Sharding-JDBC TableRule(四)

private final Collection<TableRule> tableRules;

public ShardingRule(final ShardingRuleConfiguration shardingRuleConfig, final Collection<String> dataSourceNames) {
	// ... ...
	// ******************************************************
	// 4. 
	//    4.1. 解析:ShardingRuleConfiguration.Collection<TableRuleConfiguration> 
	//    4.2. 转换成:Collection<TableRule>
	// ******************************************************
	tableRules = createTableRules(shardingRuleConfig);
	// ... ...
}

private Collection<TableRule> createTableRules(final ShardingRuleConfiguration shardingRuleConfig) {
	// 4.1 遍历:shardingRuleConfig.getTableRuleConfigs()
	return shardingRuleConfig.getTableRuleConfigs()
		 .stream()
		 // 把TableRuleConfiguration转换成:TableRule
		 .map(each -> new TableRule(each, shardingDataSourceNames, getDefaultGenerateKeyColumn(shardingRuleConfig)))
		 .collect(Collectors.toList());
}

public TableRule(final TableRuleConfiguration tableRuleConfig, final ShardingDataSourceNames shardingDataSourceNames, final String defaultGenerateKeyColumn) {
	// 逻辑表名称
	logicTable = tableRuleConfig.getLogicTable().toLowerCase();
	// 数据节点(这时,已经对表达式进行了解析)
	List<String> dataNodes = new InlineExpressionParser(tableRuleConfig.getActualDataNodes()).splitAndEvaluate();
	
	dataNodeIndexMap = new HashMap<>(dataNodes.size(), 1);
	actualDataNodes = isEmptyDataNodes(dataNodes)
		? generateDataNodes(tableRuleConfig.getLogicTable(), shardingDataSourceNames.getDataSourceNames()) : generateDataNodes(dataNodes, shardingDataSourceNames.getDataSourceNames());
	actualTables = getActualTables();
	
	// ************************************************************************************
	// 6. 通过ShardingStrategyFactory.newInstance,创建:ShardingStrategy
	//    这是典型的工厂模式
	// ************************************************************************************
	databaseShardingStrategy = 
	            (null == tableRuleConfig.getDatabaseShardingStrategyConfig()) ? 
				null : 
				// 
				ShardingStrategyFactory.newInstance(tableRuleConfig.getDatabaseShardingStrategyConfig());
	tableShardingStrategy = null == tableRuleConfig.getTableShardingStrategyConfig() ? null : ShardingStrategyFactory.newInstance(tableRuleConfig.getTableShardingStrategyConfig());
	final KeyGeneratorConfiguration keyGeneratorConfiguration = tableRuleConfig.getKeyGeneratorConfig();
	generateKeyColumn = null != keyGeneratorConfiguration && !Strings.isNullOrEmpty(keyGeneratorConfiguration.getColumn()) ? keyGeneratorConfiguration.getColumn() : defaultGenerateKeyColumn;
	
	// ************************************************************************************
	// 10. 通过:ShardingKeyGeneratorServiceLoader创建:ShardingKeyGenerator
	//     通过SPI来加载
	// ************************************************************************************
	shardingKeyGenerator = containsKeyGeneratorConfiguration(tableRuleConfig)
			? new ShardingKeyGeneratorServiceLoader().newService(tableRuleConfig.getKeyGeneratorConfig().getType(), tableRuleConfig.getKeyGeneratorConfig().getProperties()) : null;
	checkRule(dataNodes);
}

public static ShardingStrategy newInstance(final ShardingStrategyConfiguration shardingStrategyConfig) {
	if (shardingStrategyConfig instanceof StandardShardingStrategyConfiguration) {
		// 精确分片算法
		return new StandardShardingStrategy((StandardShardingStrategyConfiguration) shardingStrategyConfig);
	}
	if (shardingStrategyConfig instanceof InlineShardingStrategyConfiguration) {
		// Inline分片算法
		return new InlineShardingStrategy((InlineShardingStrategyConfiguration) shardingStrategyConfig);
	}
	if (shardingStrategyConfig instanceof ComplexShardingStrategyConfiguration) {
		// 复合分片算法
		return new ComplexShardingStrategy((ComplexShardingStrategyConfiguration) shardingStrategyConfig);
	}
	if (shardingStrategyConfig instanceof HintShardingStrategyConfiguration) {
		// Hint分片算法
		return new HintShardingStrategy((HintShardingStrategyConfiguration) shardingStrategyConfig);
	}
	// 不进行分片
	return new NoneShardingStrategy();
}

// **************************************YamlComplexShardingStrategyConfiguration**************************************
// 1. 对应的配置信息如下:  
// spring.shardingsphere.sharding.tables.t_order.database-strategy.complex.sharding-columns=user_id,order_id
// spring.shardingsphere.sharding.tables.t_order.database-strategy.complex.algorithm-class-name=help.lixin.CustomerComplexKeysShardingAlgorithm

public final class YamlComplexShardingStrategyConfiguration 
             implements YamlBaseShardingStrategyConfiguration {
	// 分片columns,多个之间用逗号隔开			 
    private String shardingColumns;
	// 分片的算法名称(需要全名称)
    private String algorithmClassName;
} // end YamlComplexShardingStrategyConfiguration


// **************************************// ShardingStrategyConfigurationYamlSwapper**************************************
// 2. help.lixin.CustomerComplexKeysShardingAlgorithm加载时机.
public ShardingStrategyConfiguration swap(final YamlShardingStrategyConfiguration yamlConfiguration) {
	// ... ...
	if (null != yamlConfiguration.getComplex()) {
		shardingStrategyConfigCount++;
		result = new ComplexShardingStrategyConfiguration(
		        yamlConfiguration.getComplex().getShardingColumns(), 
				// *****************************************************************
				// Class.forName(shardingAlgorithmClassName);
				// 通过反射加载自定义的分片算法来着的.
				// *****************************************************************
				ShardingAlgorithmFactory.newInstance(yamlConfiguration.getComplex().getAlgorithmClassName(),ComplexKeysShardingAlgorithm.class));
	}
	// ... ...
	Preconditions.checkArgument(shardingStrategyConfigCount <= 1, "Only allowed 0 or 1 sharding strategy configuration.");
	return result;
}

public final class ShardingKeyGeneratorServiceLoader 
            extends TypeBasedSPIServiceLoader<ShardingKeyGenerator> {
    static {
		// 1. 通过SPI,加载:ShardingKeyGenerator的所有实现
        NewInstanceServiceLoader.register(ShardingKeyGenerator.class);
    }
    
    public ShardingKeyGeneratorServiceLoader() {
		// 2. 定义要加载的类型为:ShardingKeyGenerator
        super(ShardingKeyGenerator.class);
    }
} //end ShardingKeyGeneratorServiceLoader

public abstract class TypeBasedSPIServiceLoader<T extends TypeBasedSPI> {
	// ShardingKeyGenerator
    private final Class<T> classType;
	
	public final T newService(final String type, final Properties props) {
		// type = "SNOWFLAKE"
		// 1. loadTypeBasedServices
		Collection<T> typeBasedServices = loadTypeBasedServices(type);
		if (typeBasedServices.isEmpty()) {
			throw new RuntimeException(String.format("Invalid `%s` SPI type `%s`.", classType.getName(), type));
		}
		T result = typeBasedServices.iterator().next();
		result.setProperties(props);
		return result;
	} // end newService
	
	private Collection<T> loadTypeBasedServices(final String type) {
		// 4. 加载:ShardingKeyGenerator的所有实现,并获取实例中:getType() == SNOWFLAKE的ShardingKeyGenerator对象
		return Collections2.filter(
			// 2. 加载:ShardingKeyGenerator的所有实现类,并进行实例化.
			NewInstanceServiceLoader.newServiceInstances(classType), 
			// 3. 所有:ShardingKeyGenerator的实现类,都要实现:getType()方法
			input -> type.equalsIgnoreCase(input.getType()));
	} // end loadTypeBasedServices
}