springboot+mybatis实现数据库读写分离

本文不包含数据库主从配置。

实现思路：在项目中配置多数据源，通过代码控制访问哪一个数据源。

spring-jdbc为我们提供了AbstractRoutingDataSource，DataSource的抽象实现，基于查找键，返回不通不同的数据源。编写我们自己的动态数据源类DynamicDataSource继承AbstractRoutingDataSource，实现determineCurrentLookupKey方法。

配置一个spring config类DataSourceConfig，把DynamicDataSource初始化。

配置SqlSessionFactory,注入我们自定义的数据源DynamicDataSource。

通过AOP切入设置所需要的数据源，比如插入或者更新使用主数据源，查询使用从读数据源

#主数据库设置
spring.datasource.master.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8
spring.datasource.master.driverClassName=com.mysql.jdbc.Driver
spring.datasource.master.username=root
spring.datasource.master.password=root
spring.datasource.maseter.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.master.initialSize=5
spring.datasource.master.minIdle=1
spring.datasource.master.maxActive=50
spring.datasource.master.maxWait=60000
spring.datasource.master.minEvictableIdleTimeMillis=300000

#从数据库设置
spring.datasource.slave.url=jdbc:mysql://localhost:3306/test1?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT%2B8
spring.datasource.slave.driverClassName=com.mysql.jdbc.Driver
spring.datasource.slave.username=root
spring.datasource.slave.password=root
spring.datasource.slave.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.slave.initialSize=5
spring.datasource.slave.minIdle=1
spring.datasource.slave.maxActive=50
spring.datasource.slave.maxWait=60000
spring.datasource.slave.minEvictableIdleTimeMillis=300000

@Configuration
public class DataSourceConfig {


    @Value("${spring.datasource.master.url}")
    private String masterUrl;
    @Value("${spring.datasource.master.driverClassName}")
    private String masterDriverClassName;
    @Value("${spring.datasource.master.username}")
    private String masterUsername;
    @Value("${spring.datasource.master.password}")
    private String masterPassword;
    @Value("${spring.datasource.master.initialSize}")
    private Integer masterInitialSize;
    @Value("${spring.datasource.master.minIdle}")
    private Integer masterMinIdle;
    @Value("${spring.datasource.master.maxWait}")
    private Long masterMaxWait;
    @Value("${spring.datasource.master.maxActive}")
    private Integer masterMaxActive;
    @Value("${spring.datasource.master.minEvictableIdleTimeMillis}")
    private Integer masterMinEvictableIdleTimeMillis;

    @Value("${spring.datasource.slave.url}")
    private String slaveUrl;
    @Value("${spring.datasource.slave.driverClassName}")
    private String slaveDriverClassName;
    @Value("${spring.datasource.slave.username}")
    private String slaveUsername;
    @Value("${spring.datasource.slave.password}")
    private String slavePassword;
    @Value("${spring.datasource.slave.initialSize}")
    private Integer slaveInitialSize;
    @Value("${spring.datasource.slave.minIdle}")
    private Integer slaveMinIdle;
    @Value("${spring.datasource.slave.maxWait}")
    private Long slaveMaxWait;
    @Value("${spring.datasource.slave.maxActive}")
    private Integer slaveMaxActive;
    @Value("${spring.datasource.slave.minEvictableIdleTimeMillis}")
    private Integer slaveMinEvictableIdleTimeMillis;

    public DataSourceConfig() {
        System.out.println("#DataSourceConfig#");
    }

    public DataSource master() {
        System.out.println("# master druid#");
        DruidDataSource datasource = new DruidDataSource();
        datasource.setUrl(masterUrl);
        datasource.setDriverClassName(masterDriverClassName);
        datasource.setUsername(masterUsername);
        datasource.setPassword(masterPassword);
        datasource.setInitialSize(masterInitialSize);
        datasource.setMinIdle(masterMinIdle);
        datasource.setMaxWait(masterMaxWait);
        datasource.setMaxActive(masterMaxActive);
        datasource.setMinEvictableIdleTimeMillis(masterMinEvictableIdleTimeMillis);
        try {
            datasource.setFilters("stat,wall");
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return datasource;
    }

    public DataSource salve() {
        System.out.println("# slave slave#");
        DruidDataSource datasource = new DruidDataSource();
        datasource.setUrl(slaveUrl);
        datasource.setDriverClassName(slaveDriverClassName);
        datasource.setUsername(slaveUsername);
        datasource.setPassword(slavePassword);
        datasource.setInitialSize(slaveInitialSize);
        datasource.setMinIdle(slaveMinIdle);
        datasource.setMaxWait(slaveMaxWait);
        datasource.setMaxActive(slaveMaxActive);
        datasource.setMinEvictableIdleTimeMillis(slaveMinEvictableIdleTimeMillis);
        try {
            datasource.setFilters("stat,wall");
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return datasource;
    }
public class DynamicDataSource extends AbstractRoutingDataSource {

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

    @Override
    protected Object determineCurrentLookupKey() {
        return contextHolder.get();
    }

    public static enum DatabaseType {
        Master,Slave
    }

    public static void master() {
        contextHolder.set(DatabaseType.Master);
    }

    public static void slave() {
        contextHolder.set(DatabaseType.Slave);
    }


}

    @Bean
    public DynamicDataSource dynamicDataSource() {
        DataSource master = master();
        DataSource slave = salve();
        Map<Object,Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DynamicDataSource.DatabaseType.Master, master);
        targetDataSources.put(DynamicDataSource.DatabaseType.Slave, slave);
        DynamicDataSource dataSource = new DynamicDataSource();
        dataSource.setTargetDataSources(targetDataSources);
        dataSource.setDefaultTargetDataSource(master);
        return dataSource;
    }
}
@Configuration
@AutoConfigureAfter({DataSourceConfig.class})
public class MybatisConfig {

    @Bean("sqlSessionFactory")
    public SqlSessionFactory sqlSessionFactory(DynamicDataSource dynamicDataSource) {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dynamicDataSource);
        SqlSessionFactory sqlSessionFactory = null;
        try {
            sqlSessionFactory = bean.getObject();
        } catch (Exception e) {
            e.printStackTrace();
        }
        MapperHelper mapperHelper = new MapperHelper();
        Config config = new Config();
        config.setNotEmpty(true);
        mapperHelper.setConfig(config);
        mapperHelper.registerMapper(Mapper.class);
        mapperHelper.processConfiguration(sqlSessionFactory.getConfiguration());
        return sqlSessionFactory;
    }

    @Bean
    public MapperScannerConfigurer scannerConfigurer() {
        MapperScannerConfigurer configurer = new MapperScannerConfigurer();
        configurer.setSqlSessionFactoryBeanName("sqlSessionFactory");
//        configurer.setSqlSessionTemplateBeanName("sqlSession");
        configurer.setBasePackage("com.luke.hu.dao");
        configurer.setMarkerInterface(Mapper.class);
        return configurer;
    }
}
@Aspect
@Component
public class DataSourceAOP {

    @Before("execution(* com.luke.hu.dao..*.insert*(..)) || execution(* com.luke.hu.dao..*.update*(..))")
    public void setWriteDataSourceType() {
        DynamicDataSource.master();
        System.out.println("切换到master");
    }

    @Before("execution(* com.luke.hu.dao..*.select*(..))")
    public void setReadDataSourceType() {
        DynamicDataSource.slave();
        System.out.println("切换到slave");
    }
}