SpringBoot DataSource数据源实现自动配置流程详解

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-jdbc</artifactId>
</dependency>

<properties>
	<mysql.version>5.1.49</mysql.version>
</properties>
...
<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
	<version>${mysql.version}</version>
</dependency>

@AutoConfiguration(
    before = {SqlInitializationAutoConfiguration.class}
)
@ConditionalOnClass({DataSource.class, EmbeddedDatabaseType.class})
@ConditionalOnMissingBean(
    type = {"io.r2dbc.spi.ConnectionFactory"}
)
@EnableConfigurationProperties({DataSourceProperties.class})
@Import({DataSourcePoolMetadataProvidersConfiguration.class})
public class DataSourceAutoConfiguration {
    public DataSourceAutoConfiguration() {
    }
    ...

@ConfigurationProperties(
    prefix = "spring.datasource"
)
public class DataSourceProperties implements BeanClassLoaderAware, InitializingBean {
    private ClassLoader classLoader;
    private boolean generateUniqueName = true;
    private String name;
    private Class<? extends DataSource> type;
    private String driverClassName;
    private String url;
    private String username;
    private String password;
    private String jndiName;
    private EmbeddedDatabaseConnection embeddedDatabaseConnection;
    private DataSourceProperties.Xa xa = new DataSourceProperties.Xa();
    private String uniqueName;
    ...

@Configuration(
    proxyBeanMethods = false
)
@Conditional({DataSourceAutoConfiguration.PooledDataSourceCondition.class})
@ConditionalOnMissingBean({DataSource.class, XADataSource.class})
@Import({Hikari.class, Tomcat.class, Dbcp2.class, OracleUcp.class, Generic.class, DataSourceJmxConfiguration.class})
protected static class PooledDataSourceConfiguration {
    protected PooledDataSourceConfiguration() {
    }
}

@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnClass({HikariDataSource.class})
@ConditionalOnMissingBean({DataSource.class})
@ConditionalOnProperty(
    name = {"spring.datasource.type"},
    havingValue = "com.zaxxer.hikari.HikariDataSource",
    matchIfMissing = true
)
static class Hikari {
    Hikari() {
    }
    @Bean
    @ConfigurationProperties(
        prefix = "spring.datasource.hikari"
    )
    HikariDataSource dataSource(DataSourceProperties properties) {
        HikariDataSource dataSource = (HikariDataSource)DataSourceConfiguration.createDataSource(properties, HikariDataSource.class);
        if (StringUtils.hasText(properties.getName())) {
            dataSource.setPoolName(properties.getName());
        }
        return dataSource;
    }
}

@AutoConfiguration(
    after = {DataSourceAutoConfiguration.class}
)
@ConditionalOnClass({DataSource.class, JdbcTemplate.class})
@ConditionalOnSingleCandidate(DataSource.class)
@EnableConfigurationProperties({JdbcProperties.class})
@Import({DatabaseInitializationDependencyConfigurer.class, JdbcTemplateConfiguration.class, NamedParameterJdbcTemplateConfiguration.class})
public class JdbcTemplateAutoConfiguration {
    public JdbcTemplateAutoConfiguration() {
    }
}

@ConfigurationProperties(
    prefix = "spring.jdbc"
)
public class JdbcProperties {
    private final JdbcProperties.Template template = new JdbcProperties.Template();
    public JdbcProperties() {
    }
    public JdbcProperties.Template getTemplate() {
        return this.template;
    }

@Configuration(
    proxyBeanMethods = false
)
@ConditionalOnMissingBean({JdbcOperations.class})
class JdbcTemplateConfiguration {
    JdbcTemplateConfiguration() {
    }
    @Bean
    @Primary
    JdbcTemplate jdbcTemplate(DataSource dataSource, JdbcProperties properties) {
        JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
        Template template = properties.getTemplate();
        jdbcTemplate.setFetchSize(template.getFetchSize());
        jdbcTemplate.setMaxRows(template.getMaxRows());
        if (template.getQueryTimeout() != null) {
            jdbcTemplate.setQueryTimeout((int)template.getQueryTimeout().getSeconds());
        }
        return jdbcTemplate;
    }
}

package com.decade;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.jdbc.core.JdbcTemplate;
@SpringBootTest
@Slf4j
class SpringbootWebApplicationTests {
    @Autowired
    private JdbcTemplate jdbcTemplate;
    @Test
    void contextLoads() {
        final Long count = jdbcTemplate.queryForObject("select count(*) from t_decade_user", Long.class);
        log.info("该表中数据总数为{}", count);
    }
}