Mybatis源码分析（二）初始化

时间：2023-07-01

Mybatis 初始化解析

//将XML配置文件构建为Configuration配置类//通过加载配置文件流构建一个SqlSessionFactory 解析xml文件String resource = "mybatis-config.xml";Reader reader = Resources.getResourceAsReader(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);

SqlSessionFactoryBuilder.build

public SqlSessionFactory build(Reader reader, String environment, Properties properties) { try { XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties); return build(parser.parse()); } catch (Exception e) { throw ExceptionFactory.wrapException("Error building SqlSession.", e); } finally { ErrorContext.instance().reset(); try { reader.close(); } catch (IOException e) { // Intentionally ignore、Prefer previous error. } } }

XMLConfigBuilder.parse 解析成 Configuration

public Configuration parse() { if (parsed) { throw new BuilderException("Each XMLConfigBuilder can only be used once."); } parsed = true; parseConfiguration(parser.evalNode("/configuration")); return configuration; }

解析configuration节点 parseConfiguration(parser.evalNode("/configuration"))

private void parseConfiguration(XNode root) { try { propertiesElement(root.evalNode("properties")); Properties settings = settingsAsProperties(root.evalNode("settings")); loadCustomVfs(settings); loadCustomLogImpl(settings); typeAliasesElement(root.evalNode("typeAliases")); pluginElement(root.evalNode("plugins")); objectFactoryElement(root.evalNode("objectFactory")); objectWrapperFactoryElement(root.evalNode("objectWrapperFactory")); reflectorFactoryElement(root.evalNode("reflectorFactory")); // 设置settings 和默认值到configuration settingsElement(settings); environmentsElement(root.evalNode("environments")); databaseIdProviderElement(root.evalNode("databaseIdProvider")); typeHandlerElement(root.evalNode("typeHandlers")); mapperElement(root.evalNode("mappers")); } catch (Exception e) { throw new BuilderException("Error parsing SQL Mapper Configuration、Cause: " + e, e); } }

解析mappers节点 mapperElement(root.evalNode(“mappers”))

private void mapperElement(XNode parent) throws Exception { if (parent != null) { for (XNode child : parent.getChildren()) { if ("package".equals(child.getName())) { String mapperPackage = child.getStringAttribute("name"); configuration.addMappers(mapperPackage); } else { String resource = child.getStringAttribute("resource"); String url = child.getStringAttribute("url"); String mapperClass = child.getStringAttribute("class"); if (resource != null && url == null && mapperClass == null) { ErrorContext.instance().resource(resource); InputStream inputStream = Resources.getResourceAsStream(resource); XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments()); mapperParser.parse(); } else if (resource == null && url != null && mapperClass == null) { ErrorContext.instance().resource(url); InputStream inputStream = Resources.getUrlAsStream(url); XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments()); mapperParser.parse(); } else if (resource == null && url == null && mapperClass != null) { Class<?> mapperInterface = Resources.classForName(mapperClass); configuration.addMapper(mapperInterface); } else { throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one."); } } } } }

解析mapper package 方式
configuration.addMappers(mapperPackage) -> mapperRegistry.addMappers(packageName) -> addMappers(packageName, Object.class)

public void addMappers(String packageName, Class<?> superType) { // 根据包找到所有类 ResolverUtil> resolverUtil = new ResolverUtil<>(); resolverUtil.find(new ResolverUtil.IsA(superType), packageName); Set>> mapperSet = resolverUtil.getClasses(); // 循环所有的类 for (Class<?> mapperClass : mapperSet) { addMapper(mapperClass); } }

解析Mapper过滤

创建一个MapperProxyFactory 把我们的Mapper接口保存到工厂类中，该工厂用于创建 MapperProxy

public void addMapper(Class type) { if (type.isInterface()) { if (hasMapper(type)) { throw new BindingException("Type " + type + " is already known to the MapperRegistry."); } boolean loadCompleted = false; try { knownMappers.put(type, new MapperProxyFactory<>(type)); // It's important that the type is added before the parser is run // otherwise the binding may automatically be attempted by the // mapper parser、If the type is already known, it won't try、 mapper注解构造器 MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type); parser.parse(); loadCompleted = true; } finally { if (!loadCompleted) { knownMappers.remove(type); } } } }

解析Mapper

xml解析 loadXmlResource()注解解析 parseStatement(method)

public void parse() { String resource = type.toString(); // 是否已经解析mapper接口对应的xml if (!configuration.isResourceLoaded(resource)) { // 根据mapper接口名获取 xml文件并解析，解析里面所有东西放到configuration loadXmlResource(); // 添加已解析的标记 configuration.addLoadedResource(resource); assistant.setCurrentNamespace(type.getName()); parseCache(); parseCacheRef(); // 获取所有方法看是不是用了注解 Method[] methods = type.getMethods(); for (Method method : methods) { try { // issue #237 if (!method.isBridge()) { // 是不是用了注解用了注解会将注解解析成MappedStatement parseStatement(method); } } catch (IncompleteElementException e) { configuration.addIncompleteMethod(new MethodResolver(this, method)); } } } parsePendingMethods(); }

根据mapper接口名获取xml文件并解析,解析里面所有东西放到configuration
loadXmlResource

private void loadXmlResource() { // Spring may not know the real resource name so we check a flag // to prevent loading again a resource twice // this flag is set at XMLMapperBuilder#bindMapperForNamespace if (!configuration.isResourceLoaded("namespace:" + type.getName())) { String xmlResource = type.getName().replace('.', '/') + ".xml"; // #1347 InputStream inputStream = type.getResourceAsStream("/" + xmlResource); if (inputStream == null) { // Search XML mapper that is not in the module but in the classpath. try { inputStream = Resources.getResourceAsStream(type.getClassLoader(), xmlResource); } catch (IOException e2) { // ignore, resource is not required } } if (inputStream != null) { XMLMapperBuilder xmlParser = new XMLMapperBuilder(inputStream, assistant.getConfiguration(), xmlResource, configuration.getSqlFragments(), type.getName()); xmlParser.parse(); } } }

XMLMapperBuilder.parse

public void parse() { if (!configuration.isResourceLoaded(resource)) { configurationElement(parser.evalNode("/mapper")); configuration.addLoadedResource(resource); bindMapperForNamespace(); } parsePendingResultMaps(); parsePendingCacheRefs(); parsePendingStatements(); }

正式解析mapper节点 configurationElement(parser.evalNode("/mapper"))

cache 一级二级缓存

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、The XML location is '" + resource + "'、Cause: " + e, e); } }

插入题cache

private void cacheElement(XNode context) { if (context != null) { //解析cache节点的type属性 String type = context.getStringAttribute("type", "PERPETUAL"); // 根据别名（或完整限定名）加载为Class Class<? extends Cache> typeClass = typeAliasRegistry.resolveAlias(type); String eviction = context.getStringAttribute("eviction", "LRU"); Class<? extends Cache> evictionClass = typeAliasRegistry.resolveAlias(eviction); //flushInterval（刷新间隔）属性可以被设置为任意的正整数，设置的值应该是一个以毫秒为单位的合理时间量。默认情况是不设置，也就是没有刷新间隔，缓存仅仅会在调用语句时刷新。 Long flushInterval = context.getLongAttribute("flushInterval"); //size（引用数目）属性可以被设置为任意正整数，要注意欲缓存对象的大小和运行环境中可用的内存资源。默认值是 1024。 Integer size = context.getIntAttribute("size"); //只读）属性可以被设置为 true 或 false。只读的缓存会给所有调用者返回缓存对象的相同实例。因此这些对象不能被修改。这就提供了可观的性能提升。而可读写的缓存会（通过序列化）返回缓存对象的拷贝。速度上会慢一些，但是更安全，因此默认值是 false boolean readWrite = !context.getBooleanAttribute("readOnly", false); boolean blocking = context.getBooleanAttribute("blocking", false); Properties props = context.getChildrenAsProperties(); //把缓存节点加入到Configuration中 builderAssistant.useNewCache(typeClass, evictionClass, flushInterval, size, readWrite, blocking, props); } }

XMLStatementBuilderMappedStatement

private void buildStatementFromContext(List list, String requiredDatabaseId) { for (XNode context : list) { final XMLStatementBuilder statementParser = new XMLStatementBuilder(configuration, builderAssistant, context, requiredDatabaseId); try { statementParser.parseStatementNode(); } catch (IncompleteElementException e) { configuration.addIncompleteStatement(statementParser); } } }

创建MappedStatement对象 XMLStatementBuilder.parseStatementNode()

SqlSource DynamicSqlSource 和 RawSqlSource

public void parseStatementNode() { String id = context.getStringAttribute("id"); String databaseId = context.getStringAttribute("databaseId"); if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) { return; } String nodeName = context.getNode().getNodeName(); SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH)); boolean isSelect = sqlCommandType == SqlCommandType.SELECT; boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect); boolean useCache = context.getBooleanAttribute("useCache", isSelect); boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false); // Include Fragments before parsing XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant); includeParser.applyIncludes(context.getNode()); String parameterType = context.getStringAttribute("parameterType"); // 把参数类型字符串转化为class Class<?> parameterTypeClass = resolveClass(parameterType); String lang = context.getStringAttribute("lang"); LanguageDriver langDriver = getLanguageDriver(lang); // Parse selectKey after includes and remove them. processSelectKeyNodes(id, parameterTypeClass, langDriver); // Parse the SQL (pre: and were parsed and removed) KeyGenerator keyGenerator; String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX; keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true); if (configuration.hasKeyGenerator(keyStatementId)) { keyGenerator = configuration.getKeyGenerator(keyStatementId); } else { keyGenerator = context.getBooleanAttribute("useGeneratedKeys", configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType)) ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE; } SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass); StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString())); Integer fetchSize = context.getIntAttribute("fetchSize"); Integer timeout = context.getIntAttribute("timeout"); String parameterMap = context.getStringAttribute("parameterMap"); String resultType = context.getStringAttribute("resultType"); Class<?> resultTypeClass = resolveClass(resultType); String resultMap = context.getStringAttribute("resultMap"); String resultSetType = context.getStringAttribute("resultSetType"); ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType); if (resultSetTypeEnum == null) { resultSetTypeEnum = configuration.getDefaultResultSetType(); } String keyProperty = context.getStringAttribute("keyProperty"); String keyColumn = context.getStringAttribute("keyColumn"); String resultSets = context.getStringAttribute("resultSets"); builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType, fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass, resultSetTypeEnum, flushCache, useCache, resultOrdered, keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets); }

SqlSource SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass)

public SqlSource createSqlSource(Configuration configuration, XNode script, Class<?> parameterType) { XMLscriptBuilder builder = new XMLscriptBuilder(configuration, script, parameterType); return builder.parsescriptNode(); }

XMLscriptBuilder.parsescriptNode

public SqlSource parsescriptNode() { MixedSqlNode rootSqlNode = parseDynamicTags(context); SqlSource sqlSource; if (isDynamic) { // 动态Sql源 // 动态Sql 就是还需要后续执行时根据传入参数动态解析Sql（因为有等,还要拼接${}sql） // 和参数ParameterMappings 也会在后续执行解析，因为动态条件肯定会有动态参数 sqlSource = new DynamicSqlSource(configuration, rootSqlNode); } else { // 静态Sql源如果没有动态标签(、等) 以及没有${} 就是静态Sql源 // 静态Sql 就是在这里就解析了Sql 和参数ParameterMappings 后续执行就不用解析了 sqlSource = new RawSqlSource(configuration, rootSqlNode, parameterType); } // 其实他们的区别就是动态sql 需要在查询的时候解析因为有动态sql 和拼接${} // 静态sql 已经在这里确定好sql、和参数ParameterMapping, return sqlSource; }

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