java - A question in druid-spring-boot-starter

Question

Post the code first

@Configuration
@ConditionalOnClass(com.alibaba.druid.pool.DruidDataSource.class)
@EnableConfigurationProperties(DruidStatProperties.class)
@Import({DruidSpringAopConfiguration.class,
         DruidStatViewServletConfiguration.class,
         DruidWebStatFilterConfiguration.class})
public class DruidDataSourceAutoConfigure {

    @Bean
    @ConfigurationProperties("spring.datasource.druid")
    @ConditionalOnMissingBean
    public DataSource dataSource(Environment env) {
        DruidDataSource dataSource = DruidDataSourceBuilder.create().build();

        //if not found prefix 'spring.datasource.druid' settings,'spring.datasource' prefix settings will be used.
        if (dataSource.getUsername() == null) {
            dataSource.setUsername(env.getProperty("spring.datasource.username"));
        }
        if (dataSource.getPassword() == null) {
            dataSource.setPassword(env.getProperty("spring.datasource.password"));
        }
        if (dataSource.getUrl() == null) {
            dataSource.setUrl(env.getProperty("spring.datasource.url"));
        }
        if (dataSource.getDriverClassName() == null) {
            dataSource.setDriverClassName(env.getProperty("spring.datasource.driver-class-name"));
        }
        // set filters default value on StatViewServlet enabled.
        if (! "false".equals(env.getProperty("spring.datasource.druid.StatViewServlet.enabled"))) {
            try {
                dataSource.setFilters("stat");
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return dataSource;
    }
}

public class DruidDataSourceBuilder {

    private Map<String, String> properties = new HashMap<String, String>();

    public static DruidDataSourceBuilder create() {
        return new DruidDataSourceBuilder();
    }

    public DruidDataSource build() {
        DruidDataSource dataSource = new DruidDataSource();
        maybeGetDriverClassName();
        bind(dataSource);
        return dataSource;
    }

    //use spring boot relaxed binding by reflection config druid . detail see Spring Boot Reference Relaxed binding section.
    private void bind(DruidDataSource result) {
        MutablePropertyValues properties = new MutablePropertyValues(this.properties);
        new RelaxedDataBinder(result)
                .withAlias("url", "jdbcUrl")
                .withAlias("username", "user")
                .bind(properties);
    }

    private void maybeGetDriverClassName() {
        if (!this.properties.containsKey("driverClassName")
                && this.properties.containsKey("url")) {
            String url = this.properties.get("url");
            String driverClass = DatabaseDriver.fromJdbcUrl(url).getDriverClassName();
            this.properties.put("driverClassName", driverClass);
        }
    }
}

What I don’t understand is the maybeGetDriverClassName method of DruidDataSourceBuilder. Obviously, when the dataSource method in DruidDataSourceAutoConfigure is used in DruidDataSourceBuilder, the properties in DruidDataSourceBuilder have no attributes. In this case, isn’t the maybeGetDriverClassName method meaningless?
Another point is the if judgment in the dataSource method of DruidDataSourceAutoConfigure. The dataSource should not have injected attributes in the method. Isn't it meaningless to judge like this?

Answer 1

Maybe it’s to leave room for adding other properties to properties in the future.