org.apache.ibatis.session.ResultHandler Java Examples

@Test
public void shouldHandleStop() throws Exception {
  SqlSession sqlSession = sqlSessionFactory.openSession();
  final SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
  final List<Account> accounts = new ArrayList<Account>();
  try {
    Date targetMonth = fmt.parse("2014-01-01");
    sqlSession.select("collectPageByBirthMonth", targetMonth, new ResultHandler() {
      @Override
      public void handleResult(ResultContext context) {
        Account account = (Account) context.getResultObject();
        accounts.add(account);
        if (accounts.size() > 1)
          context.stop();
      }
    });
  } finally {
    sqlSession.close();
  }
  assertEquals(2, accounts.size());
  assertEquals("Bob1", accounts.get(0).getAccountName());
  assertEquals("Bob2", accounts.get(1).getAccountName());
}
 

@Override
public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler)
{
    long startTime = System.currentTimeMillis();
    PassThroughMetricsResultsHandler passThroughHandler = new PassThroughMetricsResultsHandler(handler, startTime, statement);
    try
    {
        this.sqlSession.select(statement, parameter, rowBounds, passThroughHandler);
    }
    finally
    {
        if (!passThroughHandler.hasQueryExecutionTimeBeenReported())
        {
            reportQueryExecuted(startTime, SELECT_LABEL, statement);
        }
    }
}
 

protected final void testAndVerifySelect() throws Exception {
    // Given
    final String selectId = "selectId";
    SqlSession sqlSession = getSqlSession();
    // When
    sqlSession.select(selectId, new DefaultResultHandler());
    sqlSession.select(selectId, new Object(), new DefaultResultHandler());
    sqlSession.select(selectId, new Object(), RowBounds.DEFAULT, new DefaultResultHandler());
    // Then
    PluginTestVerifier verifier = PluginTestVerifierHolder.getInstance();
    Method select1 = sqlSession.getClass().getDeclaredMethod("select", String.class, ResultHandler.class);
    verifier.verifyTrace(event("MYBATIS", select1, Expectations.cachedArgs(selectId)));
    Method select2 = sqlSession.getClass().getDeclaredMethod("select", String.class, Object.class,
            ResultHandler.class);
    verifier.verifyTrace(event("MYBATIS", select2, Expectations.cachedArgs(selectId)));
    Method select3 = sqlSession.getClass().getDeclaredMethod("select", String.class, Object.class, RowBounds.class,
            ResultHandler.class);
    verifier.verifyTrace(event("MYBATIS", select3, Expectations.cachedArgs(selectId)));
}
 

@Override
@SuppressWarnings("rawtypes")
public List<NodePropertyEntity> selectNodePropertiesByTypes(Set<QName> qnames)
{
    final List<NodePropertyEntity> properties = new ArrayList<NodePropertyEntity>();

    // qnames of properties that are encrypted
    Set<Long> qnameIds = qnameDAO.convertQNamesToIds(qnames, false);
    if(qnameIds.size() > 0)
    {
        IdsEntity param = new IdsEntity();
        param.setIds(new ArrayList<Long>(qnameIds));
        // TODO - use a callback approach
        template.select(SELECT_PROPERTIES_BY_TYPES, param, new ResultHandler()
        {
            @Override
            public void handleResult(ResultContext context)
            {
                properties.add((NodePropertyEntity)context.getResultObject());
            }
        });
    }

    return properties;
}
 

@SuppressWarnings("rawtypes")
@Override
public List<NodePropertyEntity> selectNodePropertiesByDataType(QName dataType, long minNodeId, long maxNodeId)
{
    int typeOrdinal = NodePropertyValue.convertToTypeOrdinal(dataType);
    
    IdsEntity ids = new IdsEntity();
    ids.setIdOne((long)typeOrdinal);
    ids.setIdTwo(minNodeId);
    ids.setIdThree(maxNodeId);
    final List<NodePropertyEntity> properties = new ArrayList<NodePropertyEntity>();
    
    template.select(SELECT_PROPERTIES_BY_ACTUAL_TYPE, ids, new ResultHandler()
    {
        @Override
        public void handleResult(ResultContext context)
        {
            properties.add((NodePropertyEntity)context.getResultObject());
        }
    });
    
    return properties;
}
 

@Override
protected void selectNodesWithAspects(
        List<Long> qnameIds,
        Long minNodeId, Long maxNodeId,
        final NodeRefQueryCallback resultsCallback)
{
    @SuppressWarnings("rawtypes")
    ResultHandler resultHandler = new ResultHandler()
    {
        public void handleResult(ResultContext context)
        {
            NodeEntity entity = (NodeEntity) context.getResultObject();
            Pair<Long, NodeRef> nodePair = new Pair<Long, NodeRef>(entity.getId(), entity.getNodeRef());
            resultsCallback.handle(nodePair);
        }
    };
    
    IdsEntity parameters = new IdsEntity();
    parameters.setIdOne(minNodeId);
    parameters.setIdTwo(maxNodeId);
    parameters.setIds(qnameIds);
    template.select(SELECT_NODES_WITH_ASPECT_IDS, parameters, resultHandler);
}
 

/**
 * @param keyProperties         the properties that make up the unique key
 * @param collectionProperty    the property mapped using a nested <b>ResultMap</b>
 * @param resultHandler         the result handler that will receive the rolled-up results
 * @param maxResults            the maximum number of results to retrieve (-1 for no limit).
 *                              Make sure that the query result limit is large enough to produce this
 *                              at least this number of results
 */
public RollupResultHandler(Configuration configuration, String[] keyProperties, String collectionProperty, ResultHandler resultHandler, int maxResults)
{
    if (keyProperties == null || keyProperties.length == 0)
    {
        throw new IllegalArgumentException("RollupRowHandler can only be used with at least one key property.");
    }
    if (collectionProperty == null)
    {
        throw new IllegalArgumentException("RollupRowHandler must have a collection property.");
    }
    this.configuration = configuration;
    this.keyProperties = keyProperties;
    this.collectionProperty = collectionProperty;
    this.resultHandler = resultHandler;
    this.maxResults = maxResults;
    this.rawResults = new ArrayList<Object>(100);
}
 

protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
  this.configuration = mappedStatement.getConfiguration();
  this.executor = executor;
  this.mappedStatement = mappedStatement;
  this.rowBounds = rowBounds;

  this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
  this.objectFactory = configuration.getObjectFactory();

  if (boundSql == null) { // issue #435, get the key before calculating the statement
    generateKeys(parameterObject);
    boundSql = mappedStatement.getBoundSql(parameterObject);
  }

  this.boundSql = boundSql;

  //生成parameterHandler
  this.parameterHandler = configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);
  //生成resultSetHandler
  this.resultSetHandler = configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);
}
 

@Test
// issue #542
public void testGetPersonWithHandler() {
  SqlSession sqlSession = sqlSessionFactory.openSession();
  try {
    sqlSession.select("getPersons", new ResultHandler() {
      public void handleResult(ResultContext context) {
        Person person = (Person) context.getResultObject();
        if ("grandma".equals(person.getName())) {
          Assert.assertEquals(2, person.getItems().size());
        }
      }
    });
  } finally {
    sqlSession.close();
  }
}
 

@SuppressWarnings("rawtypes")
private Long executeQueryCount(Executor executor, MappedStatement countMs, Object parameter,
                               BoundSql boundSql, RowBounds rowBounds,
                               ResultHandler resultHandler) throws IllegalAccessException,
        SQLException {
    CacheKey countKey = executor.createCacheKey(countMs, parameter, RowBounds.DEFAULT,
            boundSql);

    String orignSql = boundSql.getSql().replaceAll(";$", "");
    // count sql
    String countSql = PageSqlUtils.getCountSql(orignSql);

    BoundSql countBoundSql = new BoundSql(countMs.getConfiguration(), countSql,
            boundSql.getParameterMappings(), parameter);
    // 执行 count 查询
    Object countResultList = executor.query(countMs, parameter, RowBounds.DEFAULT,
            resultHandler, countKey, countBoundSql);
    Long count = (Long) ((List) countResultList).get(0);
    return count;
}
 

@SuppressWarnings("rawtypes")
	private Long executeQueryCount(Executor executor, MappedStatement countMs,
            Object parameter, BoundSql boundSql,
			RowBounds rowBounds, ResultHandler resultHandler) throws IllegalAccessException, SQLException {
		CacheKey countKey = executor.createCacheKey(countMs, parameter, RowBounds.DEFAULT, boundSql);
		
		String orignSql = StringUtils.replace(boundSql.getSql(), ";$", StringUtils.EMPTY);
		// count sql
		String countSql = PageSqlUtils.getCountSql(orignSql);
		
		BoundSql countBoundSql = new BoundSql(countMs.getConfiguration(), countSql, boundSql.getParameterMappings(),
				parameter);
//		for (ParameterMapping parameterMapping : boundSql.getParameterMappings()) {
//			String propertyName = parameterMapping.getProperty();
//			if(boundSql.hasAdditionalParameter(propertyName)){
//				countBoundSql.setAdditionalParameter(propertyName, boundSql.getAdditionalParameter(propertyName));
//			}
//		}
		// 执行 count 查询
		Object countResultList = executor.query(countMs, parameter, RowBounds.DEFAULT, resultHandler, countKey,
				countBoundSql);
		Long count = (Long) ((List) countResultList).get(0);
		return count;
	}
 

@SuppressWarnings("rawtypes")
private List executeQuery(Executor executor, MappedStatement ms,
           Object parameter, BoundSql boundSql,
		RowBounds rowBounds, ResultHandler resultHandler,PageParams pageParams) throws IllegalAccessException, SQLException {
	CacheKey countKey = executor.createCacheKey(ms, parameter, RowBounds.DEFAULT, boundSql);
	
	String orignSql = StringUtils.replace(boundSql.getSql(), ";$", StringUtils.EMPTY);
	
	String pageSql = PageSqlUtils.getLimitSQL(dbType,orignSql,pageParams);
	
	BoundSql countBoundSql = new BoundSql(ms.getConfiguration(), pageSql, boundSql.getParameterMappings(),
			parameter);
	
	List<?> resultList = executor.query(ms, parameter, RowBounds.DEFAULT, resultHandler, countKey,
			countBoundSql);
	return resultList;
}
 

private void handleRowValuesForNestedResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
  final DefaultResultContext resultContext = new DefaultResultContext();
  skipRows(rsw.getResultSet(), rowBounds);
  Object rowValue = null;
  while (shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {
    final ResultMap discriminatedResultMap = resolveDiscriminatedResultMap(rsw.getResultSet(), resultMap, null);
    final CacheKey rowKey = createRowKey(discriminatedResultMap, rsw, null);
    Object partialObject = nestedResultObjects.get(rowKey);
    // issue #577 && #542
    if (mappedStatement.isResultOrdered()) {
      if (partialObject == null && rowValue != null) {
        nestedResultObjects.clear();
        storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
      }
      rowValue = getRowValue(rsw, discriminatedResultMap, rowKey, rowKey, null, partialObject);
    } else {
      rowValue = getRowValue(rsw, discriminatedResultMap, rowKey, rowKey, null, partialObject);
      if (partialObject == null) {
        storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
      }
    }
  }
  if (rowValue != null && mappedStatement.isResultOrdered() && shouldProcessMoreRows(resultContext, rowBounds)) {
    storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
  }
}
 

@Override
public Object intercept(Invocation invocation) throws Throwable {
       List<Sort> sortList = getSortList();
       if (sortList == null || sortList.size() == 0) {
           return invocation.proceed();
       }

       Executor executor = (Executor) invocation.getTarget();
       Object[] args = invocation.getArgs();
       MappedStatement ms = (MappedStatement) args[0];
       Object parameter = args[1];
       RowBounds rowBounds = (RowBounds) args[2];
       ResultHandler resultHandler = (ResultHandler) args[3];

       // 计算修改BoundSql
       BoundSql boundSql = ms.getBoundSql(parameter);
       MetaObject boundSqlHandler = MetaObject.forObject(boundSql, new DefaultObjectFactory(), new DefaultObjectWrapperFactory());
       Dialect dialect = DialectParser.parse(ms.getConfiguration());
       String sql = (String) boundSqlHandler.getValue("sql");
       sql = dialect.addSortString(sql, sortList);
       boundSqlHandler.setValue("sql", sql);

       // 继续执行原来的代码
       CacheKey key = executor.createCacheKey(ms, parameter, rowBounds, boundSql);
       return executor.query(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
 

@Test
public void shouldHandleRowBounds() throws Exception {
  SqlSession sqlSession = sqlSessionFactory.openSession();
  final SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
  Date targetMonth = fmt.parse("2014-01-01");
  final List<Account> accounts = new ArrayList<Account>();
  try {
    sqlSession.select("collectPageByBirthMonth", targetMonth, new RowBounds(1, 2), new ResultHandler() {
      @Override
      public void handleResult(ResultContext context) {
        Account account = (Account) context.getResultObject();
        accounts.add(account);
      }
    });
  } finally {
    sqlSession.close();
  }
  assertEquals(2, accounts.size());
  assertEquals("Bob2", accounts.get(0).getAccountName());
  assertEquals("Bob3", accounts.get(1).getAccountName());
}
 

@Test(expected=PersistenceException.class)
public void testUnorderedGetPersonWithHandler() {
  SqlSession sqlSession = sqlSessionFactory.openSession();
  try {
    sqlSession.select("getPersonsWithItemsOrdered", new ResultHandler() {
      public void handleResult(ResultContext context) {
        Person person = (Person) context.getResultObject();
        if ("grandma".equals(person.getName())) {
          Assert.assertEquals(2, person.getItems().size());
        }
      }
    });
  } finally {
    sqlSession.close();
  }
}
 

@Override
public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
  Statement stmt = null;
  try {
    Configuration configuration = ms.getConfiguration();
    //新建一个StatementHandler
    //这里看到ResultHandler传入了
    StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
    //准备语句
    stmt = prepareStatement(handler, ms.getStatementLog());
    //StatementHandler.query
    return handler.<E>query(stmt, resultHandler);
  } finally {
    closeStatement(stmt);
  }
}
 

@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
    throws SQLException {
  Cache cache = ms.getCache();
  //默认情况下是没有开启缓存的(二级缓存).要开启二级缓存,你需要在你的 SQL 映射文件中添加一行: <cache/>
  //简单的说，就是先查CacheKey，查不到再委托给实际的执行器去查
  if (cache != null) {
    flushCacheIfRequired(ms);
    if (ms.isUseCache() && resultHandler == null) {
      ensureNoOutParams(ms, parameterObject, boundSql);
      @SuppressWarnings("unchecked")
      List<E> list = (List<E>) tcm.getObject(cache, key);
      if (list == null) {
        list = delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
        tcm.putObject(cache, key, list); // issue #578 and #116
      }
      return list;
    }
  }
  return delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
 

public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {

    //根据语句类型，委派到不同的语句处理器(STATEMENT|PREPARED|CALLABLE)
    switch (ms.getStatementType()) {
      case STATEMENT:
        delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      case PREPARED:
        delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      case CALLABLE:
        delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
        break;
      default:
        throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
    }

  }
 

@Test
public void shouldHandleRowBounds() throws Exception {
  SqlSession sqlSession = sqlSessionFactory.openSession();
  final SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
  Date targetMonth = fmt.parse("2014-01-01");
  final List<Account> accounts = new ArrayList<Account>();
  try {
    sqlSession.select("collectPageByBirthMonth", targetMonth, new RowBounds(1, 2), new ResultHandler() {
      @Override
      public void handleResult(ResultContext context) {
        Account account = (Account) context.getResultObject();
        accounts.add(account);
      }
    });
  } finally {
    sqlSession.close();
  }
  assertEquals(2, accounts.size());
  assertEquals("Bob2", accounts.get(0).getAccountName());
  assertEquals("Bob3", accounts.get(1).getAccountName());
}
 

private void handleRowValuesForNestedResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
  final DefaultResultContext resultContext = new DefaultResultContext();
  skipRows(rsw.getResultSet(), rowBounds);
  Object rowValue = null;
  while (shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {
    final ResultMap discriminatedResultMap = resolveDiscriminatedResultMap(rsw.getResultSet(), resultMap, null);
    final CacheKey rowKey = createRowKey(discriminatedResultMap, rsw, null);
    Object partialObject = nestedResultObjects.get(rowKey);
    // issue #577 && #542
    if (mappedStatement.isResultOrdered()) {
      if (partialObject == null && rowValue != null) {
        nestedResultObjects.clear();
        storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
      }
      rowValue = getRowValue(rsw, discriminatedResultMap, rowKey, rowKey, null, partialObject);
    } else {
      rowValue = getRowValue(rsw, discriminatedResultMap, rowKey, rowKey, null, partialObject);
      if (partialObject == null) {
        storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
      }
    }
  }
  if (rowValue != null && mappedStatement.isResultOrdered() && shouldProcessMoreRows(resultContext, rowBounds)) {
    storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
  }
}
 

private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
  List<E> list;
  //先向缓存中放入占位符？？？
  localCache.putObject(key, EXECUTION_PLACEHOLDER);
  try {
    list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
  } finally {
    //最后删除占位符
    localCache.removeObject(key);
  }
  //加入缓存
  localCache.putObject(key, list);
  //如果是存储过程，OUT参数也加入缓存
  if (ms.getStatementType() == StatementType.CALLABLE) {
    localOutputParameterCache.putObject(key, parameter);
  }
  return list;
}
 

@Override
public <E> List<E> doQuery(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql)
    throws SQLException {
  Statement stmt = null;
  try {
    flushStatements();
    Configuration configuration = ms.getConfiguration();
    StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameterObject, rowBounds, resultHandler, boundSql);
    Connection connection = getConnection(ms.getStatementLog());
    stmt = handler.prepare(connection);
    handler.parameterize(stmt);
    return handler.<E>query(stmt, resultHandler);
  } finally {
    closeStatement(stmt);
  }
}
 

private SortedMap<Integer, String> getParams(Method method, boolean hasNamedParameters) {
  //用一个TreeMap,这样就保证还是按参数的先后顺序
  final SortedMap<Integer, String> params = new TreeMap<Integer, String>();
  final Class<?>[] argTypes = method.getParameterTypes();
  for (int i = 0; i < argTypes.length; i++) {
    //是否不是RowBounds/ResultHandler类型的参数
    if (!RowBounds.class.isAssignableFrom(argTypes[i]) && !ResultHandler.class.isAssignableFrom(argTypes[i])) {
      //参数名字默认为0,1,2，这就是为什么xml里面可以用#{1}这样的写法来表示参数了
      String paramName = String.valueOf(params.size());
      if (hasNamedParameters) {
        //还可以用注解@Param来重命名参数
        paramName = getParamNameFromAnnotation(method, i, paramName);
      }
      params.put(i, paramName);
    }
  }
  return params;
}
 

@Override
@SuppressWarnings("rawtypes")
public Pair<Long, Long> getNodeIdsIntervalForType(QName type, Long startTxnTime, Long endTxnTime)
{
    final Pair<Long, Long> intervalPair = new Pair<Long, Long>(LONG_ZERO, LONG_ZERO);
    Pair<Long, QName> typePair = qnameDAO.getQName(type);
    if (typePair == null)
    {
        // Return default
        return intervalPair;
    }
    TransactionQueryEntity txnQuery = new TransactionQueryEntity();
    txnQuery.setTypeQNameId(typePair.getFirst());
    txnQuery.setMinCommitTime(startTxnTime);
    txnQuery.setMaxCommitTime(endTxnTime);
    
    ResultHandler resultHandler = new ResultHandler()
    {
        @SuppressWarnings("unchecked")
        public void handleResult(ResultContext context)
        {
            Map<Long, Long> result = (Map<Long, Long>) context.getResultObject();
            if (result != null)
            {
                intervalPair.setFirst(result.get("minId"));
                intervalPair.setSecond(result.get("maxId"));
            }
        }
    };
    template.select(SELECT_NODE_INTERVAL_BY_TYPE, txnQuery, resultHandler);
    return intervalPair;
}
 

private Class<?> getParameterType(Method method) {
  Class<?> parameterType = null;
  Class<?>[] parameterTypes = method.getParameterTypes();
  for (int i = 0; i < parameterTypes.length; i++) {
    if (!RowBounds.class.isAssignableFrom(parameterTypes[i]) && !ResultHandler.class.isAssignableFrom(parameterTypes[i])) {
      if (parameterType == null) {
        parameterType = parameterTypes[i];
      } else {
        // issue #135
        parameterType = ParamMap.class;
      }
    }
  }
  return parameterType;
}
 

private void storeObject(ResultHandler resultHandler, DefaultResultContext resultContext, Object rowValue, ResultMapping parentMapping, ResultSet rs) throws SQLException {
  if (parentMapping != null) {
    linkToParents(rs, parentMapping, rowValue);
  } else {
    callResultHandler(resultHandler, resultContext, rowValue);
  }
}
 

@SuppressWarnings("unchecked")
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
  ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
  //如果已经关闭，报错
  if (closed) {
    throw new ExecutorException("Executor was closed.");
  }
  //先清局部缓存，再查询.但仅查询堆栈为0，才清。为了处理递归调用
  if (queryStack == 0 && ms.isFlushCacheRequired()) {
    clearLocalCache();
  }
  List<E> list;
  try {
    //加一,这样递归调用到上面的时候就不会再清局部缓存了
    queryStack++;
    //先根据cachekey从localCache去查
    list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
    if (list != null) {
      //若查到localCache缓存，处理localOutputParameterCache
      handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
    } else {
      //从数据库查
      list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
    }
  } finally {
    //清空堆栈
    queryStack--;
  }
  if (queryStack == 0) {
    //延迟加载队列中所有元素
    for (DeferredLoad deferredLoad : deferredLoads) {
      deferredLoad.load();
    }
    // issue #601
    //清空延迟加载队列
    deferredLoads.clear();
    if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
      // issue #482
  	//如果是STATEMENT，清本地缓存
      clearLocalCache();
    }
  }
  return list;
}
 

@Override
public void select(String statement, Object parameter, ResultHandler handler) {
  long start = System.currentTimeMillis();

  super.select(statement, parameter, handler);

  long duration = System.currentTimeMillis() - start;
  logStatement(SqlStatementType.SELECT, parameter, statement, duration);
}
 

@Override
public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
  CallableStatement cs = (CallableStatement) statement;
  cs.execute();
  List<E> resultList = resultSetHandler.<E>handleResultSets(cs);
  resultSetHandler.handleOutputParameters(cs);
  return resultList;
}