20、Springboot 与数据访问（JDBC/自动配置）

spring:
  datasource:
    username: root
    password: 1234
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/users?serverTimezone=GMT

@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"
    )
    public HikariDataSource dataSource(DataSourceProperties properties) {
        HikariDataSource dataSource = (HikariDataSource)DataSourceConfiguration.createDataSource(properties, HikariDataSource.class);
        if (StringUtils.hasText(properties.getName())) {
            dataSource.setPoolName(properties.getName());
        }

        return dataSource;
    }
}

@ConditionalOnMissingBean({DataSource.class})
@ConditionalOnProperty(
    name = {"spring.datasource.type"}
)
static class Generic {
    Generic() {
    }

    @Bean
    public 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();
    }
}

private List<Resource> getScripts(String propertyName, List<String> resources, String fallback) {
    if (resources != null) {
        return this.getResources(propertyName, resources, true);
    } else {
        String platform = this.properties.getPlatform();
        List<String> fallbackResources = new ArrayList();
        fallbackResources.add("classpath*:" + fallback + "-" + platform + ".sql");
        fallbackResources.add("classpath*:" + fallback + ".sql");
        return this.getResources(propertyName, fallbackResources, false);
    }
}

private void runScripts(List<Resource> resources, String username, String password) {
    if (!resources.isEmpty()) {
        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());
        }
        Iterator var5 = resources.iterator();

        while(var5.hasNext()) {
            Resource resource = (Resource)var5.next();
            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);
    }
}

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/users?serverTimezone=GMT
spring.datasource.username=root
spring.datasource.password=1234
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.schema=classpath:/dept.sql
spring.datasource.initialization-mode=always

@Configuration
@ConditionalOnClass({DataSource.class, JdbcTemplate.class})
@ConditionalOnSingleCandidate(DataSource.class)
@AutoConfigureAfter({DataSourceAutoConfiguration.class})
@EnableConfigurationProperties({JdbcProperties.class})
public class JdbcTemplateAutoConfiguration {
    public JdbcTemplateAutoConfiguration() {
    }

    @Configuration
    @Import({JdbcTemplateAutoConfiguration.JdbcTemplateConfiguration.class})
    static class NamedParameterJdbcTemplateConfiguration {
        NamedParameterJdbcTemplateConfiguration() {
        }

        @Bean
        @Primary
        @ConditionalOnSingleCandidate(JdbcTemplate.class)
        @ConditionalOnMissingBean({NamedParameterJdbcOperations.class})
        public NamedParameterJdbcTemplate namedParameterJdbcTemplate(JdbcTemplate jdbcTemplate) {
            return new NamedParameterJdbcTemplate(jdbcTemplate);
        }
    }

    @Configuration
    static class JdbcTemplateConfiguration {
        private final DataSource dataSource;
        private final JdbcProperties properties;

        JdbcTemplateConfiguration(DataSource dataSource, JdbcProperties properties) {
            this.dataSource = dataSource;
            this.properties = properties;
        }

        @Bean
        @Primary
        @ConditionalOnMissingBean({JdbcOperations.class})
        public JdbcTemplate jdbcTemplate() {
            JdbcTemplate jdbcTemplate = new JdbcTemplate(this.dataSource);
            Template template = this.properties.getTemplate();
            jdbcTemplate.setFetchSize(template.getFetchSize());
            jdbcTemplate.setMaxRows(template.getMaxRows());
            if (template.getQueryTimeout() != null) {
                jdbcTemplate.setQueryTimeout((int)template.getQueryTimeout().getSeconds());
            }

            return jdbcTemplate;
        }
    }
}