Create a database connection pool by implementing the Servletcontextlistener interface (C3P0 mode)

Using the Listener step

1. Defining the Listener implementation class

2. Configuring (or using annotation) in Web. xml

Create a jar package to add a database connection pool using the C3p0 method

1.c3p0-0.9.5.jar

2.c3p0-oracle-thin-extras-0.9.5.jar

3.mchange-commons-java-0.2.9.jar

1 package cn.sdut.lah.listener;
Two
3 import java.sql.Connection;
4 import javax.servlet.ServletContext;
5 import javax.servlet.ServletContextEvent;
6 import javax.servlet.ServletContextListener;
Seven
8 import com.mchange.v2.c3p0.ComboPooledDataSource;
Nine
Ten
11 public class GetConnListener implements ServletContextListener {
Twelve
13 / / when starting the web application, this method is called
14     @Override
15     public void contextInitialized(ServletContextEvent sce) {
16         try {
17 / / obtain the ServletContext instance of the application
18             ServletContext application = sce.getServletContext();
Nineteen
20 / / get the driver from the configuration parameter
21             String driver = application.getInitParameter("driver");
22 / / get the database URL from the configuration parameter
23             String url = application.getInitParameter("url");
24 / / get the user name from the configuration parameter
25             String user = application.getInitParameter("user");
26 / / obtain the password from the configuration parameter
27             String password = application.getInitParameter("pass");
Twenty-eight
29 / / create connection pool instance
30             ComboPooledDataSource cpds = new ComboPooledDataSource();
31 / / set the drivers required by the connection pool to connect to the database
32             cpds.setDriverClass(driver);
33 / / set the driver required to connect to the database
34             cpds.setJdbcUrl(url);
35 / / set the user name to connect to the database
36             cpds.setUser(user);
37 / / set the password to connect to the database
38             cpds.setPassword(password);
39 / / set the maximum number of connections in the connection pool
40             cpds.setMaxPoolSize(40);
41 / / set the minimum number of connections in the connection pool
42             cpds.setMinPoolSize(2);
43 / / set the initial number of connections in the connection pool
44             cpds.setInitialPoolSize(10);
45 / / set the maximum number of cached statements for the connection pool
46             cpds.setMaxStatements(180);
Forty-seven
48 / / set datasource to application scoped property
49             application.setAttribute("ds", cpds);
Fifty
51         } catch (Exception e) {
52             e.printStackTrace();
53}
Fifty-four
55}
Fifty-six
57 / / close web application
58     @Override
59     public void contextDestroyed(ServletContextEvent sce) {
60         ServletContext application = sce.getServletContext();
61         ComboPooledDataSource ds = (ComboPooledDataSource) application
62                 .getAttribute("ds");
63         try {
64             Connection conn = ds.getConnection();
65             if (conn != null) {
66                 conn.close();
67             }
68         } catch (Exception e) {
69             e.printStackTrace();
70}
Seventy-one
72}
Seventy-three
74} 

Configuring parameters in Web. xml

 
 
 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app version="3.0"
 3     xmlns="http://java.sun.com/xml/ns/javaee"
 4     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 5     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
 6     
 7   <context-param>
 8           <param-name>driver</param-name>
 9            <param-value>com.mysql.jdbc.Driver</param-value>
10   </context-param>
11   
12   <context-param>
13            <param-name>url</param-name>
14            <param-value>jdbc:mysql://localhost:3306/javaee</param-value>
15   </context-param>
16   
17   <context-param>
18            <param-name>user</param-name>
19            <param-value>root</param-value>
20   </context-param>
21    
22   <context-param>
23         <param-name>pass</param-name>
24         <param-value>ab123456</param-value>
25   </context-param>
36   
37   <listener>
38       <listener-class>cn.sdut.lah.listener.GetConnListener</listener-class>
39   </listener>  
40   
41 </web-app>

Create a database connection pool by implementing the Servletcontextlistener interface (C3P0 mode)