springboot基于Mybatis mysql实现读写分离

mysql> CREATE USER 'repl'@'%' IDENTIFIED BY '123456';#创建用户
mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'%';#分配权限
mysql>flush privileges; #刷新权限

[mysqld]
server-id=1
log-bin=master-bin
log-bin-index=master-bin.index

[mysqld]
server-id=2
relay-log-index=slave-relay-bin.index
relay-log=slave-relay-bin

CHANGE MASTER TO
  MASTER_HOST='192.168.226.5',
  MASTER_USER='root',
  MASTER_PASSWORD='123456',
  MASTER_LOG_FILE='master-bin.000003',
  MASTER_LOG_POS=154;

# 不同步哪些数据库
binlog-ignore-db = mysql
binlog-ignore-db = test
binlog-ignore-db = information_schema
# 只同步哪些数据库，除此之外，其他不同步
binlog-do-db = game

mysql:
 datasource:
 #读库数目
 num: 1
 type-aliases-package: com.example.dxfl.dao
 mapper-locations: classpath:/mapper/*.xml
 config-location: classpath:/mybatis-config.xml
 write:
 url: jdbc:mysql://192.168.226.5:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=true
 username: root
 password: 123456
 driver-class-name: com.mysql.jdbc.Driver
 read:
 url: jdbc:mysql://192.168.226.6:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=true
 username: root
 password: 123456
 driver-class-name: com.mysql.jdbc.Driver

/**
 * Description 这里切换读/写模式
 * 原理是利用ThreadLocal保存当前线程是否处于读模式（通过开始READ_ONLY注解在开始操作前设置模式为读模式，
 * 操作结束后清除该数据，避免内存泄漏，同时也为了后续在该线程进行写操作时任然为读模式
 * @author fxb
 * @date 2018-08-31
 */
public class DbContextHolder {

 private static Logger log = LoggerFactory.getLogger(DbContextHolder.class);
 public static final String WRITE = "write";
 public static final String READ = "read";

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

 public static void setDbType(String dbType) {
 if (dbType == null) {
  log.error("dbType为空");
  throw new NullPointerException();
 }
 log.info("设置dbType为：{}",dbType);
 contextHolder.set(dbType);
 }

 public static String getDbType() {
 return contextHolder.get() == null ? WRITE : contextHolder.get();
 }

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

public class MyAbstractRoutingDataSource extends AbstractRoutingDataSource {

 @Value("${mysql.datasource.num}")
 private int num;

 private final Logger log = LoggerFactory.getLogger(this.getClass());

 @Override
 protected Object determineCurrentLookupKey() {
 String typeKey = DbContextHolder.getDbType();
 if (typeKey == DbContextHolder.WRITE) {
  log.info("使用了写库");
  return typeKey;
 }
 //使用随机数决定使用哪个读库
 int sum = NumberUtil.getRandom(1, num);
 log.info("使用了读库{}", sum);
 return DbContextHolder.READ + sum;
 }
}

@ConfigurProperties 自动生成数据源：
 /**
 * 写数据源
 *
 * @Primary 标志这个 Bean 如果在多个同类 Bean 候选时，该 Bean 优先被考虑。
 * 多数据源配置的时候注意，必须要有一个主数据源，用 @Primary 标志该 Bean
 */
 @Primary
 @Bean
 @ConfigurationProperties(prefix = "mysql.datasource.write")
 public DataSource writeDataSource() {
 return new DruidDataSource();
 }

 /**
 * 设置数据源路由，通过该类中的determineCurrentLookupKey决定使用哪个数据源
 */
 @Bean
 public AbstractRoutingDataSource routingDataSource() {
 MyAbstractRoutingDataSource proxy = new MyAbstractRoutingDataSource();
 Map<Object, Object> targetDataSources = new HashMap<>(2);
 targetDataSources.put(DbContextHolder.WRITE, writeDataSource());
 targetDataSources.put(DbContextHolder.READ+"1", read1());
 proxy.setDefaultTargetDataSource(writeDataSource());
 proxy.setTargetDataSources(targetDataSources);
 return proxy;
 }

 /**
 * 多数据源需要自己设置sqlSessionFactory
 */
 @Bean
 public SqlSessionFactory sqlSessionFactory() throws Exception {
 SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
 bean.setDataSource(routingDataSource());
 ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
 // 实体类对应的位置
 bean.setTypeAliasesPackage(typeAliasesPackage);
 // mybatis的XML的配置
 bean.setMapperLocations(resolver.getResources(mapperLocation));
 bean.setConfigLocation(resolver.getResource(configLocation));
 return bean.getObject();
 }

 /**
 * 设置事务，事务需要知道当前使用的是哪个数据源才能进行事务处理
 */
 @Bean
 public DataSourceTransactionManager dataSourceTransactionManager() {
 return new DataSourceTransactionManager(routingDataSource());
 }

@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ReadOnly {
}

@Aspect
@Component
public class ReadOnlyInterceptor implements Ordered {
 private static final Logger log= LoggerFactory.getLogger(ReadOnlyInterceptor.class);

 @Around("@annotation(readOnly)")
 public Object setRead(ProceedingJoinPoint joinPoint,ReadOnly readOnly) throws Throwable{
 try{
  DbContextHolder.setDbType(DbContextHolder.READ);
  return joinPoint.proceed();
 }finally {
  //清楚DbType一方面为了避免内存泄漏，更重要的是避免对后续在本线程上执行的操作产生影响
  DbContextHolder.clearDbType();
  log.info("清除threadLocal");
 }
 }

 @Override
 public int getOrder() {
 return 0;
 }
}