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数据库连接池

  • 概述：我们访问数据库要频繁的建立连接和关闭连接，会是系统资源的浪费，这时候可是使用一个 Connection 的连接池来管理这些连接，我们需要建立连接的时候通过连接池索要连接，不用到的连接由连接池回收，并不是真正的关闭，而是实现了动态管理。
  • 常用连接池：DBCP(tomcat 内置),PO3
  • 规范：Java 为数据库连接池提供了公共的接口：javax.sql.DataSource，各个厂商需要让自己的连接池实现这个接口。这样应用程序可以方便的切换不同厂商的连接池

创建工具类

public class DBCPDemo {

</span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">创建连接池</span>
<span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String DRIVER = "com.mysql.jdbc.Driver"<span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String URL = "jdbc:mysql://localhost:3306/mybase"<span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String USERNAME = "root"<span style="color: rgba(0, 0, 0, 1)">;
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">final</span> String PASSWORD = "123456"<span style="color: rgba(0, 0, 0, 1)">;

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> BasicDataSource dataSource=<span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> BasicDataSource();

</span><span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)">{
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">对连接池对象 进行基本的配置</span>
        dataSource.setDriverClassName(DRIVER); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)"> 这是要连接的数据库的驱动</span>
        dataSource.setUrl(URL); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">指定要连接的数据库地址</span>
        dataSource.setUsername(USERNAME); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">指定要连接数据的用户名</span>
        dataSource.setPassword(PASSWORD); <span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">指定要连接数据的密码</span>



    }


</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span><span style="color: rgba(0, 0, 0, 1)"> DataSource getDataSource(){
    </span><span style="color: rgba(0, 128, 0, 1)">//</span><span style="color: rgba(0, 128, 0, 1)">通过该函数获取连接池对象</span>
    <span style="color: rgba(0, 0, 255, 1)">return</span><span style="color: rgba(0, 0, 0, 1)"> dataSource;
}



}

测试代码

public class test {

</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> main(String[] args) {
    query();
}
</span><span style="color: rgba(0, 0, 255, 1)">private</span> <span style="color: rgba(0, 0, 255, 1)">static</span> QueryRunner qr=<span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> QueryRunner(DBCPDemo.getDataSource());
</span><span style="color: rgba(0, 0, 255, 1)">public</span> <span style="color: rgba(0, 0, 255, 1)">static</span> <span style="color: rgba(0, 0, 255, 1)">void</span><span style="color: rgba(0, 0, 0, 1)"> query(){
    String sql</span>="select * from sort"<span style="color: rgba(0, 0, 0, 1)">;
    </span><span style="color: rgba(0, 0, 255, 1)">try</span><span style="color: rgba(0, 0, 0, 1)">{
    List</span>&lt;Object []&gt; result=qr.query(sql, <span style="color: rgba(0, 0, 255, 1)">new</span><span style="color: rgba(0, 0, 0, 1)"> ArrayListHandler());
    </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)">(Object[] obj:result){
        </span><span style="color: rgba(0, 0, 255, 1)">for</span><span style="color: rgba(0, 0, 0, 1)">(Object o:obj){
            System.out.print(o);
        }
        System.out.println();
    }
    }</span><span style="color: rgba(0, 0, 255, 1)">catch</span><span style="color: rgba(0, 0, 0, 1)">(SQLException ex){
        ex.printStackTrace();
    }
}



}

结果：