//判斷是否是下載模板
    private String template;
    
    
    public void setTemplate(String template) {
        this.template = template;
    }

    public String download() throws Exception {
        // 創建一個要到出表的表頭
        String[] heads = { "編號", "用戶名", "郵箱", "年齡", "部門" };
        
        //查詢出要導出的數據,先展示出全部數據
 

        baseQuery.setPageSize(Integer.MAX_VALUE);
        this.pageList = employeeService.findByQuery(baseQuery);
        
        List<Employee> employees = pageList.getData();
        
        List<String[]> list = new ArrayList<>();
        if (template ==null) {
            //將 數據放入到list 中
 

            
            for (Employee employee : employees) {
                String[] content = new String[heads.length];
                content[0] = employee.getId().toString();
                content[1] = employee.getUsername();
                content[2] = employee.getEmail()== null? "" : employee.getEmail();
                content[
 
3] = employee.getAge() == null? "":employee.getAge().toString();
                content[4] = employee.getDept() == null? "" :employee.getDept().getName() ;
                
                //放到list 中
                list.add(content);
            }
        }
        
        //調用BaseService 中的方法
        //把數據放到流中，，配置Struts.xml
        this.inputStream = employeeService.download(heads, list);
        return "download";
    }
    

@Override
    public InputStream download(String[] heads, List<String[]> list) throws Exception {
        // 創建一個內存對象
        SXSSFWorkbook wb = new SXSSFWorkbook();
        //創建一個Excel 表
        Sheet sheet = wb.createSheet("sheet1");
        
        //創建第0行 
        Row row = sheet.createRow(0);
        
        // 處理到處表頭 第0行
        for (int i = 0; i < heads.length; i++) {
            Cell cell = row.createCell(i);
            //添加內容
            cell.setCellValue(heads[i]);
        }
        
        for (int j = 0; j < list.size(); j++) {// 行
            //創建 行
            Row row2 = sheet.createRow(j+1);
            for (int i = 0; i < heads.length; i++) {// 列
                //創建格子
                Cell cell = row2.createCell(i);
                //賦值
                cell.setCellValue(list.get(j)[i]);
            }
        }
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        wb.write(out);
        out.close();
        wb.dispose();
        return new ByteArrayInputStream(out.toByteArray());
    }

導入

public String execute() throws Exception {
        
        if (upload != null) {
            List<String[]> list = employeeService.importExcel(upload);
            //將list 中的值轉為Employee對象
            
            for (String[] strings : list) {
                //創建一個Employee 對象    String[] heads = { "編號", "用戶名", "郵箱", "年齡", "部門" };
                Employee employee =  new Employee();
                
                employee.setUsername(strings[1]+UUID.randomUUID().toString().substring(0, 4));
                employee.setEmail(strings[2]);
                if (StringUtils.isNotBlank(strings[3])) {
                    employee.setAge(Integer.valueOf(strings[3]));
                }
                    
                if (StringUtils.isNotBlank(strings[4])) {
                    //這裏要查出部門，所以要導入DepartmentService，並且提供一個 根據名字找部門的方法
                    Department department = departmentService.findByName(strings[4]);
                    employee.setDept(department);
                }
                
                //要持久化  保存到數據庫
                employeeService.save(employee);
                
            }
            
            putContextMap("ImportMsg", "成功導入"+list.size()+"條數據！");
            
        }
        
        
        return SUCCESS;
    }
/**
     * 導入Excel
     * */
    @Override
    public List<String[]> importExcel(File file) throws Exception {
        // 創建一個文件輸出流,讀取要導入的文件
        FileInputStream inputStream = new FileInputStream(file);
        //創建一個讀取對象，在輸入流中讀取數據
        Workbook workbook = new XSSFWorkbook(inputStream);
        
        //獲取表對象
        Sheet sheet = workbook.getSheetAt(0); //----------------------不理解
        
        //解析表對象  到list
        //定義一個List
        List<String[]> list = new ArrayList<>();
        /**
         * sheet.getLastRowNum(); 得到的是數據的總行數
         * row.getLastCellNum();獲得 一行的多少列
         * */
        
        for (int i = 0; i < sheet.getLastRowNum(); i++) {
            // 獲取行對象 ，註意 不要表頭 從1 開始
            Row row = sheet.getRow(i+1);
            
            String[] strings = new String[row.getLastCellNum()];
            for (int j = 0; j < strings.length; j++) {
                
                //獲得 格子
                Cell cell = row.getCell(j);
                strings[j] = cell.getStringCellValue();
            }
            list.add(strings);
        }
        
        
        return list;
    }

excel導入導出