标签：style blog http java color 使用 os 文件
1.我们都知道JDBC的固定步骤是以下几步组成：：
(1)Class.forName();
(2)Connection con = DriverManager.getConnection();
(3)PreparedStatement stat = con.prepareStatement(sql);
(4)stat.executeQuery();
(5)con.close();
而(1)(2)(5)步是每次JDBC操作都要执行的，重复执行是非常耗时的，为了解决重复操作的问题，引入了数据源。
2.首先在WEB应用程序中的META-INF文件夹下，建立一个context.xml的文件。以下代码表示数据源名是jdbc/sampleDS.数据库的用户名是root.root用户对应的密码是123456.
<?xml version="1.0" encoding="UTF-8"?> <Context reloadable="true"> <Resource name="jdbc/sampleDS" type="javax.sql.DataSource" maxActive="4" maxIdle="2" username="root" maxWait="5000" driverClassName="com.mysql.jdbc.Driver" password="123456" url="jdbc:mysql://127.0.0.1:3306/echarts" /> </Context>
3.通过DataSource的名字查找对应的DataSource，通过一个DataSource在连接池中获得一个Connection
4.在servlet中使用
import java.io.IOException; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import javax.naming.Context; import javax.naming.InitialContext; import javax.naming.NamingException; import javax.servlet.RequestDispatcher; 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 UserQueryServlet extends HttpServlet{ DataSource dataSource; public void init(){ try{ //创建一个上下文对象 Context context = new InitialContext(); //然后通过它的lookup方法查找数据源对象 dataSource = (DataSource)context.lookup("java:comp/env/jdbc/sampleDS"); }catch(NamingException ne){ log("Exception:" + ne); } } public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ Connection dbConnection=null; try{ //获得数据库连接对象 dbConnection = dataSource.getConnection(); }catch(SQLException se){ log("Exctption:" + se); } response.setContentType("text/html;charset=UTF-8"); String UserName,password; if( request.getParameter("username") !=null){ UserName = request.getParameter("username"); password = request.getParameter("password"); UserDAO userdao = new UserDAO(); UserBean userbean = userdao.searchUser(UserName); request.getSession().setAttribute("user", userbean); try{ String sql = "SELECT*FROM user WHERE userName=?"; System.out.println(sql); PreparedStatement pstmt = dbConnection.prepareStatement(sql); pstmt.setString(1,UserName); ResultSet rst = pstmt.executeQuery(); if(rst.next()) { UserBean user = new UserBean(); user.setUserName(rst.getString("userName")); user.setPassword(rst.getString("userPassword")); request.getSession().setAttribute("username", UserName); if(user.getPassword().equals(password)){ RequestDispatcher view = request.getRequestDispatcher("/showUser.jsp"); view .forward(request, response); }else{ RequestDispatcher view = request.getRequestDispatcher("/error.jsp"); view .forward(request, response); } }else{ RequestDispatcher view = request.getRequestDispatcher("/error.jsp"); view .forward(request, response); } }catch(SQLException e){ log("Exception: ",e); }finally{ try{ dbConnection.close(); }catch(SQLException e){} } } } public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ doPost(request,response); } }
5.在JSP中使用
<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %> <%@ page import="javax.naming.*,java.sql.*,javax.sql.*" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>测试Tomcat局部数据源</title> </head> <body> <% //初始化Context，使用InitialContext初始化Context Context ctx=new InitialContext(); /* 通过JNDI查找数据源，该JNDI为java:comp/env/jdbc/dstest，分成两个部分 java:comp/env是Tomcat固定的，Tomcat提供的JNDI绑定都必须加该前缀 jdbc/dstest是定义数据源时的数据源名 */ DataSource ds=(DataSource)ctx.lookup("java:comp/env/jdbc/echarts"); //获取数据库连接 Connection conn=ds.getConnection(); //获取Statement Statement stmt=conn.createStatement(); //执行查询，返回ResulteSet对象 ResultSet rs=stmt.executeQuery("select * from adminstore"); while(rs.next()) { out.println(rs.getString(1) + "\t" + rs.getString(2) + "<br/>"); } %> </body> </html>
标签：style blog http java color 使用 os 文件
原文地址：http://www.cnblogs.com/michaeljunlove/p/3866422.html
