JavaEE--JNDI(下,实现)

参考:https://blog.csdn.net/ouyida3/article/details/46699023

　　 https://www.landui.com/help/show-6158.html

　　 https://blog.csdn.net/yan372397390/article/details/50450332

以tomcat,mysql为例.

1配置tomcat的conf/context.xml

<Resource 
　　driverClassName="com.mysql.jdbc.Driver" 
　　maxActive="4" 
　　maxIdle="2"
　　maxWait="50" 
　　name="jdbc/mysql" 
　　password="mysql" 
　　type="javax.sql.DataSource" url="jdbc:mysql://192.168.3.138:3306/test" 
　　username="root"
/>

2将mysql的jar包放入tomcat的lib下.

3在项目的web.xml中引入

<resource-ref>
  <res-ref-name>jdbc/mysql</res-ref-name>
  <res-type>javax.sql.DataSource</res-type>
  <res-auth>Container</res-auth>
</resource-ref>

注意res-ref-name要和context.xml中配置的name一致.

4获取连接

Context ctx = new InitialContext();
DataSource ds = (DataSource) ctx.lookup("java:comp/env/jdbc/mysql");
Connection conn = ds.getConnection();

源码:

package org.wzh.testjndi.controller;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.naming.Context;
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;

@SuppressWarnings("serial")
public class ServletDemo extends HttpServlet {

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        try (PrintWriter pw = resp.getWriter()) {
            pw.print(0);
            Context ctx = new InitialContext();
            DataSource ds = (DataSource) ctx.lookup("java:comp/env/jdbc/mysql");
            Connection conn = ds.getConnection();
            
            Statement statement = conn.createStatement();
            ResultSet resultSet = statement.executeQuery("select * from info");
            while(resultSet.next()) {
                System.out.println(resultSet.getInt(1) + " **** " + resultSet.getString(2));
                pw.print(resultSet.getInt(1) + " **** " + resultSet.getString(2));
            }
            pw.print(1);
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">
    <display-name>TestJndi</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>

    <resource-ref>
        <res-ref-name>jdbc/mysql</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
    </resource-ref>

    <servlet>
        <servlet-name>demo</servlet-name>
        <servlet-class>org.wzh.testjndi.controller.ServletDemo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>demo</servlet-name>
        <url-pattern>/demo</url-pattern>
    </servlet-mapping>
</web-app>