SpringBoot-默认数据源HikariDataSource对数据库操作及自动装配原理

默认数据源HikariDataSource对数据库操作

在创建项目时选择JDBC以及MySQL驱动，让SpringBoot自动装配所需组件

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创建完成后默认的pom.xml文件如下

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.1.7.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.guih</groupId><artifactId>spring-boot-data-jdbc</artifactId><version>0.0.1-SNAPSHOT</version><name>spring-boot-data-jdbc</name><description>JDBC Demo project for Spring Boot</description><properties><java.version>1.8</java.version></properties><dependencies><!-- SpringBoot集成的JDBC以及数据库连接包 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jdbc</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

创建 application.yml 文件，配置连接数据库的参数

spring:datasource:username: rootpassword: 123456driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf8&useSSL=false

测试是否能获取到数据源

// 单元测试代码
@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringBootDataJdbcApplicationTests {@Autowiredprivate DataSource dataSource;@Testpublic void test() throws SQLException {Connection data = dataSource.getConnection();System.out.println("------" + data.getClass());System.out.println("------" + dataSource.getClass());data.close();}}

输出结果如下，数据源获取成功，说明SpringBoot2.1.7默认使用的是Hikari连接池**（SpringBoot2.0之前使用的是tomcat连接池）**

------class com.zaxxer.hikari.pool.HikariProxyConnection
------class com.zaxxer.hikari.HikariDataSource

使用数据源对数据库进行操作

为了方便测试，这里使用的数据库是本机上的数据库

编写代码测试访问数据库

@Controller
public class JDBCTest {@Autowiredprivate JdbcTemplate jdbcTemplate;@RequestMapping("/query")@ResponseBodypublic Map<String, Object> query() {List<Map<String, Object>> list = jdbcTemplate.queryForList("SELECT * FROM test1");return list.get(0);} 
}

启动SpringBoot程序并使用Postman进行测试

SpringBoot默认数据源自动装配原理

参考org.springframework.boot.autoconfigure.jdbc包下的DataSourceConfigration类

package org.springframework.boot.autoconfigure.jdbc;import javax.sql.DataSource;import com.zaxxer.hikari.HikariDataSource;import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DatabaseDriver;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.util.StringUtils;abstract class DataSourceConfiguration {@SuppressWarnings("unchecked")protected static <T> T createDataSource(DataSourceProperties properties, Class<? extends DataSource> type) {return (T) properties.initializeDataSourceBuilder().type(type).build();}// 根据容器中的情况来进行逻辑判断，添加不同的数据源@Configuration@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)@ConditionalOnMissingBean(DataSource.class)@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.tomcat.jdbc.pool.DataSource",matchIfMissing = true)static class Tomcat {@Bean@ConfigurationProperties(prefix = "spring.datasource.tomcat")public org.apache.tomcat.jdbc.pool.DataSource dataSource(DataSourceProperties properties) {org.apache.tomcat.jdbc.pool.DataSource dataSource = createDataSource(properties,org.apache.tomcat.jdbc.pool.DataSource.class);DatabaseDriver databaseDriver = DatabaseDriver.fromJdbcUrl(properties.determineUrl());String validationQuery = databaseDriver.getValidationQuery();if (validationQuery != null) {dataSource.setTestOnBorrow(true);dataSource.setValidationQuery(validationQuery);}return dataSource;}}@Configuration@ConditionalOnClass(HikariDataSource.class)@ConditionalOnMissingBean(DataSource.class)@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "com.zaxxer.hikari.HikariDataSource",matchIfMissing = true)static class Hikari {@Bean@ConfigurationProperties(prefix = "spring.datasource.hikari")public HikariDataSource dataSource(DataSourceProperties properties) {HikariDataSource dataSource = createDataSource(properties, HikariDataSource.class);if (StringUtils.hasText(properties.getName())) {dataSource.setPoolName(properties.getName());}return dataSource;}}// 也可以指定其他的数据源@Configuration@ConditionalOnClass(org.apache.commons.dbcp2.BasicDataSource.class)@ConditionalOnMissingBean(DataSource.class)@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.commons.dbcp2.BasicDataSource",matchIfMissing = true)static class Dbcp2 {@Bean@ConfigurationProperties(prefix = "spring.datasource.dbcp2")public org.apache.commons.dbcp2.BasicDataSource dataSource(DataSourceProperties properties) {return createDataSource(properties, org.apache.commons.dbcp2.BasicDataSource.class);}}@Configuration@ConditionalOnMissingBean(DataSource.class)@ConditionalOnProperty(name = "spring.datasource.type")static class Generic {@Beanpublic DataSource dataSource(DataSourceProperties properties) {// 使用DataSourceBuilder创建数据源，利用反射创建响应type的数据源，并且绑定相关属性return properties.initializeDataSourceBuilder().build();}}}

从代码中可以看出SpringBoot是根据用户的配置来自动配置不同的数据源，目前支持的数据源有以下三种

com.zaxxer.hikari.HikariDataSource （Spring Boot 2.0 以上，默认使用此数据源）org.apache.tomcat.jdbc.pool.DataSourceorg.apache.commons.dbcp2.BasicDataSource

还可以在配置文件中使用 “spring.datasource.type” 属性来配置用户指定的数据源

在同一个包下的另一个类 DataSourceInitializer，当我们要在SpringBoot启动时运行sql建表语句或插入数据时就会用得上

// DataSourceInitializer类部分代码public boolean createSchema() {List<Resource> scripts = getScripts("spring.datasource.schema", this.properties.getSchema(), "schema");if (!scripts.isEmpty()) {if (!isEnabled()) {logger.debug("Initialization disabled (not running DDL scripts)");return false;}String username = this.properties.getSchemaUsername();String password = this.properties.getSchemaPassword();runScripts(scripts, username, password);}return !scripts.isEmpty();}public void initSchema() {List<Resource> scripts = getScripts("spring.datasource.data", this.properties.getData(), "data");if (!scripts.isEmpty()) {if (!isEnabled()) {logger.debug("Initialization disabled (not running data scripts)");return;}String username = this.properties.getDataUsername();String password = this.properties.getDataPassword();runScripts(scripts, username, password);}}private void runScripts(List<Resource> resources, String username, String password) {if (resources.isEmpty()) {return;}ResourceDatabasePopulator populator = new ResourceDatabasePopulator();populator.setContinueOnError(this.properties.isContinueOnError());populator.setSeparator(this.properties.getSeparator());if (this.properties.getSqlScriptEncoding() != null) {populator.setSqlScriptEncoding(this.properties.getSqlScriptEncoding().name());}for (Resource resource : resources) {populator.addScript(resource);}DataSource dataSource = this.dataSource;if (StringUtils.hasText(username) && StringUtils.hasText(password)) {dataSource = DataSourceBuilder.create(this.properties.getClassLoader()).driverClassName(this.properties.determineDriverClassName()).url(this.properties.determineUrl()).username(username).password(password).build();}DatabasePopulatorUtils.execute(populator, dataSource);}