spring-boot integrate with mybatis

Add below pom dependency

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <artifactId>1.0.14</artifactId>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.2.8</version>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>1.2.2</version>
</dependency>

We can use below tool to generate the mybatis code
https://github.com/spawpaw/mybatis-generator-gui-extension

Configure the datasource

spring.datasource.type=com.alibaba.druid.pool.DruidDataSource  
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/flux?useUnicode=true&characterEncoding=utf-8&useOldAliasMetadataBehavior=true
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

druid.spring.datasource.initialSize=5  
druid.spring.datasource.minIdle=5  
druid.spring.datasource.maxActive=20  
druid.spring.datasource.maxWait=60000  
druid.spring.datasource.timeBetweenEvictionRunsMillis=60000  
druid.spring.datasource.minEvictableIdleTimeMillis=300000  
druid.spring.datasource.validationQuery=SELECT 1 FROM DUAL  
druid.spring.datasource.testWhileIdle=true  
druid.spring.datasource.testOnBorrow=false  
druid.spring.datasource.testOnReturn=false  
druid.spring.datasource.poolPreparedStatements=false  
druid.spring.datasource.maxPoolPreparedStatementPerConnectionSize=20  
druid.spring.datasource.filters=stat,wall,log4j  
druid.spring.datasource.connectionProperties=druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000

@Configuration
@MapperScan(basePackages="<the mapper interface class package path>")
public class MyBatisConfigure {

    // you can use this env to get the properties from application.properties
    // e.g. dbUrl : env.getProperty("spring.datasource.url");
    @AutoWried
    private Environment env;
    // configure datasource
    @Bean
    public DataSource dataSource() throws Exception {
            DruidDataSource datasource = new DruidDataSource();
            datasource.setUrl(dbUrl);
            datasource.setUsername(username);
            datasource.setPassword(password);
            datasource.setDriverClassName(driverClassName);
            // configuration
            datasource.setInitialSize(initialSize);
            datasource.setMinIdle(minIdle);
            datasource.setMaxActive(maxActive);
            datasource.setMaxWait(maxWait);
            datasource.setTimeBetweenEvictionRunsMillis(timeBetweenEvictionRunsMillis);
            datasource.setMinEvictableIdleTimeMillis(minEvictableIdleTimeMillis);
            datasource.setValidationQuery(validationQuery);
            datasource.setTestWhileIdle(testWhileIdle);
            datasource.setTestOnBorrow(testOnBorrow);
            datasource.setTestOnReturn(testOnReturn);
            datasource.setPoolPreparedStatements(poolPreparedStatements);
            datasource.setMaxPoolPreparedStatementPerConnectionSize(maxPoolPreparedStatementPerConnectionSize);
            datasource.setFilters(filters);
            datasource.setConnectionProperties(connectionProperties);
            return datasource;
        }
    // configure SqlSessionFactory
    @Bean
    public SqlSessionFactory sqlSessionFactory(DataSrouce ds) throws Exception {
        SqlSessionFactory fb = new SqlSessionFactoryBean();
        fb.setDataSrouce(ds);
        fb.setTypeAliasesPackage("<the domain model POJO package path>");
        fb.setMapperLocations(new PathMatchingResourcesPatternResolver().getResources("classpath:<path>/*.xml"));
        return fb.getObject();
    }
}

Configure another datasource

public enum DatabaseType {
    DRUID_DS1,DRUID_DS2
}

public class DatabaseContextHolder {
    // each thread holds its own specific datasource
    private static final ThreadLocal<DatabaseType> contextHolder = new ThreadLocal<>();

    public static void setDatabaseType(DatabaseType type) {
        contextHolder.set(type);
    }

    public static DatabaseType getDatabaseType() {
        return contextHolder.get();
    }
}

public class DynamicDataSource extends AbstractRoutingDataSource() {
    protected Object determineCurrentLookupKey() {
        return DatabaseContextHolder.getDatasourceType();
    }
}

Refactor the MyBatisConfigure

@Bean
public DataSource druidDataSource1() throws Exception {
    // TODO
}
@Bean
public DataSource druidDataSource2() throws Exception {
    // TODO
}
@Bean
@Primary
public DynamicDataSource dataSource(@Qualifier("druidDataSource1") DataSource druidDataSource1,@Qualifier("druidDataSource2") DataSource druidDataSource2) {
    Map<Object, Object> targetDataSource = new HashMap<>();
    targetDataSource.put(DatabaseType.DRUID_DS1, druidDataSource1);
    targetDataSource.put(DatabaseType.DRUID_DS2, druidDataSource2);
    DynamicDataSource dataSource = new DynamicDataSource();
    dataSource.setTargetDataSources(targetDataSource);
    dataSource.setDefaultTargetDataSource(druidDataSource1);
    return dataSource;
}
@Bean
public SqlSessionFactory sqlSessionFactory(DynamicDataSource ds) throws Exception {
    // TODO
}

If you want use druidDataSource2 to query data, you need write the code like below:

@Repository
public class UserDAO {
    @Autowired
    private UserMapper userMapper;
    public List<User> selectById(long uid) {
        // choose the data source before query
        DatabaseContextHolder.setDatabaseType(DatabaseType.DRUID_DS2);
        // TODO
    }
}

or create an aspect class to set the datasource:

@Aspect
@Component
public class DataSourceAspect() {
    @Before("execution(* <DAO package path>.*.*(..))")
    public void setDataSourceKey(JoinPoint point) {
        if (point.getTarget() instanceof UserDAO) {
             DatabaseContextHolder.setDatabaseType(DatabaseType.DRUID_DS2);
        }
    }
}

Reference

《Java微服务实战》- 赵计刚