Mybatis3.3.0 Po类有LocalDateTime字段报错
想写本文的原因是设计了一个Po类,里面有LocalDateTime,启动Mybatis就报错了,下面就分析分析为啥报错
一 解析ResultMap的入口
XMLMapperBuilder.configurationElement
private void configurationElement(XNode context) { try { String namespace = context.getStringAttribute("namespace"); if (namespace == null || namespace.equals("")) { throw new BuilderException("Mapper's namespace cannot be empty"); } builderAssistant.setCurrentNamespace(namespace); cacheRefElement(context.evalNode("cache-ref")); cacheElement(context.evalNode("cache")); parameterMapElement(context.evalNodes("/mapper/parameterMap")); resultMapElements(context.evalNodes("/mapper/resultMap")); sqlElement(context.evalNodes("/mapper/sql")); buildStatementFromContext(context.evalNodes("select|insert|update|delete")); } catch (Exception e) { throw new BuilderException("Error parsing Mapper XML. Cause: " + e, e); } }
private ResultMap resultMapElement(XNode resultMapNode, List<ResultMapping> additionalResultMappings) throws Exception { ErrorContext.instance().activity("processing " + resultMapNode.getValueBasedIdentifier()); String id = resultMapNode.getStringAttribute("id", resultMapNode.getValueBasedIdentifier()); String type = resultMapNode.getStringAttribute("type", resultMapNode.getStringAttribute("ofType", resultMapNode.getStringAttribute("resultType", resultMapNode.getStringAttribute("javaType")))); String extend = resultMapNode.getStringAttribute("extends"); Boolean autoMapping = resultMapNode.getBooleanAttribute("autoMapping"); Class<?> typeClass = resolveClass(type); Discriminator discriminator = null; List<ResultMapping> resultMappings = new ArrayList<ResultMapping>(); resultMappings.addAll(additionalResultMappings); List<XNode> resultChildren = resultMapNode.getChildren(); for (XNode resultChild : resultChildren) {//对每个字段的映射做处理 if ("constructor".equals(resultChild.getName())) { processConstructorElement(resultChild, typeClass, resultMappings); } else if ("discriminator".equals(resultChild.getName())) { discriminator = processDiscriminatorElement(resultChild, typeClass, resultMappings); } else { List<ResultFlag> flags = new ArrayList<ResultFlag>(); if ("id".equals(resultChild.getName())) { flags.add(ResultFlag.ID); } resultMappings.add(buildResultMappingFromContext(resultChild, typeClass, flags));//把每个属性的映射都放进一个List中 } } ResultMapResolver resultMapResolver = new ResultMapResolver(builderAssistant, id, typeClass, extend, discriminator, resultMappings, autoMapping); try { return resultMapResolver.resolve(); } catch (IncompleteElementException e) { configuration.addIncompleteResultMap(resultMapResolver); throw e; } }
重点分析 buildResultMappingFromContext
private ResultMapping buildResultMappingFromContext(XNode context, Class<?> resultType, List<ResultFlag> flags) throws Exception { String property = context.getStringAttribute("property"); String column = context.getStringAttribute("column"); String javaType = context.getStringAttribute("javaType"); String jdbcType = context.getStringAttribute("jdbcType"); String nestedSelect = context.getStringAttribute("select"); String nestedResultMap = context.getStringAttribute("resultMap", processNestedResultMappings(context, Collections.<ResultMapping> emptyList())); String notNullColumn = context.getStringAttribute("notNullColumn"); String columnPrefix = context.getStringAttribute("columnPrefix"); String typeHandler = context.getStringAttribute("typeHandler");//如果不显示配置,这里是null String resulSet = context.getStringAttribute("resultSet"); String foreignColumn = context.getStringAttribute("foreignColumn"); boolean lazy = "lazy".equals(context.getStringAttribute("fetchType", configuration.isLazyLoadingEnabled() ? "lazy" : "eager")); Class<?> javaTypeClass = resolveClass(javaType); @SuppressWarnings("unchecked") Class<? extends TypeHandler<?>> typeHandlerClass = (Class<? extends TypeHandler<?>>) resolveClass(typeHandler); JdbcType jdbcTypeEnum = resolveJdbcType(jdbcType); return builderAssistant.buildResultMapping(resultType, property, column, javaTypeClass, jdbcTypeEnum, nestedSelect, nestedResultMap, notNullColumn, columnPrefix, typeHandlerClass, flags, resulSet, foreignColumn, lazy); }
public ResultMapping buildResultMapping( Class<?> resultType, String property, String column, Class<?> javaType, JdbcType jdbcType, String nestedSelect, String nestedResultMap, String notNullColumn, String columnPrefix, Class<? extends TypeHandler<?>> typeHandler, List<ResultFlag> flags, String resultSet, String foreignColumn, boolean lazy) { Class<?> javaTypeClass = resolveResultJavaType(resultType, property, javaType); TypeHandler<?> typeHandlerInstance = resolveTypeHandler(javaTypeClass, typeHandler); List<ResultMapping> composites = parseCompositeColumnName(column); if (composites.size() > 0) { column = null; } ResultMapping.Builder builder = new ResultMapping.Builder(configuration, property, column, javaTypeClass); builder.jdbcType(jdbcType); builder.nestedQueryId(applyCurrentNamespace(nestedSelect, true)); builder.nestedResultMapId(applyCurrentNamespace(nestedResultMap, true)); builder.resultSet(resultSet); builder.typeHandler(typeHandlerInstance); builder.flags(flags == null ? new ArrayList<ResultFlag>() : flags); builder.composites(composites); builder.notNullColumns(parseMultipleColumnNames(notNullColumn)); builder.columnPrefix(columnPrefix); builder.foreignColumn(foreignColumn); builder.lazy(lazy); return builder.build(); }
记住,此时的 typeHandlerInstance 还是null的
public ResultMapping build() { // lock down collections resultMapping.flags = Collections.unmodifiableList(resultMapping.flags); resultMapping.composites = Collections.unmodifiableList(resultMapping.composites); resolveTypeHandler();//这里才是解决typeHandler的核心 validate(); return resultMapping; }
最终执行的是 TypeHandlerRegistry.getTypeHandler
private <T> TypeHandler<T> getTypeHandler(Type type, JdbcType jdbcType) {//type是String,jdbcType是Char Map<JdbcType, TypeHandler<?>> jdbcHandlerMap = TYPE_HANDLER_MAP.get(type); TypeHandler<?> handler = null; if (jdbcHandlerMap != null) { handler = jdbcHandlerMap.get(jdbcType); if (handler == null) { handler = jdbcHandlerMap.get(null); } } if (handler == null && type != null && type instanceof Class && Enum.class.isAssignableFrom((Class<?>) type)) { handler = new EnumTypeHandler((Class<?>) type); } // type drives generics here return (TypeHandler<T>) handler;//最终找到的StringTypeHandler }
如果是3.3.0之前的版本mybatis是没有LocalDateTime类型的,所以这里返回的handler只能是null,最终会抛出异常