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 MybatisMapperMethod 类 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);
}
}
}
}
MybatisPlusInterceptor 的 intercept(Invocation invocation) 方法
@Override
public Object intercept(Invocation invocation) throws Throwable {
Object target = invocation.getTarget();
Object[] args = invocation.getArgs();
if (target instanceof Executor) {
final Executor executor = (Executor) target;
Object parameter = args[1];
boolean isUpdate = args.length == 2;
MappedStatement ms = (MappedStatement) args[0];
if (!isUpdate && ms.getSqlCommandType() == SqlCommandType.SELECT) {
RowBounds rowBounds = (RowBounds) args[2];
ResultHandler resultHandler = (ResultHandler) args[3];
BoundSql boundSql;
if (args.length == 4) {
// 走这里获取 sql 语句封装方法
boundSql = ms.getBoundSql(parameter);
} else {
// 几乎不可能走进这里面,除非使用Executor的代理对象调用query[args[6]]
boundSql = (BoundSql) args[5];
}
for (InnerInterceptor query : interceptors) {
// 进入循环有2个 第一个这里会构建分页总数查询
if (!query.willDoQuery(executor, ms, parameter, rowBounds, resultHandler, boundSql)) {
return Collections.emptyList();
}
query.beforeQuery(executor, ms, parameter, rowBounds, resultHandler, boundSql);
}
CacheKey cacheKey = executor.createCacheKey(ms, parameter, rowBounds, boundSql);
return executor.query(ms, parameter, rowBounds, resultHandler, cacheKey, boundSql);
} else if (isUpdate) {
for (InnerInterceptor update : interceptors) {
if (!update.willDoUpdate(executor, ms, parameter)) {
return -1;
}
update.beforeUpdate(executor, ms, parameter);
}
}
} else {
// StatementHandler
final StatementHandler sh = (StatementHandler) target;
// 目前只有StatementHandler.getBoundSql方法args才为null
if (null == args) {
for (InnerInterceptor innerInterceptor : interceptors) {
innerInterceptor.beforeGetBoundSql(sh);
}
} else {
Connection connections = (Connection) args[0];
Integer transactionTimeout = (Integer) args[1];
for (InnerInterceptor innerInterceptor : interceptors) {
innerInterceptor.beforePrepare(sh, connections, transactionTimeout);
}
}
}
return invocation.proceed();
}// InnerInterceptor 接口的方法
default boolean willDoQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
return true;
}
// PaginationInnerInterceptor 类的实现
@Override
public boolean willDoQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
IPage<?> page = ParameterUtils.findPage(parameter).orElse(null);
if (page == null || page.getSize() < 0 || !page.searchCount()) {
return true;
}
BoundSql countSql;
MappedStatement countMs = buildCountMappedStatement(ms, page.countId());
if (countMs != null) {
countSql = countMs.getBoundSql(parameter);
} else {
countMs = buildAutoCountMappedStatement(ms);
// 构建分页总数查询语句，这里包含 count 是否优化的拼接方法
String countSqlStr = autoCountSql(page, boundSql.getSql());
PluginUtils.MPBoundSql mpBoundSql = PluginUtils.mpBoundSql(boundSql);
countSql = new BoundSql(countMs.getConfiguration(), countSqlStr, mpBoundSql.parameterMappings(), parameter);
PluginUtils.setAdditionalParameter(countSql, mpBoundSql.additionalParameters());
}
CacheKey cacheKey = executor.createCacheKey(countMs, parameter, rowBounds, countSql);
// 执行查询
List<Object> result = executor.query(countMs, parameter, rowBounds, resultHandler, cacheKey, countSql);
long total = 0;
if (CollectionUtils.isNotEmpty(result)) {
// 个别数据库 count 没数据不会返回 0 -- 原注释
Object o = result.get(0);
if (o != null) {
total = Long.parseLong(o.toString());
}
}
page.setTotal(total);
return continuePage(page);
}/**
* 获取自动优化的 countSql
*
* @param page 参数
* @param sql sql
* @return countSql
*/
protected String autoCountSql(IPage<?> page, String sql) {
if (!page.optimizeCountSql()) {
return lowLevelCountSql(sql);
}
try {
Select select = (Select) CCJSqlParserUtil.parse(sql);
SelectBody selectBody = select.getSelectBody();
// https://github.com/baomidou/mybatis-plus/issues/3920 分页增加union语法支持
if (selectBody instanceof SetOperationList) {
return lowLevelCountSql(sql);
}
PlainSelect plainSelect = (PlainSelect) select.getSelectBody();
Distinct distinct = plainSelect.getDistinct();
GroupByElement groupBy = plainSelect.getGroupBy();
List<OrderByElement> orderBy = plainSelect.getOrderByElements();
if (CollectionUtils.isNotEmpty(orderBy)) {
boolean canClean = true;
if (groupBy != null) {
// 包含groupBy 不去除orderBy
canClean = false;
}
if (canClean) {
for (OrderByElement order : orderBy) {
// order by 里带参数,不去除order by
Expression expression = order.getExpression();
if (!(expression instanceof Column) && expression.toString().contains(StringPool.QUESTION_MARK)) {
canClean = false;
break;
}
}
}
if (canClean) {
plainSelect.setOrderByElements(null);
}
}
//#95 Github, selectItems contains #{} ${}, which will be translated to ?, and it may be in a function: power(#{myInt},2)
for (SelectItem item : plainSelect.getSelectItems()) {
if (item.toString().contains(StringPool.QUESTION_MARK)) {
return lowLevelCountSql(select.toString());
}
}
// 包含 distinct、groupBy不优化
if (distinct != null || null != groupBy) {
return lowLevelCountSql(select.toString());
}
// 包含 join 连表,进行判断是否移除 join 连表
if (optimizeJoin && page.optimizeJoinOfCountSql()) {
List<Join> joins = plainSelect.getJoins();
if (CollectionUtils.isNotEmpty(joins)) {
boolean canRemoveJoin = true;
String whereS = Optional.ofNullable(plainSelect.getWhere()).map(Expression::toString).orElse(StringPool.EMPTY);
// 不区分大小写
whereS = whereS.toLowerCase();
for (Join join : joins) {
if (!join.isLeft()) {
canRemoveJoin = false;
break;
}
FromItem rightItem = join.getRightItem();
String str = "";
if (rightItem instanceof Table) {
Table table = (Table) rightItem;
str = Optional.ofNullable(table.getAlias()).map(Alias::getName).orElse(table.getName()) + StringPool.DOT;
} else if (rightItem instanceof SubSelect) {
SubSelect subSelect = (SubSelect) rightItem;
/* 如果 left join 是子查询，并且子查询里包含 ?(代表有入参) 或者 where 条件里包含使用 join 的表的字段作条件,就不移除 join */
if (subSelect.toString().contains(StringPool.QUESTION_MARK)) {
canRemoveJoin = false;
break;
}
str = subSelect.getAlias().getName() + StringPool.DOT;
}
// 不区分大小写
str = str.toLowerCase();
if (whereS.contains(str)) {
/* 如果 where 条件里包含使用 join 的表的字段作条件,就不移除 join */
canRemoveJoin = false;
break;
}
for (Expression expression : join.getOnExpressions()) {
if (expression.toString().contains(StringPool.QUESTION_MARK)) {
/* 如果 join 里包含 ?(代表有入参) 就不移除 join */
canRemoveJoin = false;
break;
}
}
}
if (canRemoveJoin) {
plainSelect.setJoins(null);
}
}
}
// 优化 SQL
plainSelect.setSelectItems(COUNT_SELECT_ITEM);
return select.toString();
} catch (JSQLParserException e) {
// 无法优化使用原 SQL
logger.warn("optimize this sql to a count sql has exception, sql:\"" + sql + "\", exception:\n" + e.getCause());
} catch (Exception e) {
logger.warn("optimize this sql to a count sql has error, sql:\"" + sql + "\", exception:\n" + e);
}
return lowLevelCountSql(sql);
}