JavaWeb6.1【資料庫連線池、C3P0資料庫連線池技術】
阿新 • • 發佈：2021-06-25
1 package com.haifei.datasource.c3p0; 2 3 import com.mchange.v2.c3p0.ComboPooledDataSource; 4 5 import javax.sql.DataSource; 6 import java.sql.Connection; 7 import java.sql.SQLException; 8 9 /* 10 資料庫連線池 11 12 1. 概念：其實就是一個容器(集合)，存放資料庫連線的容器。 13 當系統初始化好後，容器被建立，容器中會申請一些連線物件，當用戶來訪問資料庫時，從容器中獲取連線物件，使用者訪問完之後，會將連線物件歸還給容器。14 15 2. 好處： 16 1. 節約資源 17 2. 使用者訪問高效 18 19 3. 實現： 20 1. 標準介面：DataSource javax.sql包下的 21 1. 方法： 22 * 獲取連線：getConnection() 23 * 歸還連線：Connection.close()。如果連線物件Connection是從連線池中獲取的，那麼呼叫Connection.close()方法，則不會再關閉連線了。而是歸還連線 2425 2. 一般我們不去實現它，有資料庫廠商來實現 26 1. C3P0：資料庫連線池技術 27 2. Druid：資料庫連線池實現技術，由阿里巴巴提供的 28 29 4. C3P0：資料庫連線池技術 30 1. 匯入jar包 (兩個) c3p0-0.9.5.2.jar 和 mchange-commons-java-0.2.12.jar ， 31 * 不要忘記匯入資料庫驅動jar包mysql-connector-java-5.1.37-bin.jar 32 * 即一共所需3個jar包33 2. 定義配置檔案： 34 * 名稱： c3p0.properties 或者 c3p0-config.xml 35 * 路徑：直接將檔案放在src目錄下即可。 36 37 3. 建立核心物件 資料庫連線池物件 ComboPooledDataSource 38 4. 獲取連線： getConnection 39 */ 40 public class C3P0Demo1 { 41 public static void main(String[] args) throws SQLException { 42 //1 建立資料庫連線池物件 43 DataSource ds = new ComboPooledDataSource(); 44 45 //2 獲取連線物件 46 Connection conn = ds.getConnection(); 47 System.out.println(conn); //com.mchange.v2.c3p0.impl.NewProxyConnection@550ee7e5 [wrapping: com.mysql.jdbc.JDBC4Connection@5f9b2141] 48 49 50 } 51 }
1 package com.haifei.datasource.c3p0; 2 3 import com.mchange.v2.c3p0.ComboPooledDataSource; 4 5 import javax.sql.DataSource; 6 import java.sql.Connection; 7 import java.sql.SQLException; 8 9 public class C3P0Demo2 { 10 public static void main(String[] args) throws SQLException { 11 // testDefaultConfig(); 12 testNamedConfig(); 13 } 14 15 16 public static void testDefaultConfig() throws SQLException{ 17 //獲取資料庫連線池物件，使用預設配置<default-config> 18 DataSource ds = new ComboPooledDataSource(); 19 20 // for (int i=1; i<=10; i++){ 21 for (int i=1; i<=11; i++){ 22 Connection conn = ds.getConnection(); 23 System.out.println(i + ":" + conn); 24 25 /*if(i == 5){ 26 conn.close(); //#11號之前#5提前主動歸還連線物件 27 }*/ 28 } 29 30 /* 31 1:com.mchange.v2.c3p0.impl.NewProxyConnection@3514a4c0 [wrapping: com.mysql.jdbc.JDBC4Connection@212b5695] 32 2:com.mchange.v2.c3p0.impl.NewProxyConnection@69997e9d [wrapping: com.mysql.jdbc.JDBC4Connection@793be5ca] 33 3:com.mchange.v2.c3p0.impl.NewProxyConnection@37654521 [wrapping: com.mysql.jdbc.JDBC4Connection@15aab8c6] 34 4:com.mchange.v2.c3p0.impl.NewProxyConnection@4de4b452 [wrapping: com.mysql.jdbc.JDBC4Connection@50b5ac82] 35 5:com.mchange.v2.c3p0.impl.NewProxyConnection@6babf3bf [wrapping: com.mysql.jdbc.JDBC4Connection@3059cbc] 36 6:com.mchange.v2.c3p0.impl.NewProxyConnection@24fcf36f [wrapping: com.mysql.jdbc.JDBC4Connection@10feca44] 37 7:com.mchange.v2.c3p0.impl.NewProxyConnection@ea6147e [wrapping: com.mysql.jdbc.JDBC4Connection@4d02f94e] 38 8:com.mchange.v2.c3p0.impl.NewProxyConnection@1e683a3e [wrapping: com.mysql.jdbc.JDBC4Connection@2053d869] 39 9:com.mchange.v2.c3p0.impl.NewProxyConnection@14555e0a [wrapping: com.mysql.jdbc.JDBC4Connection@4bb33f74] 40 10:com.mchange.v2.c3p0.impl.NewProxyConnection@3c73951 [wrapping: com.mysql.jdbc.JDBC4Connection@3d5c822d] 41 42 //Exception in thread "main" java.sql.SQLException: An attempt by a client to checkout a Connection has timed out. 43 */ 44 } 45 46 47 public static void testNamedConfig() throws SQLException{ 48 //獲取資料庫連線池物件，使用指定配置<named-config name="otherc3p0"> 49 DataSource ds = new ComboPooledDataSource("otherc3p0"); 50 51 for (int i=1; i<=10; i++){ 52 Connection conn = ds.getConnection(); 53 System.out.println(i + ":" + conn); 54 } 55 56 /* 57 1:com.mchange.v2.c3p0.impl.NewProxyConnection@6bedbc4d [wrapping: com.mysql.jdbc.JDBC4Connection@932bc4a] 58 2:com.mchange.v2.c3p0.impl.NewProxyConnection@2fd1433e [wrapping: com.mysql.jdbc.JDBC4Connection@29d89d5d] 59 3:com.mchange.v2.c3p0.impl.NewProxyConnection@212b5695 [wrapping: com.mysql.jdbc.JDBC4Connection@446293d] 60 4:com.mchange.v2.c3p0.impl.NewProxyConnection@793be5ca [wrapping: com.mysql.jdbc.JDBC4Connection@2df9b86] 61 5:com.mchange.v2.c3p0.impl.NewProxyConnection@15aab8c6 [wrapping: com.mysql.jdbc.JDBC4Connection@33990a0c] 62 6:com.mchange.v2.c3p0.impl.NewProxyConnection@50b5ac82 [wrapping: com.mysql.jdbc.JDBC4Connection@101952da] 63 7:com.mchange.v2.c3p0.impl.NewProxyConnection@3059cbc [wrapping: com.mysql.jdbc.JDBC4Connection@7ea9e1e2] 64 8:com.mchange.v2.c3p0.impl.NewProxyConnection@10feca44 [wrapping: com.mysql.jdbc.JDBC4Connection@3fb1549b] 65 66 Exception in thread "main" java.sql.SQLException: An attempt by a client to checkout a Connection has timed out. 67 */ 68 } 69 70 71 }
<c3p0-config>
<!-- 使用預設的配置讀取連線池物件 -->
<default-config>
<!-- 連線引數 -->
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/hm_db2</property>
<property name="user">root</property>
<property name="password">root</property>
<!-- 連線池引數 -->
<property name="initialPoolSize">5</property><!-- 初始化申請的連線數量 -->
<property name="maxPoolSize">10</property><!-- 最大的連線數量 -->
<property name="checkoutTimeout">3000</property><!-- 超時時間 -->
</default-config>
<named-config name="otherc3p0">
<!-- 連線引數 -->
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://localhost:3306/hm_db2</property>
<property name="user">root</property>
<property name="password">root</property>
<!-- 連線池引數 -->
<property name="initialPoolSize">5</property>
<property name="maxPoolSize">8</property>
<property name="checkoutTimeout">1000</property>
</named-config>
</c3p0-config>