03-02：Hikari数据源

使用Java语言编写程序访问数据库之前，除了需要导入对应数据库的驱动程序外，还必须通过驱动管理器创建数据库连接。在SpringBoot 2.x项目中，默认使用Hikari连接池管理数据源。当项目pom.xml引入spring-boot-starter-jdbc启动器依赖后，即可自动导入Hikari，该启动器不但依赖它，还会对其自动配置并创建数据源。我们以MySQL数据库为例，介绍如何使用Hikari。

1. 在Idea中通过Spring Initializr方式，创建名称为springboot0302-hikari的SpringBoot项目并加入如图所示依赖。本案例中Spring Boot的版本为2.4.11。

2. 项目创建成功后，其pom.xml配置如下。

    4.0.0

    
        org.springframework.boot
        spring-boot-starter-parent
        2.4.11
         
    

    com.company
    springboot0302-hikari
    0.0.1-SNAPSHOT
    springboot0302-hikari
    Demo project for Spring Boot
    
        1.8
    

    

        
            org.springframework.boot
            spring-boot-starter-web
        

        
            org.springframework.boot
            spring-boot-starter-test
            test
        

        
            org.springframework.boot
            spring-boot-configuration-processor
            true
        

        
            org.springframework.boot
            spring-boot-devtools
            runtime
            true
        






        
            org.springframework.boot
            spring-boot-starter-jdbc
        

        
            mysql
            mysql-connector-java
            runtime
        

        
            org.projectlombok
            lombok
            true
        

    

    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
                
                    
                        
                            org.projectlombok
                            lombok
                        
                    
                
            
        
    

3. 运行主启动程序Application，控制台日志中有一条警告信息，而且导致应用程序启动失败。

...
2021-10-12 01:24:43.277  WARN 19552 --- [  restartedMain] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dataSource' defined in class path resource [org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration$Hikari.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.zaxxer.hikari.HikariDataSource]: Factory method 'dataSource' threw exception; nested exception is org.springframework.boot.autoconfigure.jdbc.DataSourceProperties$DataSourceBeanCreationException: Failed to determine a suitable driver class
2021-10-12 01:24:43.282  INFO 19552 --- [  restartedMain] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2021-10-12 01:24:43.295  INFO 19552 --- [  restartedMain] ConditionevaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-10-12 01:24:43.313 ERROR 19552 --- [  restartedMain] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.

Reason: Failed to determine a suitable driver class


Action:

Consider the following:
	If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
	If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).


Process finished with exit code 0

通过分析上述日志得知，应用程序在启动时，配置名称叫dataSource的数据源Bean失败，是因为其url属性未指定导致不能确定合适的驱动程序类，而且也无法配置嵌入式数据源。

注意：默认情况下，驱动程序类是根据url确定的，故可以不配置。具体原理和过程参考如下源码。

• org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration
• org.springframework.boot.autoconfigure.jdbc.DataSourceProperties
• org.springframework.boot.jdbc.DatabaseDriver

1.在全局配置文件application.properties中，增加spring.datasource.url配置。

spring.datasource.url=jdbc:mysql://localhost:3306/springbootdata?serverTimezone=UTC&useSSL=false

2.重新运行主启动程序Application，应用程序即可启动成功。

...
2021-10-12 01:53:00.660  INFO 1992 --- [  restartedMain] com.company.project.Application          : Started Application in 2.141 seconds (JVM running for 3.246)

注意：url的jdbc和mysql这两部分书写正确即可启动应用程序，说明根据url确定驱动程序类型并将其加载成功，但此时并没有创建数据源，否则会报如下异常。

java.lang.IllegalArgumentException: URL must start with 'jdbc'

1.在主启动程序单元测试类ApplicationTests中加入自动装配、显示dataSource信息的代码。

package com.company.project;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import javax.sql.DataSource;
import java.sql.SQLException;

@SpringBootTest
public class ApplicationTests {

    @Autowired
    private DataSource dataSource;

    @Test
    void contextLoads() {
    }

    @Test
    void showDataSource() {
        System.out.println("DataSource:" + dataSource);
        
        System.out.println("DataSourceClassName:" + dataSource.getClass().getName());
        try {
            System.out.println("Connection:" + dataSource.getConnection().toString());
            System.out.println("ConnectionIsClosed:" + dataSource.getConnection().isClosed());
            System.out.println("ConnectionIsReadOnly:" + dataSource.getConnection().isReadOnly());
            System.out.println("ConnectionAutoCommit:" + dataSource.getConnection().getAutoCommit());
            System.out.println("ConnectionTransactionIsolation:" + dataSource.getConnection().getTransactionIsolation());
            System.out.println("ConnectionNetworkTimeout:" + dataSource.getConnection().getNetworkTimeout());
            System.out.println("ConnectionClassName:" + dataSource.getConnection().getClass().getName());
            System.out.println("ConnectionCatalog:" + dataSource.getConnection().getCatalog());
            
			System.out.println("DataSource:" + dataSource);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

}

2.运行showDataSource()单元测试方法，尽管已经执行成功，但是，根据控制台日志可知，容器只有在获取dataSource时才去创建它的Bean，其类名为com.zaxxer.hikari.HikariDataSource。而且，由于本次登录默认使用了当前Windows用户名和空密码导致dataSource的连接池创建失败，故其名称为null。

DataSource:HikariDataSource (null)
DataSourceClassName:com.zaxxer.hikari.HikariDataSource
2021-10-12 02:04:53.303  INFO 8616 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-10-12 02:04:54.684 ERROR 8616 --- [           main] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Exception during pool initialization.

java.sql.SQLException: Access denied for user 'liuzh'@'localhost' (using password: NO)
...

3.在全局配置文件application.properties中，增加spring.datasource.username和spring.datasource.password配置。

spring.datasource.username=root
spring.datasource.password=123456

4.再次运行showDataSource()单元测试方法，执行成功，dataSource的连接池名称默认为HikariPool-1。

DataSource:HikariDataSource (null)
DataSourceClassName:com.zaxxer.hikari.HikariDataSource
2021-10-12 02:20:59.480  INFO 14180 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2021-10-12 02:20:59.821  INFO 14180 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
Connection:HikariProxyConnection@80052821 wrapping com.mysql.cj.jdbc.ConnectionImpl@eac3a26
ConnectionIsClosed:false
ConnectionIsReadOnly:false
ConnectionAutoCommit:true
ConnectionTransactionIsolation:4
ConnectionNetworkTimeout:0
ConnectionClassName:com.zaxxer.hikari.pool.HikariProxyConnection
ConnectionCatalog:springbootdata
DataSource:HikariDataSource (HikariPool-1)

由于启动器spring-boot-starter-data-jpa依赖spring-boot-starter-jdbc，省事期间，我们可以在pom.xml中直接引入它。

    org.springframework.boot
    spring-boot-starter-data-jpa

spring-boot-starter-data-jpa.pom文件参考：

  4.0.0
  org.springframework.boot
  spring-boot-starter-data-jpa
  2.4.11
  spring-boot-starter-data-jpa
  Starter for using Spring Data JPA with Hibernate
  https://spring.io/projects/spring-boot

...

  
    
      org.springframework.boot
      spring-boot-starter-aop
      2.4.11
      compile
    
    
    
      org.springframework.boot
      spring-boot-starter-jdbc
      2.4.11
      compile
    
    
    
      jakarta.transaction
      jakarta.transaction-api
      1.3.3
      compile
    
    
    
      jakarta.persistence
      jakarta.persistence-api
      2.2.3
      compile
    
    
    
      org.hibernate
      hibernate-core
      5.4.32.Final
      compile
      
        
          jaxb-api
          javax.xml.bind
        
        
          javax.activation-api
          javax.activation
        
        
          javax.persistence-api
          javax.persistence
        
        
          jboss-transaction-api_1.2_spec
          org.jboss.spec.javax.transaction
        
      
    
    
    
      org.springframework.data
      spring-data-jpa
      2.4.13
      compile
      
        
          aspectjrt
          org.aspectj
        
      
    
    
    
      org.springframework
      spring-aspects
      5.3.10
      compile
    
    
  

5、Hikari完整配置