SXSSFWorkbook的简单使用

在工作中使用到SXSSFWorkbook来导出Excel，写一篇博客记录一下SXSSFWorkbook的使用方法

1.介绍

SXSSFWorkbook是apache的开源项目，从其官网上可以看出SXSSFWorkbook实现了Workbook接口

Streaming version of XSSFWorkbook implementing the "BigGridDemo" strategy. 
This allows to write very large files without running out of memory as 
only a configurable portion of the rows are kept in memory at any one time.

SXSSFWorkbook是实现“BigGridDemo”策略的XSSFWorkbook的流媒体版本。SXSSFWorkbook允许编写非常大的文件而不会耗尽内存，
因为在任何时候，只有可配置的一部分行保存在内存中。

2.使用

首先我们定义一个列的实体类，包含列的名称，样式等

import org.apache.poi.ss.usermodel.CellStyle;

/**
 * @describe 定义excel列
 *
 */
public class ExcelColumnInfo {
    private String columnName;
    private String columnCode;
    /**
     * 单元格样式
     */
    private CellStyle cellStyle;
    }

    public ExcelColumnInfo(String columnName, String columnCode) {
        super();
        this.columnName = columnName;
        this.columnCode = columnCode;
    }

    public ExcelColumnInfo(String columnName, String columnCode, CellStyle cellStyle) {
        super();
        this.columnName = columnName;
        this.columnCode = columnCode;
        this.cellStyle = cellStyle;
    }

    public String getColumnName() {
        return columnName;
    }
    public void setColumnName(String columnName) {
        this.columnName = columnName;
    }
    public String getColumnCode() {
        return columnCode;
    }
    public void setColumnCode(String columnCode) {
        this.columnCode = columnCode;
    }

    public CellStyle getCellStyle() {
        return cellStyle;
    }

    public void setCellStyle(CellStyle cellStyle) {
        this.cellStyle = cellStyle;
    }

}

再定义一个Excel写入单元格数据的工具类

/**
 * Excel辅助类
 */
public class ExcelUtil {

    public static void setCell(Cell cell, Object obj) {
        if (obj == null) {
            cell.setCellValue("");
        } else if (obj instanceof Integer) {
            cell.setCellValue((int) obj);
        } else if (obj instanceof BigDecimal) {
            cell.setCellValue(((BigDecimal) obj).doubleValue());
        } else if (obj instanceof String) {
            cell.setCellValue((String) obj);
        } else if (obj instanceof Double) {
            cell.setCellValue((double) obj);
        } else if (obj instanceof Long) {
            cell.setCellValue((long) obj);
        }
    }

    public static void setCell(Cell cell, Object obj, CellStyle cellStyle) {
        cell.setCellStyle(cellStyle);
        if (obj instanceof Integer) {
            cell.setCellValue((int) obj);
        } else if (obj instanceof BigDecimal) {
            cell.setCellValue(((BigDecimal) obj).doubleValue());
        } else if (obj instanceof String) {
            cell.setCellValue((String) obj);
        } else if (obj instanceof Double) {
            cell.setCellValue((double) obj);
        } else if (obj instanceof Long) {
            cell.setCellValue((long) obj);
        } else {
            cell.setCellValue("");
        }
    }
}

然后开始写导出的方法

@Service
public class ExportSystemLogService{

    @Autowired
    private SystemLogMapper mapper;

    public SXSSFWorkbook exportExcel(Map<String, Object> params) throws IOException {

        SXSSFWorkbook wb = new SXSSFWorkbook(1000);
        //获取表格列信息
        LinkedHashMap<String, List<ExcelColumnInfo>> excelInfo = getExcelInfo(wb);
        for(String sheetName : excelInfo.keySet()){
            //创建sheet页
            Sheet sheet = wb.createSheet(sheetName);
            //获取该sheet页的列信息
            List<ExcelColumnInfo> excelColumnInfo = excelInfo.get(sheetName);
            //生成Excel数据
            generateExcelData(sheet,excelColumnInfo,params);
        }
        return wb;
    }

    protected LinkedHashMap<String, List<ExcelColumnInfo>> getExcelInfo(Workbook wb) {
        LinkedHashMap<String, List<ExcelColumnInfo>> excelInfo = new LinkedHashMap<>();
        List<ExcelColumnInfo> columns = new ArrayList<>();CellStyle wrapStyle = wb.createCellStyle();
        wrapStyle.setWrapText(true);    //设置自动换行

        columns.add(new ExcelColumnInfo("日志编号", "LOG_ID"));    //后面的columnCode与从数据库中查询出来的字段名一致
        columns.add(new ExcelColumnInfo("操作时间", "CREATE_TIME"));
        columns.add(new ExcelColumnInfo("操作人", "CREATE_USER"));
        columns.add(new ExcelColumnInfo("操作模块", "OPERATION_MODULE"));
        columns.add(new ExcelColumnInfo("操作类型", "OPERATION_TYPE"));
        columns.add(new ExcelColumnInfo("详情", "OPERATION_DETAIL",wrapStyle));
        columns.add(new ExcelColumnInfo("日志级别", "LOG_LEVEL"));
        columns.add(new ExcelColumnInfo("备注", "REMARK",wrapStyle));

        excelInfo.put("系统日志", columns);
        return excelInfo;
    }

    private void generateExcelData(Sheet sheet,List<ExcelColumnInfo> excelColumnInfo,Map<String, Object> params) {
        //设置列的宽度，第一个参数为列的序号，从0开始，第二参数为列宽，单位1/256个字节
        sheet.setColumnWidth(0, 12*256);
        sheet.setColumnWidth(2, 16*256);
        sheet.setColumnWidth(5, 12*256);
        sheet.setColumnWidth(6, 26*256);
        sheet.setColumnWidth(7, 26*256);
        //设置开始行和开始列
        int rowIndex = 0;
        int columnIndex = 0;
        Row row = sheet.createRow(rowIndex);
        //创建表头
        for (ExcelColumnInfo column : excelColumnInfo) {
            ExcelUtil.setCell(row.createCell(columnIndex++), column.getColumnName());
        }
        //获取导出数据
        List<HashMap<String, Object>> data = mapper.getSystemLog(params);
        rowIndex = 1;
        for (HashMap<String, Object> tmp : data) {
            Row row1 = sheet.createRow(rowIndex);
            columnIndex = 0;
            for(ExcelColumnInfo column : excelColumnInfo){
                Cell cell = row1.createCell(columnIndex);
                //设置单元格样式
                if (column.getCellStyle() != null) {
                    cell.setCellStyle(column.getCellStyle());
                }
                ExcelUtil.setCell(cell,tmp.get(column.getColumnCode()));
                columnIndex++;
            }
            rowIndex++;
        }
    }
}

其中Mapper接口与xml文件配置如下

@Mapper
@Repository
public interface SystemLogMapper {

    List<HashMap<String, Object>> getSystemLog(@Param("params") Map<String, Object> params);
}

<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.XXX.XXX.SystemLogMapper">

    <select id="getSystemLog" parameterType="java.util.HashMap" resultType="java.util.HashMap">
        SELECT
        LOG_ID,
        CREATE_TIME,
        CREATE_USER,
        OPERATION_MODULE,
        OPERATION_TYPE,
        OPERATION_DETAIL,
        LOG_LEVEL,
        REMARK
        FORM SYSTEM_LOG
        ORDER BY CREATE_TIME DESC
    </select>
</mapper>

在调用时，只需在Controller层调用ExportSystemLogService.exportExcel(params)方法即可。