資料庫連線池---C3P0

關於c3p0，首先要匯入一個jar包：c3p0-0.9.1.2.jar才能使用

程式碼：

package cn.hncu.c3p0;

import java.sql.Connection;

import org.junit.Test;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class C3p0Demo {
	@Test//純Java方法使用c3p0
	public void c3p0Demo() throws Exception{
		ComboPooledDataSource pool=new ComboPooledDataSource();
		pool.setUser("root");
		pool.setPassword("");
		pool.setJdbcUrl("jdbc:mysql:///mydata?useUnicode=true&characterEncoding=utf-8");
		pool.setDriverClass("com.mysql.jdbc.Driver");
		
		//System.out.println(pool);
		//可以在此呼叫pool.setters()方法對pool進行定製 
		pool.setAcquireIncrement(5);
		//pool.setMaxPoolSize(20);
		
		//跟dbcp不同之處，連線關閉之後，記憶體會被釋放，下次取時會重新開(記憶體地址不共用)
		for (int i=0;i<20;i++){
			Connection con=pool.getConnection();
			System.out.println(i+":"+con.hashCode());
			if(i%2==0){
				con.close();
			}
			System.out.println(i+":"+con.hashCode());
		}
	}
	
	@Test//演示採用配置檔案的方式使用c3p0
	public void c3p0PropertyDemo() throws Exception{
		ComboPooledDataSource pool = new ComboPooledDataSource();//空參，自動到classpath目錄下面載入“c3p0-config.xml”配置檔案---配置檔案的儲存位置和名稱必須是這樣，且使用“預設配置”
		//ComboPooledDataSource pool = new ComboPooledDataSource("hncu");//載入“c3p0-config.xml”檔案中定義的“hncu”這個配置元素
		for (int i=0;i<20;i++){
			Connection con=pool.getConnection();
			System.out.println(i+":"+con.hashCode());
			if (i%2==0){
				con.close();
			}
		}
	}
}
 

<c3p0-config>
	<!-- 預設配置，如果沒有指定則使用這個配置 -->
	<default-config>
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">
			<![CDATA[jdbc:mysql://127.0.0.1:3306/mydb?useUnicode=true&characterEncoding=UTF-8]]>
		</property>
		<property name="user">root</property>
		<property name="password">1234</property>
		<!-- 初始化池大小 -->
		<property name="initialPoolSize">2</property>
		<!-- 最大空閒時間 -->
		<property name="maxIdleTime">30</property>
		<!-- 最多有多少個連線 -->
		<property name="maxPoolSize">10</property>
		<!-- 最少幾個連線 -->
		<property name="minPoolSize">2</property>
		<!-- 每次最多可以執行多少個批處理語句 -->
		<property name="maxStatements">50</property>
	</default-config> 
	<!-- 命名的配置 -->
	<named-config name="hncu">
		<property name="driverClass">com.mysql.jdbc.Driver</property>
		<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/mydb</property>
		<property name="user">root</property>
		<property name="password">1234</property>
		<property name="acquireIncrement">5</property><!-- 如果池中資料連線不夠時一次增長多少個 -->
		<property name="initialPoolSize">100</property>
		<property name="minPoolSize">50</property>
		<property name="maxPoolSize">1000</property>
		<property name="maxStatements">0</property>
		<property name="maxStatementsPerConnection">5</property> <!-- he's important, but there's only one of him -->
	</named-config>
</c3p0-config>