; i < columnNames.size(); i++) {
            head.createCell(i).setCellValue(columnNames.get(i));
        }
        // set all fields accessible
        rowFields.forEach(f -> f.setAccessible(true));
        // write data to sheet
        for (int i = 0; i < rowObjs.length; i++) {
            // create new row
            HSSFRow dataRow = sheet.createRow(i+1);
            // get object for current row
            Object rowObj = rowObjs[i];
            for (int j = 0; j < rowFields.size(); j++) {
                // get current field value
                Field field = rowFields.get(j);
                Object cellValue = field.get(rowObj);
                // set cell value with correct type
                if(cellValue == null) {continue;}
                if (field.getType() == boolean.class) {
                    dataRow.createCell(j).setCellValue((boolean)cellValue);
                } else if (field.getType() == Calendar.class || field.getType() == Date.class) {
                    // generate Date format
                    HSSFCell cell = dataRow.createCell(j);
                    CellStyle cellStyle = workbook.createCellStyle();
                    CreationHelper helper = workbook.getCreationHelper();
                    String dateFormat = getDateFormat(field);
                    cellStyle.setDataFormat(helper.createDataFormat().getFormat(dateFormat));
                    if (field.getType() == Calendar.class) {
                        cell.setCellValue((Calendar) cellValue);
                    } else {
                        cell.setCellValue((Date) cellValue);
                    }
                    cell.setCellStyle(cellStyle);
                } else if (field.getType() == String.class) {
                    dataRow.createCell(j).setCellValue(cellValue.toString());
                } else {
                    String cellValueString = cellValue.toString();
                    try {
                        // if cell value can be convert to double
                        double cellValueDouble = Double.parseDouble(cellValueString);
                        dataRow.createCell(j).setCellValue(cellValueDouble);
                    } catch (NumberFormatException e) {
                        // if not, convert to string by default
                        dataRow.createCell(j).setCellValue(cellValueString);
                    }
                }
            }
        }
    }

    public byte[] generateExcelFileContent() throws IOException {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        workbook.write(outputStream);
        return outputStream.toByteArray();
    }

    public static String generateExcelFileNameWithDate(String name) {
        String date = DateUtils.formatDate(new Date(), "yyyy-MM-dd");
        return  name + date + ".xls";
    }

    public static String generateExcelFileNameWithDateUTF8(String name) {
        try {
            return URLEncoder.encode(generateExcelFileNameWithDate(name), "UTF-8");
        } catch (UnsupportedEncodingException e) {
            return "";
        }
    }

    public ResponseEntity generateResponseEntity(String name) {
        try {
            byte[] body = this.generateExcelFileContent();
            String fileName = generateExcelFileNameWithDateUTF8(name);

            return ResponseEntity.ok()
                    .contentLength(body.length)
                    .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + fileName)
                    .contentType(MediaType.parseMediaType("application/vnd.ms-excel"))
                    .body(body);
        } catch (Exception e) {
            return ResponseEntity.badRequest().build();
        }
    }
}

3.程式碼示例

import com.pingan.haofang.common.excelutil.ExcelColumnName;
import com.pingan.haofang.common.excelutil.ExcelGenerator;
import com.pingan.haofang.leshan.common.constants.WebConstants;
import io.swagger.annotations.Api;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;
import java.util.Date;

/**
 * Excel生成示例
 */
@RestController
@RequestMapping(WebConstants.WEB_PREFIX + "/example")
@Api(tags = "ExcelExample", description = "Excel生成示例")
public class ExcelExampleController {
    @RequestMapping(value = "/download", method = RequestMethod.GET)
    public ResponseEntity GenerateExcelFile() {
        // 示例資料Array
        ExampleClass[] exampleData = {
                new ExampleClass("張三", "111222333", (float)-99.999, new Date("03/15/2018")),
                new ExampleClass("隔壁老王", "444555666", (float)100.1, new Date("03/15/2018"))};

        ExcelGenerator excelGenerator = new ExcelGenerator();
        try {
            excelGenerator.addSheetFromArray("Contacts", ExampleClass.class, exampleData);
            byte[] body = excelGenerator.generateExcelFileContent();
			String nowTime = DateFormatUtils.format(new Date(), "yyyy-MM-dd");
            return ResponseEntity.ok()
                    .contentLength(body.length)
                    .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename="+ URLEncoder.encode("測試示例", "UTF-8")+nowTime+".xls")
                    .contentType(MediaType.parseMediaType("application/vnd.ms-excel"))
                    .body(body);

        } catch (IllegalAccessException e) {

        } catch (IOException e) {

        }
        return  ResponseEntity.notFound().build();

    }

    // 需要轉換為Excel的資料類
    class ExampleClass{

        // 新增annotation註明該列表頭的名稱
        @ExcelColumnName(name = "姓名")
        private String name;
        @ExcelColumnName(name = "電話號碼")
        private String phoneNumber;
        @ExcelColumnName(name = "薪水")
        private float salary;
        @ExcelColumnName(name = "過期", dateFormat = "yyyy-MM-dd")
        private Date expriy;

        public ExampleClass(String name, String phoneNumber, float salary, Date expiry) {
            this.name = name;
            this.phoneNumber = phoneNumber;
            this.salary = salary;
            this.expriy = expiry;
        }
    }
}