第一步：实现一个Java类：
package com.logistic.data;
import java.sql.*;
import javax.sql.*;
import javax.naming.*;
import java.sql.Date;
//import java.text.SimpleDateFormat;
public class DataConnect {
private Connection con;
private Statement stmt;
private ResultSet rs;
private PreparedStatement pstmt;
public static int error=0;
public static synchronized Connection getCon()throws Exception{
Context ctx;
DataSource ds;
try{
ctx = new InitialContext();
ds = (DataSource)ctx.lookup("java:comp/env/jdbc/DBPool");
if(ds==null){
System.err.println();
System.err.println("数据连接打开+"+(++error));
}
return ds.getConnection();
}catch(SQLException e){
System.out.print(e);
throw e;
}
catch(NamingException e){
System.out.print(e);
throw e;
}
}
public Statement getStmtread(){
try{
con=getCon();
stmt=con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
}catch(Exception e){
System.out.println("getStmtread");
System.out.println(e.getMessage());
}
return stmt;
}
public int getRowCount(String sql){
int count=0;;
try{
stmt=this.getStmtread();
rs=stmt.executeQuery("SELECT COUNT(*) FROM "+sql);
rs.getMetaData();
if(rs.next()){
count=rs.getInt(1);
}else{
count=-1;
}
}catch(Exception e){
System.out.println("getRowCount");
System.out.println(e.getMessage());
count=-2;
}finally{
this.close();
}
return count;
}
public Statement getStmt(){
try{
con=getCon();
stmt=con.createStatement();
}catch(Exception e){
System.out.println("getStmt");
System.out.println(e.getMessage());
}
return stmt;
}
public PreparedStatement getPstmt(String sql){
try{
con=getCon();
pstmt=con.prepareStatement(sql);
}catch(Exception e){
System.out.println("getPstmt");
System.out.println(e.getMessage());
}
return pstmt;
}
public void close(){
try{
if(rs!=null)rs.close();
}catch(Exception e){
}
try{
if(stmt!=null)stmt.close();
}catch(Exception e){
}
try{
if(con!=null){
con.close();
con=null;
System.err.println();
System.err.println("数据连接关闭-"+(--error));
}
}catch(Exception e){
System.out.println("close");
System.out.println(e.getMessage());
}
}
public String inStr(String str){
String tempstr=null;
if(str==null){
str="";
}else{
try{
tempstr=new String(str.getBytes("ISO-8859-1"),"GB2312");
//tempstr=str.replace('\'',(char)1);
}catch(Exception e){
System.out.println("inStr");
System.out.println(e.getMessage());
}
}
return tempstr;
}
public String outStr(String str){
if(str==null){
str="";
}else{
try{
str=str.replace((char)1,'\'');
}catch(Exception e){
System.out.println("outStr");
System.out.println(e.getMessage());
}
}
return str;
}
public int selectdata(String sqls){
int k=-10;
try{
k=0;
rs=this.getStmtread().executeQuery(sqls);
while(rs.next()){
k++;
}
}catch(Exception ex){
k=-1;
System.out.println("select");
System.out.println(ex.getMessage());
this.close();
}finally{
this.close();}
return k;
}
public int updata(String sqls){
int k=-10;
try{
k=0;
k=this.getStmt().executeUpdate(sqls);
}catch(Exception ex){
k=-1;
System.out.println("updata");
System.out.println(ex.getMessage());
this.close();
}finally{this.close();}
return k;
}
public Date StrConvertDate(String strdate)
{
Date convertdate=null;
try{
convertdate= Date.valueOf(strdate);
System.out.print("打印日期");
System.out.print(convertdate.toString());
}catch(Exception ex){ex.printStackTrace();}
return convertdate;
}
}
通过getCon()就可以获取到连接了，其他是多余的
接下来是重点，也就是getCon()是如何获取到连接的
第二步：
配置web.xml文件
<!-- JNDI -->
<resource-ref>
<description>MySQL DB Connection Pool</description>
<res-ref-name>jdbc/DBPool</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
红色字体与Java文件中的必需一致，编译时时通过这些描述符来实现映射
java:comp/env/jdbc/DBPool(虚地址) ------> 映射描述符 ------> jdbc/DBPool(实际的地址)
单单这样子还是不够的，在Tomcat中还需要和该web.xml文件建立连接
第三步：配置Tomcat目录下conn文件夹中的context.xml配置文件
在<Context>
<Resource
name="jdbc/DBPool"
type="javax.sql.DataSource"
password=""
driverClassName="com.mysql.jdbc.Driver"
maxIdle="20"
maxWait="5000"
username="root"
url="jdbc:mysql://localhost:3306/logistic"
/>
</Context>
以上是以MySql作为数据库，如果用其他数据库，改变url和driverClassName即可，但必需保证用户名、密码正确。
完成以后，还要将连接数据库的jar包，放在 Tomcat6/lib 目录下，而 Tomcat6/bin 下不需要放此jar包 。
可能有的网友调试的时候会报这个错误：
javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initialException in thread "main" javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initial
at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:645)
at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:288)
at javax.naming.InitialContext.getURLOrDefaultInitCtx(InitialContext.java:325)
at javax.naming.InitialContext.lookup(InitialContext.java:392)
at gzgl.DataConnect.getCon(DataConnect.java:31)
at gzgl.DataConnect.main(DataConnect.java:23)
这是因为通过JNDI获取连接，程序必须通过Tomcat容器来加载连接，即通过web.xml来建立连接，如果只是在Java代码里面测试，是无法获取到连接的，因此，可以通过JSP（如index,jsp里面）进行如下测试：
<%@ page language="java" pageEncoding="UTF-8"%>
<%@page contentType="text/html; charset=UTF-8"%>
<%@page import="java.sql.*" %>
<%@page import="javax.naming.*" %>
<%@page import="javax.sql.DataSource" %>
<%@page import="com.logistic.data.*" %>
<head>
<title>Tomcat6.0 JNDI!</title>
</head>
<body>
This is my JSP page. <br>
JNDI ... <br>
<%
try {
DataConnect.getCon();
out.println("连接成功...");
} catch (Exception e) {
e.printStackTrace();
}
%>
</body>
</html>
在浏览器输入地址，可以看到运行结果：
OK，连接成功！