EasyExcel 通过注解 添加单元格下拉框信息

自定义注解：

import java.lang.annotation.*;
/**
* @author li
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD})
public @interface ExplicitConstraint {
//定义固定下拉内容
    String[]source()default {};
//定义动态下拉内容，
    Class[]sourceClass()default {};
}

自定义动态下拉框内容接口：

/**
 * @author li
 */
public interface ExplicitInterface {
    /**
     * 下拉列表的内容数组
     * @return
     */
    String[] source();
}

动态下拉框内容实现类：

import main.java.demo.explicitinterface.ExplicitInterface;

public class RoleNameExplicitConstraint implements ExplicitInterface {
    public String[] source() {
        return new String[]{"角色1","角色2","角色3","角色4","角色5"};
    }
}

定义导出对象：

import main.java.demo.annotation.ExplicitConstraint;
import main.java.demo.explicitinterface.imp.RoleNameExplicitConstraint;

public class UserModel {
	@ExcelProperty("名字")
    private String name;
    @ExcelProperty("年龄")
    private Integer age;
    @ExplicitConstraint(source = {"男","女"}) //固定下拉内容
    @ExcelProperty("性别")
    private String sex;
    @ExplicitConstraint(sourceClass = RoleNameExplicitConstraint.class) //动态下拉内容
    private String roleName;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public String getRoleName() {
        return roleName;
    }
    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

导出：

import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.write.handler.SheetWriteHandler;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
import main.java.demo.annotation.ExplicitConstraint;
import main.java.demo.explicitinterface.ExplicitInterface;
import main.java.demo.model.UserModel;
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.CellRangeAddress;
import org.apache.poi.ss.util.CellRangeAddressList;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

public class EasyExcelMain {

    public static void main(String arg[]) throws IOException {

        File file = new File("D:/test.xlsx");
        file.createNewFile();
        FileOutputStream fileOutputStream = new FileOutputStream(file);

//        处理下拉列表
        //下拉列表集合
        Map<Integer, String[]> explicitListConstraintMap = new HashMap<>();

//循环获取对应列得下拉列表信息
        Field[] declaredFields = UserModel.class.getDeclaredFields();
        for (int i = 0; i < declaredFields.length; i++) {
            Field field = declaredFields[i];
            //解析注解信息
            ExplicitConstraint explicitConstraint = field.getAnnotation(ExplicitConstraint.class);
            String[] explicitArray = resolveExplicitConstraint(explicitConstraint);
            if (explicitArray != null && explicitArray.length > 0) {
                explicitListConstraintMap.put(i, explicitArray);
            }
        }

        ExcelWriter excelWriter = EasyExcel.write(fileOutputStream, UserModel.class).registerWriteHandler(new SheetWriteHandler() {
            public void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
            }
            public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
                //通过sheet处理下拉信息
                Sheet sheet = writeSheetHolder.getSheet();
                DataValidationHelper helper = sheet.getDataValidationHelper();
                explicitListConstraintMap.forEach((k, v) -> {
                    CellRangeAddressList rangeList = new CellRangeAddressList();
                    CellRangeAddress addr = new CellRangeAddress(1, 1000, k, k);
                    rangeList.addCellRangeAddress(addr);
                    DataValidationConstraint constraint = helper.createExplicitListConstraint(v);
                    DataValidation validation = helper.createValidation(constraint, rangeList);
                    sheet.addValidationData(validation);
                });
            }
        }).build();
        WriteSheet sheet = EasyExcel.writerSheet().build();
        excelWriter.write(null,sheet).finish();
    }

    /**
     * 解析注解内容 获取下列表信息
     * @param explicitConstraint
     * @return
     */
    public static String[] resolveExplicitConstraint(ExplicitConstraint explicitConstraint){
        if (explicitConstraint == null) {
            return null;
        }
        //固定下拉信息
        String[] source = explicitConstraint.source();
        if (source.length > 0) {
            return source;
        }
        //动态下拉信息
        Class<? extends ExplicitInterface>[] classes = explicitConstraint.sourceClass();
        if (classes.length>0){
            ExplicitInterface explicitInterface = null;
            try {
                explicitInterface = classes[0].newInstance();
                String[] source1 = explicitInterface.source();
                if (source1.length>0){
                    return source1;
                }
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        return null;
    }
}