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：