只使用displaytag的导出功能，表单展示用jqgrid实现。只需要后台修改一部分代码，其他的表单都能使用这个功能导出。导出四种文件格式：csv，excel，xml，pdf。

思路：在过滤器中处理，过滤器类中获取查询的数据，生成文件流传给前台。表单是分页显示的，导出需要全部内容，将rows的值设成-1，page设成1即可；请求中传入显示的字段和对应的名称，用逗号隔开；加上表单查询条件；

1 　　　　　　　　　　<ahref='<c:urlvalue="/bus/home/page?6578706f7274=1&rows=-1&page=1">
2                     <c:paramname="filename"value="用户信息TIME.csv"></c:param>
3                     <c:paramname="fields"value="name;age;sex"></c:param>
4                     <c:paramname="titles"value="姓名;年龄;性别"></c:param>
5                 </c:url>'><spanclass="export csv">CSV </span></a>|

displaytag通过判断请求的参数中是否包含6578706f7274来判断是否为导出，我把这个保留下来并修改下：6578706f7274=1导出csv,6578706f7274=2导出excel,6578706f7274=3导出xml,6578706f7274=4导出pdf。

1 　　public voiddoFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)2         throwsIOException, ServletException3 {4
5         if (servletRequest.getParameter(TableTagParameters.PARAMETER_EXPORTING) == null)6 {7 filterChain.doFilter(servletRequest, servletResponse);8             return;9 }10         int exportType =Integer.valueOf(servletRequest.getParameter(TableTagParameters.PARAMETER_EXPORTING));11         HttpServletRequest request =(HttpServletRequest) servletRequest;12
13         BufferedResponseWrapper wrapper = newBufferedResponseWrapper13Impl((HttpServletResponse) servletResponse);14
15 filterChain.doFilter(request, wrapper);16
17         switch(exportType) {18         case 1:19 ExportCsv.writeExport((HttpServletResponse) servletResponse, servletRequest, wrapper);20             break;21         case 2:22 ExportExcel.writeExport((HttpServletResponse) servletResponse, servletRequest, wrapper);23             break;24         case 3:25 ExportXml.writeExport((HttpServletResponse) servletResponse, servletRequest, wrapper);26             break;27         case 4:28 ExportPdf.writeExport((HttpServletResponse) servletResponse, servletRequest, wrapper);29             break;30
31         default: break;32 }33
34     }

导出csv文件：

displaytag导出cvs文件的实现：把数据放到字符串中，字符串需要按照cvs内容格式拼接好：每行的数据用逗号(,)分开，每行最后加上换行即可，然后把数据字符串放入响应的流中传到前台产生csv文件。

1 　　public static voidwriteExport(HttpServletResponse response,2 ServletRequest request, BufferedResponseWrapper wrapper)3             throwsIOException {4
5         if(request.getParameter("fields") == null){6             return;7 }8         if(request.getParameter("titles") == null){9             return;10 }11         if(request.getParameter("filename") == null){12             return;13 }14
15         String filename = request.getParameter("filename").replace("TIME", DateUtils.dateToString(new Date(), "yyyyMMddHHmmss"));16         String[] fields = request.getParameter("fields").split(";");17         String[] titles = new String( request.getParameter("titles").getBytes("ISO8859-1"),"UTF-8").split(";");18         String contentType = "text/csv; charset=GB2312";19         response.setHeader("Content-Disposition", "attachment; filename=\""
20                 + filename + "\"");21
22 response.setContentType(contentType);23         String strCon =wrapper.getContentAsString();24         JSONObject object =JSONObject.fromObject(strCon);25         JSONArray array = object.getJSONArray("rows");26         String cons =formatContentCsv(array, titles, fields);27         response.setContentLength(cons.getBytes("GB2312").length);28         PrintWriter out =response.getWriter();29 out.write(cons);30 out.flush();31
32 }33
34     private staticString formatContentCsv(JSONArray array, String[] titles, String[] fields) {35         StringBuffer res = newStringBuffer();36         Iterator iterator =array.iterator();37         for(String s : titles) {38             res.append(s + ",");39 }40         res.append("\r");41         while(iterator.hasNext()) {42             JSONObject jsonObj =(JSONObject) iterator.next();43
44             for(String s : fields) {45                 res.append(jsonObj.getString(s)+",");46 }47             res.append("\r");48 }49         returnres.toString();50
51     }

导出xml文件：

导出xml文件基本和导出csv文件相同，都是把数据以字符串形式放入流中传到前台。区别就是字符串拼接成xml内容格式和response.setContentType("text/xml; charset=UTF-8");

代码略。

导出excel文件：

displaytag导出excel文件也是使用POI提供的导出功能。创建HSSFWorkbook wb = new HSSFWorkbook();然后将数据遍历放入wb中，然后将wb写入字节流中传入前台。

1 　　public static voidwriteExport(HttpServletResponse response,2 ServletRequest request, BufferedResponseWrapper wrapper)3             throwsIOException {4         if(request.getParameter("fields") == null){5             return;6 }7         if(request.getParameter("titles") == null){8             return;9 }10         if(request.getParameter("filename") == null){11             return;12 }13
14         String filename = request.getParameter("filename").replace("TIME", DateUtils.dateToString(new Date(), "yyyyMMddHHmmss"));15         String[] fields = request.getParameter("fields").split(";");16         String[] titles = new String( request.getParameter("titles").getBytes("ISO8859-1"),"UTF-8").split(";");17         String contentType = "application/vnd.ms-excel; charset=utf-8";18         response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");19
20 response.setContentType(contentType);21         String strCon =wrapper.getContentAsString();22         JSONObject object =JSONObject.fromObject(strCon);23         JSONArray array = object.getJSONArray("rows");24         OutputStream out =response.getOutputStream();25         try{26 createExcel(out, array, titles, fields);27         } catch(JspException e) {28 e.printStackTrace();29 }30 out.flush();31 out.close();32
33 }34
35     public static void createExcel(OutputStream out, JSONArray array, String[] titles, String[] fields) throwsJspException  {36         try
37 {38             HSSFWorkbook wb = newHSSFWorkbook();39 HSSFSheet sheet;40             sheet = wb.createSheet("-");41
42             int rowNum = 0;43             int colNum = 0;44
45             //Create an header row
46             HSSFRow xlsTitleRow = sheet.createRow(rowNum++);47
48             HSSFCellStyle headerStyle =wb.createCellStyle();49             HSSFFont bold =wb.createFont();50 bold.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);51 headerStyle.setFont(bold);52
53             for(String s: titles){54                 HSSFCell cell = xlsTitleRow.createCell((short) colNum);55 cell.setCellValue(s);56 cell.setCellStyle(headerStyle);57                 sheet.setColumnWidth(colNum, 33*180);58                 colNum++;59 }60             Iterator ite =array.iterator();61             while(ite.hasNext())62 {63                 HSSFRow xlsRow = sheet.createRow(rowNum++);64                 colNum = 0;65                 JSONObject jsonObj =(JSONObject)ite.next();66                 for(String s: fields){67                     int index =colNum;68                     HSSFCell cell = xlsRow.createCell((short) colNum++);69 cell.setCellValue(jsonObj.getString(s));70 }71
72 }73 wb.write(out);74 }75         catch(Exception e)76 {77             e.printStackTrace();78 }79 }80     

导出pdf文件：

displaytag导出pdf文件需要导入itext包，如果有中文，不要使用FontFactory.getFont()设置字体，否则中文不显示（我用BaseFont.createFont可以正确显示中文）。

1     private staticTable tablePDF;2     private staticFont smallFont;3     private staticBaseFont bfChinese;4     public static voidwriteExport(HttpServletResponse response,5 ServletRequest request, BufferedResponseWrapper wrapper)6             throwsIOException {7
8         if(request.getParameter("fields") == null){9             return;10 }11         if(request.getParameter("titles") == null){12             return;13 }14         if(request.getParameter("filename") == null){15             return;16 }17
18         String filename = request.getParameter("filename").replace("TIME", DateUtils.dateToString(new Date(), "yyyyMMddHHmmss"));19         String[] fields = request.getParameter("fields").split(";");20         String[] titles = new String( request.getParameter("titles").getBytes("ISO8859-1"),"UTF-8").split(";");21         String contentType = "application/pdf; charset=utf-8";22         response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");23
24 response.setContentType(contentType);25         String strCon =wrapper.getContentAsString();26         JSONObject object =JSONObject.fromObject(strCon);27         JSONArray array = object.getJSONArray("rows");28         OutputStream out =response.getOutputStream();29         try{30 createPdf(out, array, titles, fields);31         } catch(JspException e) {32 e.printStackTrace();33 }34 out.flush();35 out.close();36
37 }38
39     public static void createPdf(OutputStream out, JSONArray array, String[] titles, String[] fields) throwsJspException  {40         try
41 {42 initTable(titles.length);43              //Initialize the Document and register it with PdfWriter listener and the OutputStream
44             Document document = new Document(PageSize.A4.rotate(), 60, 60, 40, 40);45 document.addCreationDate();46
47             HeaderFooter footer = new HeaderFooter(new Phrase(TagConstants.EMPTY_STRING, smallFont), true);48 footer.setBorder(Rectangle.NO_BORDER);49 footer.setAlignment(Element.ALIGN_CENTER);50
51 PdfWriter.getInstance(document, out);52
53             //Fill the virtual PDF table with the necessary data
54
55
56             for(String s: titles){57                 Cell hdrCell =getCell(s);58                 hdrCell.setGrayFill(0.9f);59                 hdrCell.setHeader(true);60 tablePDF.addCell(hdrCell);61 }62             Iterator ite =array.iterator();63             while(ite.hasNext())64 {65                 JSONObject jsonObj =(JSONObject)ite.next();66                 for(String s: fields){67                     Cell cell =getCell(jsonObj.getString(s));68 tablePDF.addCell(cell);69 }70
71 }72 document.open();73 document.setFooter(footer);74 document.add(tablePDF);75 document.close();76 }77         catch(Exception e)78 {79            e.printStackTrace();80 }81 }82     private static Cell getCell(String value) throwsBadElementException83 {84         Cell cell = new Cell(newChunk(StringUtils.trimToEmpty(value), smallFont));85 cell.setVerticalAlignment(Element.ALIGN_TOP);86         cell.setLeading(8);87         returncell;88 }89     private static void initTable(int colNums) throwsBadElementException90 {91         tablePDF = newTable(colNums);92 tablePDF.setDefaultVerticalAlignment(Element.ALIGN_TOP);93         tablePDF.setCellsFitPage(true);94         tablePDF.setWidth(100);95
96         tablePDF.setPadding(2);97         tablePDF.setSpacing(0);98         try{99             bfChinese = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H", BaseFont.NOT_EMBEDDED);100         } catch(DocumentException e) {101             //TODO Auto-generated catch block
102 e.printStackTrace();103         } catch(IOException e) {104             //TODO Auto-generated catch block
105 e.printStackTrace();106 }107 //smallFont = FontFactory.getFont(FontFactory.HELVETICA, 7, Font.NORMAL, new Color(0, 0, 0));
108         smallFont = new Font(bfChinese, 7, Font.NORMAL);109
110     }

由于本人对一些原理上的理解还有些不足，所以解释的不是很多，不过基本所有代码都以贴上，功能已经实现。