servlet JDBC mysql数据库连接池

具体操作过程：

1、配置全局数据库连接池

在<tomcat安装目录>\conf\server.xml文件中找到<GlobalNamingResources>标签，添加下列配置：

<Resource name="jdbc/webdb" 
		  auth="Container"
              type="javax.sql.DataSource"
              driverClassName="com.mysql.jdbc.Driver"
              url="jdbc:mysql://localhost:3306/webdb?characterEncoding=UTF-8"
              username="root"
	  	  password="root"
	  	  maxActive="200"
	  	  maxIdle="50"
	  	  maxWait="3000" />

2、下载JDBC驱动的jar包，放在tomcat的lib目录下
3、在创建的webdemo工程中web.xml文件中增加下列配置：

<resource-ref>
 	<res-ref-name>jdbc/webdb</res-ref-name>
 	<res-type>javax.sql.DataSource</res-type>
 	<res-auth>Container</res-auth>
 	<res-sharing-scope>Shareable</res-sharing-scope>
 </resource-ref>

4、在webdemo工程的META-INF目录下增加一个context.xml文件，内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<Context>
  <Listener className="org.apache.catalina.startup.TldConfig"/>
  <Listener className="org.apache.catalina.startup.TldConfig"/>
  <Listener className="org.apache.catalina.startup.TldConfig"/>
  <Listener className="org.apache.catalina.startup.TldConfig"/>
  <Resource
   auth="Container"
    description="webdb"
    name="jdbc/webdb"
    password="root"
    username="root"
    type="javax.sql.DataSource"
    driverClassName="com.mysql.jdbc.Driver"
    url="jdbc:mysql://localhost:3306/webdb?characterEncoding=UTF-8" />
</Context>

5、访问数据库事例java文件

package chapter4;

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;

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

public class Helloworld extends HttpServlet {

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

		response.setContentType("text/html; charset=UTF-8");
		PrintWriter out = response.getWriter();

		try
		{
			javax.naming.Context ctx = new javax.naming.InitialContext();
			javax.sql.DataSource ds = (javax.sql.DataSource)ctx.lookup("java:/comp/env/jdbc/webdb");


			Connection conn = ds.getConnection();
			PreparedStatement pst = conn.prepareStatement("SELECT * FROM t_dictionary");
			ResultSet rs = pst.executeQuery();
			StringBuilder table = new StringBuilder();
			table.append("<table border='1'>");
			table.append("<tr><td>eg-name</td><td>ch-name</td></tr>");
			while(rs.next())
			{
				table.append("<tr><td>"+rs.getString("english")+"</td><td>");
				table.append(rs.getString("chinese")+"</td></tr>");
			}
			table.append("</table>");
			out.println(table.toString());
			pst.close();
		}
		catch(Exception e)
		{
			out.println(e.getMessage());
		}
	}

}

差不多servlet访问mysql数据库能测试成功。