public class DefaultResultSetHandler implements ResultSetHandler {
private static final Object DEFERED = new Object();
private final Executor executor;
private final Configuration configuration;
private final MappedStatement mappedStatement;
private final RowBounds rowBounds;
private final ParameterHandler parameterHandler;
private final ResultHandler<?> resultHandler;
private final BoundSql boundSql;
private final TypeHandlerRegistry typeHandlerRegistry;
private final ObjectFactory objectFactory;
private final ReflectorFactory reflectorFactory;
// nested resultmaps
private final Map<CacheKey, Object> nestedResultObjects = new HashMap<>();
private final Map<String, Object> ancestorObjects = new HashMap<>();
private Object previousRowValue;
// multiple resultsets
private final Map<String, ResultMapping> nextResultMaps = new HashMap<>();
private final Map<CacheKey, List<PendingRelation>> pendingRelations = new HashMap<>();
// Cached Automappings
private final Map<String, List<UnMappedColumnAutoMapping>> autoMappingsCache = new HashMap<>();
// temporary marking flag that indicate using constructor mapping (use field to reduce memory usage)
private boolean useConstructorMappings;
private static class PendingRelation {
public MetaObject metaObject;
public ResultMapping propertyMapping;
}
private static class UnMappedColumnAutoMapping {
private final String column;
private final String property;
private final TypeHandler<?> typeHandler;
private final boolean primitive;
public UnMappedColumnAutoMapping(String column, String property, TypeHandler<?> typeHandler, boolean primitive) {
this.column = column;
this.property = property;
this.typeHandler = typeHandler;
this.primitive = primitive;
}
}
public DefaultResultSetHandler(Executor executor, MappedStatement mappedStatement, ParameterHandler parameterHandler, ResultHandler<?> resultHandler, BoundSql boundSql,
RowBounds rowBounds) {
this.executor = executor;
this.configuration = mappedStatement.getConfiguration();
this.mappedStatement = mappedStatement;
this.rowBounds = rowBounds;
this.parameterHandler = parameterHandler;
this.boundSql = boundSql;
this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
this.objectFactory = configuration.getObjectFactory();
this.reflectorFactory = configuration.getReflectorFactory();
this.resultHandler = resultHandler;
}
//
// HANDLE OUTPUT PARAMETER
//
@Override
public void handleOutputParameters(CallableStatement cs) throws SQLException {
final Object parameterObject = parameterHandler.getParameterObject();
final MetaObject metaParam = configuration.newMetaObject(parameterObject);
final List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
for (int i = 0; i < parameterMappings.size(); i++) {
final ParameterMapping parameterMapping = parameterMappings.get(i);
if (parameterMapping.getMode() == ParameterMode.OUT || parameterMapping.getMode() == ParameterMode.INOUT) {
if (ResultSet.class.equals(parameterMapping.getJavaType())) {
handleRefCursorOutputParameter((ResultSet) cs.getObject(i + 1), parameterMapping, metaParam);
} else {
final TypeHandler<?> typeHandler = parameterMapping.getTypeHandler();
metaParam.setValue(parameterMapping.getProperty(), typeHandler.getResult(cs, i + 1));
}
}
}
}
private void handleRefCursorOutputParameter(ResultSet rs, ParameterMapping parameterMapping, MetaObject metaParam) throws SQLException {
if (rs == null) {
return;
}
try {
final String resultMapId = parameterMapping.getResultMapId();
final ResultMap resultMap = configuration.getResultMap(resultMapId);
final ResultSetWrapper rsw = new ResultSetWrapper(rs, configuration);
if (this.resultHandler == null) {
final DefaultResultHandler resultHandler = new DefaultResultHandler(objectFactory);
handleRowValues(rsw, resultMap, resultHandler, new RowBounds(), null);
metaParam.setValue(parameterMapping.getProperty(), resultHandler.getResultList());
} else {
handleRowValues(rsw, resultMap, resultHandler, new RowBounds(), null);
}
} finally {
// issue #228 (close resultsets)
closeResultSet(rs);
}
}
//
// HANDLE RESULT SETS
//
@Override
public List<Object> handleResultSets(Statement stmt) throws SQLException {
ErrorContext.instance().activity("handling results").object(mappedStatement.getId());
//用于保存结果集对象
final List<Object> multipleResults = new ArrayList<>();
int resultSetCount = 0;
//statment可能返回多个结果集对象，这里先取出第一个结果集
ResultSetWrapper rsw = getFirstResultSet(stmt);
//获取结果集对应resultMap，本质就是获取字段与java属性的映射规则
List<ResultMap> resultMaps = mappedStatement.getResultMaps();
int resultMapCount = resultMaps.size();
validateResultMapsCount(rsw, resultMapCount);//结果集和resultMap不能为空，为空抛出异常
while (rsw != null && resultMapCount > resultSetCount) {
//获取当前结果集对应的resultMap
ResultMap resultMap = resultMaps.get(resultSetCount);
//根据映射规则（resultMap）对结果集进行转化，转换成目标对象以后放入multipleResults中
handleResultSet(rsw, resultMap, multipleResults, null);
rsw = getNextResultSet(stmt);//获取下一个结果集
cleanUpAfterHandlingResultSet();//清空nestedResultObjects对象
resultSetCount++;
}
//获取多结果集。多结果集一般出现在存储过程的执行，存储过程返回多个resultset，
//mappedStatement.resultSets属性列出多个结果集的名称，用逗号分割；
//多结果集的处理不是重点，暂时不分析
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);
}
@Override
public <E> Cursor<E> handleCursorResultSets(Statement stmt) throws SQLException {
ErrorContext.instance().activity("handling cursor results").object(mappedStatement.getId());
ResultSetWrapper rsw = getFirstResultSet(stmt);
List<ResultMap> resultMaps = mappedStatement.getResultMaps();
int resultMapCount = resultMaps.size();
validateResultMapsCount(rsw, resultMapCount);
if (resultMapCount != 1) {
throw new ExecutorException("Cursor results cannot be mapped to multiple resultMaps");
}
ResultMap resultMap = resultMaps.get(0);
return new DefaultCursor<>(this, resultMap, rsw, rowBounds);
}
private ResultSetWrapper getFirstResultSet(Statement stmt) throws SQLException {
ResultSet rs = stmt.getResultSet();
while (rs == null) {
// move forward to get the first resultset in case the driver
// doesn't return the resultset as the first result (HSQLDB 2.1)
if (stmt.getMoreResults()) {
rs = stmt.getResultSet();
} else {
if (stmt.getUpdateCount() == -1) {
// no more results. Must be no resultset
break;
}
}
}
return rs != null ? new ResultSetWrapper(rs, configuration) : null;
}
private ResultSetWrapper getNextResultSet(Statement stmt) {
// Making this method tolerant of bad JDBC drivers
try {
if (stmt.getConnection().getMetaData().supportsMultipleResultSets()) {
// Crazy Standard JDBC way of determining if there are more results
if (!(!stmt.getMoreResults() && stmt.getUpdateCount() == -1)) {
ResultSet rs = stmt.getResultSet();
if (rs == null) {
return getNextResultSet(stmt);
} else {
return new ResultSetWrapper(rs, configuration);
}
}
}
} catch (Exception e) {
// Intentionally ignored.
}
return null;
}
private void closeResultSet(ResultSet rs) {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
// ignore
}
}
private void cleanUpAfterHandlingResultSet() {
nestedResultObjects.clear();
}
private void validateResultMapsCount(ResultSetWrapper rsw, int resultMapCount) {
if (rsw != null && resultMapCount < 1) {
throw new ExecutorException("A query was run and no Result Maps were found for the Mapped Statement '" + mappedStatement.getId()
+ "'. It's likely that neither a Result Type nor a Result Map was specified.");
}
}
private void handleResultSet(ResultSetWrapper rsw, ResultMap resultMap, List<Object> multipleResults, ResultMapping parentMapping) throws SQLException {
try {
if (parentMapping != null) {//处理多结果集的嵌套映射
handleRowValues(rsw, resultMap, null, RowBounds.DEFAULT, parentMapping);
} else {
if (resultHandler == null) {//如果resultHandler为空，实例化一个人默认的resultHandler
DefaultResultHandler defaultResultHandler = new DefaultResultHandler(objectFactory);
//对ResultSet进行映射，映射结果暂存在resultHandler中
handleRowValues(rsw, resultMap, defaultResultHandler, rowBounds, null);
//将暂存在resultHandler中的映射结果，填充到multipleResults
multipleResults.add(defaultResultHandler.getResultList());
} else {
//使用指定的rusultHandler进行转换
handleRowValues(rsw, resultMap, resultHandler, rowBounds, null);
}
}
} finally {
// issue #228 (close resultsets)
//调用resultset.close()关闭结果集
closeResultSet(rsw.getResultSet());
}
}
@SuppressWarnings("unchecked")
private List<Object> collapseSingleResultList(List<Object> multipleResults) {
return multipleResults.size() == 1 ? (List<Object>) multipleResults.get(0) : multipleResults;
}
//
// HANDLE ROWS FOR SIMPLE RESULTMAP
//
public void handleRowValues(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
if (resultMap.hasNestedResultMaps()) {//处理有嵌套resultmap的情况
ensureNoRowBounds();
checkResultHandler();
handleRowValuesForNestedResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
} else {//处理没有嵌套resultmap的情况
handleRowValuesForSimpleResultMap(rsw, resultMap, resultHandler, rowBounds, parentMapping);
}
}
private void ensureNoRowBounds() {
if (configuration.isSafeRowBoundsEnabled() && rowBounds != null && (rowBounds.getLimit() < RowBounds.NO_ROW_LIMIT || rowBounds.getOffset() > RowBounds.NO_ROW_OFFSET)) {
throw new ExecutorException("Mapped Statements with nested result mappings cannot be safely constrained by RowBounds. "
+ "Use safeRowBoundsEnabled=false setting to bypass this check.");
}
}
protected void checkResultHandler() {
if (resultHandler != null && configuration.isSafeResultHandlerEnabled() && !mappedStatement.isResultOrdered()) {
throw new ExecutorException("Mapped Statements with nested result mappings cannot be safely used with a custom ResultHandler. "
+ "Use safeResultHandlerEnabled=false setting to bypass this check "
+ "or ensure your statement returns ordered data and set resultOrdered=true on it.");
}
}
//简单映射处理
private void handleRowValuesForSimpleResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping)
throws SQLException {
//创建结果上下文，所谓的上下文就是专门在循环中缓存结果对象的
DefaultResultContext<Object> resultContext = new DefaultResultContext<>();
//1.根据分页信息，定位到指定的记录
skipRows(rsw.getResultSet(), rowBounds);
//2.shouldProcessMoreRows判断是否需要映射后续的结果，实际还是翻页处理，避免超过limit
while (shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {
//3.进一步完善resultMap信息，主要是处理鉴别器的信息
ResultMap discriminatedResultMap = resolveDiscriminatedResultMap(rsw.getResultSet(), resultMap, null);
//4.读取resultSet中的一行记录并进行映射，转化并返回目标对象
Object rowValue = getRowValue(rsw, discriminatedResultMap);
//5.保存映射结果对象
storeObject(resultHandler, resultContext, rowValue, parentMapping, rsw.getResultSet());
}
}
//保存映射结果对象
private void storeObject(ResultHandler<?> resultHandler, DefaultResultContext<Object> resultContext, Object rowValue, ResultMapping parentMapping, ResultSet rs) throws SQLException {
if (parentMapping != null) {//如果是嵌套结果或嵌套查询，将对象保存至父对象
linkToParents(rs, parentMapping, rowValue);
} else {//普通映射则把对象保存至resultHandler和resultContext
callResultHandler(resultHandler, resultContext, rowValue);
}
}
@SuppressWarnings("unchecked" /* because ResultHandler<?> is always ResultHandler<Object>*/)
private void callResultHandler(ResultHandler<?> resultHandler, DefaultResultContext<Object> resultContext, Object rowValue) {
resultContext.nextResultObject(rowValue);
((ResultHandler<Object>) resultHandler).handleResult(resultContext);
}
private boolean shouldProcessMoreRows(ResultContext<?> context, RowBounds rowBounds) {
//检测上下文的stop状态，并检测映射的行数是否达到了limit的上限
return !context.isStopped() && context.getResultCount() < rowBounds.getLimit();
}
//映射之前处理翻页信息
private void skipRows(ResultSet rs, RowBounds rowBounds) throws SQLException {
//根据ResultSet的类型定位
if (rs.getType() != ResultSet.TYPE_FORWARD_ONLY) {
if (rowBounds.getOffset() != RowBounds.NO_ROW_OFFSET) {
rs.absolute(rowBounds.getOffset());//直接定位到offset指定的记录
}
} else {
//通过多次调用next移动到目标记录
for (int i = 0; i < rowBounds.getOffset(); i++) {
rs.next();
}
}
}
//
// GET VALUE FROM ROW FOR SIMPLE RESULT MAP
//
//4.读取resultSet中的一行记录并进行映射，转化并返回目标对象
private Object getRowValue(ResultSetWrapper rsw, ResultMap resultMap) throws SQLException {
final ResultLoaderMap lazyLoader = new ResultLoaderMap();
//4.1 根据resultMap的type属性，实例化目标对象
Object rowValue = createResultObject(rsw, resultMap, lazyLoader, null);
if (rowValue != null && !hasTypeHandlerForResultObject(rsw, resultMap.getType())) {
//4.2 对目标对象进行封装得到metaObjcect,为后续的赋值操作做好准备
final MetaObject metaObject = configuration.newMetaObject(rowValue);
boolean foundValues = this.useConstructorMappings;//取得是否使用构造函数初始化属性值
if (shouldApplyAutomaticMappings(resultMap, false)) {//是否使用自动映射
//4.3一般情况下 autoMappingBehavior默认值为PARTIAL，对未明确指定映射规则的字段进行自动映射
foundValues = applyAutomaticMappings(rsw, resultMap, metaObject, null) || foundValues;
}
//4.4 映射resultMap中明确指定需要映射的列
foundValues = applyPropertyMappings(rsw, resultMap, metaObject, lazyLoader, null) || foundValues;
foundValues = lazyLoader.size() > 0 || foundValues;
//4.5 如果没有一个映射成功的属性，则根据<returnInstanceForEmptyRow>的配置返回null或者结果对象
rowValue = foundValues || configuration.isReturnInstanceForEmptyRow() ? rowValue : null;
}
return rowValue;
}
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();
}
}
}
//
// PROPERTY MAPPINGS
//
private boolean applyPropertyMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, ResultLoaderMap lazyLoader, String columnPrefix)
throws SQLException {
//从resultMap中获取明确需要转换的列名集合
final List<String> mappedColumnNames = rsw.getMappedColumnNames(resultMap, columnPrefix);
boolean foundValues = false;
//获取ResultMapping集合
final List<ResultMapping> propertyMappings = resultMap.getPropertyResultMappings();
for (ResultMapping propertyMapping : propertyMappings) {
String column = prependPrefix(propertyMapping.getColumn(), columnPrefix);//获得列名，注意前缀的处理
if (propertyMapping.getNestedResultMapId() != null) {
// the user added a column attribute to a nested result map, ignore it
//如果属性通过另外一个resultMap映射，则忽略
column = null;
}
if (propertyMapping.isCompositeResult()//如果是嵌套查询，column={prop1=col1,prop2=col2}
|| (column != null && mappedColumnNames.contains(column.toUpperCase(Locale.ENGLISH)))//基本类型映射
|| propertyMapping.getResultSet() != null) {//嵌套查询的结果
//获得属性值
Object value = getPropertyMappingValue(rsw.getResultSet(), metaObject, propertyMapping, lazyLoader, columnPrefix);
// issue #541 make property optional
//获得属性名称
final String property = propertyMapping.getProperty();
if (property == null) {//属性名为空跳出循环
continue;
} else if (value == DEFERED) {//属性名为DEFERED，延迟加载的处理
foundValues = true;
continue;
}
if (value != null) {
foundValues = true;
}
if (value != null || (configuration.isCallSettersOnNulls() && !metaObject.getSetterType(property).isPrimitive())) {
// gcode issue #377, call setter on nulls (value is not 'found')
//通过metaObject为目标对象设置属性值
metaObject.setValue(property, value);
}
}
}
return foundValues;
}
//获得属性值
private Object getPropertyMappingValue(ResultSet rs, MetaObject metaResultObject, ResultMapping propertyMapping, ResultLoaderMap lazyLoader, String columnPrefix)
throws SQLException {
if (propertyMapping.getNestedQueryId() != null) {//嵌套查询的处理
return getNestedQueryMappingValue(rs, metaResultObject, propertyMapping, lazyLoader, columnPrefix);
} else if (propertyMapping.getResultSet() != null) {//嵌套结果的处理
addPendingChildRelation(rs, metaResultObject, propertyMapping); // TODO is that OK?
return DEFERED;
} else {//基本类型直接通过typeHandler获取属性值
final TypeHandler<?> typeHandler = propertyMapping.getTypeHandler();
final String column = prependPrefix(propertyMapping.getColumn(), columnPrefix);
return typeHandler.getResult(rs, column);
}
}
//获取resultSet中存在的，但是ResultMap中没有明确映射的列，填充至autoMapping中
private List<UnMappedColumnAutoMapping> createAutomaticMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, String columnPrefix) throws SQLException {
final String mapKey = resultMap.getId() + ":" + columnPrefix;
List<UnMappedColumnAutoMapping> autoMapping = autoMappingsCache.get(mapKey);//从缓存中获取
if (autoMapping == null) {
autoMapping = new ArrayList<>();
//获取未映射的列名
final List<String> unmappedColumnNames = rsw.getUnmappedColumnNames(resultMap, columnPrefix);
for (String columnName : unmappedColumnNames) {
String propertyName = columnName;
if (columnPrefix != null && !columnPrefix.isEmpty()) {//前缀的处理，如果有前缀，属性名为列名去除前缀
// When columnPrefix is specified,
// ignore columns without the prefix.
if (columnName.toUpperCase(Locale.ENGLISH).startsWith(columnPrefix)) {//如果有前缀，属性名为列名去除前缀
propertyName = columnName.substring(columnPrefix.length());
} else {
continue;
}
}
//在结果对象中查找指定的属性名
final String property = metaObject.findProperty(propertyName, configuration.isMapUnderscoreToCamelCase());
//检查该属性是否有setter方法
if (property != null && metaObject.hasSetter(property)) {
if (resultMap.getMappedProperties().contains(property)) {//如果该属性在resultMap中已经指定，则忽略此属性
continue;
}
final Class<?> propertyType = metaObject.getSetterType(property);
if (typeHandlerRegistry.hasTypeHandler(propertyType, rsw.getJdbcType(columnName))) {//判断是否有匹配的typeHandler
final TypeHandler<?> typeHandler = rsw.getTypeHandler(propertyType, columnName);//找到类型转换器
//创建UnMappedColumnAutoMapping，并填充至autoMapping
autoMapping.add(new UnMappedColumnAutoMapping(columnName, property, typeHandler, propertyType.isPrimitive()));
} else {
configuration.getAutoMappingUnknownColumnBehavior()
.doAction(mappedStatement, columnName, property, propertyType);
}
} else {
configuration.getAutoMappingUnknownColumnBehavior()
.doAction(mappedStatement, columnName, (property != null) ? property : propertyName, null);
}
}
autoMappingsCache.put(mapKey, autoMapping);
}
return autoMapping;
}
//对未明确指定映射规则的字段进行自动映射
private boolean applyAutomaticMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, String columnPrefix) throws SQLException {
//获取resultSet中存在的，但是ResultMap中没有明确映射的列，填充至autoMapping中
List<UnMappedColumnAutoMapping> autoMapping = createAutomaticMappings(rsw, resultMap, metaObject, columnPrefix);
boolean foundValues = false;
if (!autoMapping.isEmpty()) {
//遍历autoMapping，通过自动匹配的方式为属性复制
for (UnMappedColumnAutoMapping mapping : autoMapping) {
//通过typeHandler从resultset中拿值
final Object value = mapping.typeHandler.getResult(rsw.getResultSet(), mapping.column);
if (value != null) {
foundValues = true;
}
if (value != null || (configuration.isCallSettersOnNulls() && !mapping.primitive)) {
// gcode issue #377, call setter on nulls (value is not 'found')
//通过metaObject给属性赋值
metaObject.setValue(mapping.property, value);
}
}
}
return foundValues;
}
// MULTIPLE RESULT SETS
private void linkToParents(ResultSet rs, ResultMapping parentMapping, Object rowValue) throws SQLException {
CacheKey parentKey = createKeyForMultipleResults(rs, parentMapping, parentMapping.getColumn(), parentMapping.getForeignColumn());
List<PendingRelation> parents = pendingRelations.get(parentKey);
if (parents != null) {
for (PendingRelation parent : parents) {
if (parent != null && rowValue != null) {
linkObjects(parent.metaObject, parent.propertyMapping, rowValue);
}
}
}
}
private void addPendingChildRelation(ResultSet rs, MetaObject metaResultObject, ResultMapping parentMapping) throws SQLException {
CacheKey cacheKey = createKeyForMultipleResults(rs, parentMapping, parentMapping.getColumn(), parentMapping.getColumn());
PendingRelation deferLoad = new PendingRelation();
deferLoad.metaObject = metaResultObject;
deferLoad.propertyMapping = parentMapping;
List<PendingRelation> relations = pendingRelations.computeIfAbsent(cacheKey, k -> new ArrayList<>());
// issue #255
relations.add(deferLoad);
ResultMapping previous = nextResultMaps.get(parentMapping.getResultSet());
if (previous == null) {
nextResultMaps.put(parentMapping.getResultSet(), parentMapping);
} else {
if (!previous.equals(parentMapping)) {
throw new ExecutorException("Two different properties are mapped to the same resultSet");
}
}
}
private CacheKey createKeyForMultipleResults(ResultSet rs, ResultMapping resultMapping, String names, String columns) throws SQLException {
CacheKey cacheKey = new CacheKey();
cacheKey.update(resultMapping);
if (columns != null && names != null) {
String[] columnsArray = columns.split(",");
String[] namesArray = names.split(",");
for (int i = 0; i < columnsArray.length; i++) {
Object value = rs.getString(columnsArray[i]);
if (value != null) {
cacheKey.update(namesArray[i]);
cacheKey.update(value);
}
}
}
return cacheKey;
}
//
// INSTANTIATION & CONSTRUCTOR MAPPING
//
private Object createResultObject(ResultSetWrapper rsw, ResultMap resultMap, ResultLoaderMap lazyLoader, String columnPrefix) throws SQLException {
this.useConstructorMappings = false; // reset previous mapping result
final List<Class<?>> constructorArgTypes = new ArrayList<>();
final List<Object> constructorArgs = new ArrayList<>();
Object resultObject = createResultObject(rsw, resultMap, constructorArgTypes, constructorArgs, columnPrefix);
if (resultObject != null && !hasTypeHandlerForResultObject(rsw, resultMap.getType())) {
final List<ResultMapping> propertyMappings = resultMap.getPropertyResultMappings();
for (ResultMapping propertyMapping : propertyMappings) {
// issue gcode #109 && issue #149
if (propertyMapping.getNestedQueryId() != null && propertyMapping.isLazy()) {
resultObject = configuration.getProxyFactory().createProxy(resultObject, lazyLoader, configuration, objectFactory, constructorArgTypes, constructorArgs);
break;
}
}
}
this.useConstructorMappings = resultObject != null && !constructorArgTypes.isEmpty(); // set current mapping result
return resultObject;
}
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);
}
Object createParameterizedResultObject(ResultSetWrapper rsw, Class<?> resultType, List<ResultMapping> constructorMappings,
List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix) {
boolean foundValues = false;
for (ResultMapping constructorMapping : constructorMappings) {
final Class<?> parameterType = constructorMapping.getJavaType();
final String column = constructorMapping.getColumn();
final Object value;
try {
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));
}
} catch (ResultMapException | SQLException e) {
throw new ExecutorException("Could not process result for mapping: " + constructorMapping, e);
}
constructorArgTypes.add(parameterType);
constructorArgs.add(value);
foundValues = value != null || foundValues;
}
return foundValues ? objectFactory.create(resultType, constructorArgTypes, constructorArgs) : null;
}
private Object createByConstructorSignature(ResultSetWrapper rsw, Class<?> resultType, List<Class<?>> constructorArgTypes, List<Object> constructorArgs,
String columnPrefix) throws SQLException {
final Constructor<?>[] constructors = resultType.getDeclaredConstructors();
final Constructor<?> defaultConstructor = findDefaultConstructor(constructors);
if (defaultConstructor != null) {
return createUsingConstructor(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix, defaultConstructor);
} else {
for (Constructor<?> constructor : constructors) {
if (allowedConstructorUsingTypeHandlers(constructor, rsw.getJdbcTypes())) {
return createUsingConstructor(rsw, resultType, constructorArgTypes, constructorArgs, columnPrefix, constructor);
}
}
}
throw new ExecutorException("No constructor found in " + resultType.getName() + " matching " + rsw.getClassNames());
}
private Object createUsingConstructor(ResultSetWrapper rsw, Class<?> resultType, List<Class<?>> constructorArgTypes, List<Object> constructorArgs, String columnPrefix, Constructor<?> constructor) throws SQLException {
boolean foundValues = false;
for (int i = 0; i < constructor.getParameterTypes().length; i++) {
Class<?> parameterType = constructor.getParameterTypes()[i];
String columnName = rsw.getColumnNames().get(i);
TypeHandler<?> typeHandler = rsw.getTypeHandler(parameterType, columnName);
Object value = typeHandler.getResult(rsw.getResultSet(), prependPrefix(columnName, columnPrefix));
constructorArgTypes.add(parameterType);
constructorArgs.add(value);
foundValues = value != null || foundValues;
}
return foundValues ? objectFactory.create(resultType, constructorArgTypes, constructorArgs) : null;
}
private Constructor<?> findDefaultConstructor(final Constructor<?>[] constructors) {
if (constructors.length == 1) return constructors[0];
for (final Constructor<?> constructor : constructors) {
if (constructor.isAnnotationPresent(AutomapConstructor.class)) {
return constructor;
}
}
return null;
}
private boolean allowedConstructorUsingTypeHandlers(final Constructor<?> constructor, final List<JdbcType> jdbcTypes) {
final Class<?>[] parameterTypes = constructor.getParameterTypes();
if (parameterTypes.length != jdbcTypes.size()) return false;
for (int i = 0; i < parameterTypes.length; i++) {
if (!typeHandlerRegistry.hasTypeHandler(parameterTypes[i], jdbcTypes.get(i))) {
return false;
}
}
return true;
}
private Object createPrimitiveResultObject(ResultSetWrapper rsw, ResultMap resultMap, String columnPrefix) throws SQLException {
final Class<?> resultType = resultMap.getType();
final String columnName;
if (!resultMap.getResultMappings().isEmpty()) {
final List<ResultMapping> resultMappingList = resultMap.getResultMappings();
final ResultMapping mapping = resultMappingList.get(0);
columnName = prependPrefix(mapping.getColumn(), columnPrefix);
} else {
columnName = rsw.getColumnNames().get(0);
}
final TypeHandler<?> typeHandler = rsw.getTypeHandler(resultType, columnName);
return typeHandler.getResult(rsw.getResultSet(), columnName);
}
//
// NESTED QUERY
//
private Object getNestedQueryConstructorValue(ResultSet rs, ResultMapping constructorMapping, String columnPrefix) throws SQLException {
final String nestedQueryId = constructorMapping.getNestedQueryId();
final MappedStatement nestedQuery = configuration.getMappedStatement(nestedQueryId);
final Class<?> nestedQueryParameterType = nestedQuery.getParameterMap().getType();
final Object nestedQueryParameterObject = prepareParameterForNestedQuery(rs, constructorMapping, nestedQueryParameterType, columnPrefix);
Object value = null;
if (nestedQueryParameterObject != null) {
final BoundSql nestedBoundSql = nestedQuery.getBoundSql(nestedQueryParameterObject);
final CacheKey key = executor.createCacheKey(nestedQuery, nestedQueryParameterObject, RowBounds.DEFAULT, nestedBoundSql);
final Class<?> targetType = constructorMapping.getJavaType();
final ResultLoader resultLoader = new ResultLoader(configuration, executor, nestedQuery, nestedQueryParameterObject, targetType, key, nestedBoundSql);
value = resultLoader.loadResult();
}
return value;
}
private Object getNestedQueryMappingValue(ResultSet rs, MetaObject metaResultObject, ResultMapping propertyMapping, ResultLoaderMap lazyLoader, String columnPrefix)
throws SQLException {
final String nestedQueryId = propertyMapping.getNestedQueryId();
final String property = propertyMapping.getProperty();
final MappedStatement nestedQuery = configuration.getMappedStatement(nestedQueryId);
final Class<?> nestedQueryParameterType = nestedQuery.getParameterMap().getType();
final Object nestedQueryParameterObject = prepareParameterForNestedQuery(rs, propertyMapping, nestedQueryParameterType, columnPrefix);
Object value = null;
if (nestedQueryParameterObject != null) {
final BoundSql nestedBoundSql = nestedQuery.getBoundSql(nestedQueryParameterObject);
final CacheKey key = executor.createCacheKey(nestedQuery, nestedQueryParameterObject, RowBounds.DEFAULT, nestedBoundSql);
final Class<?> targetType = propertyMapping.getJavaType();
if (executor.isCached(nestedQuery, key)) {
executor.deferLoad(nestedQuery, metaResultObject, property, key, targetType);
value = DEFERED;
} else {
final ResultLoader resultLoader = new ResultLoader(configuration, executor, nestedQuery, nestedQueryParameterObject, targetType, key, nestedBoundSql);
if (propertyMapping.isLazy()) {
lazyLoader.addLoader(property, metaResultObject, resultLoader);
value = DEFERED;
} else {
value = resultLoader.loadResult();
}
}
}
return value;
}
private Object prepareParameterForNestedQuery(ResultSet rs, ResultMapping resultMapping, Class<?> parameterType, String columnPrefix) throws SQLException {
if (resultMapping.isCompositeResult()) {
return prepareCompositeKeyParameter(rs, resultMapping, parameterType, columnPrefix);
} else {
return prepareSimpleKeyParameter(rs, resultMapping, parameterType, columnPrefix);
}
}
private Object prepareSimpleKeyParameter(ResultSet rs, ResultMapping resultMapping, Class<?> parameterType, String columnPrefix) throws SQLException {
final TypeHandler<?> typeHandler;
if (typeHandlerRegistry.hasTypeHandler(parameterType)) {
typeHandler = typeHandlerRegistry.getTypeHandler(parameterType);
} else {
typeHandler = typeHandlerRegistry.getUnknownTypeHandler();
}
return typeHandler.getResult(rs, prependPrefix(resultMapping.getColumn(), columnPrefix));
}
private Object prepareCompositeKeyParameter(ResultSet rs, ResultMapping resultMapping, Class<?> parameterType, String columnPrefix) throws SQLException {
final Object parameterObject = instantiateParameterObject(parameterType);
final MetaObject metaObject = configuration.newMetaObject(parameterObject);
boolean foundValues = false;
for (ResultMapping innerResultMapping : resultMapping.getComposites()) {
final Class<?> propType = metaObject.getSetterType(innerResultMapping.getProperty());
final TypeHandler<?> typeHandler = typeHandlerRegistry.getTypeHandler(propType);
final Object propValue = typeHandler.getResult(rs, prependPrefix(innerResultMapping.getColumn(), columnPrefix));
// issue #353 & #560 do not execute nested query if key is null
if (propValue != null) {
metaObject.setValue(innerResultMapping.getProperty(), propValue);
foundValues = true;
}
}
return foundValues ? parameterObject : null;
}
private Object instantiateParameterObject(Class<?> parameterType) {
if (parameterType == null) {
return new HashMap<>();
} else if (ParamMap.class.equals(parameterType)) {
return new HashMap<>(); // issue #649
} else {
return objectFactory.create(parameterType);
}
}
//
// DISCRIMINATOR
//
public ResultMap resolveDiscriminatedResultMap(ResultSet rs, ResultMap resultMap, String columnPrefix) throws SQLException {
Set<String> pastDiscriminators = new HashSet<>();
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 Object getDiscriminatorValue(ResultSet rs, Discriminator discriminator, String columnPrefix) throws SQLException {
final ResultMapping resultMapping = discriminator.getResultMapping();
final TypeHandler<?> typeHandler = resultMapping.getTypeHandler();
return typeHandler.getResult(rs, prependPrefix(resultMapping.getColumn(), columnPrefix));
}
private String prependPrefix(String columnName, String prefix) {
if (columnName == null || columnName.length() == 0 || prefix == null || prefix.length() == 0) {
return columnName;
}
return prefix + columnName;
}
//
// HANDLE NESTED RESULT MAPS
//
private void handleRowValuesForNestedResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
final DefaultResultContext<Object> resultContext = new DefaultResultContext<>();
skipRows(rsw.getResultSet(), rowBounds);
Object rowValue = previousRowValue;
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, null, partialObject);
} else {
rowValue = getRowValue(rsw, discriminatedResultMap, 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());
previousRowValue = null;
} else if (rowValue != null) {
previousRowValue = rowValue;
}
}
//
// GET VALUE FROM ROW FOR NESTED RESULT MAP
//
private Object getRowValue(ResultSetWrapper rsw, ResultMap resultMap, CacheKey combinedKey, String columnPrefix, Object partialObject) throws SQLException {
final String resultMapId = resultMap.getId();
Object rowValue = partialObject;
if (rowValue != null) {
final MetaObject metaObject = configuration.newMetaObject(rowValue);
putAncestor(rowValue, resultMapId);
applyNestedResultMappings(rsw, resultMap, metaObject, columnPrefix, combinedKey, false);
ancestorObjects.remove(resultMapId);
} else {
final ResultLoaderMap lazyLoader = new ResultLoaderMap();
rowValue = createResultObject(rsw, resultMap, lazyLoader, columnPrefix);
if (rowValue != null && !hasTypeHandlerForResultObject(rsw, resultMap.getType())) {
final MetaObject metaObject = configuration.newMetaObject(rowValue);
boolean foundValues = this.useConstructorMappings;
if (shouldApplyAutomaticMappings(resultMap, true)) {
foundValues = applyAutomaticMappings(rsw, resultMap, metaObject, columnPrefix) || foundValues;
}
foundValues = applyPropertyMappings(rsw, resultMap, metaObject, lazyLoader, columnPrefix) || foundValues;
putAncestor(rowValue, resultMapId);
foundValues = applyNestedResultMappings(rsw, resultMap, metaObject, columnPrefix, combinedKey, true) || foundValues;
ancestorObjects.remove(resultMapId);
foundValues = lazyLoader.size() > 0 || foundValues;
rowValue = foundValues || configuration.isReturnInstanceForEmptyRow() ? rowValue : null;
}
if (combinedKey != CacheKey.NULL_CACHE_KEY) {
nestedResultObjects.put(combinedKey, rowValue);
}
}
return rowValue;
}
private void putAncestor(Object resultObject, String resultMapId) {
ancestorObjects.put(resultMapId, resultObject);
}
//
// NESTED RESULT MAP (JOIN MAPPING)
//
private boolean applyNestedResultMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, String parentPrefix, CacheKey parentRowKey, boolean newObject) {
boolean foundValues = false;
for (ResultMapping resultMapping : resultMap.getPropertyResultMappings()) {
final String nestedResultMapId = resultMapping.getNestedResultMapId();
if (nestedResultMapId != null && resultMapping.getResultSet() == null) {
try {
final String columnPrefix = getColumnPrefix(parentPrefix, resultMapping);
final ResultMap nestedResultMap = getNestedResultMap(rsw.getResultSet(), nestedResultMapId, columnPrefix);
if (resultMapping.getColumnPrefix() == null) {
// try to fill circular reference only when columnPrefix
// is not specified for the nested result map (issue #215)
Object ancestorObject = ancestorObjects.get(nestedResultMapId);
if (ancestorObject != null) {
if (newObject) {
linkObjects(metaObject, resultMapping, ancestorObject); // issue #385
}
continue;
}
}
final CacheKey rowKey = createRowKey(nestedResultMap, rsw, columnPrefix);
final CacheKey combinedKey = combineKeys(rowKey, parentRowKey);
Object rowValue = nestedResultObjects.get(combinedKey);
boolean knownValue = rowValue != null;
instantiateCollectionPropertyIfAppropriate(resultMapping, metaObject); // mandatory
if (anyNotNullColumnHasValue(resultMapping, columnPrefix, rsw)) {
rowValue = getRowValue(rsw, nestedResultMap, combinedKey, columnPrefix, rowValue);
if (rowValue != null && !knownValue) {
linkObjects(metaObject, resultMapping, rowValue);
foundValues = true;
}
}
} catch (SQLException e) {
throw new ExecutorException("Error getting nested result map values for '" + resultMapping.getProperty() + "'. Cause: " + e, e);
}
}
}
return foundValues;
}
private String getColumnPrefix(String parentPrefix, ResultMapping resultMapping) {
final StringBuilder columnPrefixBuilder = new StringBuilder();
if (parentPrefix != null) {
columnPrefixBuilder.append(parentPrefix);
}
if (resultMapping.getColumnPrefix() != null) {
columnPrefixBuilder.append(resultMapping.getColumnPrefix());
}
return columnPrefixBuilder.length() == 0 ? null : columnPrefixBuilder.toString().toUpperCase(Locale.ENGLISH);
}
private boolean anyNotNullColumnHasValue(ResultMapping resultMapping, String columnPrefix, ResultSetWrapper rsw) throws SQLException {
Set<String> notNullColumns = resultMapping.getNotNullColumns();
if (notNullColumns != null && !notNullColumns.isEmpty()) {
ResultSet rs = rsw.getResultSet();
for (String column : notNullColumns) {
rs.getObject(prependPrefix(column, columnPrefix));
if (!rs.wasNull()) {
return true;
}
}
return false;
} else if (columnPrefix != null) {
for (String columnName : rsw.getColumnNames()) {
if (columnName.toUpperCase().startsWith(columnPrefix.toUpperCase())) {
return true;
}
}
return false;
}
return true;
}
private ResultMap getNestedResultMap(ResultSet rs, String nestedResultMapId, String columnPrefix) throws SQLException {
ResultMap nestedResultMap = configuration.getResultMap(nestedResultMapId);
return resolveDiscriminatedResultMap(rs, nestedResultMap, columnPrefix);
}
//
// UNIQUE RESULT KEY
//
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.isEmpty()) {
if (Map.class.isAssignableFrom(resultMap.getType())) {
createRowKeyForMap(rsw, cacheKey);
} else {
createRowKeyForUnmappedProperties(resultMap, rsw, cacheKey, columnPrefix);
}
} else {
createRowKeyForMappedProperties(resultMap, rsw, cacheKey, resultMappings, columnPrefix);
}
if (cacheKey.getUpdateCount() < 2) {
return CacheKey.NULL_CACHE_KEY;
}
return cacheKey;
}
private CacheKey combineKeys(CacheKey rowKey, CacheKey parentRowKey) {
if (rowKey.getUpdateCount() > 1 && parentRowKey.getUpdateCount() > 1) {
CacheKey combinedKey;
try {
combinedKey = rowKey.clone();
} catch (CloneNotSupportedException e) {
throw new ExecutorException("Error cloning cache key. Cause: " + e, e);
}
combinedKey.update(parentRowKey);
return combinedKey;
}
return CacheKey.NULL_CACHE_KEY;
}
private List<ResultMapping> getResultMappingsForRowKey(ResultMap resultMap) {
List<ResultMapping> resultMappings = resultMap.getIdResultMappings();
if (resultMappings.isEmpty()) {
resultMappings = resultMap.getPropertyResultMappings();
}
return resultMappings;
}
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 || configuration.isReturnInstanceForEmptyRow()) {
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(), reflectorFactory);
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 void createRowKeyForMap(ResultSetWrapper rsw, CacheKey cacheKey) throws SQLException {
List<String> columnNames = rsw.getColumnNames();
for (String columnName : columnNames) {
final String value = rsw.getResultSet().getString(columnName);
if (value != null) {
cacheKey.update(columnName);
cacheKey.update(value);
}
}
}
private void linkObjects(MetaObject metaObject, ResultMapping resultMapping, Object rowValue) {
final Object collectionProperty = instantiateCollectionPropertyIfAppropriate(resultMapping, metaObject);
if (collectionProperty != null) {
final MetaObject targetMetaObject = configuration.newMetaObject(collectionProperty);
targetMetaObject.add(rowValue);
} else {
metaObject.setValue(resultMapping.getProperty(), rowValue);
}
}
private Object instantiateCollectionPropertyIfAppropriate(ResultMapping resultMapping, MetaObject metaObject) {
final String propertyName = resultMapping.getProperty();
Object propertyValue = metaObject.getValue(propertyName);
if (propertyValue == null) {
Class<?> type = resultMapping.getJavaType();
if (type == null) {
type = metaObject.getSetterType(propertyName);
}
try {
if (objectFactory.isCollection(type)) {
propertyValue = objectFactory.create(type);
metaObject.setValue(propertyName, propertyValue);
return propertyValue;
}
} catch (Exception e) {
throw new ExecutorException("Error instantiating collection property for result '" + resultMapping.getProperty() + "'. Cause: " + e, e);
}
} else if (objectFactory.isCollection(propertyValue.getClass())) {
return propertyValue;
}
return null;
}
private boolean hasTypeHandlerForResultObject(ResultSetWrapper rsw, Class<?> resultType) {
if (rsw.getColumnNames().size() == 1) {
return typeHandlerRegistry.hasTypeHandler(resultType, rsw.getJdbcType(rsw.getColumnNames().get(0)));
}
return typeHandlerRegistry.hasTypeHandler(resultType);
}
}
解析 sql 标签的代码;
查询从表，建议添加前缀
private boolean applyPropertyMappings(ResultSetWrapper rsw, ResultMap resultMap, MetaObject metaObject, ResultLoaderMap lazyLoader, String columnPrefix)
throws SQLException {
//从resultMap中获取明确需要转换的列名集合
final List<String> mappedColumnNames = rsw.getMappedColumnNames(resultMap, columnPrefix);
boolean foundValues = false;
//获取ResultMapping集合
final List<ResultMapping> propertyMappings = resultMap.getPropertyResultMappings();
for (ResultMapping propertyMapping : propertyMappings) {
String column = prependPrefix(propertyMapping.getColumn(), columnPrefix);//获得列名，注意前缀的处理
if (propertyMapping.getNestedResultMapId() != null) {
// the user added a column attribute to a nested result map, ignore it
//如果属性通过另外一个resultMap映射，则忽略
column = null;
}
if (propertyMapping.isCompositeResult()//如果是嵌套查询，column={prop1=col1,prop2=col2}
|| (column != null && mappedColumnNames.contains(column.toUpperCase(Locale.ENGLISH)))//基本类型映射
|| propertyMapping.getResultSet() != null) {//嵌套查询的结果
//获得属性值
Object value = getPropertyMappingValue(rsw.getResultSet(), metaObject, propertyMapping, lazyLoader, columnPrefix);
// issue #541 make property optional
//获得属性名称
final String property = propertyMapping.getProperty();
if (property == null) {//属性名为空跳出循环
continue;
} else if (value == DEFERED) {//属性名为DEFERED，延迟加载的处理
foundValues = true;
continue;
}
if (value != null) {
foundValues = true;
}
if (value != null || (configuration.isCallSettersOnNulls() && !metaObject.getSetterType(property).isPrimitive())) {
// gcode issue #377, call setter on nulls (value is not 'found')
//通过metaObject为目标对象设置属性值
metaObject.setValue(property, value);
}
}
}
return foundValues;
}