import java.io.BufferedOutputStream;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.Collection;

import java.util.Iterator;  

import javax.servlet.http.HttpServletResponse;  

import org.apache.poi.xssf.usermodel.XSSFCell;

import org.apache.poi.xssf.usermodel.XSSFRichTextString;

import org.apache.poi.xssf.usermodel.XSSFRow;

import org.apache.poi.xssf.usermodel.XSSFSheet;

import org.apache.poi.xssf.usermodel.XSSFWorkbook;  

public class ExportExcelUtil<T> {

    public void exportExcel(String[] headers,Collection<T> dataset, String fileName,HttpServletResponse response) {

        // 声明一个工作薄

        XSSFWorkbook workbook = new XSSFWorkbook();

        // 生成一个表格

        XSSFSheet sheet = workbook.createSheet(fileName);

        // 设置表格默认列宽度为15个字节

        sheet.setDefaultColumnWidth((short) 20);

        // 产生表格标题行

        XSSFRow row = sheet.createRow(0);

        for (short i = 0; i < headers.length; i++) {

            XSSFCell cell = row.createCell(i);

            XSSFRichTextString text = new XSSFRichTextString(headers[i]);

            cell.setCellValue(text);

        }

        try {

            // 遍历集合数据，产生数据行

            Iterator<T> it = dataset.iterator();

            int index = 0;

            while (it.hasNext()) {

                index++;

                row = sheet.createRow(index);

                T t = (T) it.next();

                // 利用反射，根据javabean属性的先后顺序，动态调用getXxx()方法得到属性值

                Field[] fields = t.getClass().getDeclaredFields();

                for (short i = 0; i < headers.length; i++) {

                    XSSFCell cell = row.createCell(i);

                    Field field = fields[i];

                    String fieldName = field.getName();

                    String getMethodName = "get" + fieldName.substring(0, 1).toUpperCase() + fieldName.substring(1);

                    Class tCls = t.getClass();

                    Method getMethod = tCls.getMethod(getMethodName, new Class[] {});

                    Object value = getMethod.invoke(t, new Object[] {});

                    // 判断值的类型后进行强制类型转换

                    String textValue = null;

                    // 其它数据类型都当作字符串简单处理

                    if(value != null && value != ""){

                        textValue = value.toString();

                    }

                    if (textValue != null) {

                        XSSFRichTextString richString = new XSSFRichTextString(textValue);

                        cell.setCellValue(richString);

                    }

                }

            }

            getExportedFile(workbook, fileName,response);

        } catch (Exception e) {

            e.printStackTrace();

        }

    }  

    /**

     *

     * 方法说明: 指定路径下生成EXCEL文件

     * @return

     */

    public void getExportedFile(XSSFWorkbook workbook, String name,HttpServletResponse response) throws Exception {

        BufferedOutputStream fos = null;

        try {

            String fileName = name + ".xlsx";

            response.setContentType("application/x-msdownload");

            response.setHeader("Content-Disposition", "attachment;filename=" + new String( fileName.getBytes("gb2312"), "ISO8859-1" ));

            fos = new BufferedOutputStream(response.getOutputStream());

            workbook.write(fos);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            if (fos != null) {

                fos.close();

            }

        }

    }  

}  

    /**

     * 导出数据库

     * @param response

     */

    @RequestMapping(value="exportExcel.do",method=RequestMethod.GET,

            produces="application/json;charset=utf-8")

    @ResponseBody

    public void exportExcel(HttpServletResponse response){

        Map<String, Object> map = new HashMap<String, Object>();

        map = msgService.findAllMsg();

        List<Msg> msgList = (List<Msg>) map.get("data");

        ExportExcelUtil<Msg> ee= new ExportExcelUtil<Msg>();

        String[] headers = { "序号", "发送用户", "接收用户", "时间" ,"聊天信息"};

        String fileName = "用户聊天信息表";

        ee.exportExcel(headers,msgList,fileName,response);

    }