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Mybatis initialization is completed by SqlSessionFactoryBuilder, the main work is to parse the XML file, and encapsulate the parsed class content into the Configuration class, and finally encapsulate the Configuration class into SqlSessionFactory and return, since then the initialization is completed.

The parsing of the XML file is completed by three classes: XMLConfigBuilder, XMLMapperBuilder, and XMLStatementBuilder:

XMLConfigBuilder: responsible for parsing except mappers nodes in the global configuration file (mybatis-config.xml).

XMLMapperBuilder: responsible for parsing the cache-ref, cache, parameterMap, resultMap, sql nodes in the xxxMapper.xml mapping file; registering the dynamic proxy factory of the Mapper interface into MapperRegistry according to namespace.

XMLStatementBuilder: responsible for parsing SQL statement nodes in xxxMapper.xml mapping files, such as select, insert, update, delete.

XMLScriptBuilder: responsible for parsing the SQL script and then encapsulating it into SqlSource.

Mybatis initialization process SqlSessionFactoryBuilder

SqlSessionFactoryBuilder will delegate the parsing task to the XMLConfigBuilder class. The source code is as follows:

Public SqlSessionFactory build (InputStream inputStream, String environment, Properties properties) {try {/ / entrusts XMLConfigBuilder to parse the configuration file XMLConfigBuilder parser = new XMLConfigBuilder (inputStream, environment, properties); / / starts parsing return build (parser.parse ());}.} public SqlSessionFactory build (Configuration config) {return new DefaultSqlSessionFactory (config);} XMLConfigBuilder

Responsible for parsing except mappers nodes in the global configuration file (mybatis-config.xml). The parsing node delegates to the XMLMapperBuilder parser.

Private void parseConfiguration (XNode root) {try {/ / issue # 117 read properties first / / parsing node propertiesElement (root.evalNode ("properties")); / / parsing node Properties settings = settingsAsProperties (root.evalNode ("settings")); loadCustomVfs (settings); loadCustomLogImpl (settings); / / parsing node typeAliasesElement (root.evalNode ("typeAliases")); pluginElement (root.evalNode ("plugins")) ObjectFactoryElement (root.evalNode ("objectFactory")); objectWrapperFactoryElement (root.evalNode ("objectWrapperFactory")); reflectorFactoryElement (root.evalNode ("reflectorFactory")); settingsElement (settings); / / read it after objectFactory and objectWrapperFactory issue # 631 environmentsElement (root.evalNode ("environments")); databaseIdProviderElement (root.evalNode ("databaseIdProvider")); typeHandlerElement (root.evalNode ("typeHandlers")); / / parse node mapperElement (root.evalNode ("mappers")) } catch (Exception e) {throw new BuilderException ("Error parsing SQL Mapper Configuration. Cause: "+ e, e);}} 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); / / delegate XMLMapperBuilder to parse the mapping file 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); / / delegate XMLMapperBuilder to parse the mapping file 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.");} XMLMapperBuilder

Responsible for parsing the cache-ref, cache, parameterMap, resultMap, sql nodes in the xxxMapper.xml mapping file; registering the dynamic proxy factory (MapperProxyFactory) of the Mapper interface into the MapperRegistry according to namespace.

Public void parse () {/ / prevent repeated parsing of if (! configuration.isResourceLoaded (resource)) {/ / parsing the mapper node configurationElement (parser.evalNode ("/ mapper")) in the xxxMapper.xml mapping file; / / marking that configuration.addLoadedResource (resource) has been loaded; / / registering the dynamic proxy factory of the Mapper interface to MapperRegistry according to namespace bindMapperForNamespace ();} / / underside parsePendingResultMaps () ParsePendingCacheRefs (); parsePendingStatements ();} 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); / / parsing node cacheRefElement (context.evalNode (" cache-ref ")) / / parsing node cacheElement (context.evalNode ("cache")); / / parsing node parameterMapElement (context.evalNodes ("/ mapper/parameterMap")); / / parsing node resultMapElements (context.evalNodes ("/ mapper/resultMap")); sqlElement (context.evalNodes ("/ mapper/sql")); / / parsing node 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);}} private void buildStatementFromContext (List list) {if (configuration.getDatabaseId ()! = null) {buildStatementFromContext (list, configuration.getDatabaseId ());} buildStatementFromContext (list, null);} private void buildStatementFromContext (List list, String requiredDatabaseId) {for (XNode context: list) {/ parse node to XMLStatementBuilder final XMLStatementBuilder statementParser = new XMLStatementBuilder (configuration, builderAssistant, context, requiredDatabaseId); try {statementParser.parseStatementNode () } catch (IncompleteElementException e) {configuration.addIncompleteStatement (statementParser);} XMLStatementBuilder

Responsible for parsing SQL statement nodes in xxxMapper.xml mapping files, such as select, insert, update, delete. The parsing node delegates to the XMLStatementBuilder parser.

Public void parseStatementNode () {String id = context.getStringAttribute ("id"); String databaseId = context.getStringAttribute ("databaseId"); if (! databaseIdMatchesCurrent (id, databaseId, this.requiredDatabaseId) {return;} / / determine the type of SQL statement based on the name of the node (select | insert | update | delete) 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 / / parse node XMLIncludeTransformer includeParser = new XMLIncludeTransformer (configuration, builderAssistant); includeParser.applyIncludes (context.getNode ()); String parameterType = context.getStringAttribute ("parameterType"); Class parameterTypeClass = resolveClass (parameterType); String lang = context.getStringAttribute ("lang"); LanguageDriver langDriver = getLanguageDriver (lang) / / Parse selectKey after includes and remove them. / / parse the node and delete the node processSelectKeyNodes (id, parameterTypeClass, langDriver) in XML; / / 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;} / / parses the SQL statement and encapsulates it into SqlSource 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") / use builder mode to build MappedStatement object builderAssistant.addMappedStatement (id, sqlSource, statementType, sqlCommandType, fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass, resultSetTypeEnum, flushCache, useCache, resultOrdered, keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);} Mybatis initialization flowchart

Core data structure class Configuration

Configuration is actually the Java form of the XML configuration file. Configuration is a singleton, and the life cycle is application-level.

ResultMap

Corresponds to the resultMap node in the xxxMapper.xml mapping file. The child nodes in the node are encapsulated using ResultMapping, such as:, and so on.

MappedStatement

Corresponds to the, and nodes in the xxxMapper.xml mapping file.

SqlSource

Corresponding to the sql statement in the xxxMapper.xml mapping file, the statement contained in the parsed SqlSource only contains? Placeholder, which can be submitted directly to the database for execution

MapperRegistry

It is the registry of the Mapper interface dynamic proxy factory class. In MyBatis, the InvocationHandler interface is implemented through MapperProxy, and the instance object of dynamic agent is generated through MapperProxyFactory.

MyBatis Builder Class Diagram

The builder mode is used throughout the initialization process of Mybatis. The builder pattern is more suitable for generating complex objects, mainly focusing on the instantiation details of the objects.

Mybatis Source Code Chinese Notes

Https://github.com/xiaolyuh/mybatis

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