Flex Excel下载

最近做Flex里的Excel下载，用as3xls进行Excel导出后，Excel修改编辑后老出现：不能以当前格式保存。。。若要保存所做的更改，请单击“确定”，然后将其另存为最新的格式。

最后通过JAVA的POI实现Excel下载的，具体实现思路：
1.DataGrid数据传到服务器。
2.打开Excel模板。
3.向模板写入数据。
4.客户端下载写好的Excel。

前台Flex代码

            public function ToExcel(dg:AdvancedDataGrid,name:String)
            {
                var url:String="http://localhost:8080/Demo/servlet/ExcelServlet";
                var variables:URLVariables = new URLVariables();
                variables.head = convertDGHead(dg);
                variables.data = convertDGData(dg);   

                var request:URLRequest = new URLRequest(url);
                request.method = URLRequestMethod.POST;
                request.data = variables;  

                var fileReference:FileReference=new FileReference();
                fileReference.download(request,name+".xls");
                fileReference.addEventListener(Event.COMPLETE,doEvent);

            }
            private function doEvent(evt:Event):void {
                Alert.show("下载完成");
            }
            //表头转为字符串，用";"隔开
            private  function convertDGHead(dg:AdvancedDataGrid):String {
                var str:String = '';
                for(var i:int = 0;i<dg.columns.length;i++) {
                    if(dg.columns[i].headerText != undefined) {
                        str+=dg.columns[i].headerText+";";
                    } else {
                        str+=dg.columns[i].dataField+";";
                    }
                }
                return str;
            }   

            //表内容转为字符串，用";"隔开
            private  function convertDGData(dg:AdvancedDataGrid):String {
                var str:String = '';
                for(var j:int =0;j<dg.dataProvider.length;j++)
                {
                    for(var k:int=0; k < dg.columns.length; k++) {
                        if(dg.dataProvider.getItemAt(j) != undefined && dg.dataProvider.getItemAt(j) != null) {
                            if(dg.columns[k].labelFunction != undefined) {
                                str += dg.columns[k].labelFunction(dg.dataProvider.getItemAt(j),dg.columns[k].dataField)+";";
                            } else {
                                str += dg.dataProvider.getItemAt(j)[dg.columns[k].dataField]+";";
                            }
                        }
                    }
                }
                return str;
            }
            

web.xml中增加：

　　　　　　<servlet>
	    <servlet-name>ExcelServlet</servlet-name>
	    <servlet-class>com.test.ExcelServlet</servlet-class>
	</servlet>   

	<servlet-mapping>
	    <servlet-name>ExcelServlet</servlet-name>
	    <url-pattern>/servlet/ExcelServlet</url-pattern>
	</servlet-mapping>

后台JAVA代码：

package com.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFCellStyle;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;

public class ExcelServlet extends HttpServlet {
	 private static final long serialVersionUID = 1L;

	    public ExcelServlet() {
	        super();
	    }

	    public void destroy() {
	        super.destroy(); // Just puts "destroy" string in log
	        // Put your code here
	    }

	    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	        doMainDispatch(request, response);
	    }

	    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	        doMainDispatch(request, response);
	    }

	    public void init() throws ServletException {
	        // Put your code here
	    }

	    protected void doMainDispatch(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
	        String filename = "excel.xls";
	        resp.reset();
	        req.setCharacterEncoding("UTF-8");
	        resp.setCharacterEncoding("UTF-8");
	        resp.setContentType("application/vnd.ms-excel");
	        resp.addHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
	        String head = req.getParameter("head");
	        String data = req.getParameter("data");
	        HSSFWorkbook wb = generateExcel(head,data);
	        wb.write(resp.getOutputStream());
	        resp.getOutputStream().flush();
	        resp.getOutputStream().close();
	        req.getInputStream().close();
	    }

	    private HSSFWorkbook generateExcel(String head, String data) throws IOException {
	        String tmp = (new File("")).getCanonicalPath();
	        //如果不是只有一级 如："d:\tomcat6\bin"
	        if(tmp.indexOf("bin") != -1)
	        {
	            tmp = tmp.substring(0, tmp.lastIndexOf("\\"))
	                + "\\webapps\\Demo\\model\\Model.xls";
	        }
	        else //只有一级 如："d:\tomcat6"
	        {
	            tmp += "\\webapps\\Demo\\model\\Model.xls";
	        }

	        //创建输出数据文件
			File modelFile =new File(tmp);
			// 路径下不存在此模板文件
			if (!modelFile.getParentFile().exists()) {
				return null;
			}
			else{
		        FileInputStream fileinputstream = new FileInputStream(tmp);
		        POIFSFileSystem poifsfilesystem = new POIFSFileSystem(fileinputstream);
		        HSSFWorkbook wb = new HSSFWorkbook(poifsfilesystem);
		        HSSFSheet sheet = wb.getSheetAt(0);

		        String[] headArr = head.split(";");
		        String[] dataArr = data.split(";");

		        for(int rowNum=0; rowNum<=dataArr.length/headArr.length; rowNum++)
		        {
		            HSSFRow row = sheet.getRow(rowNum);
		            HSSFCellStyle rowstyle=null;
		            if(row == null)  //如果模板中没有这一行，则新建
		              {
		                row = sheet.createRow(rowNum);
		            }
		            else  //如果有这一行，获取样式
		              {
		                rowstyle = row.getRowStyle();
		            }

		            for(int colNum=0; colNum<headArr.length; colNum++)
		            {
		                HSSFCell cell = row.getCell(colNum);
		                HSSFCellStyle cellstyle=null;
		                if(cell == null){
		                    cell = row.createCell(colNum);
		                }else{
		                    cellstyle = cell.getCellStyle();
		                }

		                if(cellstyle != null)
		                	cell.setCellStyle(cellstyle);
		                else if(rowstyle != null)
		                    cell.setCellStyle(rowstyle);
		            }
		        }
		        return wb;
			}
	    }
}

注：
1.给Servlet传值时HTTP有参数长度的限制，参数超过时必须指定为POST方法，此次传Excel文件内容，不能用GET方法，因此要加上request.method = URLRequestMethod.POST;
2.flex中隐含为utf-8编码，因此必须含有request.setCharacterEncoding("UTF-8")语句来编码接收的数据，也必须含有response.setCharacterEncoding("UTF-8");语句以编码输出数据，否则会出现汉字乱码。

3、tomcat6在默认状态下最大的post请求是2M ，以此要在server.xml文件中设maxPostSize属性

<Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443"  maxPostSize="0" />
maxPostSize： 0 表示不限制  单位为：byte

本文参考链接：http://pufan53.iteye.com/blog/903468

POST相关限制文章：http://blog.csdn.net/jackyren007/article/details/3715444

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