Mybatis中的resultType和resultMap 区别

Mybatis中的resultType和resultMap

 是mybatis 中返回类型一定用到的，但不会同时出现。mybatis返回类型肯定是map结构，然后根据返回类型是map还是对象类型，再转换。

在给对象设置属性的时候，两个方法肯定会调用。

private Object getRowValue(ResultSetWrapper rsw, ResultMap resultMap) throws SQLException {
    final ResultLoaderMap lazyLoader = new ResultLoaderMap();
    Object resultObject = createResultObject(rsw, resultMap, lazyLoader, null);
    if (resultObject != null && !typeHandlerRegistry.hasTypeHandler(resultMap.getType())) {
      final MetaObject metaObject = configuration.newMetaObject(resultObject);
      boolean foundValues = resultMap.getConstructorResultMappings().size() > 0;
      if (shouldApplyAutomaticMappings(resultMap, !AutoMappingBehavior.NONE.equals(configuration.getAutoMappingBehavior()))) {        
        foundValues = applyAutomaticMappings(rsw, resultMap, metaObject, null) || foundValues;
      }
      foundValues = applyPropertyMappings(rsw, resultMap, metaObject, lazyLoader, null) || foundValues;
      foundValues = lazyLoader.size() > 0 || foundValues;
      resultObject = foundValues ? resultObject : null;
      return resultObject;
    }
    return resultObject;
  }

private boolean applyAutomaticMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, String columnPrefix) throws SQLException {
    final List unmappedColumnNames = rsw.getUnmappedColumnNames(resultMap, columnPrefix);
     //unmappedColumnNames是配置文件中未配的resultMap中的属性，下面是自动映射规则，去设值

    boolean foundValues = false;
    for (String columnName : unmappedColumnNames) {
      String propertyName = columnName;
      if (columnPrefix != null && columnPrefix.length() > 0) {
        // When columnPrefix is specified,
        // ignore columns without the prefix.
        if (columnName.toUpperCase(Locale.ENGLISH).startsWith(columnPrefix)) {
          propertyName = columnName.substring(columnPrefix.length());
        } else {
          continue;
        }
      }

     //这个自动映射属性的规则，很普通，根据映射出的属性，利用反射查找该对象，是否存在此属性，以便设值
     final String property = metaObject.findProperty(propertyName, configuration.isMapUnderscoreToCamelCase());
      if (property != null && metaObject.hasSetter(property)) {
        final Class propertyType = metaObject.getSetterType(property);
        if (typeHandlerRegistry.hasTypeHandler(propertyType)) {
          final TypeHandler typeHandler = rsw.getTypeHandler(propertyType, columnName);
          final Object value = typeHandler.getResult(rsw.getResultSet(), columnName);
          if (value != null || configuration.isCallSettersOnNulls()) { // issue #377, call setter on nulls
            if (value != null || !propertyType.isPrimitive()) {
              metaObject.setValue(property, value);
            }
            foundValues = true;
          }
        }
      }
    }
    return foundValues;
  }

private boolean applyPropertyMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, ResultLoaderMap lazyLoader, String columnPrefix)
      throws SQLException {
    final List mappedColumnNames = rsw.getMappedColumnNames(resultMap, columnPrefix);
//mappedColumnNames 是配置文件中配置resultMap中对应的映射，如果不配，此方法体就不会执行，走上面那该自动映射规则去映射属性（非常智能，但这个智能属性对应，不怎么特殊，也没提供自动映射拓展点

     boolean foundValues = false;
    final List propertyMappings = resultMap.getPropertyResultMappings();
    for (ResultMapping propertyMapping : propertyMappings) {
      final String column = prependPrefix(propertyMapping.getColumn(), columnPrefix);
      if (propertyMapping.isCompositeResult() 
          || (column != null && mappedColumnNames.contains(column.toUpperCase(Locale.ENGLISH))) 
          || propertyMapping.getResultSet() != null) {
        Object value = getPropertyMappingValue(rsw.getResultSet(), metaObject, propertyMapping, lazyLoader, columnPrefix);
        final String property = propertyMapping.getProperty(); // issue #541 make property optional
        if (value != NO_VALUE && property != null && (value != null || configuration.isCallSettersOnNulls())) { // issue #377, call setter on nulls
          if (value != null || !metaObject.getSetterType(property).isPrimitive()) {
            metaObject.setValue(property, value);
          }
          foundValues = true;
        }
      }
    }
    return foundValues;
  }