Springboot支持配置多数据源。默认情况，在yml文件中只会配置一个数据库。如果涉及到操作多个数据库的情况，在同实例中（即同一个ip地址下的不同数据库），可以采用数据库名点数据库表的方式，实现跨库表的操作。（database.table）但这种方式属于硬编码，如果数据库名变化意味着代码也要变化，不易维护。

下面是在springboot项目中，配置多数据源。需要添加几个配置类，和相关注解的方式，实现在某个特定方法层面下切换数据源。

1、目录结构

2、具体代码

1）DataSource

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
public @interface DataSource {
    String name() default "";
}

2）DataSourceAspect

/**
 * 多数据源，切面处理类
 *
 */
@Aspect
@Component
@Order(Ordered.HIGHEST_PRECEDENCE)
public class DataSourceAspect implements Ordered {
    protected Logger logger = LoggerFactory.getLogger(getClass());

    @Pointcut("@annotation(io.installer.commons.dynamic.datasource.annotation.DataSource)")
    public void dataSourcePointCut() {

    }

    @Around("dataSourcePointCut()")
    public Object around(ProceedingJoinPoint point) throws Throwable {
        MethodSignature signature = (MethodSignature) point.getSignature();
        Method method = signature.getMethod();

        DataSource ds = method.getAnnotation(DataSource.class);
        if (ds == null) {
            DynamicDataSource.setDataSource(DataSourceNames.FIRST);
            logger.debug("set datasource is " + DataSourceNames.FIRST);
        } else {
            DynamicDataSource.setDataSource(ds.name());
            logger.debug("set datasource is " + ds.name());
        }

        try {
            return point.proceed();
        } finally {
            DynamicDataSource.clearDataSource();
            logger.debug("clean datasource");
        }
    }

    @Override
    public int getOrder() {
        return 1;
    }
}

3）DataSourceNames

public interface DataSourceNames {
    String FIRST = "first";
    String SECOND = "second";
}

4）DynamicContextHolder

/**
 * 多数据源上下文
 *
 */
public class DynamicContextHolder {
    private static final ThreadLocal<Deque<String>> CONTEXT_HOLDER = ThreadLocal.withInitial(ArrayDeque::new);

    /**
     * 获得当前线程数据源
     *
     * @return 数据源名称
     */
    public static String peek() {
        return CONTEXT_HOLDER.get().peek();
    }

    /**
     * 设置当前线程数据源
     *
     * @param dataSource 数据源名称
     */
    public static void push(String dataSource) {
        CONTEXT_HOLDER.get().push(dataSource);
    }

    /**
     * 清空当前线程数据源
     */
    public static void poll() {
        Deque<String> deque = CONTEXT_HOLDER.get();
        deque.poll();
        if (deque.isEmpty()) {
            CONTEXT_HOLDER.remove();
        }
    }

}

5）DynamicDataSource

/**
 * 多数据源
 *
 * @author Mark sunlightcs@gmail.com
 * @since 1.0.0
 */
public class DynamicDataSource extends AbstractRoutingDataSource {

    private static final ThreadLocal<String> contextHolder = new ThreadLocal<>();

    public DynamicDataSource(DataSource defaultTargetDataSource, Map<Object, Object> targetDataSources) {
      //设置默认数据源
      super.setDefaultTargetDataSource(defaultTargetDataSource);
      super.setTargetDataSources(targetDataSources);
      super.afterPropertiesSet();
      }

    @Override
    protected Object determineCurrentLookupKey() {
        //获取数据源，没有指定，则为默认数据源
        return getDataSource();
    }

    public static void setDataSource(String dataSource) {
        contextHolder.set(dataSource);
    }

    public static String getDataSource() {
        return contextHolder.get();
    }

    public static void clearDataSource() {
        contextHolder.remove();
    }

}

6）DynamicDataSourceConfig

@Configuration
@EnableConfigurationProperties(DynamicDataSourceProperties.class)
public class DynamicDataSourceConfig {

    //数据源1，读取spring.datasource.druid.first下的配置信息
    @Bean
    @ConfigurationProperties("spring.datasource.druid.first")
    public DataSource firstDataSource() {
        return DruidDataSourceBuilder.create().build();
    }


    //数据源2，读取spring.datasource.druid.second下的配置信息
    @Bean
    @ConfigurationProperties("spring.datasource.druid.second")
    public DataSource secondDataSource() {
        return DruidDataSourceBuilder.create().build();
    }


    //加了@Primary注解，表示指定DynamicDataSource为Spring的数据源
    //因为DynamicDataSource是继承与AbstractRoutingDataSource，而AbstractR
    //outingDataSource又是继承于AbstractDataSource，AbstractDataSource实现了统一
    //的DataSource接口，所以DynamicDataSource也可以当做DataSource使用
    @Bean
    @Primary
    public DynamicDataSource dataSource(DataSource firstDataSource, DataSource secondDataSource) {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceNames.FIRST, firstDataSource);
        targetDataSources.put(DataSourceNames.SECOND, secondDataSource);
        return new DynamicDataSource(firstDataSource, targetDataSources);
    }
}

7）DynamicDataSourceFactory

public class DynamicDataSourceFactory {

    public static DruidDataSource buildDruidDataSource(DataSourceProperties properties) {
        DruidDataSource druidDataSource = new DruidDataSource();
        druidDataSource.setDriverClassName(properties.getDriverClassName());
        druidDataSource.setUrl(properties.getUrl());
        druidDataSource.setUsername(properties.getUsername());
        druidDataSource.setPassword(properties.getPassword());

        druidDataSource.setInitialSize(properties.getInitialSize());
        druidDataSource.setMaxActive(properties.getMaxActive());
        druidDataSource.setMinIdle(properties.getMinIdle());
        druidDataSource.setMaxWait(properties.getMaxWait());
        druidDataSource.setTimeBetweenEvictionRunsMillis(properties.getTimeBetweenEvictionRunsMillis());
        druidDataSource.setMinEvictableIdleTimeMillis(properties.getMinEvictableIdleTimeMillis());
        druidDataSource.setMaxEvictableIdleTimeMillis(properties.getMaxEvictableIdleTimeMillis());
        druidDataSource.setValidationQuery(properties.getValidationQuery());
        druidDataSource.setValidationQueryTimeout(properties.getValidationQueryTimeout());
        druidDataSource.setTestOnBorrow(properties.isTestOnBorrow());
        druidDataSource.setTestOnReturn(properties.isTestOnReturn());
        druidDataSource.setPoolPreparedStatements(properties.isPoolPreparedStatements());
        druidDataSource.setMaxOpenPreparedStatements(properties.getMaxOpenPreparedStatements());
        druidDataSource.setSharePreparedStatements(properties.isSharePreparedStatements());

        try {
            // druidDataSource.setFilters(properties.getFilters());
            druidDataSource.init();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return druidDataSource;
    }
}

8）DataSourceProperties

public class DataSourceProperties {
    private String driverClassName;
    private String url;
    private String username;
    private String password;

    /**
     * Druid默认参数
     */
    private int initialSize = 2;
    private int maxActive = 10;
    private int minIdle = -1;
    private long maxWait = 60 * 1000L;
    private long timeBetweenEvictionRunsMillis = 60 * 1000L;
    private long minEvictableIdleTimeMillis = 1000L * 60L * 30L;
    private long maxEvictableIdleTimeMillis = 1000L * 60L * 60L * 7;
    private String validationQuery = "select 1";
    private int validationQueryTimeout = -1;
    private boolean testOnBorrow = false;
    private boolean testOnReturn = false;
    private boolean testWhileIdle = true;
    private boolean poolPreparedStatements = false;
    private int maxOpenPreparedStatements = -1;
    private boolean sharePreparedStatements = false;
    private String filters = "stat,wall";

    public String getDriverClassName() {
        return driverClassName;
    }

    public void setDriverClassName(String driverClassName) {
        this.driverClassName = driverClassName;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getInitialSize() {
        return initialSize;
    }

    public void setInitialSize(int initialSize) {
        this.initialSize = initialSize;
    }

    public int getMaxActive() {
        return maxActive;
    }

    public void setMaxActive(int maxActive) {
        this.maxActive = maxActive;
    }

    public int getMinIdle() {
        return minIdle;
    }

    public void setMinIdle(int minIdle) {
        this.minIdle = minIdle;
    }

    public long getMaxWait() {
        return maxWait;
    }

    public void setMaxWait(long maxWait) {
        this.maxWait = maxWait;
    }

    public long getTimeBetweenEvictionRunsMillis() {
        return timeBetweenEvictionRunsMillis;
    }

    public void setTimeBetweenEvictionRunsMillis(long timeBetweenEvictionRunsMillis) {
        this.timeBetweenEvictionRunsMillis = timeBetweenEvictionRunsMillis;
    }

    public long getMinEvictableIdleTimeMillis() {
        return minEvictableIdleTimeMillis;
    }

    public void setMinEvictableIdleTimeMillis(long minEvictableIdleTimeMillis) {
        this.minEvictableIdleTimeMillis = minEvictableIdleTimeMillis;
    }

    public long getMaxEvictableIdleTimeMillis() {
        return maxEvictableIdleTimeMillis;
    }

    public void setMaxEvictableIdleTimeMillis(long maxEvictableIdleTimeMillis) {
        this.maxEvictableIdleTimeMillis = maxEvictableIdleTimeMillis;
    }

    public String getValidationQuery() {
        return validationQuery;
    }

    public void setValidationQuery(String validationQuery) {
        this.validationQuery = validationQuery;
    }

    public int getValidationQueryTimeout() {
        return validationQueryTimeout;
    }

    public void setValidationQueryTimeout(int validationQueryTimeout) {
        this.validationQueryTimeout = validationQueryTimeout;
    }

    public boolean isTestOnBorrow() {
        return testOnBorrow;
    }

    public void setTestOnBorrow(boolean testOnBorrow) {
        this.testOnBorrow = testOnBorrow;
    }

    public boolean isTestOnReturn() {
        return testOnReturn;
    }

    public void setTestOnReturn(boolean testOnReturn) {
        this.testOnReturn = testOnReturn;
    }

    public boolean isTestWhileIdle() {
        return testWhileIdle;
    }

    public void setTestWhileIdle(boolean testWhileIdle) {
        this.testWhileIdle = testWhileIdle;
    }

    public boolean isPoolPreparedStatements() {
        return poolPreparedStatements;
    }

    public void setPoolPreparedStatements(boolean poolPreparedStatements) {
        this.poolPreparedStatements = poolPreparedStatements;
    }

    public int getMaxOpenPreparedStatements() {
        return maxOpenPreparedStatements;
    }

    public void setMaxOpenPreparedStatements(int maxOpenPreparedStatements) {
        this.maxOpenPreparedStatements = maxOpenPreparedStatements;
    }

    public boolean isSharePreparedStatements() {
        return sharePreparedStatements;
    }

    public void setSharePreparedStatements(boolean sharePreparedStatements) {
        this.sharePreparedStatements = sharePreparedStatements;
    }

    public String getFilters() {
        return filters;
    }

    public void setFilters(String filters) {
        this.filters = filters;
    }
}

9）DynamicDataSourceProperties

@ConfigurationProperties(prefix = "dynamic")
public class DynamicDataSourceProperties {
    private Map<String, DataSourceProperties> datasource = new LinkedHashMap<>();

    public Map<String, DataSourceProperties> getDatasource() {
        return datasource;
    }

    public void setDatasource(Map<String, DataSourceProperties> datasource) {
        this.datasource = datasource;
    }
}

10）yml配置

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    druid:
      first:
        #MySQL
        url: jdbc:mysql://localhost:3306/database1?useSSL=false&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true&serverTimezone=GMT%2B8
        username: root
        password: root
      second:
        #MySQL
        url: jdbc:mysql://localhost:3306/database2?useSSL=false&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true&serverTimezone=GMT%2B8
        username: root
        password: root
      driver-class-name: com.mysql.cj.jdbc.Driver
      initial-size: 10
      max-active: 100
      min-idle: 10
      max-wait: 6000
      pool-prepared-statements: true
      max-pool-prepared-statement-per-connection-size: 20
      time-between-eviction-runs-millis: 60000
      min-evictable-idle-time-millis: 300000
      #Oracle需要打开注释
      #      validation-query: SELECT 1 FROM DUAL
      test-while-idle: true
      test-on-borrow: false
      test-on-return: false
      stat-view-servlet:
        enabled: true
        url-pattern: /druid/*

3、测试代码

1）DynamicDataSourceTestService

/**
 * 测试多数据源
 *
 * @author Mark sunlightcs@gmail.com
 */
@Service
//@DataSource(name = DataSourceNames.FIRST)
public class DynamicDataSourceTestService {
    @Resource
    private SysUserDao sysUserDao;

    //@Transactional
    public void updateUser(Long id) {
        SysUserEntity user = new SysUserEntity();
        user.setId(id);
        user.setMobile("13500000000");
        //sysUserDao.updateById(user);
        System.out.println(sysUserDao.selectById(id));
    }

    @DataSource(name = DataSourceNames.SECOND)
    @Transactional
    public void updateUserBySlave1(Long id) {
        SysUserEntity user = new SysUserEntity();
        user.setId(id);
        user.setMobile("13500000001");
        //sysUserDao.updateById(user);
        System.out.println(sysUserDao.selectById(id));
    }

//    @DataSource(name = DataSourceNames.SECOND)
//    @Transactional
//    public void updateUserBySlave2(Long id){
//        SysUserEntity user = new SysUserEntity();
//        user.setId(id);
//        user.setMobile("13500000002");
//        sysUserDao.updateById(user);
//
//        //测试事物
//        int i = 1/0;
//    }
}

2）DynamicDataSourceTest

@RunWith(SpringRunner.class)
@SpringBootTest
public class DynamicDataSourceTest {
    @Resource
    private DynamicDataSourceTestService dynamicDataSourceTestService;

    @Test
    public void test() {
        Long id = 1067246875800000001L;

//        dynamicDataSourceTestService.updateUser(id);
//        dynamicDataSourceTestService.updateUserBySlave1(id);
        dynamicDataSourceTestService.updateUserBySlave2(id);
    }


}