SSM实现Mysql数据库的读写分离

搭建Mysql的主从配置

前面已经介绍过，这里就偷个懒不再多说，不懂的可以查看MySQL主从同步

代码层的读写分离

在读写分离的实现上，Spring为我们提供了路由数据源的AbstractRoutingDataSource抽象类，我们只需编写一个新的类继承它，即可在不改变原有的代码的基础上实现读写分离。

1.创建 DyncmicDataSourceHolder 类

public class DyncmicDataSourceHolder {
    private static Logger logger=LoggerFactory.getLogger(DyncmicDataSourceHolder.class);

   /**
   * 保证线程安全，使用线程threadlocal
   */
    private static ThreadLocal contextHolder=new ThreadLocal();

    public static final String DB_MASTER="master";

    public static final String DB_SLAVE="slave";

   /**
   * @return java.lang.String
   * @description 获取连接类型
   */
    public static String getDbType(){
        String db=contextHolder.get();
        if (StringUtils.isBlank(db)) {
            db=DB_MASTER;
        }
        return db;
    }

    /**
     * 设置数据源类型
     * @param str
     */
    public static void setDbType(String str){
        logger.debug("使用数据源类型---"+str);
        contextHolder.set(str);
    }

    /**
     * 清理连接类型
     */
    public static void clearDaType(){
        contextHolder.remove();
    }

}

2.创建 DynamicDataSource，继承AbstractRoutingDataSource

public class DynamicDataSource extends AbstractRoutingDataSource {

  @Override
  protected Object determineCurrentLookupKey() {
    return DynamicDataSouceHolder.getDbType();
  }
}

3 创建DyncmicDataSourceInterceptor，mybatis拦截器

@Intercepts({@Signature(type = Executor.class, method = "update", args = {MappedStatement.class,
    Object.class}),
    @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class,
        RowBounds.class, ResultHandler.class})})
public class DynamicDataSourceInterceptor implements Interceptor {

  private static Logger logger = LoggerFactory.getLogger(DynamicDataSourceInterceptor.class);
  // 写操作的正则表达式
  private static final String REGEX = ".*insert\\u0020.*||.*delete\\u0020|.*update\\u0020.*";

  @Override
  public Object intercept(Invocation invocation) throws Throwable {
    // 判断方法是否是被事务管理的
    boolean synchronizationAction = TransactionSynchronizationManager.isActualTransactionActive();
    //获取sql 中的参数
    Object[] objects = invocation.getArgs();
    MappedStatement mappedStatement = (MappedStatement) objects[0];
    //数据源key
    String lookupKey = DynamicDataSouceHolder.DB_MASTER;
    if (!synchronizationAction) {
      // 读方法
      if (mappedStatement.getSqlCommandType().equals(SqlCommandType.SELECT)) {
        //selectKey为自增id查询主键（SELECT LAST_INSERT_ID）方法
        if (mappedStatement.getId().contains(SelectKeyGenerator.SELECT_KEY_SUFFIX)) {
          lookupKey = DynamicDataSouceHolder.DB_MASTER;
        } else {
          //获取sql 语句
          BoundSql boundSql = mappedStatement.getSqlSource().getBoundSql(objects[1]);
          String sql = boundSql.getSql().toLowerCase(Locale.CHINA).replace("\\t\\n\\r", " ");
          if (sql.matches(REGEX)) {
            lookupKey = DynamicDataSouceHolder.DB_MASTER;
          } else {
            lookupKey = DynamicDataSouceHolder.DB_SLAVE;
          }
        }
      }
    } else {
      lookupKey = DynamicDataSouceHolder.DB_MASTER;
    }
    logger.debug("设置方法[{}] use [{}] Strategy,SqlCommandType [{}]...", mappedStatement.getId(),
        lookupKey, mappedStatement.getSqlCommandType().name());
    DynamicDataSouceHolder.setDbType(lookupKey);
    return invocation.proceed();
  }

  @Override
  public Object plugin(Object target) {
    //Executor表示含有增删改查的操作 的对象
    if (target instanceof Executor) {
      //有增删改查的操作,就调用拦截方法
      return Plugin.wrap(target, this);
    } else {
      //无增删改查的操作。不做处理
      return target;
    }
  }

  @Override
  public void setProperties(Properties properties) {

  }
}

4.修改mybatis-config

5.修改spring-dao.xml

6 修改jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.master.url=jdbc:mysql://172.17.0.2:3306/o2o?useUnicode=true&characterEncoding=utf8
jdbc.slave.url=jdbc:mysql://172.17.0.3:3306/o2o?useUnicode=true&characterEncoding=utf8
jdbc.master.username=******
jdb.master.password=******
jdbc.slave.username=******
jdb.slave.password=******
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参考文章：https://blog.csdn.net/jessDL/article/details/82725957