Getting started with database connection pooling (c3p0, Druid)

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Concept

The database connection pool is actually a container ( aggregate ), Container for database connection . 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 .

benefits

1. Saving resource
2. Efficient user access

Realization

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

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

1. C3P0： Database connection pool technology
2. Druid： Database connection pool implementation technology , Provided by Alibaba

C3P0： Database connection pool technology

step ：

1. Import jar package ( Two )

<!--c3p0 Connection pool -->
<dependency>
	<groupId>com.mchange</groupId>
	<artifactId>c3p0</artifactId>
	<version>0.9.5.5</version>
</dependency>
<dependency>
	<groupId>com.mchange</groupId>
	<artifactId>mchange-commons-java</artifactId>
	<version>0.2.19</version>
</dependency>

2. Define configuration file ：

name ： c3p0.properties perhaps c3p0-config.xml route ： Put the document directly in resource Under the directory . The configuration file case is as follows ：

<c3p0-config>
  <!--  Use the default configuration to read connection pool objects  -->
  <default-config>
  	<!--  Connection parameters  -->
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost:3306/db4</property>
    <property name="user">root</property>
    <property name="password">root</property>
    
    <!--  Connection pool parameters  -->
    <!-- Number of connections to initialize the request -->
    <property name="initialPoolSize">5</property>
    <!-- Maximum number of connections -->
    <property name="maxPoolSize">10</property>
    <!-- Timeout time -->
    <property name="checkoutTimeout">3000</property>
  </default-config>

  <named-config name="otherc3p0"> 
    <!--  Connection parameters  -->
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost:3306/db3</property>
    <property name="user">root</property>
    <property name="password">root</property>
    
    <!--  Connection pool parameters  -->
    <property name="initialPoolSize">5</property>
    <property name="maxPoolSize">8</property>
    <property name="checkoutTimeout">1000</property>
  </named-config>
</c3p0-config>

3. Create core objects Database connection pool object ComboPooledDataSource
4. Get the connection ： getConnection

Code ：

public static void main(String[] args) throws SQLException {
	//1.  Create database connection pool object , Use default configuration 
	DataSource ds = new ComboPooledDataSource();

	//2. Get the connection 
	for (int i = 1; i <= 11; i++) {
		Connection conn = ds.getConnection();
		System.out.println(i + ":" + conn);

		if (i == 5) {
			conn.close();// Return connections to the connection pool 
		}
	}

	//testNamedConfig();

}

public static void testNamedConfig() throws SQLException {
	// 1.1  obtain DataSource, Configure with the specified name 
	DataSource ds = new ComboPooledDataSource("otherc3p0");
	//2. Get the connection 
	for (int i = 1; i <= 10; i++) {
		Connection conn = ds.getConnection();
		System.out.println(i + ":" + conn);
	}
}

Druid： Database connection pool implementation technology , Provided by Alibaba

step

1. Import jar package

<dependency>
	<groupId>com.alibaba</groupId>
	<artifactId>druid-spring-boot-starter</artifactId>
	<version>1.2.8</version>
</dependency>

2. Define configuration file ：

yes properties Formal You can call it anything , It can be placed in any directory 2. Load profile .Properties 2. Get database connection pool object ： From the factory  DruidDataSourceFactory 2. Get the connection ：getConnection Code ：

//3. Load profile ( stay resource Under the table of contents )
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();

Define tool classes

1. Define a class JDBCUtils
2. Provide static code block loading configuration file , Initialize connection pool object
3. Provide methods

• Get the connection method ： Get the connection through the database connection pool
• Release resources
• How to get the connection pool

Code ：

public class JDBCUtils {

	//1. Define member variables  DataSource
	private static DataSource ds ;

	static{
		try {
			//1. Load profile 
			Properties pro = new Properties();
			pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
			//2. obtain DataSource
			ds = DruidDataSourceFactory.createDataSource(pro);
		} catch (IOException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/** *  Get the connection  */
	public static Connection getConnection() throws SQLException {
		return ds.getConnection();
	}

	/** *  Release resources  */
	public static void close(Statement stmt,Connection conn){
	   /* if(stmt != null){ try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if(conn != null){ try { conn.close();// Return connection  } catch (SQLException e) { e.printStackTrace(); } }*/

	   close(null,stmt,conn);
	}


	public static void close(ResultSet rs , Statement stmt, Connection conn){


		if(rs != null){
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}


		if(stmt != null){
			try {
				stmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}

		if(conn != null){
			try {
				conn.close();// Return connection 
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}

	/** *  Get connection pool method  */

	public static DataSource getDataSource(){
		return  ds;
	}

}

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