Using Druid as a data source

Druid claims to be the best database connection pool in the Java language.

1) It can monitor database access performance. Druid provides a built-in powerful StatFilter plug-in, which can calculate the execution performance of SQL in detail, which is helpful for online analysis of database access performance.

2) Replace DBCP and C3P0 . Druid provides an efficient, powerful, and scalable database connection pool.

3) Database password encryption. It is bad behavior to directly write the database password in the configuration file, which can easily lead to security problems. Both DruidDruiver and DruidDataSource support PasswordCallback.

4) SQL execution log, Druid provides different LogFilters, which can support Common-Logging , Log4j and JdkLog. You can select the corresponding LogFilter as needed to monitor the database access of your application.

5) Can provide plug-in system based on Filter-Chain mode.

The following describes how to integrate Druid in the project:

1. maven dependencies

<dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>${druid-version}</version>
    </dependency>

2. Configure web.xml

	<!-- druid -->
	<servlet>
		<servlet-name>DruidStatView</servlet-name>
		<servlet-class>com.alibaba.druid.support.http.StatViewServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>DruidStatView</servlet-name>
		<url-pattern>/druid/*</url-pattern>
	</servlet-mapping>

	<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>*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>DruidWebStatFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

3. Configure the druid data source in spring.xml

	<!-- data source druid -->
	<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
	init-method="init" destroy-method="close">
		<property name="driverClassName" value="${jdbc.driverClassName}" />
		<property name="url" value="${jdbc.url}" />
		<property name="username" value="${jdbc.username}" />
		<property name="password" value="${jdbc.password}" />
		
		 <!-- Configure initialization size, minimum, maximum -->  
	    <property name="initialSize" value="${druid.pool.size.init}" />  
	    <property name="minIdle" value="${druid.pool.size.min}" />   
	    <property name="maxActive" value="${druid.pool.size.max}" />  
	    
	    <!-- Configure the filters for monitoring statistics interception, after removing it, the monitoring interface sql cannot be counted -->
	    <property name="filters" value="stat" />
	</bean>

Druid FAQ:

1. How to open Druid's monitoring and statistics function

Druid's monitoring and statistics function is implemented through the filter-chain extension. If you want to enable the monitoring and statistics function, configure StatFilter .

https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_StatFilter

2. How to use Druid's built-in monitoring page

The built-in monitoring page is a servlet .

https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_StatViewServlet%E9%85%8D%E7%BD%AE

3. How to configure the Web and Spring associated monitoring in the built-in monitoring?

Web Association Monitoring Configuration

https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_%E9%85%8D%E7%BD%AEWebStatFilter

Spring association monitoring configuration

https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_Druid%E5%92%8CSpring%E5%85%B3%E8%81%94%E7%9B%91%E6%8E%A7%E9%85%8D%E7%BD%AE

4. How to configure defense against SQL injection attacks

Druid provides WallFilter, which is based on SQL semantic analysis to defend against SQL injection attacks.

https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE-wallfilter

5. Is there any reference configuration for Druid?

Different business scenarios have different requirements. You can use our reference configuration, but it is recommended that you read the relevant documents carefully and make customized configurations after understanding. https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_DruidDataSource%E5%8F%82%E8%80%83%E9%85%8D%E7%BD%AE

6. I want to log the SQL executed by JDBC, how to configure it

Druid provides Log4jFilter, CommonsLogFilter and Slf4jFilter.

https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_LogFilter

7. My program may have a connection leak, what can I do?

Druid provides several means of monitoring connection leaks.

https://github.com/alibaba/druid/wiki/%E8%BF%9E%E6%8E%A5%E6%B3%84%E6%BC%8F%E7%9B%91%E6%B5%8B

8. Will the memory usage be too large when using PSCache in Druid?

Connecting to the Oracle database and opening PSCache will cause excessive memory usage in other database connection pools. Druid is the only connection pool that solves this problem.

https://github.com/alibaba/druid/wiki/Oracle%E6%95%B0%E6%8D%AE%E5%BA%93%E4%B8%8BPreparedStatementCache%E5%86%85%E5%AD%98%E9%97%AE%E9%A2%98%E8%A7%A3%E5%86%B3%E6%96%B9%E6%A1%88

9. Is there any comparison with other database connection pools?

https://github.com/alibaba/druid/wiki/%E5%90%84%E7%A7%8D%E6%95%B0%E6%8D%AE%E5%BA%93%E8%BF%9E%E6%8E%A5%E6%B1%A0%E5%AF%B9%E6%AF%94

10、从其他连接池迁移要注意什么？

不同连接池的参数参照对比：http://code.alibabatech.com/wiki/pages/viewpage.action?pageId=6947005

DBCP迁移 https://github.com/alibaba/druid/wiki/DBCP%E8%BF%81%E7%A7%BB

11、Druid中有没有类似Jboss DataSource中的ExceptionSorter

ExceptionSorter是JBoss DataSource中的优秀特性，Druid也有一样功能的ExceptionSorter，但不用手动配置，自动识别生效的。

具体看这里：http://code.alibabatech.com/wiki/display/Druid/ExceptionSorter

12、Druid中的maxIdle为什么是没用的？

maxIdle是Druid为了方便DBCP用户迁移而增加的，maxIdle是一个混乱的概念。连接池只应该有maxPoolSize和minPoolSize，druid只保留了maxActive和minIdle，分别相当于maxPoolSize和minPoolSize。

13、我的应用配置的是JNDI数据源，可以用DruidDataSource么？