EasyExcel自定义转换器，常用Format

参考：Can not find ‘Converter‘ support class List问题解决
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问题描述

com.alibaba.excel.exception.ExcelDataConvertException: Can not find ‘Converter’ support class List.
com.alibaba.excel.exception.ExcelDataConvertException: Can not find ‘Converter’ support class Set.

问题解释

EasyExcel开源框架中Converter接口的convertToExcelData只实现了转换BigDecimal、Bolean、Byte[]、btye[]、Byte、Date、Double、File、Float、InputStream、Integer、Long、Short、URL这些类型，意味着参数data最多只能是个二维数据，但是本次业务逻辑需要转换List< String >的数据。

解决办法

编写自定义Converter转换器：

Set转字符串

package com.tj.demo.utils.easyExcel;
import com.alibaba.excel.converters.Converter;
import com.alibaba.excel.metadata.GlobalConfiguration;
import com.alibaba.excel.metadata.data.WriteCellData;
import com.alibaba.excel.metadata.property.ExcelContentProperty;
import org.apache.commons.lang3.StringUtils;
import java.util.Set;
public class TjEasyExcelSetConverter implements Converter<Set> {
    @Override
    public WriteCellData<?> convertToExcelData(Set value, ExcelContentProperty contentProperty, GlobalConfiguration globalConfiguration) throws Exception {
        String res = StringUtils.join(value, ","); //把集合数组拼接字符串
        return new WriteCellData<String>(res);
    }
}

角色ID转角色名称

转换器里好像不支持查询数据库，和自己的API

package com.tj.demo.utils.easyExcel;
import com.alibaba.excel.converters.Converter;
import com.alibaba.excel.metadata.GlobalConfiguration;
import com.alibaba.excel.metadata.data.WriteCellData;
import com.alibaba.excel.metadata.property.ExcelContentProperty;
import com.alibaba.fastjson.JSON;
import com.tj.demo.system.domain.Roles;
import com.tj.demo.system.service.RolesService;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import java.util.List;
import java.util.Set;
/**
 * EasyExcel输出的时候，把角色ID转成角色名称
 */
public class TjEasyExcelRolesConverter implements Converter<Set> {
    @Autowired
    private RolesService rolesService;
    @Override
    public WriteCellData<?> convertToExcelData(Set roleIds, ExcelContentProperty contentProperty, GlobalConfiguration globalConfiguration) throws Exception {
        //查询出角色信息
        List<Roles> roles = rolesService.listByIds(roleIds);
        //字符串拼接
        StringBuilder result = new StringBuilder();
        for (Roles role : roles) {
            result.append(role.getRole());
            result.append("；");
        }
        return new WriteCellData<String>(result.toString());
    }
}

使用方法：

使用@ExcelProperty(converter = TjEasyExcelSetConverter.class)注解方法

  //角色set数组
    @TableField(exist = false)
    private Set<Long> roleIds;
    @TableField(exist = false)
    @ExcelProperty(value = "角色", converter = TjEasyExcelSetConverter.class)
    @ColumnWidth(20)
    private Set<String> roleNames;
    //部门set数组
    @TableField(exist = false)
    private Set<Long> deptIds;
    @TableField(exist = false)
    @ExcelProperty(value = "部门", converter = TjEasyExcelSetConverter.class)
    @ColumnWidth(20)
    private Set<String> deptNames;

常用Format

    @DateTimeFormat(value = "yyyy-MM-dd")