問題描述

先貼代碼

@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);} }}

不理解的地方在DruidDataSourceBuilder的maybeGetDriverClassName方法，顯然DruidDataSourceAutoConfigure中的方法dataSource在使用DruidDataSourceBuilder的時候，DruidDataSourceBuilder中的properties是沒有屬性的，這樣的話maybeGetDriverClassName方法不是沒有意義嗎？還有一點是DruidDataSourceAutoConfigure的dataSource方法中的if判斷，在方法中dataSource應該還沒注入屬性吧，這樣判斷不是也沒意義？

問題解答

可能是為以后 properties 里面添加其他屬性留余地吧。