多数据源Invalid bound statement not found

多数据源Invalid bound statement not found是由于在集成mybatis-plus时，Mapper生成的代理类存在，但是调用BaseMapper中如selectById()方法报错所导致的。这个错误通常是由于mybatis-plus的MapperScannerConfigurer扫描到了多个Mapper接口，导致生成的代理类出现了冲突，从而无法正确绑定Mapper接口中的SQL语句。

解决这个问题的方法是在配置MapperScannerConfigurer时，指定不同的basePackage，以避免扫描到重复的Mapper接口。同时，还需要在配置文件中指定每个数据源对应的Mapper接口所在的位置，以确保mybatis-plus能够正确地生成代理类并绑定SQL语句。

以下是解决这个问题的步骤：

1.在配置文件中指定每个数据源对应的Mapper接口所在的位置，例如：

mybatis-plus:
  mapper-locations:
    - classpath*:mapper/*.xml
  configuration:
    map-underscore-to-camel-case: true
  global-config:
    db-config:
      id-type: auto
  type-aliases-package: com.example.demo.entity

datasource:
  master:
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
  slave:
    url: jdbc:mysql://localhost:3306/test2?useUnicode=true&characterEncoding=utf-8&useSSL=false
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver

mybatis:
  mapper-locations: classpath*:mapper/*.xml

2.在配置MapperScannerConfigurer时，指定不同的basePackage，例如：

@Configuration
@MapperScan(basePackages = "com.example.demo.mapper.master", sqlSessionTemplateRef = "masterSqlSessionTemplate")
public class MasterDataSourceConfig {
    @Bean(name = "masterDataSource")
    @ConfigurationProperties(prefix = "datasource.master")
    public DataSource dataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "masterSqlSessionFactory")
    public SqlSessionFactory sqlSessionFactory(@Qualifier("masterDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath*:mapper/master/*.xml"));
        return bean.getObject();
    }

    @Bean(name = "masterTransactionManager")
    public DataSourceTransactionManager transactionManager(@Qualifier("masterDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "masterSqlSessionTemplate")
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("masterSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

@Configuration
@MapperScan(basePackages = "com.example.demo.mapper.slave", sqlSessionTemplateRef = "slaveSqlSessionTemplate")
public class SlaveDataSourceConfig {
    @Bean(name = "slaveDataSource")
    @ConfigurationProperties(prefix = "datasource.slave")
    public DataSource dataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "slaveSqlSessionFactory")
    public SqlSessionFactory sqlSessionFactory(@Qualifier("slaveDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath*:mapper/slave/*.xml"));
        return bean.getObject();
    }

    @Bean(name = "slaveTransactionManager")
    public DataSourceTransactionManager transactionManager(@Qualifier("slaveDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "slaveSqlSessionTemplate")
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("slaveSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

3.在Mapper接口中使用@Mapper注解，例如：

@Mapper
public interface UserMapper extends BaseMapper<User> {
}