Druid connection pool - strong self-study from 0. Those who don't understand Druid can click in. If you know not to click in, you will think I'm wordy

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Official document encyclopedia ：https://github.com/alibaba/druid/wiki/Druid%E8%BF%9E%E6%8E%A5%E6%B1%A0%E4%BB%8B%E7%BB%8D

introduction

It's all equipped in the project , In addition to the code matching , I didn't write the relevant code , We don't understand what this is , Today, let's start from scratch , Learn to be strong .

What is? Druid Connection pool ？

Druid Connection pool is an open source database connection pool project of Alibaba .

Druid Connection pools are built for monitoring , Built in powerful monitoring function , Monitoring features do not affect performance . Powerful , Can prevent SQL Inject , built-in Loging Able to diagnose Hack Applied behavior .

Oh , First Druid It's a database connection pool , For the first time , I don't know either , Then let's take a look at the database connection pool

What is a database connection pool ？

Database connection pool （Database Connection Pooling） When the program is initialized, a certain number of database connection objects are created and saved in a memory area , It allows applications to reuse an existing database connection , Instead of re establishing a ; Release the database connection whose idle time exceeds the maximum idle time to avoid database connection omission caused by not releasing the database connection .

That is, a certain number of database connections are created during program initialization , You can put it back after use , The next one goes on , The initial number of connections in the connection pool is controlled by configuring the parameters of the connection pool 、 The minimum connection 、 Maximum connection 、 Maximum idle time these parameters ensure that the number of database accesses is within a certain controllable range , Prevent system crash , Make the user experience better

Oh , I see , Like that thread pool

Let's see what it does ？

Just now I mentioned his role ： Druid Connection pools are built for monitoring , Built in powerful monitoring function , Monitoring features do not affect performance . Powerful , Can prevent SQL Inject , built-in Loging Able to diagnose Hack Applied behavior .

Oh , I see , Monitor the behavior of the database

What's the point of him ？

The meaning of database connection pool is , Ability to reuse database connections , Improve response time to requests and server performance .

Multiple database connection objects are established in advance in the connection pool , Then save the connection object to the connection pool , When a customer request comes , Take a connection object directly from the pool to serve customers , When the request is complete , The client program calls close() Method , Put the connection object back into the pool .

Oh , I see , Improve the efficiency of database connection （ Improve response time to requests and server performance ）

Then why use it ？

The performance indicators of each product are as follows ：

Druid Connection pooling is in performance 、 monitor 、 The diagnosis 、 Security 、 These aspects of scalability are far beyond the competitive products

Oh , I see , because Druid It cow

Oh , How to use it? ？

After checking for a long time, someone said that it was necessary to manage the configuration first DataSource Connect pool objects

Let's first see what it is DataSource, Don't panic about this , Just translate it into Chinese , It's the data source （ A data source is a source of data , This is equivalent to a database ）

Speaking of this, expand what is DataSource object ：

What is? DataSource object ？

DataSource The object is javax.sql An interface in the package , In fact, it can be identified as a database connection resource , The data source object should store the connected url, User name, password and other connection information .

Oh ,DataSource Object is an interface , Put database connection information

In the use of JDBC When connecting to the database , All use through DriverManager To get Connection object ,getConnection Methods need to be passed url,name.passwd Etc , In fact, this information can be used as a data source object .

What is DataSource Connection pool ？

Translated into Chinese is the data source connection pool . A data source is a source of data , It's like a database .

But the program does not directly access the database , Through an agent , That is, data connection pool , Every object referenced by a data connection pool must have a data source .DataSource There are many implementation subclasses of , Many third-party connection pools need to be implemented DataSource Of , If you create a data source with a data pool , Then there is the connection pool function .

Oh , It's actually a database connection pool

such as ：Mybatis There is a default data source implementation class （ You are here. xml Configured in ）

 <dataSource type="POOLED">
     <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
     <property name="url" value="jdbc:mysql://localhost:3306/db_test?characterEncoding=UTF-8&amp;allowMultiQueries=true"/>
     <property name="username" value="root"/>
     <property name="password" value="root"/>
 </dataSource>

You've been walking around for a long time , It's just a sentence ： First, configure the database connection pool , What is a database connection pool? I just said

For example, what we are talking about now is Druid Connection pool , Then the data source connection pool used in the project is ：DruidDataSource.

Druid Connection pool configuration

【 First step 】 add to Druid Connection pool dependency

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.16</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.47</version>
</dependency>

Be careful ： In addition to adding the above two dependencies , Don't forget to add spring-context rely on .

【 The second step 】 To configure DruidDataSource Connection pool Bean object

<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3306/spring_db"/>
    <property name="username" value="root"/>
    <property name="password" value="root"/>
</bean>

【 The third step 】 From... In the test class IOC Get the connection pool object in the container and print

public class App {
    
    public static void main(String[] args) {
    
        ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
        DataSource dataSource = (DataSource) ctx.getBean("dataSource");
        System.out.println(dataSource);
    }
}

The result is ：

Oh , There is a connection pool

Configuration parameters

<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close"> 
    <property name="url" value="${jdbc_url}" />
    <property name="username" value="${jdbc_user}" />
    <property name="password" value="${jdbc_password}" />

    <property name="filters" value="stat" />

    <property name="maxActive" value="20" />
    <property name="initialSize" value="1" />
    <property name="maxWait" value="6000" />
    <property name="minIdle" value="1" />

    <property name="timeBetweenEvictionRunsMillis" value="60000" />
    <property name="minEvictableIdleTimeMillis" value="300000" />

    <property name="testWhileIdle" value="true" />
    <property name="testOnBorrow" value="false" />
    <property name="testOnReturn" value="false" />

    <property name="poolPreparedStatements" value="true" />
    <property name="maxOpenPreparedStatements" value="20" />

    <property name="asyncInit" value="true" />
  <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close"> 
     <!--  Basic attributes  url、user、password -->
     <property name="url" value="${jdbc_url}" />
     <property name="username" value="${jdbc_user}" />
     <property name="password" value="${jdbc_password}" />
       
     <!--  Configure initialization size 、 Minimum 、 Maximum  -->
     <property name="initialSize" value="5" />
     <property name="minIdle" value="10" /> 
     <property name="maxActive" value="20" />
  
     <!--  Configure the timeout time for getting connection waiting  -->
     <property name="maxWait" value="6000" />
  
     <!--  Configure how often to test , Detects idle connections that need to be closed , In milliseconds  -->
     <property name="timeBetweenEvictionRunsMillis" value="2000" />
  
     <!--  Configure the minimum lifetime of a connection in the pool , In milliseconds  -->
     <property name="minEvictableIdleTimeMillis" value="600000" />
     <property name="maxEvictableIdleTimeMillis" value="900000" />
   
     <property name="validationQuery" value="select 1" />
     <property name="testWhileIdle" value="true" />
     <property name="testOnBorrow" value="false" />
     <property name="testOnReturn" value="false" />
  
     <!--  Configure monitoring statistics interception filters -->
     <property name="filters" value="stat" /> 
 </bean></bean>

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