原文地址：https://blog.csdn.net/tengxing007/article/details/78424645

前言

在開發過程中可能需要用到多個數據源，比如一個專案（MySQL）就是和（SQL Server）混合使用，就需要使用多資料來源；如果業務場景比較復炸，可以使用動態資料來源，靈活切換，典型的應用就是讀寫分離。下面分兩個模組來配置資料來源，大家可以根據自己實際情況配置。

多資料來源

禁用DataSourceAutoConfiguration

如果DataSourceAutoConfiguration不禁用的話，就會報錯，多個數據源，無法裝配哪一個。在springBoot的主程式入口的註解

@SpringBootApplication
 
(exclude = {
        DataSourceAutoConfiguration.class
})

• 配置application.properties

#datasource 這是自動裝配的預設配置禁止，這裡不能使用
#spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
#spring.datasource.driver-class-name=com.mysql.jdbc.Driver
#spring.datasource.url=jdbc:mysql://127.0.0.1:3306/api_resources?#autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
 

#spring.datasource.username=api
#spring.datasource.password=api
#db1
spring.datasource.db1.url=jdbc:mysql://127.0.0.1:3306/api_resources?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
spring.datasource.db1.username=api
spring.datasource.db1.password=api
spring.datasource
 
.db1.driver-class-name=com.mysql.jdbc.Driver
#db2
spring.datasource.db2.url=jdbc:mysql://127.0.0.1:3306/ssm?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true
spring.datasource.db2.username=api
spring.datasource.db2.password=api
spring.datasource.db2.driver-class-name=com.mysql.jdbc.Driver

配置dataSource

配置兩個資料來源，分別為db1，和db2

/**
 * Author: Starry.Teng
 * Email: [email protected]
 * Date: 17-11-1
 * Time: 下午9:14
 * Describe: DataSource Config
 */
@Configuration
public class DataSourceConfig {
    @Autowired
    Environment env;

    @Bean(name = "ds1")
    public DataSource dataSource1() {
        DruidDataSource dataSource = new DruidDataSource();

        dataSource.setUrl(env.getProperty("spring.datasource.db1.url"));
        dataSource.setUsername(env.getProperty("spring.datasource.db1.username"));
        dataSource.setPassword(env.getProperty("spring.datasource.db1.password"));
        dataSource.setDriverClassName(env.getProperty("spring.datasource.db1.driver-class-name"));
        return dataSource;
    }

    @Bean(name = "ds2")
    public DataSource dataSource2() {
        DruidDataSource dataSource = new DruidDataSource();

        dataSource.setUrl(env.getProperty("spring.datasource.db2.url"));
        dataSource.setUsername(env.getProperty("spring.datasource.db2.username"));
        dataSource.setPassword(env.getProperty("spring.datasource.db2.password"));
        dataSource.setDriverClassName(env.getProperty("spring.datasource.db2.driver-class-name"));
        return dataSource;
    }

}

Mybatis配置

為兩個資料來源分貝配置一個MybatisDb1Config類和MybatisDb2Config類，對資料來源進行管理，注意他們所管理的包是不同的。

/**
 * Author: Starry.Teng
 * Email: [email protected]
 * Date: 17-11-1
 * Time: 下午9:15
 * Describe: MybatisDb1 Config
 */
@Configuration
@MapperScan(basePackages = {"cn.yjxxclub.demo.datasource.dao.db1"}, sqlSessionFactoryRef = "sqlSessionFactory1")
public class MybatisDb1Config {

    @Qualifier("ds1")
    @Autowired
    DataSource dataSource;

    @Bean(name = "sqlSessionFactory1")
    public SqlSessionFactory sqlSessionFactory1() throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource);
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        factoryBean.setMapperLocations(resolver.getResources("classpath:mappers/db1/*.xml"));
        factoryBean.setTypeAliasesPackage("cn.yjxxclub.demo.datasource.model");
        return factoryBean.getObject();

    }

    @Bean
    public SqlSessionTemplate sqlSessionTemplate1() throws Exception {
        SqlSessionTemplate template = new SqlSessionTemplate(sqlSessionFactory1()); // 使用上面配置的Factory
        return template;
    }
}

/**
 * Author: Starry.Teng
 * Email: [email protected]
 * Date: 17-11-1
 * Time: 下午9:26
 * Describe: MybatisDb2 Config
 */
@Configuration
@MapperScan(basePackages = {"cn.yjxxclub.demo.datasource.dao.db2"}, sqlSessionFactoryRef = "sqlSessionFactory2")
public class MybatisDb2Config {

    @Qualifier("ds2")
    @Autowired
    DataSource dataSource;

    @Bean(name = "sqlSessionFactory2")
    public SqlSessionFactory sqlSessionFactory2() throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource);
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        factoryBean.setMapperLocations(resolver.getResources("classpath:mappers/db2/*.xml"));
        factoryBean.setTypeAliasesPackage("cn.yjxxclub.demo.datasource.model");
        return factoryBean.getObject();

    }

    @Bean
    public SqlSessionTemplate sqlSessionTemplate2() throws Exception {
        SqlSessionTemplate template = new SqlSessionTemplate(sqlSessionFactory2());
        return template;
    }
}

編寫Dao和Mapper

Mapper.java和mapper.xml在basePackages和classpath對應放置即可，和springboot整合Mybtis一樣，這裡就不說了，然後正常啟動即可。程式碼在此：https://github.com/tengxing/Multiple-dataSources

資料來源動態切換

資料來源註冊

/**
 * Author: Starry.Teng
 * Email: [email protected]
 * Date: 17-11-1
 * Time: 下午9:14
 * Describe: DataSource Config
 */
@Configuration
public class DataSourceConfig {
    @Autowired
    Environment env;

    @Bean(name = "ds1")
    public DataSource dataSource1() {
        DruidDataSource dataSource = new DruidDataSource();

        dataSource.setUrl(env.getProperty("spring.datasource.db1.url"));
        dataSource.setUsername(env.getProperty("spring.datasource.db1.username"));
        dataSource.setPassword(env.getProperty("spring.datasource.db1.password"));
        dataSource.setDriverClassName(env.getProperty("spring.datasource.db1.driver-class-name"));
        return dataSource;
    }

    @Bean(name = "ds2")
    public DataSource dataSource2() {
        DruidDataSource dataSource = new DruidDataSource();

        dataSource.setUrl(env.getProperty("spring.datasource.db2.url"));
        dataSource.setUsername(env.getProperty("spring.datasource.db2.username"));
        dataSource.setPassword(env.getProperty("spring.datasource.db2.password"));
        dataSource.setDriverClassName(env.getProperty("spring.datasource.db2.driver-class-name"));
        return dataSource;
    }

    @Bean(name = "dynamicDS1")//注意這個bean是mybatis的sqlSessionFacatory所管理的dataSource
    public DataSource dataSource() {
        DynamicDataSource dynamicDataSource = new DynamicDataSource();
        // 預設資料來源
        dynamicDataSource.setDefaultTargetDataSource(dataSource1());

        // 配置多資料來源
        Map<Object, Object> dsMap = new HashMap(5);
        dsMap.put("ds1", dataSource1());
        dsMap.put("ds2", dataSource2());

        dynamicDataSource.setTargetDataSources(dsMap);

        return dynamicDataSource;
    }

}

動態資料來源編寫

需要繼承AbstractRoutingDataSource類

/**
 * Author: http://blog.csdn.net/neosmith/article/details/61202084
 * Date: 17-11-2
 * Time: 下午2:56
 * Describe: 動態資料來源
 */
public class DynamicDataSource extends AbstractRoutingDataSource {
    private static final Logger log = LoggerFactory.getLogger(DynamicDataSource.class);

    @Override
    protected Object determineCurrentLookupKey() {
        log.debug("資料來源為{}", DataSourceContextHolder.getDB());

        return DataSourceContextHolder.getDB();
    }
}

編寫DataSourceContextHolder

/**
 * Author: http://blog.csdn.net/neosmith/article/details/61202084
 * Date: 17-11-2
 * Time: 下午2:56
 * Describe: DataSource ContextHolder
 */
public class DataSourceContextHolder {
    public static final Logger log = LoggerFactory.getLogger(DataSourceContextHolder.class);

    /**
     * 預設資料來源
     */
    public static final String DEFAULT_DS = "ds1";

    /**
     * 獲取當前執行緒
     */
    private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

    // 設定資料來源名
    public static void setDB(String dbType) {
        log.debug("切換到{}資料來源", dbType);
        contextHolder.set(dbType);
    }

    // 獲取資料來源名
    public static String getDB() {
        return (contextHolder.get());
    }

    // 清除資料來源名
    public static void clearDB() {
        contextHolder.remove();
    }
}

咋們到時候只要呼叫setDB()方法即可實現資料來源的切換，下面使用Aop的方式進行動態切換。

編寫代理類

/**
 * Author: http://blog.csdn.net/neosmith/article/details/61202084
 * Date: 17-11-2
 * Time: 下午3:01
 * Describe: 動態資料來源代理類
 * 邏輯：對方法@DB註解的方法進行切面換資料來源操作
 */
@Aspect
@Component
@Order(value=-1) //保證該AOP在@Transactional之前執行
public class DynamicDataSourceAspect {

    @Before("@annotation(DB)")
    public void beforeSwitchDS(JoinPoint point){

        //獲得當前訪問的class
        Class<?> className = point.getTarget().getClass();

        //獲得訪問的方法名
        String methodName = point.getSignature().getName();
        //得到方法的引數的型別
        Class[] argClass = ((MethodSignature)point.getSignature()).getParameterTypes();
        String dataSource = DataSourceContextHolder.DEFAULT_DS;
        try {
            // 得到訪問的方法物件
            Method method = className.getMethod(methodName, argClass);

            // 判斷是否存在@DS註解
            if (method.isAnnotationPresent(DB.class)) {
                DB annotation = method.getAnnotation(DB.class);
                // 取出註解中的資料來源名
                dataSource = annotation.value();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        // 切換資料來源
        DataSourceContextHolder.setDB(dataSource);

    }
    @After("@annotation(DB)")
    public void afterSwitchDS(JoinPoint point){

        DataSourceContextHolder.clearDB();

    }
}

自定義註解

/**
 * Author: Starry.Teng
 * Email: [email protected]
 * Date: 17-11-2
 * Time: 下午3:00
 * Describe:
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({
        ElementType.METHOD
})
public @interface DB {
    String value() default "ds1";
}

serviceImpl

    @DB("ds1")
    public Object getDs1(){

        Singer singer = singerMapper.findByName("陳奕迅");
        logger.info("/n"+singer);
        return null;
    }

    @DB("ds2")
    public Object getDs2(){
        Book book = bookMapper.findById(bookMapper.list().get(0).getId());
        logger.info(book+"/n");
        return null;
    }

兩者比較

知識點

上面的兩種方式都達到了”換資料來源”目的，只是實現的原理和方式不一樣而已，都是優虐，還是那句話，沒有最好的方法，只有在特定的環境下最適合的解決方案。