申明:本文對於連接資源關閉采用自定義的 JDBCUtils 工具:
package com.test.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public final class JDBCUtils {
private static String driver="com.mysql.jdbc.Driver";
private static String url="jdbc:mysql://localhost:3306/store28";
private static String user="root";
private static String password="root1234";
private JDBCUtils(){}
static {
/**
* 驅動注冊
*/
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
throw new ExceptionInInitializerError(e);
}
}
/**
* 獲取 Connetion
* @return
* @throws SQLException
*/
public static Connection getConnection() throws SQLException{
return DriverManager.getConnection(url, user, password);
}
/**
* 釋放資源
* @param conn
* @param st
* @param rs
*/
public static void colseResource(Connection conn,Statement st,ResultSet rs) {
closeResultSet(rs);
closeStatement(st);
closeConnection(conn);
}
/**
* 釋放連接 Connection
* @param conn
*/
public static void closeConnection(Connection conn) {
if(conn !=null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
//等待垃圾回收
conn = null;
}
/**
* 釋放語句執行者 Statement
* @param st
*/
public static void closeStatement(Statement st) {
if(st !=null) {
try {
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
//等待垃圾回收
st = null;
}
/**
* 釋放結果集 ResultSet
* @param rs
*/
public static void closeResultSet(ResultSet rs) {
if(rs !=null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
//等待垃圾回收
rs = null;
}
}
一、連接池技術基本原理
在程序初始化的時候創建一個 Connection 集合,便於快速增刪,可以使用 LinkedList 集合來存儲,
當調用工具者獲取一個 Connection 時,就從集合里移除一個 Connection 返回給調用者(期間,如果沒有則創建一個連接池)
當使用完 Connection 之后,使用 close() (Connection的 close() 方法) 將 Connection 資源歸還(添加回)List 集合中,但是其中有一個問題,原始的 Connection 中的 close() 方法將資源關閉,因此需要想辦法解決這個問題,可以使用如下技術:
裝飾者設計模式、適配器設計模式、基於接口的動態代理、基於子類的動態代理。
二、使用 DBCP 技術實現連接池
使用 properties 配置文件進行數據庫連接配置(使用 eclipse 將 dbcp.properties 文件編寫在 src 目錄下):
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/store28
username=root
password=root1234
說明:以下是全配置信息
#連接基本設置
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/sys
username=root
password=root1234
#<!--擴展配置 了解-->
#初始化連接
initialSize=10#最大連接數量
maxActive=50#<!-- 最大空閑連接 -->
maxIdle=20#<!-- 最小空閑連接 -->
minIdle=5#<!-- 超時等待時間以毫秒為單位 6000毫秒/1000等於60秒 -->
maxWait=60000#JDBC驅動建立連接時附帶的連接屬性屬性的格式必須為這樣:[屬性名=property;]
#注意:"user" 與 "password" 兩個屬性會被明確地傳遞,因此這里不需要包含他們。
connectionProperties=useUnicode=true;characterEncoding=gbk#指定由連接池所創建的連接的自動提交(auto-commit)狀態。
defaultAutoCommit=true#driver default 指定由連接池所創建的連接的只讀(read-only)狀態。
#如果沒有設置該值,則“setReadOnly”方法將不被調用。(某些驅動並不支持只讀模式,如:Informix)
defaultReadOnly=#driver default 指定由連接池所創建的連接的事務級別(TransactionIsolation)。
#可用值為下列之一:(詳情可見javadoc。)NONE,READ_UNCOMMITTED, READ_COMMITTED, REPEATABLE_READ, SERIALIZABLE
defaultTransactionIsolation=READ_UNCOMMITTED
編寫 DBCPUtils 工具類:
package com.test.utils; import java.io.InputStream; import java.sql.Connection; import java.sql.SQLException; import java.util.Properties; import javax.sql.DataSource; import org.apache.commons.dbcp.BasicDataSourceFactory; public class DBCPUtils { private static DataSource dataSource; static { try { InputStream is = DBCPUtils.class.getClassLoader().getResourceAsStream("dbcp.properties"); Properties props = new Properties(); props.load(is); dataSource = BasicDataSourceFactory.createDataSource(props); } catch (Exception e) { throw new ExceptionInInitializerError("數據源初始化失敗!"); } } public static Connection getConnection() { try { return dataSource.getConnection(); } catch (SQLException e) { throw new RuntimeException("數據連接獲取失敗!"); } } public static DataSource getDataSource() { return dataSource; } }
測試:
package com.test.jdbcTest; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import org.junit.Test; import com.test.utils.DBCPUtils; import com.test.utils.JDBCUtils; public class DBCPDmeo { @Test public void test1() throws SQLException { Connection conn = DBCPUtils.getConnection(); String sql = "select cid,cname from category"; PreparedStatement st = conn.prepareStatement(sql); ResultSet rs = st.executeQuery(); while(rs.next()) { System.out.println(rs.getString("cid")+"..."+rs.getString("cname")); } JDBCUtils.colseResource(conn, st, rs); } }
三、使用 C3P0 技術實現連接池
首先配置 c3p0-config.xml 文件(詳見 c3p0 官網)
<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>
<default-config>
<property name="automaticTestTable">con_test</property><!-- 連接數據庫配置信息 -->
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">jdbc:mysql://127.0.0.1:3306/store28</property>
<property name="user">root</property>
<property name="password">root1234</property>
<property name="checkoutTimeout">30000</property>
<property name="idleConnectionTestPeriod">30</property>
<property name="initialPoolSize">10</property>
<property name="maxIdleTime">30</property>
<property name="maxPoolSize">100</property>
<property name="minPoolSize">10</property>
<property name="maxStatements">200</property><user-overrides user="test-user">
<property name="maxPoolSize">10</property>
<property name="minPoolSize">1</property>
<property name="maxStatements">0</property>
</user-overrides></default-config>
<!-- This app is massive! -->
<named-config name="intergalactoApp">
<property name="acquireIncrement">50</property>
<property name="initialPoolSize">100</property>
<property name="minPoolSize">50</property>
<property name="maxPoolSize">1000</property><!-- intergalactoApp adopts a different approach to configuring statement
caching -->
<property name="maxStatements">0</property>
<property name="maxStatementsPerConnection">5</property><!-- he's important, but there's only one of him -->
<user-overrides user="master-of-the-universe">
<property name="acquireIncrement">1</property>
<property name="initialPoolSize">1</property>
<property name="minPoolSize">1</property>
<property name="maxPoolSize">5</property>
<property name="maxStatementsPerConnection">50</property>
</user-overrides>
</named-config>
</c3p0-config>
C3P0Utils 工具:
package com.test.utils; import java.sql.Connection; import java.sql.SQLException; import javax.sql.DataSource; import com.mchange.v2.c3p0.ComboPooledDataSource; public class C3P0Utils { private static ComboPooledDataSource dataSource = new ComboPooledDataSource(); public static Connection getConnection() { try { return dataSource.getConnection(); } catch (SQLException e) { throw new RuntimeException("數據連接獲取失敗!"); } } public static DataSource getDataSource() { return dataSource; } }
測試:
package com.test.jdbcTest; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import org.junit.Test; import com.test.utils.C3P0Utils; import com.test.utils.JDBCUtils; public class C3p0Test { @Test public void test() throws SQLException { Connection conn = C3P0Utils.getConnection(); String sql = "select cid,cname from category"; PreparedStatement st = conn.prepareStatement(sql); ResultSet rs = st.executeQuery(); while(rs.next()) { System.out.println(rs.getString("cid")+"..."+rs.getString("cname")); } JDBCUtils.colseResource(conn, st, rs); } }