Use of database connection pool and Druid

1. Concept ： It's actually a container ( aggregate ), To be responsible for the distribution of 、 Manage database connections ; Allow applications to reuse an existing database connection , Instead of building a new ;

      When the system is initialized , The container is created , Some connection objects will be requested in the container , When the user comes to access the database , Get the connection object from the container , After the user visits , The connection object is returned to the container .

2. benefits ： Resource reuse , Improve system response speed , Avoid missing database connections .

3. Realization ：

Ⅰ. Standard interface ：DataSource javax.sql Under bag

       Method ：
            Get the connection ：getConnection()
            Return connection ：Connection.close(). If the connection object Connection It's taken from the connection pool , So called Connection.close() Method , The connection will no longer be closed . But return the connection

Ⅱ. Generally we don't realize it , There are database vendors to implement

Most commonly used Druid： Database connection pool implementation technology , Provided by Alibaba

The following figure shows the configuration file , Written in src in  

1.  step ：
		1.  Import jar package  druid-1.0.9.jar
		2.  Define configuration file ：
			*  yes properties Formal 
			*  You can call it anything , It can be placed in any directory 
		3.  Load profile .Properties
		4.  Get database connection pool object ： From the factory   DruidDataSourceFactory
		5.  Get the connection ：getConnection
	*  Code ：
		 //3. Load profile 
        Properties pro = new Properties();
        InputStream is = DruidDemo.class.getClassLoader().getResourceAsStream("druid.properties");
        pro.load(is);
        //4. Get connection pool object 
        DataSource ds = DruidDataSourceFactory.createDataSource(pro);
        //5. Get the connection 
        Connection conn = ds.getConnection();