利用Mybatis拦截器对数据库水平分表

首先你要知道在哪些sql上面要处理分表？你可能需要一个注解：

package com.dusk.domyself.stock.common.split;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE })
public @interface TableSplit {
	//是否分表
	 public boolean split() default true;
	 //表名
	 public String value();
	 
	 //获取分表策略
	 public String strategy();
	 
}

然后你可能需要一个拦截器处理类：

package com.dusk.domyself.stock.common.split;

import java.sql.Connection;
import java.util.Properties;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.factory.DefaultObjectFactory;
import org.apache.ibatis.reflection.factory.ObjectFactory;
import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;

import com.dusk.domyself.stock.common.ContextHelper;

@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class }) })
public class TableSplitInterceptor implements Interceptor {
	private Log log =LogFactory.getLog(getClass());
    private static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory();
    private static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory();

	@Override
	public Object intercept(Invocation invocation) throws Throwable {
		StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
		MetaObject metaStatementHandler = MetaObject.forObject(statementHandler, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY);
		
		BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
		// Configuration configuration = (Configuration) metaStatementHandler
		// .getValue("delegate.configuration");
		Object parameterObject = metaStatementHandler.getValue("delegate.boundSql.parameterObject");
		doSplitTable(metaStatementHandler);
		// 传递给下一个拦截器处理
		return invocation.proceed();

	}

	@Override
	public Object plugin(Object target) {
		// 当目标类是StatementHandler类型时，才包装目标类，否者直接返回目标本身,减少目标被代理的次数
		if (target instanceof StatementHandler) {
			return Plugin.wrap(target, this);
		} else {
			return target;
		}
	}

	@Override
	public void setProperties(Properties properties) {

	}

	private void doSplitTable(MetaObject metaStatementHandler) throws ClassNotFoundException{
		String originalSql = (String) metaStatementHandler.getValue("delegate.boundSql.sql");
		if (originalSql != null && !originalSql.equals("")) {
			log.info("分表前的SQL："+originalSql);
			MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
			String id = mappedStatement.getId();
			String className = id.substring(0, id.lastIndexOf("."));
			Class classObj = Class.forName(className);
			// 根据配置自动生成分表SQL
			TableSplit tableSplit = classObj.getAnnotation(TableSplit.class);
			if (tableSplit != null && tableSplit.split()) {
				StrategyManager strategyManager = ContextHelper.getStrategyManager();
				Strategy strategy=strategyManager.getStrategy(tableSplit.strategy());//获取分表策略来处理分表
				String convertedSql=originalSql.replaceAll(tableSplit.value(), strategy.convert(tableSplit.value()));
				metaStatementHandler.setValue("delegate.boundSql.sql",convertedSql);
				log.info("分表后的SQL："+convertedSql);
			}
		}
	}
}

然后看一下其中的一个应用：

package com.dusk.domyself.stock.mapper;

import java.util.List;

import com.dusk.domyself.stock.common.split.TableSplit;
import com.dusk.domyself.stock.entity.StockDay;
@TableSplit(value="stock_day", strategy="YYYY")
public interface StockDayMapper {
    int deleteByPrimaryKey(Long id);

    int insert(StockDay record);

    int insertSelective(StockDay record);

    List selectBystockId(String stockId);

    int updateByPrimaryKeySelective(StockDay record);

    int updateByPrimaryKey(StockDay record);
}

配置的分表策略：

 其中分表策略实现是：

package com.dusk.domyself.stock.common.split;

import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * 按年分表
 * @author dushangkui
 *
 */
public class YYYYStrategy implements Strategy{

	@Override
	public String convert(String tableName) {
		SimpleDateFormat sdf = new SimpleDateFormat("YYYY");
		StringBuilder sb=new StringBuilder(tableName);
		sb.append("_");
		sb.append(sdf.format(new Date()));
		return sb.toString();
	}
	
}

通用策略接口是：

package com.dusk.domyself.stock.common.split;

public interface Strategy {
	/**
	 * 传入一个需要分表的表名，返回一个处理后的表名 
	 * Strategy必须包含一个无参构造器
	 * @param tableName
	 * @return
	 */
	public String convert(String tableName);
}

还有一个可能需要的地方是：

package com.dusk.domyself.stock.common;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

import com.dusk.domyself.stock.common.split.StrategyManager;

@Component
public class ContextHelper implements ApplicationContextAware {
	private static ApplicationContext context;

	@Override
	public void setApplicationContext(ApplicationContext context)
			throws BeansException {
		ContextHelper.context=context;
	}
	
	public static StrategyManager getStrategyManager(){
		return context.getBean(StrategyManager.class);
	}
}

跑起来看结果：

[2016-08-30 22:32:30,170] [http-apr-8080-exec-7] (TableSplitInterceptor.java:63) INFO  com.dusk.domyself.stock.common.split.TableSplitInterceptor - 分表前的SQL：select 
     
    id, stock_id, data_date, top_price, bottom_price, open_price, close_price, main_funds, 
    retail_funds, funds, volume
   
    from stock_day
    where stock_id = ?
[2016-08-30 22:32:30,170] [http-apr-8080-exec-7] (AbstractBeanFactory.java:249) DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Returning cached instance of singleton bean 'strategyManager'
[2016-08-30 22:32:30,171] [http-apr-8080-exec-7] (TableSplitInterceptor.java:75) INFO  com.dusk.domyself.stock.common.split.TableSplitInterceptor - 分表后的SQL：select 
     
    id, stock_id, data_date, top_price, bottom_price, open_price, close_price, main_funds, 
    retail_funds, funds, volume
   
    from stock_day_2016
    where stock_id = ?

需要其他的分表策略可以自己实现然后注册就好了


里面设计的类已经github共享：https://github.com/dushangkui/common-util