org.apache.ibatis.mapping.ResultMap Java Examples

private String processNestedResultMappings(XNode context, List<ResultMapping> resultMappings) throws Exception {
	  //处理association|collection|case
    if ("association".equals(context.getName())
        || "collection".equals(context.getName())
        || "case".equals(context.getName())) {
    	
//    	<resultMap id="blogResult" type="Blog">
//    	  <association property="author" column="author_id" javaType="Author" select="selectAuthor"/>
//    	</resultMap>
//如果不是嵌套查询
      if (context.getStringAttribute("select") == null) {
    	//则递归调用5.1 resultMapElement
        ResultMap resultMap = resultMapElement(context, resultMappings);
        return resultMap.getId();
      }
    }
    return null;
  }
 

private String processNestedResultMappings(XNode context, List<ResultMapping> resultMappings) throws Exception {
	  //处理association|collection|case
    if ("association".equals(context.getName())
        || "collection".equals(context.getName())
        || "case".equals(context.getName())) {
    	
//    	<resultMap id="blogResult" type="Blog">
//    	  <association property="author" column="author_id" javaType="Author" select="selectAuthor"/>
//    	</resultMap>
//如果不是嵌套查询
      if (context.getStringAttribute("select") == null) {
    	//则递归调用5.1 resultMapElement
        ResultMap resultMap = resultMapElement(context, resultMappings);
        return resultMap.getId();
      }
    }
    return null;
  }
 

public ResultMap resolveDiscriminatedResultMap(ResultSet rs, ResultMap resultMap, String columnPrefix) throws SQLException {
  Set<String> pastDiscriminators = new HashSet<String>();
  Discriminator discriminator = resultMap.getDiscriminator();
  while (discriminator != null) {
    final Object value = getDiscriminatorValue(rs, discriminator, columnPrefix);
    final String discriminatedMapId = discriminator.getMapIdFor(String.valueOf(value));
    if (configuration.hasResultMap(discriminatedMapId)) {
      resultMap = configuration.getResultMap(discriminatedMapId);
      Discriminator lastDiscriminator = discriminator;
      discriminator = resultMap.getDiscriminator();
      if (discriminator == lastDiscriminator || !pastDiscriminators.add(discriminatedMapId)) {
        break;
      }
    } else {
      break;
    }
  }
  return resultMap;
}
 

private void handleResultSet(ResultSetWrapper rsw, ResultMap resultMap, List<Object> multipleResults, ResultMapping parentMapping) throws SQLException {
  try {
    if (parentMapping != null) {
      handleRowValues(rsw, resultMap, null, RowBounds.DEFAULT, parentMapping);
    } else {
      if (resultHandler == null) {
        //如果没有resultHandler
        //新建DefaultResultHandler
        DefaultResultHandler defaultResultHandler = new DefaultResultHandler(objectFactory);
        //调用自己的handleRowValues
        handleRowValues(rsw, resultMap, defaultResultHandler, rowBounds, null);
        //得到记录的list
        multipleResults.add(defaultResultHandler.getResultList());
      } else {
        //如果有resultHandler
        handleRowValues(rsw, resultMap, resultHandler, rowBounds, null);
      }
    }
  } finally {
    //最后别忘了关闭结果集，这个居然出bug了
    // issue #228 (close resultsets)
    closeResultSet(rsw.getResultSet());
  }
}
 

private Object createParameterizedResultObject(ResultSetWrapper rsw, Class<?> resultType, List<ResultMapping> constructorMappings,
    List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix) throws SQLException {
  boolean foundValues = false;
  for (ResultMapping constructorMapping : constructorMappings) {
    final Class<?> parameterType = constructorMapping.getJavaType();
    final String column = constructorMapping.getColumn();
    final Object value;
    if (constructorMapping.getNestedQueryId() != null) {
      value = getNestedQueryConstructorValue(rsw.getResultSet(), constructorMapping, columnPrefix);
    } else if (constructorMapping.getNestedResultMapId() != null) {
      final ResultMap resultMap = configuration.getResultMap(constructorMapping.getNestedResultMapId());
      value = getRowValue(rsw, resultMap);
    } else {
      final TypeHandler<?> typeHandler = constructorMapping.getTypeHandler();
      value = typeHandler.getResult(rsw.getResultSet(), prependPrefix(column, columnPrefix));
    }
    constructorArgTypes.add(parameterType);
    constructorArgs.add(value);
    foundValues = value != null || foundValues;
  }
  return foundValues ? objectFactory.create(resultType, constructorArgTypes, constructorArgs) : null;
}
 

private static CustomHandler resolveNew(String id, Method method, MappedStatement ms, CustomResultHandler annotation) {
	Class<? extends CustomHandler> instanceClass = annotation.value();
	//每次都必须是一个新对象
	CustomHandler instance = ReflectUtil.instance(instanceClass);
	List<ResultMap> resultMaps = ms.getResultMaps();
	if (!instance.support(resultMaps)) {
		//如果不支持
		noCustomes.add(id);
		String string = resultMaps.stream().map((item) -> item.getType().getCanonicalName()).collect(Collectors.joining(","));
		log.warn("{}方法的返回值类型{}不被{}所支持,将不会使用该CustomHandler", id, string, instanceClass.getCanonicalName());
		return null;
	}
	cache.put(id, instanceClass);
	//在需要返回结果的情况下,需要记录下返回值类型
	CustomHandlerContext context = instance.resolveContext(method, ms.getConfiguration());
	contextCache.put(id, context);
	instance.setContext(context);
	return instance;
}
 

private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, ResultLoaderMap lazyLoader, String columnPrefix) throws SQLException {
  final List<Class<?>> constructorArgTypes = new ArrayList<Class<?>>();
  final List<Object> constructorArgs = new ArrayList<Object>();
  final Object resultObject = createResultObject(rsw, resultMap, constructorArgTypes, constructorArgs, columnPrefix);
  if (resultObject != null && !typeHandlerRegistry.hasTypeHandler(resultMap.getType())) {
    final List<ResultMapping> propertyMappings = resultMap.getPropertyResultMappings();
    for (ResultMapping propertyMapping : propertyMappings) {
      // issue gcode #109 && issue #149
      if (propertyMapping.getNestedQueryId() != null && propertyMapping.isLazy()) {
        //TODO 使用代理(cglib/javaassist)
        return configuration.getProxyFactory().createProxy(resultObject, lazyLoader, configuration, objectFactory, constructorArgTypes, constructorArgs);
      }
    }
  }
  return resultObject;
}
 

private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix)
     throws SQLException {
//得到result type
   final Class<?> resultType = resultMap.getType();
   final MetaClass metaType = MetaClass.forClass(resultType);
   final List<ResultMapping> constructorMappings = resultMap.getConstructorResultMappings();
   if (typeHandlerRegistry.hasTypeHandler(resultType)) {
     //基本型
     return createPrimitiveResultObject(rsw, resultMap, columnPrefix);
   } else if (!constructorMappings.isEmpty()) {
     //有参数的构造函数
     return createParameterizedResultObject(rsw, resultType, constructorMappings, constructorArgTypes, constructorArgs, columnPrefix);
   } else if (resultType.isInterface() || metaType.hasDefaultConstructor()) {
     //普通bean类型
     return objectFactory.create(resultType);
   } else if (shouldApplyAutomaticMappings(resultMap, false)) {
     //自动映射
     return createByConstructorSignature(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix);
   }
   throw new ExecutorException("Do not know how to create an instance of " + resultType);
 }
 

private boolean applyPropertyMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, ResultLoaderMap lazyLoader, String columnPrefix)
    throws SQLException {
  final List<String> mappedColumnNames = rsw.getMappedColumnNames(resultMap, columnPrefix);
  boolean foundValues = false;
  final List<ResultMapping> 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);
      // issue #541 make property optional
      final String property = propertyMapping.getProperty();
      // issue #377, call setter on nulls
      if (value != NO_VALUE && property != null && (value != null || configuration.isCallSettersOnNulls())) {
        if (value != null || !metaObject.getSetterType(property).isPrimitive()) {
          metaObject.setValue(property, value);
        }
        foundValues = true;
      }
    }
  }
  return foundValues;
}
 

private Object getRowValue(ResultSetWrapper rsw, ResultMap resultMap) throws SQLException {
  //实例化ResultLoaderMap(延迟加载器)
  final ResultLoaderMap lazyLoader = new ResultLoaderMap();
  //调用自己的createResultObject,内部就是new一个对象(如果是简单类型，new完也把值赋进去)
  Object resultObject = createResultObject(rsw, resultMap, lazyLoader, null);
  if (resultObject != null && !typeHandlerRegistry.hasTypeHandler(resultMap.getType())) {
    //一般不是简单类型不会有typehandler,这个if会进来
    final MetaObject metaObject = configuration.newMetaObject(resultObject);
    boolean foundValues = !resultMap.getConstructorResultMappings().isEmpty();
    if (shouldApplyAutomaticMappings(resultMap, false)) {        
      //自动映射咯
      //这里把每个列的值都赋到相应的字段里去了
  	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 void handleResultSet(ResultSetWrapper rsw, ResultMap resultMap, List<Object> multipleResults, ResultMapping parentMapping) throws SQLException {
  try {
    if (parentMapping != null) {
      handleRowValues(rsw, resultMap, null, RowBounds.DEFAULT, parentMapping);
    } else {
      if (resultHandler == null) {
        //如果没有resultHandler
        //新建DefaultResultHandler
        DefaultResultHandler defaultResultHandler = new DefaultResultHandler(objectFactory);
        //调用自己的handleRowValues
        handleRowValues(rsw, resultMap, defaultResultHandler, rowBounds, null);
        //得到记录的list
        multipleResults.add(defaultResultHandler.getResultList());
      } else {
        //如果有resultHandler
        handleRowValues(rsw, resultMap, resultHandler, rowBounds, null);
      }
    }
  } finally {
    //最后别忘了关闭结果集，这个居然出bug了
    // issue #228 (close resultsets)
    closeResultSet(rsw.getResultSet());
  }
}
 

private Object createParameterizedResultObject(ResultSetWrapper rsw, Class<?> resultType, List<ResultMapping> constructorMappings,
    List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix) throws SQLException {
  boolean foundValues = false;
  for (ResultMapping constructorMapping : constructorMappings) {
    final Class<?> parameterType = constructorMapping.getJavaType();
    final String column = constructorMapping.getColumn();
    final Object value;
    if (constructorMapping.getNestedQueryId() != null) {
      value = getNestedQueryConstructorValue(rsw.getResultSet(), constructorMapping, columnPrefix);
    } else if (constructorMapping.getNestedResultMapId() != null) {
      final ResultMap resultMap = configuration.getResultMap(constructorMapping.getNestedResultMapId());
      value = getRowValue(rsw, resultMap);
    } else {
      final TypeHandler<?> typeHandler = constructorMapping.getTypeHandler();
      value = typeHandler.getResult(rsw.getResultSet(), prependPrefix(column, columnPrefix));
    }
    constructorArgTypes.add(parameterType);
    constructorArgs.add(value);
    foundValues = value != null || foundValues;
  }
  return foundValues ? objectFactory.create(resultType, constructorArgTypes, constructorArgs) : null;
}
 

public static MappedStatement createSelectAuthorWithIDof99MappedStatement(final Configuration config) {
  final TypeHandlerRegistry registry = config.getTypeHandlerRegistry();
  MappedStatement ms = new MappedStatement.Builder(config, "selectAuthor", new StaticSqlSource(config,"SELECT * FROM author WHERE id = 99"), SqlCommandType.SELECT)
      .statementType(StatementType.STATEMENT)
      .parameterMap(new ParameterMap.Builder(config, "defaultParameterMap", Author.class, new ArrayList<ParameterMapping>()).build())
      .resultMaps(new ArrayList<ResultMap>() {
        {
          add(new ResultMap.Builder(config, "defaultResultMap", Author.class, new ArrayList<ResultMapping>() {
            {
              add(new ResultMapping.Builder(config, "id", "id", registry.getTypeHandler(int.class)).build());
              add(new ResultMapping.Builder(config, "username", "username", registry.getTypeHandler(String.class)).build());
              add(new ResultMapping.Builder(config, "password", "password", registry.getTypeHandler(String.class)).build());
              add(new ResultMapping.Builder(config, "email", "email", registry.getTypeHandler(String.class)).build());
              add(new ResultMapping.Builder(config, "bio", "bio", registry.getTypeHandler(String.class)).build());
            }
          }).build());
        }
      }).build();
  return ms;
}
 

protected void checkLocallyForDiscriminatedNestedResultMaps(ResultMap rm) {
	if (!rm.hasNestedResultMaps() && rm.getDiscriminator() != null) {
		for (Map.Entry<String, String> entry : rm.getDiscriminator()
				.getDiscriminatorMap().entrySet()) {
			String discriminatedResultMapName = entry.getValue();
			if (hasResultMap(discriminatedResultMapName)) {
				ResultMap discriminatedResultMap = resultMaps
						.get(discriminatedResultMapName);
				if (discriminatedResultMap.hasNestedResultMaps()) {
					rm.forceNestedResultMaps();
					break;
				}
			}
		}
	}
}
 

public static MappedStatement prepareSelectAuthorViaOutParams(final Configuration config) {
  final TypeHandlerRegistry registry = config.getTypeHandlerRegistry();
  MappedStatement ms = new MappedStatement.Builder(config, "selectAuthorViaOutParams", new StaticSqlSource(config, "{call selectAuthorViaOutParams(?,?,?,?,?)}"), SqlCommandType.SELECT)
      .statementType(StatementType.CALLABLE)
      .parameterMap(new ParameterMap.Builder(config, "defaultParameterMap", Author.class,
          new ArrayList<ParameterMapping>() {
            {
              add(new ParameterMapping.Builder(config, "id", registry.getTypeHandler(int.class)).build());
              add(new ParameterMapping.Builder(config, "username", registry.getTypeHandler(String.class)).jdbcType(JdbcType.VARCHAR).mode(ParameterMode.OUT).build());
              add(new ParameterMapping.Builder(config, "password", registry.getTypeHandler(String.class)).jdbcType(JdbcType.VARCHAR).mode(ParameterMode.OUT).build());
              add(new ParameterMapping.Builder(config, "email", registry.getTypeHandler(String.class)).jdbcType(JdbcType.VARCHAR).mode(ParameterMode.OUT).build());
              add(new ParameterMapping.Builder(config, "bio", registry.getTypeHandler(String.class)).jdbcType(JdbcType.VARCHAR).mode(ParameterMode.OUT).build());
            }
          }).build())
      .resultMaps(new ArrayList<ResultMap>())
      .cache(authorCache).build();
  return ms;
}
 

private void createRowKeyForMappedProperties(ResultMap resultMap, ResultSetWrapper rsw, CacheKey cacheKey, List<ResultMapping> resultMappings, String columnPrefix) throws SQLException {
  for (ResultMapping resultMapping : resultMappings) {
    if (resultMapping.getNestedResultMapId() != null && resultMapping.getResultSet() == null) {
      // Issue #392
      final ResultMap nestedResultMap = configuration.getResultMap(resultMapping.getNestedResultMapId());
      createRowKeyForMappedProperties(nestedResultMap, rsw, cacheKey, nestedResultMap.getConstructorResultMappings(),
          prependPrefix(resultMapping.getColumnPrefix(), columnPrefix));
    } else if (resultMapping.getNestedQueryId() == null) {
      final String column = prependPrefix(resultMapping.getColumn(), columnPrefix);
      final TypeHandler<?> th = resultMapping.getTypeHandler();
      List<String> mappedColumnNames = rsw.getMappedColumnNames(resultMap, columnPrefix);
      // Issue #114
      if (column != null && mappedColumnNames.contains(column.toUpperCase(Locale.ENGLISH))) {
        final Object value = th.getResult(rsw.getResultSet(), column);
        if (value != null) {
          cacheKey.update(column);
          cacheKey.update(value);
        }
      }
    }
  }
}
 

private void createRowKeyForUnmappedProperties(ResultMap resultMap, ResultSetWrapper rsw, CacheKey cacheKey, String columnPrefix) throws SQLException {
  final MetaClass metaType = MetaClass.forClass(resultMap.getType());
  List<String> unmappedColumnNames = rsw.getUnmappedColumnNames(resultMap, columnPrefix);
  for (String column : unmappedColumnNames) {
    String property = column;
    if (columnPrefix != null && !columnPrefix.isEmpty()) {
      // When columnPrefix is specified, ignore columns without the prefix.
      if (column.toUpperCase(Locale.ENGLISH).startsWith(columnPrefix)) {
        property = column.substring(columnPrefix.length());
      } else {
        continue;
      }
    }
    if (metaType.findProperty(property, configuration.isMapUnderscoreToCamelCase()) != null) {
      String value = rsw.getResultSet().getString(column);
      if (value != null) {
        cacheKey.update(column);
        cacheKey.update(value);
      }
    }
  }
}
 

private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix)
     throws SQLException {
//得到result type
   final Class<?> resultType = resultMap.getType();
   final MetaClass metaType = MetaClass.forClass(resultType);
   final List<ResultMapping> constructorMappings = resultMap.getConstructorResultMappings();
   if (typeHandlerRegistry.hasTypeHandler(resultType)) {
     //基本型
     return createPrimitiveResultObject(rsw, resultMap, columnPrefix);
   } else if (!constructorMappings.isEmpty()) {
     //有参数的构造函数
     return createParameterizedResultObject(rsw, resultType, constructorMappings, constructorArgTypes, constructorArgs, columnPrefix);
   } else if (resultType.isInterface() || metaType.hasDefaultConstructor()) {
     //普通bean类型
     return objectFactory.create(resultType);
   } else if (shouldApplyAutomaticMappings(resultMap, false)) {
     //自动映射
     return createByConstructorSignature(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix);
   }
   throw new ExecutorException("Do not know how to create an instance of " + resultType);
 }
 

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());
  }
}
 

protected MappedStatement copyFromMappedStatement(MappedStatement ms,
                                                  SqlSource newSqlSource, String newMsId) {
    MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), newMsId, newSqlSource, ms.getSqlCommandType());
    builder.resource(ms.getResource());
    builder.fetchSize(ms.getFetchSize());
    builder.statementType(ms.getStatementType());
    builder.keyGenerator(ms.getKeyGenerator());
    // setStatementTimeout()
    builder.timeout(ms.getTimeout());
    // setParameterMap()
    builder.parameterMap(ms.getParameterMap());
    // setStatementResultMap()
    List<ResultMap> resultMaps = ms.getResultMaps();
    builder.resultMaps(resultMaps);
    builder.resultSetType(ms.getResultSetType());
    // setStatementCache()
    builder.cache(ms.getCache());
    builder.flushCacheRequired(ms.isFlushCacheRequired());
    builder.useCache(ms.isUseCache());
    return builder.build();
}
 

public ResultMap resolveDiscriminatedResultMap(ResultSet rs, ResultMap resultMap, String columnPrefix) throws SQLException {
  Set<String> pastDiscriminators = new HashSet<String>();
  Discriminator discriminator = resultMap.getDiscriminator();
  while (discriminator != null) {
    final Object value = getDiscriminatorValue(rs, discriminator, columnPrefix);
    final String discriminatedMapId = discriminator.getMapIdFor(String.valueOf(value));
    if (configuration.hasResultMap(discriminatedMapId)) {
      resultMap = configuration.getResultMap(discriminatedMapId);
      Discriminator lastDiscriminator = discriminator;
      discriminator = resultMap.getDiscriminator();
      if (discriminator == lastDiscriminator || !pastDiscriminators.add(discriminatedMapId)) {
        break;
      }
    } else {
      break;
    }
  }
  return resultMap;
}
 

private boolean shouldApplyAutomaticMappings(ResultMap resultMap, boolean isNested) {
  if (resultMap.getAutoMapping() != null) {
    return resultMap.getAutoMapping();
  } else {
    if (isNested) {
      return AutoMappingBehavior.FULL == configuration.getAutoMappingBehavior();
    } else {
      return AutoMappingBehavior.NONE != configuration.getAutoMappingBehavior();
    }
  }
}
 

private List<ResultMapping> getResultMappingsForRowKey(ResultMap resultMap) {
  List<ResultMapping> resultMappings = resultMap.getIdResultMappings();
  if (resultMappings.size() == 0) {
    resultMappings = resultMap.getPropertyResultMappings();
  }
  return resultMappings;
}
 

private void handleRefCursorOutputParameter(ResultSet rs, ParameterMapping parameterMapping, MetaObject metaParam) throws SQLException {
  try {
    final String resultMapId = parameterMapping.getResultMapId();
    final ResultMap resultMap = configuration.getResultMap(resultMapId);
    final DefaultResultHandler resultHandler = new DefaultResultHandler(objectFactory);
    final ResultSetWrapper rsw = new ResultSetWrapper(rs, configuration);
    //里面就和一般ResultSet处理没两样了
    handleRowValues(rsw, resultMap, resultHandler, new RowBounds(), null);
    metaParam.setValue(parameterMapping.getProperty(), resultHandler.getResultList());
  } finally {
    // issue #228 (close resultsets)
    closeResultSet(rs);
  }
}
 

private void setStatementResultMap(
    String resultMap,
    Class<?> resultType,
    ResultSetType resultSetType,
    MappedStatement.Builder statementBuilder) {
  resultMap = applyCurrentNamespace(resultMap, true);

  List<ResultMap> resultMaps = new ArrayList<ResultMap>();
  if (resultMap != null) {
    //2.1 resultMap是高级功能
    String[] resultMapNames = resultMap.split(",");
    for (String resultMapName : resultMapNames) {
      try {
        resultMaps.add(configuration.getResultMap(resultMapName.trim()));
      } catch (IllegalArgumentException e) {
        throw new IncompleteElementException("Could not find result map " + resultMapName, e);
      }
    }
  } else if (resultType != null) {
    //2.2 resultType,一般用这个足矣了
    //<select id="selectUsers" resultType="User">
    //这种情况下,MyBatis 会在幕后自动创建一个 ResultMap,基于属性名来映射列到 JavaBean 的属性上。
    //如果列名没有精确匹配,你可以在列名上使用 select 字句的别名来匹配标签。
    //创建一个inline result map, 把resultType设上就OK了，
    //然后后面被DefaultResultSetHandler.createResultObject()使用
    //DefaultResultSetHandler.getRowValue()使用
    ResultMap.Builder inlineResultMapBuilder = new ResultMap.Builder(
        configuration,
        statementBuilder.id() + "-Inline",
        resultType,
        new ArrayList<ResultMapping>(),
        null);
    resultMaps.add(inlineResultMapBuilder.build());
  }
  statementBuilder.resultMaps(resultMaps);

  statementBuilder.resultSetType(resultSetType);
}
 

@Test
public void testLowercase(){
    EntityHelper.initEntityNameMap(UserLowercase.class, config);
    EntityTable entityTable = EntityHelper.getEntityTable(UserLowercase.class);
    Assert.assertNotNull(entityTable);
    Assert.assertEquals("userlowercase", entityTable.getName());

    Set<EntityColumn> columns = entityTable.getEntityClassColumns();
    Assert.assertEquals(1, columns.size());

    for (EntityColumn column : columns) {
        Assert.assertEquals("username", column.getColumn());
        Assert.assertEquals("userName", column.getProperty());

        Assert.assertEquals("username = #{userName}", column.getColumnEqualsHolder());
        Assert.assertEquals("username = #{record.userName}", column.getColumnEqualsHolder("record"));
        Assert.assertEquals("#{userName}", column.getColumnHolder());
        Assert.assertEquals("#{record.userName}", column.getColumnHolder("record"));
        Assert.assertEquals("#{record.userName}", column.getColumnHolder("record", "suffix"));
        Assert.assertEquals("#{record.userNamesuffix},", column.getColumnHolder("record", "suffix", ","));
        Assert.assertNull(column.getTypeHandler());
    }

    ResultMap resultMap = entityTable.getResultMap(configuration);
    Assert.assertEquals("[USERNAME]", resultMap.getMappedColumns().toString());

    Assert.assertEquals(1, resultMap.getResultMappings().size());

    ResultMapping resultMapping = resultMap.getResultMappings().get(0);
    Assert.assertEquals("username", resultMapping.getColumn());
    Assert.assertEquals("userName", resultMapping.getProperty());
    Assert.assertNull(resultMapping.getJdbcType());
    Assert.assertEquals(StringTypeHandler.class, resultMapping.getTypeHandler().getClass());
}
 

protected void checkLocallyForDiscriminatedNestedResultMaps(ResultMap rm) {
  if (!rm.hasNestedResultMaps() && rm.getDiscriminator() != null) {
    for (Map.Entry<String, String> entry : rm.getDiscriminator().getDiscriminatorMap().entrySet()) {
      String discriminatedResultMapName = entry.getValue();
      if (hasResultMap(discriminatedResultMapName)) {
        ResultMap discriminatedResultMap = resultMaps.get(discriminatedResultMapName);
        if (discriminatedResultMap.hasNestedResultMaps()) {
          rm.forceNestedResultMaps();
          break;
        }
      }
    }
  }
}
 

public static MappedStatement prepareComplexSelectBlogMappedStatement(final Configuration config) {
  final TypeHandlerRegistry registry = config.getTypeHandlerRegistry();
  final SqlSource sqlSource = new StaticSqlSource(config, "SELECT b.id, b.author_id, b.title, a.username, a.password, a.email, a.bio" +
      " FROM blog b" +
      " INNER JOIN author a ON b.author_id = a.id" +
      " WHERE b.id = ?");
  final ParameterMap parameterMap = new ParameterMap.Builder(config, "defaultParameterMap", int.class,
      new ArrayList<ParameterMapping>() {
        {
          add(new ParameterMapping.Builder(config, "id", registry.getTypeHandler(int.class)).build());
        }
      }).build();
  final ResultMap resultMap = new ResultMap.Builder(config, "defaultResultMap", Blog.class, new ArrayList<ResultMapping>() {
    {
      add(new ResultMapping.Builder(config, "id", "id", registry.getTypeHandler(int.class))
          .flags(new ArrayList<ResultFlag>() {
            {
              add(ResultFlag.ID);
            }
          }).build());
      add(new ResultMapping.Builder(config, "title", "title", registry.getTypeHandler(String.class)).build());
      add(new ResultMapping.Builder(config, "author.id", "author_id", registry.getTypeHandler(int.class)).build());
      add(new ResultMapping.Builder(config, "author.username", "username", registry.getTypeHandler(String.class)).build());
      add(new ResultMapping.Builder(config, "author.password", "password", registry.getTypeHandler(String.class)).build());
      add(new ResultMapping.Builder(config, "author.email", "email", registry.getTypeHandler(String.class)).build());
      add(new ResultMapping.Builder(config, "author.bio", "bio", registry.getTypeHandler(String.class)).build());
      add(new ResultMapping.Builder(config, "posts", "id", registry.getTypeHandler(int.class)).javaType(List.class).nestedQueryId("selectPostsForBlog").build());
    }
  }).build();

  return new MappedStatement.Builder(config, "selectBlogById", sqlSource, SqlCommandType.SELECT)
      .parameterMap(parameterMap)
      .resultMaps(new ArrayList<ResultMap>() {
        {
          add(resultMap);
        }
      }).build();
}
 

private CacheKey createRowKey(ResultMap resultMap, ResultSetWrapper rsw, String columnPrefix) throws SQLException {
  final CacheKey cacheKey = new CacheKey();
  cacheKey.update(resultMap.getId());
  List<ResultMapping> resultMappings = getResultMappingsForRowKey(resultMap);
  if (resultMappings.size() == 0) {
    if (Map.class.isAssignableFrom(resultMap.getType())) {
      createRowKeyForMap(rsw, cacheKey);
    } else {
      createRowKeyForUnmappedProperties(resultMap, rsw, cacheKey, columnPrefix);
    }
  } else {
    createRowKeyForMappedProperties(resultMap, rsw, cacheKey, resultMappings, columnPrefix);
  }
  return cacheKey;
}
 

private boolean applyAutomaticMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, String columnPrefix) throws SQLException {
  final List<String> unmappedColumnNames = rsw.getUnmappedColumnNames(resultMap, columnPrefix);
  boolean foundValues = false;
  for (String columnName : unmappedColumnNames) {
    String propertyName = columnName;
    if (columnPrefix != null && !columnPrefix.isEmpty()) {
      // When columnPrefix is specified,
      // ignore columns without the prefix.
      if (columnName.toUpperCase(Locale.ENGLISH).startsWith(columnPrefix)) {
        propertyName = columnName.substring(columnPrefix.length());
      } else {
        continue;
      }
    }
    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);
        //巧妙的用TypeHandler取得结果
        final Object value = typeHandler.getResult(rsw.getResultSet(), columnName);
        // issue #377, call setter on nulls
        if (value != null || configuration.isCallSettersOnNulls()) {
          if (value != null || !propertyType.isPrimitive()) {
            //然后巧妙的用反射来设置到对象
            metaObject.setValue(property, value);
          }
          foundValues = true;
        }
      }
    }
  }
  return foundValues;
}