springboot多数据源读写分离和主库数据源service层事务控制

读写分离如果撇开框架无非就是实现多个数据源，主库用写的数据源，从库用读的数据源。

因为想研究数据库读写分离和分库分表的设计，所以就自己搭建了一套springboot+druid+mybatis+aop 实现一主多从的设计。 
第一步：首先需要自定义数据源的配置项，springboot默认解析的是带前缀spring.datasource.下面的配置项，为了不冲突，就直接定义datasource.当成我们的前缀， 
@ConfigurationProperties(prefix = “datasource.write”)可以用来加载指定前缀的配置项，非常方便 
因为使用druid，所以需要生成datasource的时候需要指定类型。

DataSourceBuilder.create().type(dataSourceType).build()

readSize是用来定义从库的大小，有多少从库就要配置多少个从库datasource 
第二步：从库的负载均衡，主要是MyAbstractRoutingDataSource这个类 
第三步，从写springboot-mybatis架包的MybatisAutoConfiguration类的创建SqlSessionFactory方法，将里面的数据源换成我们自定义的AbstractRoutingDataSource 
第四步骤。自定义事务MyDataSourceTransactionManagerAutoConfiguration

完整代码和单元测试： 
github:https://github.com/ggj2010/javabase.git

主要的架包

<!-- jdbc driver begin-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!--mybatis springboot-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
        <!-- jdbc driver end-->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
        </dependency>

自定义数据源配置项：

#多数据源 1主2从
datasource:
 #从库数量
  readSize: 2
   # 使用druid数据源
  type: com.alibaba.druid.pool.DruidDataSource
#主库
  write:
    url: jdbc:mysql://localhost:3306/master?useUnicode=true&characterEncoding=utf-8
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
    filters: stat
    maxActive: 20
    initialSize: 1
    maxWait: 60000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQueryTimeout: 900000
    validationQuery: SELECT SYSDATE() from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    maxOpenPreparedStatements: 20
  read1:
    url: jdbc:mysql://localhost:3306/slave1?useUnicode=true&characterEncoding=utf-8
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
    filters: stat
    maxActive: 20
    initialSize: 1
    maxWait: 60000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQueryTimeout: 900000
    validationQuery: SELECT SYSDATE() from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    maxOpenPreparedStatements: 20
  read2:
    url: jdbc:mysql://localhost:3306/slave2?useUnicode=true&characterEncoding=utf-8
    username: root
    password: root
    driver-class-name: com.mysql.jdbc.Driver
    filters: stat
    maxActive: 20
    initialSize: 1
    maxWait: 60000
    minIdle: 1
    timeBetweenEvictionRunsMillis: 60000
    minEvictableIdleTimeMillis: 300000
    validationQueryTimeout: 900000
    validationQuery: SELECT SYSDATE() from dual
    testWhileIdle: true
    testOnBorrow: false
    testOnReturn: false
    poolPreparedStatements: true
    maxOpenPreparedStatements: 20

解析配置项：

@Configuration
@Slf4j
public class DataSourceConfiguration {

    @Value("${datasource.type}")
    private Class<? extends DataSource> dataSourceType;

    @Bean(name = "writeDataSource")
    @Primary
    @ConfigurationProperties(prefix = "datasource.write")
    public DataSource writeDataSource() {
        log.info("-------------------- writeDataSource init ---------------------");
        return DataSourceBuilder.create().type(dataSourceType).build();
    }

    /**
     * 有多少个从库就要配置多少个
     * @return
     */
    @Bean(name = "readDataSource1")
    @ConfigurationProperties(prefix = "datasource.read1")
    public DataSource readDataSourceOne() {
        log.info("-------------------- readDataSourceOne init ---------------------");
        return DataSourceBuilder.create().type(dataSourceType).build();
    }

    @Bean(name = "readDataSource2")
    @ConfigurationProperties(prefix = "datasource.read2")
    public DataSource readDataSourceTwo() {
        log.info("-------------------- readDataSourceTwo init ---------------------");
        return DataSourceBuilder.create().type(dataSourceType).build();
    }
}

重写SqlSessionFactory

@Configuration
@AutoConfigureAfter({ DataSourceConfiguration.class })
@Slf4j
public class MybatisConfiguration extends MybatisAutoConfiguration {
    @Value("${datasource.readSize}")
    private String dataSourceSize;

    @Bean
    public SqlSessionFactory sqlSessionFactorys() throws Exception {
        log.info("-------------------- 重载父类 sqlSessionFactory init ---------------------");
        return super.sqlSessionFactory(roundRobinDataSouceProxy());
    }

    /**
     * 有多少个数据源就要配置多少个bean
     * @return
     */
    @Bean
    public AbstractRoutingDataSource roundRobinDataSouceProxy() {
        int size = Integer.parseInt(dataSourceSize);
        MyAbstractRoutingDataSource proxy = new MyAbstractRoutingDataSource(size);
        Map<Object, Object> targetDataSources = new HashMap<Object, Object>();
        DataSource writeDataSource = SpringContextHolder.getBean("writeDataSource");
        // 写
        targetDataSources.put(DataSourceType.write.getType(), SpringContextHolder.getBean("writeDataSource"));

        for (int i = 0; i < size; i++) {
            targetDataSources.put(i, SpringContextHolder.getBean("readDataSource" + (i + 1)));
        }
        proxy.setDefaultTargetDataSource(writeDataSource);
        proxy.setTargetDataSources(targetDataSources);
        return proxy;
    }

}

本地线程全局变量

public class DataSourceContextHolder {
    private static final ThreadLocal<String> local = new ThreadLocal<String>();

    public static ThreadLocal<String> getLocal() {
        return local;
    }

    /**
     * 读可能是多个库
     */
    public static void read() {
        local.set(DataSourceType.read.getType());
    }

    /**
     * 写只有一个库
     */
    public static void write() {
        local.set(DataSourceType.write.getType());
    }

    public static String getJdbcType() {
        return local.get();
    }
}

多数据源切换

public class MyAbstractRoutingDataSource extends AbstractRoutingDataSource {
    private final int dataSourceNumber;
    private AtomicInteger count = new AtomicInteger(0);

    public MyAbstractRoutingDataSource(int dataSourceNumber) {
        this.dataSourceNumber = dataSourceNumber;
    }

    @Override
    protected Object determineCurrentLookupKey() {
        String typeKey = DataSourceContextHolder.getJdbcType();
        if (typeKey.equals(DataSourceType.write.getType()))
            return DataSourceType.write.getType();
        // 读 简单负载均衡
        int number = count.getAndAdd(1);
        int lookupKey = number % dataSourceNumber;
        return new Integer(lookupKey);
    }
}

enum类型

public enum DataSourceType {
    read("read", "从库"), write("write", "主库");
    @Getter
    private String type;
    @Getter
    private String name;

    DataSourceType(String type, String name) {
        this.type = type;
        this.name = name;
    }
}

aop拦截设置本地线程变量

@Aspect
@Component
@Slf4j
public class DataSourceAop {

    @Before("execution(* com.ggj.encrypt.modules.*.dao..*.find*(..)) or execution(* com.ggj.encrypt.modules.*.dao..*.get*(..))")
    public void setReadDataSourceType() {
        DataSourceContextHolder.read();
        log.info("dataSource切换到：Read");
    }

    @Before("execution(* com.ggj.encrypt.modules.*.dao..*.insert*(..)) or execution(* com.ggj.encrypt.modules.*.dao..*.update*(..))")
    public void setWriteDataSourceType() {
        DataSourceContextHolder.write();
        log.info("dataSource切换到：write");
    }
}

自定义事务

@Configuration
@EnableTransactionManagement
@Slf4j
public class MyDataSourceTransactionManagerAutoConfiguration extends DataSourceTransactionManagerAutoConfiguration {
    /**
     * 自定义事务
     * MyBatis自动参与到spring事务管理中，无需额外配置，只要org.mybatis.spring.SqlSessionFactoryBean引用的数据源与DataSourceTransactionManager引用的数据源一致即可，否则事务管理会不起作用。
     * @return
     */
    @Bean(name = "transactionManager")
    public DataSourceTransactionManager transactionManagers() {
        log.info("-------------------- transactionManager init ---------------------");
        return new DataSourceTransactionManager(SpringContextHolder.getBean("roundRobinDataSouceProxy"));
    }
}

转载于:https://my.oschina.net/u/2285351/blog/716980