TSharding源码阅读-MapperShardingInitializer之生成mapper xml

Posted 2020-08-14 穿林度水

/**
 * 增强Mapper处理总入口：Mapper被mybatis初始化后，在这里做进一步的处理和增强
 *
 * @author qigong on 5/1/15
 */
public class MapperShardingInitializer implements ApplicationContextAware {


    Logger logger = LoggerFactory.getLogger(getClass());

    private String needEnhancedClasses;
    private String[] needEnhancedClassesArray;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        Map<String, SqlSessionFactory> sqlSessionFactories = applicationContext.getBeansOfType(SqlSessionFactory.class);
        if (sqlSessionFactories.isEmpty()) {
            return;
        }
        MapperHelperForSharding mapperHelperForSharding = new MapperHelperForSharding();
        List<SqlSession> sqlSessions = new ArrayList<>(sqlSessionFactories.size());
        for (SqlSessionFactory sqlSessionFactory : sqlSessionFactories.values()) {
            SqlSession sqlSession = new SqlSessionTemplate(sqlSessionFactory);
            sqlSessions.add(sqlSession);
        }
        //Mapper代码增强 每个方法扩展出一个ShardingMapper类，增强为512个方法。
        this.needEnhancedClassesArray = needEnhancedClasses.split(",");
        this.enhanceMapperClass();
        mapperHelperForSharding.setMappers(needEnhancedClassesArray);
        mapperHelperForSharding.setSqlSessions(sqlSessions.toArray(new SqlSession[0]));
        mapperHelperForSharding.initMapper();
    }

    private void enhanceMapperClass() {
        for (String mapperClass : needEnhancedClassesArray) {
            try {
                MapperEnhancer.enhanceMapperClass(mapperClass);
            } catch (Exception e) {
                logger.error("Enhance {} class error", mapperClass, e);
            }
        }
    }

    public void setNeedEnhancedClasses(String needEnhancedClasses) {
        this.needEnhancedClasses = needEnhancedClasses;
    }
}

 

3.1 this.enhanceMapperClass();

　　

 /**
     * 对mapper进行增强，生成新的mapper，并主动加载新mapper类到classloader
     *
     * @param mapperClassName
     */
    public static void enhanceMapperClass(String mapperClassName) throws Exception {
        //com.mogujie.service.tsharding.mapper.ShopOrderMapper
        Class originClass = Class.forName(mapperClassName);//获取A
        Method[] originMethods = originClass.getDeclaredMethods();//获取A的方法，

        CtClass cc = pool.get(mapperClassName);//获取到class定义的容器ClassPool，通过它获取已经编译好的类A

        for (CtMethod ctMethod : cc.getDeclaredMethods()) {//遍历A的所有方法
            CtClass enhanceClass = pool.makeInterface(mapperClassName + "Sharding" + ctMethod.getName());//针对A的每一个方法新建一个接口B
            //com.mogujie.service.tsharding.mapper.ShopOrderMapperShardinggetShopOrderByShopOrderId
            for (long i = 0L; i < 512; i++) {//生成512个方法
                CtMethod newMethod = new CtMethod(ctMethod.getReturnType(), ctMethod.getName() + ShardingCaculator.getNumberWithZeroSuffix(i), ctMethod.getParameterTypes(), enhanceClass);
                //CtMethod 和CtConstructor 提供了 insertBefore()、insertAfter()和 addCatch()方法，它们可以插入一个souce文本到存在的方法的相应的位置
                Method method = getOriginMethod(newMethod, originMethods);//获取A的方法
                if(method.getParameterAnnotations()[0].length > 0) {//如果带注解
                    ClassFile ccFile = enhanceClass.getClassFile();
                    ConstPool constPool = ccFile.getConstPool();

                    //拷贝注解信息和注解内容，以支持mybatis mapper类的动态绑定
                    newMethod.getMethodInfo().addAttribute(MapperAnnotationEnhancer.duplicateParameterAnnotationsAttribute(constPool, method));
                }
                enhanceClass.addMethod(newMethod);//B增加方法
            }
            Class<?> loadThisClass = enhanceClass.toClass();

            //2015.09.22后不再输出类到本地
            enhanceClass.writeFile(".");
        }
    }

　　需要增强的类

@DataSourceRouting(handler=TShardingRoutingHandler.class)
public abstract interface ShopOrderMapper
{
  @ShardingExtensionMethod(type=MapperResourceEnhancer.class, method="enhancedShardingSQL")
  public abstract ShopOrder getShopOrderByShopOrderId(@ShardingOrderPara Long paramLong);

  @ShardingExtensionMethod(type=MapperResourceEnhancer.class, method="enhancedShardingSQL")
  public abstract List<ShopOrder> getShopOrderByShopOrderIds(@ShardingOrderPara List<Long> paramList);

  @ShardingExtensionMethod(type=MapperResourceEnhancer.class, method="enhancedShardingSQL")
  public abstract int batchUpdateShopOrderByShopOrderIds(@ShardingOrderPara @Param("shopOrderIds") List<Long> paramList, @Param("shopOrder") ShopOrder paramShopOrder);
}

增强后针对每一个方法都生成了一个类

public abstract interface ShopOrderMapperShardingbatchUpdateShopOrderByShopOrderIds
{
  public abstract int batchUpdateShopOrderByShopOrderIds0000(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder);

  public abstract int batchUpdateShopOrderByShopOrderIds0001(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder);

  public abstract int batchUpdateShopOrderByShopOrderIds0002(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder);

  public abstract int batchUpdateShopOrderByShopOrderIds0003(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder);

  public abstract int batchUpdateShopOrderByShopOrderIds0004(@ShardingOrderPara("orderId") @Param("shopOrderIds") List paramList, @Param("shopOrder") ShopOrder paramShopOrder);

public abstract interface ShopOrderMapperShardinggetShopOrderByShopOrderId
{
  public abstract ShopOrder getShopOrderByShopOrderId0000(@ShardingOrderPara("orderId") Long paramLong);

  public abstract ShopOrder getShopOrderByShopOrderId0001(@ShardingOrderPara("orderId") Long paramLong);

  public abstract ShopOrder getShopOrderByShopOrderId0002(@ShardingOrderPara("orderId") Long paramLong);

  public abstract ShopOrder getShopOrderByShopOrderId0003(@ShardingOrderPara("orderId") Long paramLong);

  public abstract ShopOrder getShopOrderByShopOrderId0004(@ShardingOrderPara("orderId") Long paramLong);

  public abstract ShopOrder getShopOrderByShopOrderId0005(@ShardingOrderPara("orderId") Long paramLong);

  public abstract ShopOrder getShopOrderByShopOrderId0006(@ShardingOrderPara("orderId") Long paramLong);

  public abstract ShopOrder getShopOrderByShopOrderId0007(@ShardingOrderPara("orderId") Long paramLong);
}

public abstract interface ShopOrderMapperShardinggetShopOrderByShopOrderIds
{
  public abstract List getShopOrderByShopOrderIds0000(@ShardingOrderPara("orderId") List paramList);

  public abstract List getShopOrderByShopOrderIds0001(@ShardingOrderPara("orderId") List paramList);

  public abstract List getShopOrderByShopOrderIds0002(@ShardingOrderPara("orderId") List paramList);

  public abstract List getShopOrderByShopOrderIds0003(@ShardingOrderPara("orderId") List paramList);

  public abstract List getShopOrderByShopOrderIds0004(@ShardingOrderPara("orderId") List paramList);

  public abstract List getShopOrderByShopOrderIds0005(@ShardingOrderPara("orderId") List paramList);

  public abstract List getShopOrderByShopOrderIds0006(@ShardingOrderPara("orderId") List paramList);

  public abstract List getShopOrderByShopOrderIds0007(@ShardingOrderPara("orderId") List paramList);
}

 

3.2 mapperHelperForSharding.setMappers(needEnhancedClassesArray);
　　通过ShopOrderMapper.java，获取注解配置 @ShardingExtensionMethod(type = MapperResourceEnhancer.class, method = "enhancedShardingSQL")，
　　生成MapperEnhancer，以ShopOrderMapper的方法名为key,MapperResourceEnhancer.enhancedShardingSQL 为value,保存在MapperResourceEnhancer.methodMap中。
　　返回MapperEnhancer，再以ShopOrderMappe 为key,MapperEnhancer为value,保存在MapperHelperForSharding.registerMapper中，供后续使用
3.3 mapperHelperForSharding.setSqlSessions(sqlSessions.toArray(new SqlSession[0]));
　　把sqlSession保存在mapperHelperForSharding.sqlSessions
3.4 mapperHelperForSharding.initMapper();（ Spring4 is necessary）
　　类关系:SqlSession>Configuration>MappedStatement>DynamicSqlSource||RawSqlSource
　　遍历 sqlSessions，处理Configuration中全部的MappedStatement，重新设置SqlSource。
　　重新设置SqlSource：获取MapperTemplate（3.2mapperHelperForSharding.registerMapper中保存的MapperEnhancer）。
　　然后 mapperEnhancer.setSqlSource(ms, configuration);代码增强 扩充为512个方法。 

　　

public void setSqlSource(MappedStatement ms, Configuration configuration) throws Exception {
                    Method method = methodMap.get(getMethodName(ms));//3.2中保存的enhancedShardingSQL方法
                    try {
                        if (method.getReturnType() == Void.TYPE) {
                            method.invoke(this, ms);
                        } else if (SqlSource.class.isAssignableFrom(method.getReturnType())) {
                            //代码增强 扩充为512个方法。
                            for (long i = 0; i < 512; i++) {

                                //新的带sharding的sql
                                SqlSource sqlSource = (SqlSource) method.invoke(this, ms, configuration, i);

                                String newMsId = ms.getId() + ShardingCaculator.getNumberWithZeroSuffix(i);
                                newMsId = newMsId.replace("Mapper.", "MapperSharding" + getMethodName(ms) + ".");

                                //添加到ms库中
                                MappedStatement newMs = copyFromMappedStatement(ms, sqlSource, newMsId);
                                configuration.addMappedStatement(newMs);
                                setSqlSource(newMs, sqlSource);
                            }
                        } else {
                            throw new RuntimeException("自定义Mapper方法返回类型错误,可选的返回类型为void和SqlNode!");
                        }
                    } catch (IllegalAccessException e) {
                        throw new RuntimeException(e);
                    } catch (InvocationTargetException e) {
                        throw new RuntimeException(e.getTargetException() != null ? e.getTargetException() : e);
                    }
                }

 

3.4.1 SqlSource sqlSource = (SqlSource) method.invoke(this, ms, configuration, i);
　　实际调用com.mogujie.trade.tsharding.route.orm.MapperResourceEnhancer;enhancedShardingSQL
　　  （SqlSession>Configuration>MappedStatement>DynamicSqlSource||RawSqlSource）
　　 　　DynamicSqlSource中存在mapperxml中每个节点的语句。
　　　    awSqlSource中存在mapperxml中的sql语句。根据分片参数替换成对应的表名，比如TradeOrder0066
　　　　最终生成的sql语句类似(SELECT orderId, buyerUserId,sellerUserId FROM TradeOrder0066 WHERE orderId = ? limit 1)
　　用新ID，创建MappedStatement（mapperxml节点），添加到Configuration，设置数据源
　　　　 新ID格式：com.mogujie.service.tsharding.mapper.ShopOrderMapperShardinggetShopOrderByShopOrderId.getShopOrderByShopOrderId0000