初探Druid

说到连接池，最常见的就是dbcp和c3p0，关于druid，官方定义是为监控而生的数据库连接池。

官方中文文档地址：https://github.com/alibaba/druid/wiki/%E5%B8%B8%E8%A7%81%E9%97%AE%E9%A2%98

下面我介绍如何在servlet即不使用任何框架的时刻下使用druid并显示监控页面。

连接池之间的性能测试

1、首先导入下面这2个jar包

链接：https://pan.baidu.com/s/1e9lLS3e0xFdUFsPTu9rSQA 密码：xj6v

2、在web.xml文件中加入如下配置：

<filter>

        <filter-name>druidWebStatFilter</filter-name>

        <filter-class>com.alibaba.druid.support.http.WebStatFilter</filter-class>

        <init-param>

            <param-name>exclusions</param-name>

            <param-value>/public/*,*.js,*.css,/druid*,*.jsp,*.swf</param-value>

        </init-param>

    </filter>

    <filter-mapping>

        <filter-name>druidWebStatFilter</filter-name>

        <url-pattern>/*</url-pattern>

    </filter-mapping>

    <servlet>

        <servlet-name>DruidStatView</servlet-name>

        <servlet-class>com.alibaba.druid.support.http.StatViewServlet</servlet-class>

        <init-param>

            <param-name>allow</param-name>

            <param-value>127.0.0.1</param-value>

        </init-param>

    </servlet>

    <servlet-mapping>

        <servlet-name>DruidStatView</servlet-name>

        <url-pattern>/druid/*</url-pattern>

    </servlet-mapping>

3、在src下建一个db_server.properties的配置文件

内容如下，可根据自身需求调整

driverClassName=com.mysql.jdbc.Driver

url=jdbc:mysql:///kaoqin?useSSL=true

username=root

password=root

filters=stat

initialSize=2

maxActive=300

maxWait=60000

timeBetweenEvictionRunsMillis=60000

minEvictableIdleTimeMillis=300000

validationQuery=SELECT 1

testWhileIdle=true

testOnBorrow=false

testOnReturn=false

poolPreparedStatements=false

maxPoolPreparedStatementPerConnectionSize=200

4、创建一个DruidConnection类

public class DruidConnection {

    private static Properties properties = null;

    private static DataSource dataSource = null;

    private volatile static DruidConnection instatce = null;

    private Connection connection = null;

    //私有构造函数,防止实例化对象

    private DruidConnection() {

    }

    static {

        try {

            properties = new Properties();

            // 1.加载properties文件

            InputStream is = DruidConnection.class.getClassLoader().getResourceAsStream("db_server.properties");

            // 2.加载输入流

            properties.load(is);

            // 3.获取数据源

            dataSource = getDatasource();

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    /**

     * 用简单单例模式确保只返回一个链接对象

     *

     * @return

     */

    public static  DruidConnection getInstace() {

        if(instatce == null) {

            synchronized (DruidConnection.class) {

                if(instatce == null) {

                    instatce = new DruidConnection();

                }

            }

        }

        return instatce;

    }

    // 返回一个数据源

    public DataSource getDataSource() {

        return dataSource;

    }

    // 返回一个链接

    public Connection getConnection() {

        try {

            connection = dataSource.getConnection();

        } catch (SQLException e) {

            e.printStackTrace();

        }

        return connection;

    }

    // 加载数据源

    private static DataSource getDatasource() {

        DataSource source = null;

        try {

            source = DruidDataSourceFactory.createDataSource(properties);

        } catch (Exception e) {

            e.printStackTrace();

        }

        return source;

    }

}

5、创建工具类DruidUtils

public class DruidUtils {

    private static Connection connection = null;

    //获取元数据

    public static DataSource getDatasource() {

        DataSource dataSource = DruidConnection.getInstace().getDataSource();

        return dataSource;

    }

    //获取链接

    public static Connection getConnection() {

         connection = DruidConnection.getInstace().getConnection();

        return connection;

    }

    //归还资源

    public void release() {

        try {

            if(connection != null) {

                connection.close();

            }

        } catch (SQLException e) {

            e.printStackTrace();

        }

    }

}

6、在DAO层应用（举例）

public class UserDao {

    public User login(String name,String password) throws SQLException {

        // TODO Auto-generated method stub

        QueryRunner runner = new QueryRunner(DruidUtils.getDatasource());

        String sql = "select * from user where name=? and password=?";

        User user = runner.query(sql, new BeanHandler<User>(User.class), name, password);

        return user;

    }

}

7、浏览地址：${pageContext.request.contextPath}/druid/index.html

效果图：

巴特西

初探Druid

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