SpringMVC+JXLS让excel导出更便捷

工作中，我们经常会遇到一些excel导入，导出的需求。我们通常可以使用poi等提供的api来处理。但是处理起来，代码十分臃肿很不优雅。
不经意的一次，查看很久之前的代码，看到以前一位同事前辈，针对此问题就已经对excel导出做出了一次比较好的封装，使用到的技术AbstractView+Jxls,对于jxls,网上有许多资料，不了解的同学可以先找些资料了解下。
http://jxls.sourceforge.net/getting_started.html
废话不多说直接上代码：
1.controller接收web请求

    @RequestMapping("/xls")
    public ModelAndView xls() {
        List<PostDiagnoseInfoResponseBean> infoList = homeAppService.getPostDiagnoseInfo("W9432503");
        ModelMap modelMap = new ModelMap();
        String fileName = "DiagnoseInfo文件.xls";
        modelMap.put("list", infoList);
        modelMap.put("ExcelExportFileName", fileName);
        modelMap.put("ExcelTemplateFileName", "diagnose-template.xls");
        modelMap.put("fileName", fileName);
        return new ModelAndView(new JXLSExcelView(), modelMap);
    }

2.JXLSExcelView集成AbstractView,代码如下：

public class JXLSExcelView extends AbstractView {
    public static final String EXCEL_EXPORT_FILE_NAME = "ExcelExportFileName";
    public static final String EXCEL_TEMPLATE_FILE_NAME = "ExcelTemplateFileName";
    public static final String EXCEL_SHEET_NAMES = "ExcelSheetNames";
    /** The content type for an Excel response */
    private static final String CONTENT_TYPE = "application/vnd.ms-excel";
    private XLSTransformerExt transformer;

    /**
     * Default Constructor.
     * Sets the content type of the view to "application/vnd.ms-excel".
     */
    public JXLSExcelView() {
        transformer = new XLSTransformerExt();
        setContentType(CONTENT_TYPE);
    }

    @Override
    protected boolean generatesDownloadContent() {
        return true;
    }

    @SuppressWarnings("rawtypes")
    @Override
    protected void renderMergedOutputModel(Map<String, Object> model,
            HttpServletRequest request, HttpServletResponse response)
            throws Exception {
        String fileName = (String)model.get(EXCEL_EXPORT_FILE_NAME);
        String templateName = (String)model.get(EXCEL_TEMPLATE_FILE_NAME);
        List newSheetNames = (List)model.get(EXCEL_SHEET_NAMES);

        response.setHeader("content-disposition","attachment; filename="+new String(fileName.getBytes("gb2312"),"ISO8859-1"));
        String srcFilePath = "/resources/excel/" + templateName;
        ServletOutputStream out = response.getOutputStream();
        transformer.transformXLS(request.getSession().getServletContext(), srcFilePath, model, out);
        out.flush();
    }
}

3.XLSTransformerExt继承XLSTransformer,代码如下：

public class XLSTransformerExt extends XLSTransformer {
    @SuppressWarnings("rawtypes")
    public void transformXLS(ServletContext servletContext, String srcFilePath, Map beanParams, OutputStream os) {
        try {
            ServletContextResource resource = new ServletContextResource(servletContext, srcFilePath);
            Workbook workbook = transformXLS(resource.getInputStream(), beanParams);
            workbook.write(os);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4.excel模板

5.maven依赖

 <properties>
    <jxls.version>1.0</jxls.version>
  </properties>
 <!-- excel 导出或读取 -->
    <dependency>
      <groupId>net.sf.jxls</groupId>
      <artifactId>jxls-core</artifactId>
      <version>${jxls.version}</version>
    </dependency>
    <dependency>
      <groupId>net.sf.jxls</groupId>
      <artifactId>jxls-reader</artifactId>
      <version>${jxls.version}</version>
    </dependency>

---

对于上述的需求，相信应该能满足大多数的excel导出需求了。但是相信还是有不少人遇到过这种需求，导出的excel列是动态变化的，即使是同一张报表导出，针对不同的人需要导出不同的列。这种场景下，上述的解决方法就无法满足需求了。
如何解决这种需求呢，大致的解决思路应该都差不多，无非是接收一个表头header[]数组，取值key[]数组，以及数据list即可，正当磨拳擦掌准备大干一场的时候，仔细翻阅了jxls的最新版本，发现已经支持博主的类似需求,请查阅：http://jxls.sourceforge.net/samples/dynamic_grid.html，有了这个指导性文件，实现起来就很简单了:
1.controller接收web请求

    @RequestMapping("/xls2")
    public ModelAndView xls2() {
        ModelMap modelMap = new ModelMap();
        modelMap.put(JXLSExcelViewDynamicColumns.EXCEL_EXPORT_FILE_NAME, "dynamic-columns文件-20170622.xls");
        modelMap.addAttribute(JXLSExcelViewDynamicColumns.EXCEL_TEMPLATE_DATA_NAME, homeAppService.getPostDiagnoseInfo("W9432503"));
        modelMap.put(JXLSExcelViewDynamicColumns.EXCEL_TEMPLATE_HEADERS_NAME, new String[]{"模型id", "模型名称", "因子类型"});
        modelMap.put(JXLSExcelViewDynamicColumns.EXCEL_TEMPLATE_INDEXS_NAME, new String[]{"modelId", "modelName", "modelType"});

        return new ModelAndView(new JXLSExcelViewDynamicColumns(), modelMap);
    }

2.JXLSExcelViewDynamicColumns继承AbstractView

public class JXLSExcelViewDynamicColumns extends AbstractView {
    public static final String EXCEL_EXPORT_FILE_NAME = "ExcelExportFileName";
    public static final String EXCEL_TEMPLATE_FILE_NAME = "ExcelTemplateFileName";
    public static final String EXCEL_DEFAULT_TEMPLATE_FILE = "dynamic-columns.xls";


    /** The content type for an Excel response */
    private static final String CONTENT_TYPE = "application/vnd.ms-excel";

    public static final String EXCEL_TEMPLATE_HEADERS_NAME = "headers";
    public static final String EXCEL_TEMPLATE_INDEXS_NAME = "indexs";
    public static final String EXCEL_TEMPLATE_DATA_NAME = "data";

    /**
     * Default Constructor.
     * Sets the content type of the view to "application/vnd.ms-excel".
     */
    public JXLSExcelViewDynamicColumns() {
        setContentType(CONTENT_TYPE);
    }

    @Override
    protected boolean generatesDownloadContent() {
        return true;
    }

    @SuppressWarnings("rawtypes")
    @Override
    protected void renderMergedOutputModel(Map<String, Object> model,
            HttpServletRequest request, HttpServletResponse response)
            throws Exception {
        String fileName = (String)model.get(EXCEL_EXPORT_FILE_NAME);
        response.setHeader("content-disposition","attachment; filename="+new String(fileName.getBytes("gb2312"),"ISO8859-1"));

        String templateName = model.get(EXCEL_TEMPLATE_FILE_NAME) == null ? EXCEL_DEFAULT_TEMPLATE_FILE : model.get(EXCEL_TEMPLATE_FILE_NAME).toString() ;
        String srcFilePath = "/resources/excel/"  + templateName;

        ServletOutputStream out = response.getOutputStream();
        ServletContextResource resource = new ServletContextResource(request.getSession().getServletContext(), srcFilePath);

        List headers = Arrays.asList((String[])model.get(EXCEL_TEMPLATE_HEADERS_NAME));
        List indexs = Arrays.asList((String[])model.get(EXCEL_TEMPLATE_INDEXS_NAME));
        String objectProps = StringUtils.join(indexs,",");

        Context context = new Context();
        context.putVar(EXCEL_TEMPLATE_HEADERS_NAME, headers);//headers是list
        context.putVar(EXCEL_TEMPLATE_DATA_NAME, model.get(EXCEL_TEMPLATE_DATA_NAME));
        JxlsHelper.getInstance().processGridTemplate(resource.getInputStream(), out, context,objectProps );//objectProps “a,b,c”字符串
        out.flush();
    }

}

3.excel-template模板

差点忘了，最新版本jxls的maven依赖：

  <dependency>
      <groupId>org.jxls</groupId>
      <artifactId>jxls</artifactId>
      <version>2.4.0</version>
    </dependency>

    <dependency>
      <groupId>org.jxls</groupId>
      <artifactId>jxls-poi</artifactId>
      <version>1.0.9</version>
    </dependency>
    <dependency>
      <groupId>org.jxls</groupId>
      <artifactId>jxls-jexcel</artifactId>
      <version>1.0.6</version>
    </dependency>

---

未尽事宜
1.对于大数据量的导出使用分sheet页导出，暂时没有研究。（目前遇到大数据量导出只是很简单的增加服务器内存，使得程序尽可能的读取更多的数据&&保证不存溢出）
2.对于大数据量的导出性能与poi到底孰强孰弱暂未可知。

希望有过研究的同学，分享一些已知的研究成果。