package com.ssm.core.util;

import org.apache.poi.hssf.usermodel.*;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Iterator;
public class ExportExcel<T> {
    public void exportExcel(String[] headers,Collection<T> dataset, String fileName,HttpServletResponse response) {
        // 声明一个工作薄
        HSSFWorkbook workbook = new HSSFWorkbook();
        // 生成一个表格
        HSSFSheet 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
        HSSFRow row = sheet.createRow(0);
        for (short i = 0; i < headers.length; i++) {
            HSSFCell cell = row.createCell(i);
            HSSFRichTextString text = new HSSFRichTextString(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++) {
                    HSSFCell 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) {
                        HSSFRichTextString richString = new HSSFRichTextString(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(HSSFWorkbook workbook, String name,HttpServletResponse response) throws Exception {
        BufferedOutputStream fos = null;
        try {
            String fileName = name + ".xls";
            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();
            }
        }
    }
}
