我想出了一个适合我的解决方案，所以我想在这里分享一下。使用 Guice 的决定已经做出，所以没有回旋的余地。
首先，我编写了一个 MyBatis Guice 模块来注册单个数据源。它是一个PrivateModule，这样所有为一个数据源注册的 MyBatis 类不会与其他数据源的其他注册冲突。它使用了内部的 MyBatisModule 实现，因为 Java 不支持多重继承。这意味着我们不能做public class MyMyBatisModule extends PrivateModule, MyBatisModule {...}。
public class MyMyBatisModule extends PrivateModule {
private final String datasourceLabel;
private final Properies datasourceProperties;
private List< Key<?> > exposedKeys = new ArrayList< Key<?> >();
public MyMyBatisModule( String datasourceLabel, Properties datasourceProperties ) {
this.datasourceLabel = datasourceLabel;
this.datasourceProperties = datasourceProperties;
}
@Override
protected void configure() {
install( new InternalMyMyBatisModule( ) );
for( Key<?> key: keys ) {
expose( key );
}
}
private class InternalMyMyBatisModule extends MyBatisModule {
@Override
protected void initialize( ) {
environmentId( datasourceLabel );
Names.bindProperties( binder(), properties );
install( JdbcHelper.MySQL ); // See JDBC Helper commentary below
bindDataSourceProviderType( C3p0DataSourceProvider.class ); // Choose whichever one you want
bindTransactionFactoryType( JdbcTransactionFactory.class );
// Register your mapper classes here. These mapper classes will have their
// keys exposed from the PrivateModule
//
// i.e.
//
// keys.add( registerMapper( FredMapper.class );
// kets.add( registerMapper( GingerMapper.class );
}
private <T> Key<T> registerMapper( Class<T> mapperClass ) {
Key<T> key = Key.get( mapperClass, Names.named( datasourceLabel ) );
bind( key ).to( mapperClass );
addMapperClass( mapperClass );
return key;
}
}
}
JdbcHeler.MySQL：我使用JdbcHelper.MySQL 作为将属性映射到连接字符串的快捷方式，并使用com.mysql.jdbc.Driver 作为 JDBC 驱动程序。它被声明为：
MySQL("jdbc:mysql://${JDBC.host|localhost}:${JDBC.port|3306}/${JDBC.schema}", "com.mysql.jdbc.Driver"),
现在是注册所有数据源的时候了。 MyBatisModules 为我们处理这个问题。它需要一个 datasourceLabel 到 jdbc 属性的映射。
public class MyBatisModules extends AbstractModule {
private Map< String, Properties > connectionsProperties;
public MyBatisModules( Map< String, Properties > = new HashMap< String, Properties > connectionsProperties ) {
this.connectionsProperties = connectionsProperties; // consider deep copy if appropriate
}
@Override
protected void configure( ) {
for( Entry< String, Properties > datasourceConnectionProperties : this.connectionsProperties.entrySet() ) {
install( new MyMyBatisModule( datasourceConnectionProperties.getKey(), datasourceConnectionProperties.getValue() ) );
}
bind( MapperRetriever.class ); // See MapperRetriever later
// bind your DAO classes here. By wrapping MyBatis Mapper use in DAO implementations, theoretically we
// can fairly easily change from MyBatis to any other database library just by changing the DAO implementation.
// The rest of our codebase would remain the same.
//
// i.e.
//
// bind( FredDao.class ).to( FredDaoMyBatis.class );
// bind( GingerDao.class).to( GingerDaoMyBatis.class );
}
}
现在我们只需要某种方法来获取正确的 Mapper 类（它本身与正确的数据源相关联）。为此，我们实际上需要调用 Guice Injector 上的方法。我不太喜欢传递它的想法，所以我将它包裹在MapperRetriever 中。您需要为每个Mappers 实现一个检索方法。
public class MapperRetriever {
private final Injector injector;
@Inject
public MapperRetriver( Injector injector ) {
this.injector = injector;
}
// The follwing two methods use the example Mappers referenced in the MyMyBatisModule implementation above
public FredMapper getFredMapper( String datasourceLabel ) {
return this.injector.getInstance( Key.get( FredMapper.class, Names.named( datasourceLabel ) ) );
}
public GingerMapper getGingerMapper( String datasourceLabel ) {
return this.injector.getInstance( Key.get( GingerMapper.class, Names.named( datasourceLabel ) ) );
}
}
还有一个示例 DAO 实现 ...
public interface FredDao {
Fred selectFred( String datasourceLable, String fredId );
}
public class FredDaoMyBatis implements FredDao {
private MapperRetriever mapperRetriever;
@Inject
public FredDaoMyBatis( MapperRetriever mapperRetriever ) {
this.mapperRetriever = mapperRetriever;
}
@Override
public Fred selectFred( String datasourceLabel, String fredId ) {
FredMapper fredMapper = this.mapperRetriever.getFredMapper( datasourceLabel );
return fredMapper.getFred( fredId );
}
}