DataSourceBuilder 类分析

从分析DataSourceBuilder类来了解spring boot 的数据源配置.
org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder.java
源码贴这 有空再看

/**
 * Convenience class for building a {@link DataSource} with common implementations and
 * properties. If Tomcat, HikariCP or Commons DBCP are on the classpath one of them will
 * be selected (in that order with Tomcat first). In the interest of a uniform interface,
 * and so that there can be a fallback to an embedded database if one can be detected on
 * the classpath, only a small set of common configuration properties are supported. To
 * inject additional properties into the result you can downcast it, or use
 * {@code @ConfigurationProperties}.
 *
 * @author Dave Syer
 * @since 1.1.0
 */
public class DataSourceBuilder {

    private static final String[] DATA_SOURCE_TYPE_NAMES = new String[] {
            "org.apache.tomcat.jdbc.pool.DataSource",
            "com.zaxxer.hikari.HikariDataSource",
            "org.apache.commons.dbcp.BasicDataSource", // deprecated
            "org.apache.commons.dbcp2.BasicDataSource" };

    private Class<? extends DataSource> type;

    private ClassLoader classLoader;

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

    public static DataSourceBuilder create() {
        return new DataSourceBuilder(null);
    }

    public static DataSourceBuilder create(ClassLoader classLoader) {
        return new DataSourceBuilder(classLoader);
    }

    public DataSourceBuilder(ClassLoader classLoader) {
        this.classLoader = classLoader;
    }
    //构建数据源
    public DataSource build() {
       //返回数据源的类 类型
        Class<? extends DataSource> type = getType();
       //实例化这个数据源
        DataSource result = BeanUtils.instantiate(type);
       //向读取配置文件中的 driverClassName  
        maybeGetDriverClassName();
       // tm的我猜是将配置属性绑定到数据源上
        bind(result);
        return result;
    }

    private void maybeGetDriverClassName() {
        //如果this.properties不存在driverClassName 并且存在url
        if (!this.properties.containsKey("driverClassName")
                && this.properties.containsKey("url")) {
            String url = this.properties.get("url");

         //根据url 获取 DateBaseDriver 进一步获取到 驱动名 这就是为什么不配置驱动名也可以加载驱动的原因吧,通过url来判断驱动类型
            String driverClass = DatabaseDriver.fromJdbcUrl(url).getDriverClassName();
            this.properties.put("driverClassName", driverClass);
        }
    }
  //?
    private void bind(DataSource result) {
        MutablePropertyValues properties = new MutablePropertyValues(this.properties);
        new RelaxedDataBinder(result).withAlias("url", "jdbcUrl")
                .withAlias("username", "user").bind(properties);
    }

    public DataSourceBuilder type(Class<? extends DataSource> type) {
        this.type = type;
        return this;
    }

    public DataSourceBuilder url(String url) {
        this.properties.put("url", url);
        return this;
    }

    public DataSourceBuilder driverClassName(String driverClassName) {
        this.properties.put("driverClassName", driverClassName);
        return this;
    }

    public DataSourceBuilder username(String username) {
        this.properties.put("username", username);
        return this;
    }

    public DataSourceBuilder password(String password) {
        this.properties.put("password", password);
        return this;
    }

    @SuppressWarnings("unchecked")
    public Class<? extends DataSource> findType() {
        if (this.type != null) {
            return this.type;
        }
        for (String name : DATA_SOURCE_TYPE_NAMES) {
            try {
                return (Class<? extends DataSource>) ClassUtils.forName(name,
                        this.classLoader);
            }
            catch (Exception ex) {
                // Swallow and continue
            }
        }
        return null;
    }
    
    private Class<? extends DataSource> getType() {
        Class<? extends DataSource> type = findType();
        if (type != null) {
            return type;
        }
        throw new IllegalStateException("No supported DataSource type found");
    }

}

//@ConfigurationProperties