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Preface

In business requirements, we need to connect two databases to process data, and we need to use dynamic data sources. By understanding the framework of mybatis, we plan to use subcontracting to distinguish between data sources.

Principle premise:

We all have four steps to use mybatis.

1: build SqlSessionFactory

2: get the sqlSession object through SqlSessionFactory

3: get the dynamic proxy object of Mapper through sqlSession object

4: get the return value by executing the dynamic proxy object

In fact, the Environment object in the Configuration object after clicking sqlSessionFactory binds our dataSource object.

Similarly, we found through debug that the mapper object after the dynamic proxy also holds the Configuration object and binds our connection information.

Conjecture

If you need to implement different data sources by subcontracting, you need to specify different sqlSessionFactroy for different mapper, and check the annotated source code of mapperScan.

By understanding annotations, we can specify the sqlSessionFactory object of the maper dynamic proxy object. As a result, basePackages can then use different sqlSessionFactory for different packages to implement different data sources for different packages.

Implementation 1: define two data sources

The two data sources are named bit ds01,ds02, which uses a database connection pool that is both druids. For brief introduction, the detailed configuration is not shown.

2: define two SqlSessionFactory

Define two sqlSessionFactory, each binding to two data sources.

3: different packages bind different sqlSessionFactory

Use @ MapperScan to specify the scanned package and notify the specified SqlSessionFactory

@ MapperScan (basePackages = "com.lenven.demo.dao.ds02", sqlSessionFactoryRef = "salveSqlSessionFactory") @ MapperScan (basePackages = "com.lenven.demo.dao.ds01", sqlSessionFactoryRef = "masterSqlSessionFactory") 4: test

The mapper tests of two different packages can query the data correctly.

Expand:

By implementing

AbstractRoutingDataSource can also implement dynamic data sources.

This class implements the interface of DataSource, and can be configured for each data source in the

@ Nullable private Map resolvedDataSources

In this attribute.

Let's get the key of the data source we need to use by exposing a determineCurrentLookupKey. But we need to pay attention to the problem of affairs.

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