[Java]mybatis数据集包装

组装之前

解析mapper

MappedStatement

MapperBuilderAssistant

组装的过程

ResultSetHandler

@Override
public List<Object> handleResultSets(Statement stmt) throws SQLException {
  ErrorContext.instance().activity("handling results").object(mappedStatement.getId());

  final List<Object> multipleResults = new ArrayList<Object>();

  int resultSetCount = 0;
  ResultSetWrapper rsw = getFirstResultSet(stmt);

  List<ResultMap> resultMaps = mappedStatement.getResultMaps();
  int resultMapCount = resultMaps.size();
  validateResultMapsCount(rsw, resultMapCount);
  while (rsw != null && resultMapCount > resultSetCount) {
    ResultMap resultMap = resultMaps.get(resultSetCount);
    handleResultSet(rsw, resultMap, multipleResults, null);
    rsw = getNextResultSet(stmt);
    cleanUpAfterHandlingResultSet();
    resultSetCount++;
  }

  String[] resultSets = mappedStatement.getResultSets();
  if (resultSets != null) {
    while (rsw != null && resultSetCount < resultSets.length) {
      ResultMapping parentMapping = nextResultMaps.get(resultSets[resultSetCount]);
      if (parentMapping != null) {
        String nestedResultMapId = parentMapping.getNestedResultMapId();
        ResultMap resultMap = configuration.getResultMap(nestedResultMapId);
        handleResultSet(rsw, resultMap, null, parentMapping);
      }
      rsw = getNextResultSet(stmt);
      cleanUpAfterHandlingResultSet();
      resultSetCount++;
    }
  }

  return collapseSingleResultList(multipleResults);
}

private Object getRowValue(ResultSetWrapper rsw, ResultMap resultMap) throws SQLException {
  final ResultLoaderMap lazyLoader = new ResultLoaderMap();
  Object rowValue = createResultObject(rsw, resultMap, lazyLoader, null);
  if (rowValue != null && !hasTypeHandlerForResultObject(rsw, resultMap.getType())) {
    final MetaObject metaObject = configuration.newMetaObject(rowValue);
    boolean foundValues = this.useConstructorMappings;
    if (shouldApplyAutomaticMappings(resultMap, false)) {
      foundValues = applyAutomaticMappings(rsw, resultMap, metaObject, null) || foundValues;
    }
    foundValues = applyPropertyMappings(rsw, resultMap, metaObject, lazyLoader, null) || foundValues;
    foundValues = lazyLoader.size() > 0 || foundValues;
    rowValue = (foundValues || configuration.isReturnInstanceForEmptyRow()) ? rowValue : null;
  }
  return rowValue;
}

如果有注册的TypyHandler，在这里判断并使用：

private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix)
    throws SQLException {
  final Class<?> resultType = resultMap.getType();
  final MetaClass metaType = MetaClass.forClass(resultType, reflectorFactory);
  final List<ResultMapping> constructorMappings = resultMap.getConstructorResultMappings();
  if (hasTypeHandlerForResultObject(rsw, resultType)) {
    return createPrimitiveResultObject(rsw, resultMap, columnPrefix);
  } else if (!constructorMappings.isEmpty()) {
    return createParameterizedResultObject(rsw, resultType, constructorMappings, constructorArgTypes, constructorArgs, columnPrefix);
  } else if (resultType.isInterface() || metaType.hasDefaultConstructor()) {
    return objectFactory.create(resultType);
  } else if (shouldApplyAutomaticMappings(resultMap, false)) {
    return createByConstructorSignature(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix);
  }
  throw new ExecutorException("Do not know how to create an instance of " + resultType);
}

对象数据：MetaObject

private MetaObject(Object object, ObjectFactory objectFactory, ObjectWrapperFactory objectWrapperFactory, ReflectorFactory reflectorFactory) {
  this.originalObject = object;
  this.objectFactory = objectFactory;
  this.objectWrapperFactory = objectWrapperFactory;
  this.reflectorFactory = reflectorFactory;

  if (object instanceof ObjectWrapper) {
    this.objectWrapper = (ObjectWrapper) object;
  } else if (objectWrapperFactory.hasWrapperFor(object)) {
    this.objectWrapper = objectWrapperFactory.getWrapperFor(this, object);
  } else if (object instanceof Map) {
    this.objectWrapper = new MapWrapper(this, (Map) object);
  } else if (object instanceof Collection) {
    this.objectWrapper = new CollectionWrapper(this, (Collection) object);
  } else {
    this.objectWrapper = new BeanWrapper(this, object);
  }
}

对象包装类：BeanWrapper，此外还有Map和Collection的包装类

public BeanWrapper(MetaObject metaObject, Object object) {
  super(metaObject);
  this.object = object;
  this.metaClass = MetaClass.forClass(object.getClass(), metaObject.getReflectorFactory());
}

class对象：MetaClass

 private MetaClass(Class<?> type, ReflectorFactory reflectorFactory) {
this.reflectorFactory = reflectorFactory;
   this.reflector = reflectorFactory.findForClass(type);
 }

类反射获取的数据：Reflector

public Reflector(Class<?> clazz) {
  type = clazz;
  addDefaultConstructor(clazz);
  addGetMethods(clazz);
  addSetMethods(clazz);
  addFields(clazz);
  readablePropertyNames = getMethods.keySet().toArray(new String[getMethods.keySet().size()]);
  writeablePropertyNames = setMethods.keySet().toArray(new String[setMethods.keySet().size()]);
  for (String propName : readablePropertyNames) {
    caseInsensitivePropertyMap.put(propName.toUpperCase(Locale.ENGLISH), propName);
  }
  for (String propName : writeablePropertyNames) {
    caseInsensitivePropertyMap.put(propName.toUpperCase(Locale.ENGLISH), propName);
  }
}