参考地址：http://www.cnblogs.com/bmbm/archive/2011/12/08/2342261.html
感谢这位大神

1.首先下载poi-3.6-20091214.jar，下载地址如下：

http://download.csdn.net/detail/evangel_z/3895051
2.Student.java

import java.util.Date;

public class Student
{
private int id;
private String name;
private int age;
private Date birth;

public Student()
{
}

public Student(int id, String name, int age, Date birth)
{
this.id = id;
this.name = name;
this.age = age;
this.birth = birth;
}

public int getId()
{
return id;
}

public void setId(int id)
{
this.id = id;
}

public String getName()
{
return name;
}

public void setName(String name)
{
this.name = name;
}

public int getAge()
{
return age;
}

public void setAge(int age)
{
this.age = age;
}

public Date getBirth()
{
return birth;
}

public void setBirth(Date birth)
{
this.birth = birth;
}

}
3.CreateSimpleExcelToDisk.java
import java.io.FileOutputStream;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;

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;

public class CreateSimpleExcelToDisk
{
/**

• @功能：手工构建一个简单格式的Excel

*/
private static List getStudent() throws Exception
{
List list = new ArrayList();
SimpleDateFormat df = new SimpleDateFormat("yyyy-mm-dd");

Student user1 = new Student(1, "张三", 16, df.parse("1997-03-12"));
Student user2 = new Student(2, "李四", 17, df.parse("1996-08-12"));
Student user3 = new Student(3, "王五", 26, df.parse("1985-11-12"));
list.add(user1);
list.add(user2);
list.add(user3);

return list;
}

public static void main(String[] args) throws Exception
{
// 第一步，创建一个webbook，对应一个Excel文件
HSSFWorkbook wb = new HSSFWorkbook();
// 第二步，在webbook中添加一个sheet,对应Excel文件中的sheet
HSSFSheet sheet = wb.createSheet("学生表一");
// 第三步，在sheet中添加表头第0行,注意老版本poi对Excel的行数列数有限制short
HSSFRow row = sheet.createRow((int) 0);
// 第四步，创建单元格，并设置值表头 设置表头居中
HSSFCellStyle style = wb.createCellStyle();
style.setAlignment(HSSFCellStyle.ALIGN_CENTER); // 创建一个居中格式

HSSFCell cell = row.createCell((short) 0);
cell.setCellValue("学号");
cell.setCellStyle(style);
cell = row.createCell((short) 1);
cell.setCellValue("姓名");
cell.setCellStyle(style);
cell = row.createCell((short) 2);
cell.setCellValue("年龄");
cell.setCellStyle(style);
cell = row.createCell((short) 3);
cell.setCellValue("生日");
cell.setCellStyle(style);

// 第五步，写入实体数据 实际应用中这些数据从数据库得到，
List list = CreateSimpleExcelToDisk.getStudent();

for (int i = 0; i < list.size(); i++)
{
row = sheet.createRow((int) i + 1);
Student stu = (Student) list.get(i);
// 第四步，创建单元格，并设置值
row.createCell((short) 0).setCellValue((double) stu.getId());
row.createCell((short) 1).setCellValue(stu.getName());
row.createCell((short) 2).setCellValue((double) stu.getAge());
cell = row.createCell((short) 3);
cell.setCellValue(new SimpleDateFormat("yyyy-mm-dd").format(stu
.getBirth()));
}
// 第六步，将文件存到指定位置
try
{
FileOutputStream fout = new FileOutputStream("E:/students.xls");
wb.write(fout);
fout.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
-------------------------我是华丽的分割线------------------------------
下面实现下载功能：
HttpServletResponse response = ServletActionContext.getResponse();
File file = new File(path);// path是根据日志路径和文件名拼接出来的
String filename = file.getName();// 获取日志文件名称
InputStream fis = new BufferedInputStream(new FileInputStream(path));
byte[] buffer = new byte[fis.available()];
fis.read(buffer);
fis.close();
response.reset();
// 先去掉文件名称中的空格,然后转换编码格式为utf-8,保证不出现乱码,这个文件名称用于浏览器的下载框中自动显示的文件名
response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.replaceAll(" ", "").getBytes("utf-8"),"iso8859-1"));
response.addHeader("Content-Length", "" + file.length());
OutputStream os = new BufferedOutputStream(response.getOutputStream());
response.setContentType("application/octet-stream");
os.write(buffer);// 输出文件
os.flush();
os.close();