你可在每个web工程目录下的META-INF\context.xml文件中.

context.xml文件中的内容可以这样写:
<Context>

<Resource? name="jdbc/mysqlds"
?auth="Container"
?type="javax.sql.DataSource"?
?maxActive="100"?
?maxIdle="100"
?maxWait="5000"??
?username="root"??
?password="root"
?driverClassName="com.mysql.jdbc.Driver"?
?url="jdbc:mysql://127.0.0.1/liuwei"
?/>

?

</Context>

?

?package cn.com.jobedu.blog;

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import javax.naming.InitialContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;

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

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

?public void doPost(HttpServletRequest request, HttpServletResponse response)
???throws ServletException, IOException {
??request.setCharacterEncoding("UTF-8");
??System.out.println("dopost");
??String title = request.getParameter("title");
??String content = request.getParameter("content");
??String categoryId = request.getParameter("category");
??DataSource ds = null;
??try {
???// 通过在context.xml文件，设定的数据源对象的名字，获取数据源对象
???InitialContext context = new InitialContext();
???ds = (DataSource) context.lookup("java:/comp/env/jdbc/mysqlds");
??} catch (Exception e) {
???System.out.println("获取数据源时出错");
??}
??int result = 0;
??try {
???Connection conn = ds.getConnection();
???String sql = "insert into blog (title, content,category_id,createdtime) values (?, ?, ?, now())";
???PreparedStatement pstmt = conn.prepareStatement(sql);
???pstmt.setString(1, title);
???pstmt.setString(2, content);
???pstmt.setInt(3, Integer.parseInt(categoryId));
???result = pstmt.executeUpdate();
???System.out.println(result);
??} catch (SQLException e) {
???e.printStackTrace();
??}
??String message = "";
??if (result == 1) {
???message = "添加博文成功";
??} else {
???message = "添加博文失败";
??}

??request.setAttribute("message", message);
??request.getRequestDispatcher("/addBlogResult.jsp").forward(request,
????response);
?}
}

?

?

第三方对数据库的封装：dbutils

package cn.com.jobedu.blog;

import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;

import javax.naming.InitialContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;

import org.apache.commons.dbutils.QueryRunner;

public class BlogServlet extends HttpServlet {

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

?}

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

??request.setCharacterEncoding("UTF-8");
??String title = request.getParameter("title");
??String content = request.getParameter("content");
??String categoryId = request.getParameter("category");

??System.out.println(title);
??System.out.println(content);
??System.out.println(categoryId);

??DataSource ds = null;
??try {
???// 通过在context.xml文件，设定的数据源对象的名字，获取数据源对象
???InitialContext context = new InitialContext();
???ds = (DataSource) context.lookup("java:/