查询逻辑源码阅读

数据库用了一个Json字段，但查询出来时null。不知道为什么，翻翻源码在哪里没有赋值上。

代码逻辑简述

接口查询部分逻辑很简单，直接调用Mapper接口中的方法。

Mapper接口逻辑

对应的SQL，使用resultType直接映射到VO对象

<select id="queryPageList" resultType="com.aps.core.domain.vo.ApsPlanProductTaskDailyVO">
	SELECT
		*
	FROM
		aps_plan_product_task_daily apptd
	WHERE
	apptd.STATUS = 1
	ORDER BY apptd.daily_time DESC, apptd.create_time ASC, apptd.id ASC
</select>

VO对象：

@Data  
@EqualsAndHashCode(callSuper = true)  
public class ApsPlanProductTaskDailyVO extends ApsPlanProductTaskDaily implements Serializable {
	// ...一些扩展信息
	
}

@Data  
@EqualsAndHashCode(callSuper = true)  
@TableName(value = "aps_plan_product_task_daily", autoResultMap = true)  
public class ApsPlanProductTaskDaily extends BaseEntity {
	// 映射表结构对象，其余字段省略...
	
	@TableField(typeHandler = FastjsonTypeHandler.class)  
	private Map<String, Object> reqMsg;
}

跟踪代码

首先进入 MybatisMapperProxy 的 invoke 方法

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
	try {
		if (Object.class.equals(method.getDeclaringClass())) {
			return method.invoke(this, args);
		} else {
			// 走到这里，从缓存获取调用者。执行invoke方法
			return cachedInvoker(method).invoke(proxy, method, args, sqlSession);
		}
	} catch (Throwable t) {
		throw ExceptionUtil.unwrapThrowable(t);
	}
}

private MapperMethodInvoker cachedInvoker(Method method) throws Throwable {
	try {
		// 第一次进入没有缓存，需要走下面逻辑
		return CollectionUtils.computeIfAbsent(methodCache, method, m -> {
			// m 为经过回调传过来的method。具有主体的非静态方法，在接口类型中声明
			if (m.isDefault()) {
				try {
					if (privateLookupInMethod == null) {
						return new DefaultMethodInvoker(getMethodHandleJava8(method));
					} else {
						return new DefaultMethodInvoker(getMethodHandleJava9(method));
					}
				} catch (IllegalAccessException | InstantiationException | InvocationTargetException
					| NoSuchMethodException e) {
					throw new RuntimeException(e);
				}
			} else {
				// 走到这。构造一个普通调用方法。记录mapper接口实现类、调用方法、sql会话的配置
				return new PlainMethodInvoker(new MybatisMapperMethod(mapperInterface, method, sqlSession.getConfiguration()));
			}
		});
	} catch (RuntimeException re) {
		Throwable cause = re.getCause();
		throw cause == null ? re : cause;
	}
}

看下cachedInvoker(method)

MybatisMapperMethod 类用来记录和执行Mapper方法

类里只暴露了创建和execute2个方法，这个execute就是invoke调用的方法 构造方法，给command、method赋值。调用ibatis里的MapperMethod创建command和method

public MybatisMapperMethod(Class<?> mapperInterface, Method method, Configuration config) {  
	// SQL命令
	this.command = new MapperMethod.SqlCommand(config, mapperInterface, method);  
	// SQL方法
	this.method = new MapperMethod.MethodSignature(config, mapperInterface, method);  
}

// ibatis里的MapperMethod创建command
public SqlCommand(Configuration configuration, Class<?> mapperInterface, Method method) {
  // 获取查询sql的mapper里的方法名
  final String methodName = method.getName();
  // mapper的接口类
  final Class<?> declaringClass = method.getDeclaringClass();
  // 解析映射语句，取到mappedStatements
  MappedStatement ms = resolveMappedStatement(mapperInterface, methodName, declaringClass,
	  configuration);
  if (ms == null) {
	if (method.getAnnotation(Flush.class) != null) {
	  name = null;
	  type = SqlCommandType.FLUSH;
	} else {
	  throw new BindingException("Invalid bound statement (not found): "
		  + mapperInterface.getName() + "." + methodName);
	}
  } else {
    // name和type看下面图
	name = ms.getId();
	type = ms.getSqlCommandType();
	if (type == SqlCommandType.UNKNOWN) {
	  throw new BindingException("Unknown execution method for: " + name);
	}
  }
}

public MethodSignature(Configuration configuration, Class<?> mapperInterface, Method method) {
  Type resolvedReturnType = TypeParameterResolver.resolveReturnType(method, mapperInterface);
  if (resolvedReturnType instanceof Class<?>) {
	this.returnType = (Class<?>) resolvedReturnType;
  } else if (resolvedReturnType instanceof ParameterizedType) {
	this.returnType = (Class<?>) ((ParameterizedType) resolvedReturnType).getRawType();
  } else {
	this.returnType = method.getReturnType();
  }
  this.returnsVoid = void.class.equals(this.returnType);
  this.returnsMany = configuration.getObjectFactory().isCollection(this.returnType) || this.returnType.isArray();
  this.returnsCursor = Cursor.class.equals(this.returnType);
  this.returnsOptional = Optional.class.equals(this.returnType);
  this.mapKey = getMapKey(method);
  this.returnsMap = this.mapKey != null;
  this.rowBoundsIndex = getUniqueParamIndex(method, RowBounds.class);
  this.resultHandlerIndex = getUniqueParamIndex(method, ResultHandler.class);
  // 参数名称解析
  this.paramNameResolver = new ParamNameResolver(configuration, method);
}

看下invoke方法

@Override
public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {
	// 调用上面那个公开方法
	return mapperMethod.execute(sqlSession, args);
}

public Object execute(SqlSession sqlSession, Object[] args) {
	Object result;
	switch (command.getType()) {
		case INSERT: {
			Object param = method.convertArgsToSqlCommandParam(args);
			result = rowCountResult(sqlSession.insert(command.getName(), param));
			break;
		}
		case UPDATE: {
			Object param = method.convertArgsToSqlCommandParam(args);
			result = rowCountResult(sqlSession.update(command.getName(), param));
			break;
		}
		case DELETE: {
			Object param = method.convertArgsToSqlCommandParam(args);
			result = rowCountResult(sqlSession.delete(command.getName(), param));
			break;
		}
		// 我这里走到select
		case SELECT:
			// 返回空
			if (method.returnsVoid() && method.hasResultHandler()) {
				executeWithResultHandler(sqlSession, args);
				result = null;
			} else if (method.returnsMany()) {
				// 
				result = executeForMany(sqlSession, args);
			} else if (method.returnsMap()) {
				// 返回Map
				result = executeForMap(sqlSession, args);
			} else if (method.returnsCursor()) {
				// 返回游标
				result = executeForCursor(sqlSession, args);
			} else {
				// 本次查询上面都没走，走到这。这是plus对Mybatis的改造，我这里正是要返回Ipage
				// TODO 这里下面改了——源码中的注释
				if (IPage.class.isAssignableFrom(method.getReturnType())) {
					result = executeForIPage(sqlSession, args);
					// TODO 这里上面改了——源码中的注释
				} else {
					Object param = method.convertArgsToSqlCommandParam(args);
					result = sqlSession.selectOne(command.getName(), param);
					if (method.returnsOptional()
						&& (result == null || !method.getReturnType().equals(result.getClass()))) {
						result = Optional.ofNullable(result);
					}
				}
			}
			break;
		case FLUSH:
			result = sqlSession.flushStatements();
			break;
		default:
			throw new BindingException("Unknown execution method for: " + command.getName());
	}
	if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
		throw new BindingException("Mapper method '" + command.getName()
			+ " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
	}
	return result;
}

private <E> Object executeForIPage(SqlSession sqlSession, Object[] args) {
	IPage<E> result = null;
	for (Object arg : args) {
		// 有一个参数是分页信息，直接把这个对象当做响应对象使用
		if (arg instanceof IPage) {
			result = (IPage<E>) arg;
			break;
		}
	}
	Assert.notNull(result, "can't found IPage for args!");
	// 把入参转换成sql命令参数，返回的使用map，映射了参数名和值以及对应param顺序和值，效果如下图
	Object param = method.convertArgsToSqlCommandParam(args);
	List<E> list = sqlSession.selectList(command.getName(), param);
	result.setRecords(list);
	return result;
}

SqlSessionTemplate->selectList方法

可以看到在这里就已经null了

咦，好像没有看到核心代码。SqlSessionTemplate->selectList方法，一下就过去了。

SqlSessionTemplate->selectList方法

会invoke到这个方法

private class SqlSessionInterceptor implements InvocationHandler {
	@Override
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
	  SqlSession sqlSession = getSqlSession(SqlSessionTemplate.this.sqlSessionFactory,
		  SqlSessionTemplate.this.executorType, SqlSessionTemplate.this.exceptionTranslator);
	  try {
		Object result = method.invoke(sqlSession, args);
		if (!isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)) {
		  // force commit even on non-dirty sessions because some databases require
		  // a commit/rollback before calling close()
		  sqlSession.commit(true);
		}
		return result;
	  } catch (Throwable t) {
		Throwable unwrapped = unwrapThrowable(t);
		if (SqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) {
		  // release the connection to avoid a deadlock if the translator is no loaded. See issue #22
		  closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);
		  sqlSession = null;
		  Throwable translated = SqlSessionTemplate.this.exceptionTranslator
			  .translateExceptionIfPossible((PersistenceException) unwrapped);
		  if (translated != null) {
			unwrapped = translated;
		  }
		}
		throw unwrapped;
	  } finally {
		if (sqlSession != null) {
		  closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);
		}
	  }
	}
}