JAVA代码实现嵌套层级列表，POI导出嵌套层级列表

要实现POI导出EXCEL形如

--A1(LV1)

----B1(LV2)

----B2(LV2)

------C1(LV3)

------C2(LV3)

----B3(LV2)

--A1(LV1)

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" alt="" />

一.能用到的数据字段

ID(主键)、PID（父科目ID）、NAME(名称)、LEVEL（当前层级）

二.思路：

定义一个空的科目列表用来存放已经排好序的科目。创建一个迭代器传入父节点查出它的所有子节点，遍历子节点插入到科目列表的同时再次调用这个迭代器，这样程序能够在插入一个节点后如果发现有子节点继续插入子节点。最后返回排好序的科目树。

三.JAVA代码

/**
 *
 * <p>Description: 根据根节点获取嵌套科目树</p>
 * @param root 根节点，只需itemCode
 * @return 嵌套科目树
 */
public List<Subject> getSubjectListByRoot(Subject root){
    //定义一个空的科目列表
    List<Subject> subjectTree = new ArrayList<Subject>();
    //查询出根节点的具体信息
    root = this.subjectManager.searchSubjectByCode(root.getItemCode());
    //将根节点插入到嵌套科目树里，因为迭代出来的科目树是没有根节点的
    subjectTree.add(root);
    //调用迭代器
    subjectTree = SubjectIteration(root, subjectTree);
    return subjectTree;
}

/**
 *
 * <p>Description: 嵌套科目树迭代器</p>
 * @param subject 父节点
 * @param subjectTree 科目树
 * @return 嵌套科目树
 */
public List<Subject> SubjectIteration(Subject subject, List<Subject> subjectTree) {
    //根据父节点查子节点
    List<Subject> subjects = this.subjectManager.searchListSubjectByParent(subject);
    if (subjects != null) {
        //遍历子节点并迭代
        for (Subject subjectResult : subjects) {
            //将节点插入到嵌套科目树里
            subjectTree.add(subjectResult);
            SubjectIteration(subjectResult,subjectTree);
        }
    }
    return subjectTree;
}

四.SQL

根据父节点查子节点的一段SQL只需比对父节点的ID和子节点的PID即可

五.POI导出

/**
 *
 * <p>Description: 科目树导出</p>
 * @param request
 * @param response
 * @return Excel文件
 * @throws Exception
 */
public ModelAndView downloadExcel(HttpServletRequest request,
        HttpServletResponse response) throws Exception {
    //文件配置
    String fileName = new String(("科目导出文件.xls").getBytes("UTF-8"), "iso-8859-1");
    response.reset();
    response.setHeader("Content-disposition", "attachment;filename=" + fileName);
    response.setContentType("application/vnd.ms-excel;charset=utf-8");
    //创建POI-workbook文件
    XSSFWorkbook workbook = new XSSFWorkbook();
    XSSFSheet sheet = workbook.createSheet("科目树");
    //插入抬头
    PoiUtil.addRowSXSSF(sheet, 0, new String[] { "说明：", "level1", "level2", "level3", "level4", "level5", "level6",
            "level7", "level8" });
    //调整sheet样式
    //红
    CellStyle styleRed = workbook.createCellStyle();
    styleRed.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleRed.setFillForegroundColor(IndexedColors.RED.index);
    //绿
    CellStyle styleGreen = workbook.createCellStyle();
    styleGreen.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleGreen.setFillForegroundColor(IndexedColors.LIME.index);
    //灰
    CellStyle styleGrey = workbook.createCellStyle();
    styleGrey.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleGrey.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.index);
    //白
    CellStyle styleWhite = workbook.createCellStyle();
    styleWhite.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleWhite.setFillForegroundColor(IndexedColors.WHITE.index);
    //金黄
    CellStyle styleGold = workbook.createCellStyle();
    styleGold.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleGold.setFillForegroundColor(IndexedColors.GOLD.index);
    //黄
    CellStyle styleYellow = workbook.createCellStyle();
    styleYellow.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleYellow.setFillForegroundColor(IndexedColors.YELLOW.index);
    //亮黄
    CellStyle styleLight = workbook.createCellStyle();
    styleLight.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleLight.setFillForegroundColor(IndexedColors.LIGHT_YELLOW.index);
    //柠檬
    CellStyle styleLemon = workbook.createCellStyle();
    styleLemon.setFillPattern(XSSFCellStyle.SOLID_FOREGROUND);
    styleLemon.setFillForegroundColor(IndexedColors.LEMON_CHIFFON.index);
    //设置抬头颜色
    XSSFRow row = sheet.getRow(0);
    Cell cell = row.getCell(1);
    cell.setCellStyle(styleRed);
    cell = row.getCell(2);
    cell.setCellStyle(styleGreen);
    cell = row.getCell(3);
    cell.setCellStyle(styleGrey);
    cell = row.getCell(4);
    cell.setCellStyle(styleWhite);
    cell = row.getCell(5);
    cell.setCellStyle(styleGold);
    cell = row.getCell(6);
    cell.setCellStyle(styleYellow);
    cell = row.getCell(7);
    cell.setCellStyle(styleLight);
    cell = row.getCell(8);
    cell.setCellStyle(styleLemon);
    //查询Excel用科目树
    List<Subject> subjectTree = new ArrayList<Subject>();
    Subject root = new Subject();
    root.setItemCode("1001");
    subjectTree = getSubjectListByRoot(root);
    //插入数据
    int index = 0;
    for(Subject subject : subjectTree){
        index = index + 1;
        Row dataRow = sheet.createRow(index);
        String lv = subject.getLevel();
        if(lv.equals("1")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleRed);
        }
        else if(lv.equals("2")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleGreen);
        }
        else if(lv.equals("3")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleGrey);
        }
        else if(lv.equals("4")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleWhite);
        }
        else if(lv.equals("5")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleGold);
        }
        else if(lv.equals("6")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleYellow);
        }
        else if(lv.equals("7")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleLight);
        }
        else if(lv.equals("8")){
            Cell dataCell = dataRow.createCell(0);
            dataCell.setCellValue(subject.getItemName());
            dataCell.setCellStyle(styleLemon);
        }
    }
    sheet.setColumnWidth(0, 9000);
    //创建输出流，生成文件
    OutputStream out = new BufferedOutputStream(response.getOutputStream());
    workbook.write(out);
    out.flush();
    out.close();
    return null;
}