ShardingSphere-JDBC 关键字问题

使用sharding 的时候，遇到了两个问题。记录下：

1 配置问题：

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'shardingDataSource' defined in class path resource [org/apache/shardingsphere/shardingjdbc/spring/boot/SpringBootConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [javax.sql.DataSource]: Factory method 'shardingDataSource' threw exception; nested exception is java.lang.NullPointerException
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:627)
	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:456)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1321)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1160)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515)
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199)
	at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:277)

使用的springboot+mybatis+yaml 配置。版本是4.1.1

这不是常见的没有配置sharding数据源导致empty的错误。

dataSources:
  ds0: !!org.apache.commons.dbcp.BasicDataSource
    driverClassName: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/ds0
    username: root
    password: 

还需要增加type属性：

type: com.alibaba.druid.pool.DruidDataSource

关于sharding 对照官网的手册。

Yaml配置 :: ShardingSphere

我是写错了。我只写了分表算法的名称，

正确的是：

preciseAlgorithmClassName 对应的是类名，注意yaml的缩进

二 关键词错误

如果字段用了order, mutex等mysql 关键词。会导致查询时SQL 解析异常，或者更新时空指针异常等。

这里得到的提示就是，假设一个老库一堆表，只对个别表进行分表。引入sharding后虽然指定了分表的bindingTables，其余的走default-data-source 就是默认不分表的。

但是sharding会接管数据源，老表用默认的mybatis  正常，sharding 可能会报错。