做了一個利用POI導出數據庫數據到Excel的例子，并把這個例子與大家一起分享，一起學習，共同進步！
先簡單介紹一下poi，poi是apache組織的一個開源項目，最新版為poi-3.0.1,要使用poi需要到apache網站下載poi-bin3.0.1.zip壓縮包，并將poi-3.0.1.jar加入到項目的ClassPath中。

下面是完成這個實例的步驟：

1、建立好一個web工程：poi；

2、導入所需要的jar包:poi-3.0.1.jar和mysql數據庫驅動包；

3、編寫一個StudentResultSet類，用于取出數據庫中的數據；

    package org.hnylj.poi;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class StudentResultSet {
	private Connection conn;
	private PreparedStatement pstmt;
	private ResultSet rs;
	private static final String DRIVER = "com.mysql.jdbc.Driver";
	private static final String URL = "jdbc:mysql://localhost:3306/poi";
	private static final String USERNAME = "root";
	private static final String PASSWORD = "123";
    
	//查詢數據庫中的數據
	public ResultSet query() {
		try {
			Class.forName(DRIVER);
			conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
			pstmt = conn.prepareStatement("select * from student");
			rs = pstmt.executeQuery();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return rs;
	}
}
  

4、編寫一個BuildExcelServlet，用于生成Excel；

    package org.hnylj.poi;

import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;

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.HSSFRichTextString;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;

public class BuildExcelServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		StudentResultSet stuResultSet = new StudentResultSet();
		ResultSet rs = stuResultSet.query();
		String xlsName = "test.xls";
		String sheetName = "sheetName";

		HSSFWorkbook workbook = new HSSFWorkbook();
		HSSFSheet sheet = workbook.createSheet();
		workbook.setSheetName(0, sheetName);
		HSSFRow row = sheet.createRow((short) 0);
		HSSFCell cell;
		try {
			ResultSetMetaData md = rs.getMetaData();
			int nColumn = md.getColumnCount();

			for (int i = 1; i <= nColumn; i++) {
				cell = row.createCell((short) (i - 1));
				cell.setCellType(HSSFCell.CELL_TYPE_STRING);
				cell.setCellValue(new HSSFRichTextString(md.getColumnLabel(i)));
			}
			int iRow = 1;
			while (rs.next()) {
				row = sheet.createRow((short) iRow);
				;
				for (int j = 1; j <= nColumn; j++) {
					cell = row.createCell((short) (j - 1));
					cell.setCellType(HSSFCell.CELL_TYPE_STRING);
					cell.setCellValue(new HSSFRichTextString(rs.getObject(j)
							.toString()));
				}
				iRow++;
			}
			String filename = request.getRealPath("/") + xlsName;
			request.setAttribute("filename", filename);
			FileOutputStream fOut = new FileOutputStream(filename);
			workbook.write(fOut);
			fOut.flush();
			fOut.close();
			request.getRequestDispatcher("OpenExcelServlet").forward(request,
					response);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		this.doGet(request, response);
	}
}
  

5、編寫一個OpenExcelServlet，用于把生成的Excel在頁面上打開；

    package org.hnylj.poi;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;

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

public class OpenExcelServlet extends HttpServlet {

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

		response.setContentType("application/vnd.ms-excel");
		PrintWriter out = response.getWriter();
		String filePath = (String) request.getAttribute("filename");
		BufferedInputStream bis = null;
		try {
			bis = new BufferedInputStream(new FileInputStream(filePath));
			int bytesRead;
			while ((bytesRead = bis.read()) != -1) {
				out.write(bytesRead);
				out.flush();
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if (bis != null)
				bis.close();
			if (out != null)
				out.close();
		}
	}

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

6、在web.xml里配置一下servlet的映射；

            <servlet>
		<servlet-name>BuildExcelServlet</servlet-name>
		<servlet-class>org.hnylj.poi.BuildExcelServlet</servlet-class>
	</servlet>
	<servlet>
		<servlet-name>OpenExcelServlet</servlet-name>
		<servlet-class>org.hnylj.poi.OpenExcelServlet</servlet-class>
	</servlet>

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

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

7、啟動tomcat，運行程序

導出數據庫數據到Excel