使用EasyExcel导出带下拉框的Excel

1. 创建注解

import java.lang.annotation.*;

/**
 * 标注导出的列为下拉框类型，并为下拉框设置内容
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface ExcelSelected {
    /**
     * 固定下拉内容
     */
    String[] source() default {};

    /**
     * 动态下拉内容
     */
    Class<? extends ExcelDynamicSelect>[] sourceClass() default {};

    /**
     * 设置下拉框的起始行，默认为第二行
     */
    int firstRow() default 1;

    /**
     * 设置下拉框的结束行，默认为最后一行
     */
    int lastRow() default 0x10000;
}

2.创建动态下拉框的接口，设置动态下拉框都实现该接口

public interface ExcelDynamicSelect {
    /**
     * 获取动态生成的下拉框可选数据
     * @return 动态生成的下拉框可选数据
     */
    String[] getSource();
}

3.创建解析注解类

import lombok.Data;
import lombok.extern.slf4j.Slf4j;

@Data
@Slf4j
public class ExcelSelectedResolve {
    /**
     * 下拉内容
     */
    private String[] source;

    /**
     * 设置下拉框的起始行，默认为第二行
     */
    private int firstRow;

    /**
     * 设置下拉框的结束行，默认为最后一行
     */
    private int lastRow;

    public String[] resolveSelectedSource(ExcelSelected excelSelected) {
        if (excelSelected == null) {
            return null;
        }

        // 获取固定下拉框的内容
        String[] source = excelSelected.source();
        if (source.length > 0) {
            return source;
        }

        // 获取动态下拉框的内容
        Class<? extends ExcelDynamicSelect>[] classes = excelSelected.sourceClass();
        if (classes.length > 0) {
            try {
                ExcelDynamicSelect excelDynamicSelect = classes[0].newInstance();
                String[] dynamicSelectSource = excelDynamicSelect.getSource();
                if (dynamicSelectSource != null && dynamicSelectSource.length > 0) {
                    return dynamicSelectSource;
                }
            } catch (InstantiationException | IllegalAccessException e) {
                log.error("解析动态下拉框数据异常", e);
            }
        }
        return null;
    }

}

4.创建Handler，设置excel中的下拉框

import com.alibaba.excel.write.handler.SheetWriteHandler;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
import lombok.AllArgsConstructor;
import lombok.Data;
import org.apache.poi.ss.usermodel.DataValidation;
import org.apache.poi.ss.usermodel.DataValidationConstraint;
import org.apache.poi.ss.usermodel.DataValidationHelper;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.util.CellRangeAddressList;

import java.util.Map;

@Data
@AllArgsConstructor
public class SelectedSheetWriteHandler implements SheetWriteHandler {

    private final Map<Integer, ExcelSelectedResolve> selectedMap;

    /**
     * Called before create the sheet
     */
    @Override
    public void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {

    }

    /**
     * Called after the sheet is created
     */
    @Override
    public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
        // 这里可以对cell进行任何操作
        Sheet sheet = writeSheetHolder.getSheet();
        DataValidationHelper helper = sheet.getDataValidationHelper();
        selectedMap.forEach((k, v) -> {
            // 设置下拉列表的行： 首行，末行，首列，末列
            CellRangeAddressList rangeList = new CellRangeAddressList(v.getFirstRow(), v.getLastRow(), k, k);
            // 设置下拉列表的值
            DataValidationConstraint constraint = helper.createExplicitListConstraint(v.getSource());
            // 设置约束
            DataValidation validation = helper.createValidation(constraint, rangeList);
            // 阻止输入非下拉选项的值
            validation.setErrorStyle(DataValidation.ErrorStyle.STOP);
            validation.setShowErrorBox(true);
            validation.setSuppressDropDownArrow(true);
            validation.createErrorBox("提示", "请输入下拉选项中的内容");
            sheet.addValidationData(validation);
        });
    }
}

5.创建导出工具类

import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.annotation.ExcelProperty;
import com.alibaba.excel.write.metadata.WriteSheet;
import lombok.extern.slf4j.Slf4j;

import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

@Slf4j
public class EasyExcelUtil {

	/**
     * 创建即将导出的sheet页（sheet页中含有带下拉框的列）
     * @param head 导出的表头信息和配置
     * @param sheetNo sheet索引
     * @param sheetName sheet名称
     * @param  泛型
     * @return sheet页
     */
    public static <T> WriteSheet writeSelectedSheet(Class<T> head, Integer sheetNo, String sheetName) {
        Map<Integer, ExcelSelectedResolve> selectedMap = resolveSelectedAnnotation(head);

        return EasyExcel.writerSheet(sheetNo, sheetName)
                .head(head)
                .registerWriteHandler(new SelectedSheetWriteHandler(selectedMap))
                .build();
    }

    /**
     * 解析表头类中的下拉注解
     * @param head 表头类
     * @param  泛型
     * @return Map<下拉框列索引, 下拉框内容> map
     */
    private static <T> Map<Integer, ExcelSelectedResolve> resolveSelectedAnnotation(Class<T> head) {
        Map<Integer, ExcelSelectedResolve> selectedMap = new HashMap<>();

        // getDeclaredFields(): 返回全部声明的属性；getFields(): 返回public类型的属性
        Field[] fields = head.getDeclaredFields();
        for (int i = 0; i < fields.length; i++){
            Field field = fields[i];
            // 解析注解信息
            ExcelSelected selected = field.getAnnotation(ExcelSelected.class);
            ExcelProperty property = field.getAnnotation(ExcelProperty.class);
            if (selected != null) {
                ExcelSelectedResolve excelSelectedResolve = new ExcelSelectedResolve();
                String[] source = excelSelectedResolve.resolveSelectedSource(selected);
                if (source != null && source.length > 0){
                    excelSelectedResolve.setSource(source);
                    excelSelectedResolve.setFirstRow(selected.firstRow());
                    excelSelectedResolve.setLastRow(selected.lastRow());
                    if (property != null && property.index() >= 0){
                        selectedMap.put(property.index(), excelSelectedResolve);
                    } else {
                        selectedMap.put(i, excelSelectedResolve);
                    }
                }
            }
        }

        return selectedMap;
    }
}

7.测试导出

(1).创建需要导出的实体类并用该注解标注

public class UserDTO {
    @ExcelProperty(index = 0,value = "编号")
    private Long id;
    @ExcelProperty(index = 1,value = "姓名")
    private String name;
    @ExcelProperty(index = 2,value = "年龄")
    private Integer age;
    @ExcelProperty(index = 3,value = "性别")
    //静态下拉框
    @ExcelSelected(source = {"男","女"})
    private String sex;
    @ExcelProperty(index = 4,value = "出生日期")
    private Date birthday;
    @ExcelProperty(index = 5,value = "居住城市")
    //动态下拉框-去数据库中查询所有城市供其选择
    @ExcelSelected(sourceClass = CityExcelSelectedImpl.class)	
    private String city;
    @ExcelIgnore
    private Boolean isDeleted;
}

(2).创建动态下拉框配置类

这里不能用@Component注解标注该类，从而在Spring容器中通过@Resource或@Autowired获取Bean，只能通过ApplicationContext工具类获取Bean

ApplicationContext工具类

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class SpringContextUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringContextUtil.applicationContext = applicationContext;
    }

    // 获取ApplicationContext
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    // 通过class获取Bean
    public static <T> T getBean(Class<T> clazz) {
        return applicationContext.getBean(clazz);
    }

    // 通过name以及class获取Bean
    public static <T> T getBean(String name, Class<T> clazz) {
        return applicationContext.getBean(name, clazz);
    }
}

动态下拉框配置类

public class CityExcelSelectedImpl implements ExcelDynamicSelect{

    @Override
    public String[] getSource() {
        CityMapper cityMapper = SpringContextUtil.getBean(CityMapper.class);
        return cityMapper.selectAllCity().toArray(new String[]{});
    }

}

web测试

import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.example.practicevue.model.UserDTO;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;

@RestController
@Slf4j
public class exportController {

    @PostMapping("/exportSelectedExcel")
    public void export(HttpServletRequest request, HttpServletResponse response){
        String filename = "测试";
        try {
            String userAgent = request.getHeader("User-Agent");

            if (userAgent.contains("MSIE") || userAgent.contains("Trident")) {
                // 针对IE或者以IE为内核的浏览器：
                filename = java.net.URLEncoder.encode(filename, "UTF-8");
            } else {
                // 非IE浏览器的处理:
                filename = new String(filename.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1);
            }
            response.setContentType("application/vnd.ms-excel");
            response.setHeader("Content-disposition", String.format("attachment; filename=\"%s\"", filename + ".xlsx"));
            response.setHeader("Cache-Control", "no-cache");
            response.setHeader("Pragma", "no-cache");
            response.setDateHeader("Expires", -1);
            response.setCharacterEncoding("UTF-8");

            ExcelWriter excelWriter = EasyExcel.write(response.getOutputStream()).build();
            WriteSheet writeSheet = EasyExcelUtil.writeSelectedSheet(UserDTO.class, 0, "测试sheet");
            excelWriter.write(new ArrayList<String>(), writeSheet);
            excelWriter.finish();
        } catch (UnsupportedEncodingException e) {
            log.error("导出Excel编码异常", e);
        } catch (IOException e) {
            log.error("导出Excel文件异常", e);
        }
    }
}