最基本的web工程，需要的jar包只有資料庫驅動
mysql-connector-java-5.1.21.jar

jdbc.properties
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306\/test
username=root
passwd=123456

web.xml
webservlet 3.0之後兩種方式配置
1、原始的web.xml配置

<servlet>
    <servlet-name>testServlet</servlet-name>
    <servlet-class
 
>com.servlet.controller.HelloServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>testServlet</servlet-name>
    <url-pattern>/test/testServlet</url-pattern>
  </servlet-mapping>

2、註解配置
@WebServlet(name=”testServlet”, urlPatterns={“/test/testServlet”},loadOnStartup=1)
public class HelloServlet extends HttpServlet
{}
注意：註解的方式在tomcat6下無效，換成tomcat7才可以，可能版本原因

持久化類
JdbcUtils

package com.servlet.dao;


import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql
 
.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;



public class JdbcUtils 
{
    private String driver = "";
    private String url = "";
    private String username = "";
    private String passwd = "";
    private ResultSet rs = null;
    private Connection coo = null;
    JdbcUtils JdbcUtils = null;

    public JdbcUtils()
    {
        System.out.println(System.getProperty("user.dir"));///D:\soft\tomcat-6.0.28\bin
        System.out.println(this.getClass().getResource("").getPath());///D:/soft/tomcat-6.0.28/webapps/servletj/WEB-INF/classes/com/servlet/dao/
        try
        {
            if(null==coo)
            {
                Properties properties = new Properties();


                URL o = Thread.currentThread().getContextClassLoader().getResource("");
                String path = o.getPath().replace("classes", "config"); 


                BufferedReader bufferedReader = new BufferedReader(new FileReader(path+"/jdbc.properties"));
                properties.load(bufferedReader);

                //Class.forName("com.mysql.jdbc.Driver");
                driver = properties.getProperty("driver");
                Class.forName(driver);

                url = properties.getProperty("url");
                username = properties.getProperty("username");
                passwd = properties.getProperty("passwd");

                try {
                    coo = DriverManager.getConnection(url, username, passwd);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        catch(Exception e)
        {
            System.out.println("結果集解析出錯："+e.getMessage());
        }

    }


    //查詢
    public List<Map<String,String>> queryCommand(String sql,String[] parameters)
    {

        List list = new ArrayList();

        ResultSet rs = getRs(sql,parameters);



        try 
        {
            ResultSetMetaData rsmd = rs.getMetaData();
            while(rs.next())
            {
                HashMap<String, String> map =new HashMap<String,String>();

                for(int i=1;i<=rsmd.getColumnCount();i++)
                {
                    map.put(rsmd.getColumnLabel(i), String.valueOf(rs.getObject(i)));
                }
                list.add(map);

            }
        } catch (SQLException e) {
             System.out.println("結果集解析出錯："+e.getMessage());
        }

        return list;
    }

    private ResultSet getRs(String sql,String[] parameters)
    {
        try {
            PreparedStatement ps = coo.prepareStatement(sql);

            if(parameters!=null)
            {
                for(int i=0;i<parameters.length;i++)
                {
                    ps.setString(i+1, parameters[i]);
                }
            }

            rs = ps.executeQuery();


        } catch (SQLException e){
             System.out.println("結果集解析出錯："+e.getMessage());

        }

        return rs;
    }

}

HelloDao

/**
 * 
 */
package com.servlet.dao;

import java.util.List;
import java.util.Map;

/**
 * @author 44306
 *
 */
public class HelloDao 
{

    JdbcUtils utils = new JdbcUtils();

    public List<Map<String, String>> query()
    {
        String sql = "select * from users where id=?";
        String[] parameters = {"1"};
        List<Map<String, String>> map= utils.queryCommand(sql, parameters);
        return map;
    }
}

servlet類

/**
 * 
 */
package com.servlet.controller;

import java.io.PrintWriter;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.servlet.dao.HelloDao;

/**
 * @author 44306
 *
 */
@WebServlet(name="testServlet", urlPatterns={"/test/testServlet"},loadOnStartup=1)
public class HelloServlet extends HttpServlet
{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    HelloDao dao = new HelloDao();

    @Override  
    public void init(ServletConfig config) throws ServletException {  
        super.init(config);  
        System.out.println("servlet初始化...");  
    }

    @Override 
    public void doGet(HttpServletRequest request, HttpServletResponse response)
    {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/json; charset=utf-8");

        List<Map<String, String>> list = dao.query();

        PrintWriter out = null;
        System.out.println("list:"+list.toString());
        try {
            out = response.getWriter();
            out.write(list.toString());
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
        out.flush();
        out.close();
    }



}