Dec 13, 2021

Introduction to Java Database Connection Pool Tomcat

Foreword:

The Tomcat connection pool is a highly concurrent connection pool rewritten from Tomcat 7 to replace the DBCP 1 connection pool previously used in Tomcat. It can be configured for use in Tomcat or used alone. This paper mainly introduces the basic use of Tomcat connection pool. The software versions used in this paper are Java 1.8.0_191, Tomcat 8.5. 72, Spring Boot 2.3. 12. RELEASE.

1. Configuration parameters

1.1. Basic Configuration

参数	默认值	描述
factory		必须，需要是 org.apache.tomcat.jdbc.pool.DataSourceFactory
type		应该是 javax.sql.DataSource 或 javax.sql.XADataSource

1.2. System Properties

参数	默认值	描述
org.apache.tomcat.jdbc.pool.onlyAttemptCurrentClassLoader	false	是否只使用当前的类加载器(加载该连接池的类加载器)来加载动态类

1.3, 1 general parameters

These parameters and DBCP 1, but some defaults are not 1.

参数	默认值	描述
defaultAutoCommit	驱动的默认值	是否自动提交
defaultReadOnly	驱动的默认值	是否只读
defaultTransactionIsolation	驱动的默认值	默认的事务隔离级别 NONE、READ_COMMITTED、READ_UNCOMMITTED、 REPEATABLE_READ、SERIALIZABLE
defaultCatalog		默认的 catalog。(目录，类似于模式名，但比模式名更加抽象； Oracle，MySQL 不支持，MS SQL Server = 数据库名)
driverClassName		驱动名称
url		连接 url
username		用户名
password		密码
maxActive	100	最大活动连接数
maxIdle	100	最大空闲连接数
minIdle	10	最小空闲连接数
initialSize	10	初始连接数
maxWait	3000	从连接池获取连接，最大等待时间(秒)
testOnBorrow	false	从连接池获取连接时，是否验证有效性；如果验证失败，则丢弃该连接。
testOnConnect	true	连接创建时，是否验证有效性
testOnReturn	false	连接返回连接池时，是否验证有效性
testWhileIdle	false	连接空闲时，是否验证有效性
validationQuery	null	连接校验的查询sql 如果指定，该 SQL 不需要返回结果，只要不抛 SQLException；如果没有指定，则通过调用 isValid() 方法进行校验。
validationQueryTimeout	-1	校验查询的超时时间(秒)；非正数表示不启用该特性。
validatorClassName	null	校验的类名，需实现 org.apache.tomcat.jdbc.pool.Validator 接口并包含1个无参构造函数。
timeBetweenEvictionRunsMillis	5000	校验空闲连接的时间周期(毫秒)，不能设为小于 1 秒，非正表示不验证
minEvictableIdleTimeMillis	60000	空闲连接至少多长时间(毫秒)后，才会被校验
removeAbandoned	false	是否删除泄露的连接
removeAbandonedTimeout	60	连接泄露的超时时间(秒)
logAbandoned	false	连接删除时是否打印堆栈信息
connectionProperties	null	连接属性，格式为： [propertyName=property;]* "user" and "password" 将被除外，所以在此不需要包含这两个属性。

1.4. Enhanced parameters

参数	默认值	描述
initSQL	null	连接创建时，执行的初始化 SQL
jdbcInterceptors	null	jdbc 拦截器，需要继承 org.apache.tomcat.jdbc.pool.JdbcInterceptor；已存在的拦截器： org.apache.tomcat.jdbc.pool.interceptor.ConnectionState 自动提交、只读、目录和事务隔离级别的跟踪 org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer statement的跟踪，在连接返回连接池时关闭它们
validationInterval	3000	连接校验的最短间隔(毫秒)
jmxEnabled	true	是否注册连接池到 JMX
fairQueue	true	是否使用公平队列，如果为 true，获取连接时将按照 "先进先出" 的原则
abandonWhenPercentageFull	0	泄露连接达到 abandonWhenPercentageFull 比例才关闭这些连接，0 表示有泄露连接立马关闭
maxAge	0	连接最大存活时间；在从连接池获取连接和连接返回连接池时进行该项检测，如果 now - time-when-connected > maxAge，则关闭该连接；0 表示不进行该项检测。
useEquals	true	是否使用 String.equals 来判断 ProxyConnection 是否相等
suspectTimeout	0	和 removeAbandonedTimeout 类似，但该设置只是打印日志并不删除连接；大于 0 才生效。
rollbackOnReturn	false	连接在返回连接池时是否自动回滚事务。
commitOnReturn	false	连接在返回连接池时是否自动提交事务；如果 rollbackOnReturn==true 则忽略该参数。
alternateUsernameAllowed	false	从连接池获取连接时是否允许设置新的凭证。默认情况下，连接池会忽略 DataSource.getConnection(username,password) 的调用，直接返回1个已创建的连接；如果要使用不同的凭证来获取连接，即 DataSource.getConnection(username,password) 生效，可把该参数设为 true。
dataSource	null	设置数据源，连接池将从该数据源获取连接
dataSourceJNDI	null	数据源的 jndi
useDisposableConnectionFacade	true	是否使用连接外观；设置为 true 可以防止连接关闭后的重复使用。
logValidationErrors	false	是否记录校验的错误
propagateInterruptState	false	是否传播线程中断状态
ignoreExceptionOnPreLoad	false	是否忽略创建连接时的错误
useStatementFacade	true	如果希望使用包装 statement，以便在设置了 statement 代理时，在已关闭的 statement 上调用 equals() and hashCode() 方法，需将此设置为 true。

For detailed explanation, please refer to the official website document: https://tomcat.apache.org/tomcat-8. 5-doc/jdbc-pool.html

2. Use

2.1. Direct use

2.1. 1, Introducing dependencies

<dependency>

    <groupId>org.apache.tomcat</groupId>

    <artifactId>tomcat-jdbc</artifactId>

    <version>8.5.72</version>

</dependency>

2.1. 2. Use examples

package com.abc.demo.general.dbpool;

import org.apache.tomcat.jdbc.pool.DataSource;

import org.apache.tomcat.jdbc.pool.PoolProperties;

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

public class TomcatPoolCase {

    public static void main(String[] args) {

        PoolProperties poolProperties = new PoolProperties();

        poolProperties.setName("Tomcat Connection pool ");

        poolProperties.setUrl("jdbc:mysql://10.40.9.11:3306/mydb?useUnicode=true&characterEncoding=UTF-8");

        poolProperties.setDriverClassName("com.mysql.cj.jdbc.Driver");

        poolProperties.setUsername("root");

        poolProperties.setPassword("123456");

        poolProperties.setJmxEnabled(true);

        poolProperties.setTestWhileIdle(false);

        poolProperties.setTestOnBorrow(true);

        poolProperties.setValidationQuery("SELECT 1");

        poolProperties.setTestOnReturn(false);

        poolProperties.setValidationInterval(30000);

        poolProperties.setTimeBetweenEvictionRunsMillis(30000);

        poolProperties.setMaxActive(100);

        poolProperties.setInitialSize(10);

        poolProperties.setMaxWait(10000);

        poolProperties.setRemoveAbandonedTimeout(60);

        poolProperties.setMinEvictableIdleTimeMillis(30000);

        poolProperties.setMinIdle(10);

        poolProperties.setLogAbandoned(true);

        poolProperties.setRemoveAbandoned(true);

        poolProperties.setJdbcInterceptors(

                "org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;" +

                "org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer");

        DataSource datasource = new DataSource();

        datasource.setPoolProperties(poolProperties);

        Connection connection = null;

        try {

            connection = datasource.getConnection();

            Statement st = connection.createStatement();

            ResultSet rs = st.executeQuery("select version()");

            if (rs.next()) {

                System.out.println(rs.getString(1));

            }

        } catch (SQLException e) {

            e.printStackTrace();

        } finally {

            close(connection);

        }

        // In actual use 1 Generally, the data source is initialized when the application starts, and the application obtains the connection from the data source; The data source is not closed.

        datasource.close();

    }

    private static void close(Connection connection) {

        if (connection != null) {

            try {

                connection.close();

            } catch (SQLException e) {

                e.printStackTrace();

            }

        }

    }

}

2.2. Allocate as a resource in Tomcat

First, copy the driver package of the corresponding database to Tomcat Or applied lib Directory, and then in the content.xml Configure resources in,

content. xml can be located in the following location:

conf/context.xml For all applications conf/Catalina/localhost For a single application, it is suitable for Tomcat External deployment application {应用}/META-INFcontext.xml For a single application

Examples of configuring resources are as follows:

<Resource name="jdbc/testDb"

    auth="Container"

    type="javax.sql.DataSource"

    factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"

    testWhileIdle="true"

    testOnBorrow="true"

    testOnReturn="false"

    validationQuery="SELECT 1"

    validationInterval="30000"

    timeBetweenEvictionRunsMillis="30000"

    maxActive="20"

    maxIdle="20"

    minIdle="5"

    maxWait="10000"

    initialSize="5"

    removeAbandonedTimeout="60"

    removeAbandoned="true"

    logAbandoned="true"

    minEvictableIdleTimeMillis="30000"

    jmxEnabled="true"

    jdbcInterceptors="org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;

    org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer"

    username="root"

    password="123456"

    driverClassName="com.mysql.cj.jdbc.Driver"

    url="jdbc:mysql://10.40.9.11:3306/mydb?useUnicode=true&amp;characterEncoding=UTF-8" />

It can be passed through jndi To find this resource, the search method is demonstrated here through jsp:

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="UTF-8"%>

<%@ page import="javax.naming.Context,

                javax.naming.InitialContext,

                javax.sql.DataSource,

                java.sql.*"%>

<%

    Connection connection = null;

    try {

        InitialContext initialContext = new InitialContext();

        Context context = (Context) initialContext.lookup("java:comp/env");

        DataSource dataSource = (DataSource)context.lookup("jdbc/testDb");

        connection = dataSource.getConnection();

        Statement st = connection.createStatement();

        ResultSet rs = st.executeQuery("select version()");

        if (rs.next()) {

            System.out.println(rs.getString(1));

        }

    } catch (Exception e) {

        e.printStackTrace();

    } finally {

        if (connection != null) {

            try {

                connection.close();

            } catch (SQLException e) {

                e.printStackTrace();

            }

        }

    }

%>

<html>

    <body>

        <h3> Pass  jndi  Find the data source and get the version information of the database </h3>

    </body>

</html>

3.2. Use in SpringBoot

3.1. 1, Introducing dependencies

<parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>2.3.12.RELEASE</version>

    <relativePath />

</parent>

<dependencies>

    <dependency>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-web</artifactId>

    </dependency>

    <dependency>

        <groupId>org.springframework</groupId>

        <artifactId>spring-jdbc</artifactId>

    </dependency>

    <dependency>

        <groupId>org.apache.tomcat</groupId>

        <artifactId>tomcat-jdbc</artifactId>

        <version>8.5.72</version>

    </dependency>

    <dependency>

        <groupId>mysql</groupId>

        <artifactId>mysql-connector-java</artifactId>

    </dependency>

</dependencies>

3.1. 2, single data source

application. yml configuration:

spring:

  datasource:

    tomcat-pool:

      name: Tomcat Connection pool

      url: jdbc:mysql://10.40.9.11:3306/mydb?useUnicode=true&characterEncoding=UTF-8

      driver-class-name: com.mysql.cj.jdbc.Driver

      username: root

      password: 123456

      test-while-idle: true

      test-on-borrow: true

      validation-query: select 1

      test-on-return: false

      validation-interval: 30000

      time-between-eviction-runs-millis: 30000

      max-active: 100

      initial-size: 10

      max-wait: 10000

      remove-abandoned-timeout: 60

      min-evictable-idle-time-millis: 30000

      min-idle: 10

      log-abandoned: true

      remove-abandoned: true

      jdbc-interceptors: org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer

Data source configuration class:

package com.abc.demo.config;

import org.springframework.boot.context.properties.ConfigurationProperties;

import org.springframework.boot.jdbc.DataSourceBuilder;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration

public class DataSourceConfig {

    @Bean("dataSource")

    @ConfigurationProperties(prefix = "spring.datasource.tomcat-pool")

    public DataSource dataSource() {

        return DataSourceBuilder.create().type(org.apache.tomcat.jdbc.pool.DataSource.class).build();

    }

}

Use:

@Autowired

private DataSource dataSource;

3.1. 3. Multiple data sources

application. yml configuration:

spring:

  datasource:

    tomcat-pool:

      db1:

        name: Tomcat Connection pool

        url: jdbc:mysql://10.40.9.11:3306/mydb?useUnicode=true&characterEncoding=UTF-8

        driver-class-name: com.mysql.cj.jdbc.Driver

        username: root

        password: 123456

        test-while-idle: true

        test-on-borrow: true

        validation-query: select 1

        test-on-return: false

        validation-interval: 30000

        time-between-eviction-runs-millis: 30000

        max-active: 100

        initial-size: 10

        max-wait: 10000

        remove-abandoned-timeout: 60

        min-evictable-idle-time-millis: 30000

        min-idle: 10

        log-abandoned: true

        remove-abandoned: true

        jdbc-interceptors: org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer

      db2:

        name: Tomcat Connection pool

        url: jdbc:mysql://10.110.74.187:3306/egmp?useUnicode=true&characterEncoding=UTF-8

        driver-class-name: com.mysql.cj.jdbc.Driver

        username: root

        password: InsYR0ot187!

        test-while-idle: true

        test-on-borrow: true

        validation-query: select 1

        test-on-return: false

        validation-interval: 30000

        time-between-eviction-runs-millis: 30000

        max-active: 100

        initial-size: 10

        max-wait: 10000

        remove-abandoned-timeout: 60

        min-evictable-idle-time-millis: 30000

        min-idle: 10

        log-abandoned: true

        remove-abandoned: true

        jdbc-interceptors: org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer

Data source configuration class:

package com.abc.demo.config;

import org.springframework.boot.context.properties.ConfigurationProperties;

import org.springframework.boot.jdbc.DataSourceBuilder;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration

public class DataSourceConfig {

    @Bean("dataSource1")

    @ConfigurationProperties(prefix = "spring.datasource.tomcat-pool.db1")

    public DataSource dataSource1() {

        return DataSourceBuilder.create().type(org.apache.tomcat.jdbc.pool.DataSource.class).build();

    }

    @Bean("dataSource2")

    @ConfigurationProperties(prefix = "spring.datasource.tomcat-pool.db2")

    public DataSource dataSource2() {

        return DataSourceBuilder.create().type(org.apache.tomcat.jdbc.pool.DataSource.class).build();

    }

}

Use:

package com.abc.demo.general.dbpool;

import org.apache.tomcat.jdbc.pool.DataSource;

import org.apache.tomcat.jdbc.pool.PoolProperties;

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

public class TomcatPoolCase {

    public static void main(String[] args) {

        PoolProperties poolProperties = new PoolProperties();

        poolProperties.setName("Tomcat Connection pool ");

        poolProperties.setUrl("jdbc:mysql://10.40.9.11:3306/mydb?useUnicode=true&characterEncoding=UTF-8");

        poolProperties.setDriverClassName("com.mysql.cj.jdbc.Driver");

        poolProperties.setUsername("root");

        poolProperties.setPassword("123456");

        poolProperties.setJmxEnabled(true);

        poolProperties.setTestWhileIdle(false);

        poolProperties.setTestOnBorrow(true);

        poolProperties.setValidationQuery("SELECT 1");

        poolProperties.setTestOnReturn(false);

        poolProperties.setValidationInterval(30000);

        poolProperties.setTimeBetweenEvictionRunsMillis(30000);

        poolProperties.setMaxActive(100);

        poolProperties.setInitialSize(10);

        poolProperties.setMaxWait(10000);

        poolProperties.setRemoveAbandonedTimeout(60);

        poolProperties.setMinEvictableIdleTimeMillis(30000);

        poolProperties.setMinIdle(10);

        poolProperties.setLogAbandoned(true);

        poolProperties.setRemoveAbandoned(true);

        poolProperties.setJdbcInterceptors(

                "org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;" +

                "org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer");

        DataSource datasource = new DataSource();

        datasource.setPoolProperties(poolProperties);

        Connection connection = null;

        try {

            connection = datasource.getConnection();

            Statement st = connection.createStatement();

            ResultSet rs = st.executeQuery("select version()");

            if (rs.next()) {

                System.out.println(rs.getString(1));

            }

        } catch (SQLException e) {

            e.printStackTrace();

        } finally {

            close(connection);

        }

        // In actual use 1 Generally, the data source is initialized when the application starts, and the application obtains the connection from the data source; The data source is not closed.

        datasource.close();

    }

    private static void close(Connection connection) {

        if (connection != null) {

            try {

                connection.close();

            } catch (SQLException e) {

                e.printStackTrace();

            }

        }

    }

}