mybatis0080-解析xml文件，创建SqlSessionFactory

文章目录

1. 解析mybatis.xml配置文件，构建SqlSessionFactory2. mybatis.xml的配置信息都会被解析存储在Configure对象中3. 创建SqlSessionFactory

1. 解析mybatis.xml配置文件，构建SqlSessionFactory

String resource = "mybatis.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

注：SqlSessionFactory是通过builder模式构建，SqlSessionFactory在构建的时候逻辑复杂，如果直接放在构造方法中，会让代码令人难以理解，所以使用SqlSessionFactoryBuilder建造者模式构建，将逻辑分开以使个体的逻辑清晰易懂。

2. mybatis.xml的配置信息都会被解析存储在Configure对象中

// SqlSessionBuilder public SqlSessionFactory build(InputStream inputStream, String environment, Properties properties) { try { XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties); // xml的解析会在parser.parse()中进行 return build(parser.parse()); } catch (Exception e) { throw ExceptionFactory.wrapException("Error building SqlSession.", e); } finally { ErrorContext.instance().reset(); try { inputStream.close(); } catch (IOException e) { // Intentionally ignore. Prefer previous error. } } } // XmlConfigBuilder public Configuration parse() { if (parsed) { throw new BuilderException("Each XMLConfigBuilder can only be used once."); } parsed = true; // 解析 parseConfiguration(parser.evalNode("/configuration")); return configuration; } // 这里对xml文件中各个配置进行解析 // properties,settings.... mappers private void parseConfiguration(XNode root) { try { //issue #117 read properties first propertiesElement(root.evalNode("properties")); Properties settings = settingsAsProperties(root.evalNode("settings")); loadCustomVfs(settings); 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")); mapperElement(root.evalNode("mappers")); } catch (Exception e) { throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e); } }

xml的解析逻辑很多，这边不一一陈述，这边简要说一下mappers元素的解析；这是个很重要的元素，也是mybatis中我们操作最多的元素。

// MapperAnnotationBuilder void parseStatement(Method method) { Class<?> parameterTypeClass = getParameterType(method); LanguageDriver languageDriver = getLanguageDriver(method); SqlSource sqlSource = getSqlSourceFromAnnotations(method, parameterTypeClass, languageDriver); if (sqlSource != null) { Options options = method.getAnnotation(Options.class); // key final String mappedStatementId = type.getName() + "." + method.getName(); Integer fetchSize = null; Integer timeout = null; StatementType statementType = StatementType.PREPARED; ResultSetType resultSetType = ResultSetType.FORWARD_ONLY; SqlCommandType sqlCommandType = getSqlCommandType(method); boolean isSelect = sqlCommandType == SqlCommandType.SELECT; boolean flushCache = !isSelect; boolean useCache = isSelect; KeyGenerator keyGenerator; String keyProperty = "id"; String keyColumn = null; if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) { // first check for SelectKey annotation - that overrides everything else SelectKey selectKey = method.getAnnotation(SelectKey.class); if (selectKey != null) { keyGenerator = handleSelectKeyAnnotation(selectKey, mappedStatementId, getParameterType(method), languageDriver); keyProperty = selectKey.keyProperty(); } else if (options == null) { keyGenerator = configuration.isUseGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE; } else { keyGenerator = options.useGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE; keyProperty = options.keyProperty(); keyColumn = options.keyColumn(); } } else { keyGenerator = NoKeyGenerator.INSTANCE; } if (options != null) { if (FlushCachePolicy.TRUE.equals(options.flushCache())) { flushCache = true; } else if (FlushCachePolicy.FALSE.equals(options.flushCache())) { flushCache = false; } useCache = options.useCache(); fetchSize = options.fetchSize() > -1 || options.fetchSize() == Integer.MIN_VALUE ? options.fetchSize() : null; //issue #348 timeout = options.timeout() > -1 ? options.timeout() : null; statementType = options.statementType(); resultSetType = options.resultSetType(); } String resultMapId = null; ResultMap resultMapAnnotation = method.getAnnotation(ResultMap.class); if (resultMapAnnotation != null) { String[] resultMaps = resultMapAnnotation.value(); StringBuilder sb = new StringBuilder(); for (String resultMap : resultMaps) { if (sb.length() > 0) { sb.append(","); } sb.append(resultMap); } resultMapId = sb.toString(); } else if (isSelect) { resultMapId = parseResultMap(method); } assistant.addMappedStatement( mappedStatementId, sqlSource, statementType, sqlCommandType, fetchSize, timeout, // ParameterMapID null, parameterTypeClass, resultMapId, getReturnType(method), resultSetType, flushCache, useCache, // TODO gcode issue #577 false, keyGenerator, keyProperty, keyColumn, // DatabaseID null, languageDriver, // ResultSets options != null ? nullOrEmpty(options.resultSets()) : null); } } // MapperBuilderAssistant public MappedStatement addMappedStatement( String id, SqlSource sqlSource, StatementType statementType, SqlCommandType sqlCommandType, Integer fetchSize, Integer timeout, String parameterMap, Class<?> parameterType, String resultMap, Class<?> resultType, ResultSetType resultSetType, boolean flushCache, boolean useCache, boolean resultOrdered, KeyGenerator keyGenerator, String keyProperty, String keyColumn, String databaseId, LanguageDriver lang, String resultSets) { if (unresolvedCacheRef) { throw new IncompleteElementException("Cache-ref not yet resolved"); } id = applyCurrentNamespace(id, false); boolean isSelect = sqlCommandType == SqlCommandType.SELECT; MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType) .resource(resource) .fetchSize(fetchSize) .timeout(timeout) .statementType(statementType) .keyGenerator(keyGenerator) .keyProperty(keyProperty) .keyColumn(keyColumn) .databaseId(databaseId) .lang(lang) .resultOrdered(resultOrdered) .resultSets(resultSets) .resultMaps(getStatementResultMaps(resultMap, resultType, id)) .resultSetType(resultSetType) .flushCacheRequired(valueOrDefault(flushCache, !isSelect)) .useCache(valueOrDefault(useCache, isSelect)) .cache(currentCache); ParameterMap statementParameterMap = getStatementParameterMap(parameterMap, parameterType, id); if (statementParameterMap != null) { statementBuilder.parameterMap(statementParameterMap); } // value MappedStatement statement = statementBuilder.build(); configuration.addMappedStatement(statement); return statement; }

注：在解析mappers标签的时候，会将每个mapper接口的每个方法解析为一个MappedStatement 放在configuration的mappedStatements中，key为mapper接口名加方法名。

3. 创建SqlSessionFactory

// 解析完创建SqlSessionFactory public SqlSessionFactory build(Configuration config) { return new DefaultSqlSessionFactory(config); }

注：xml元素解析完成以后，返回DefaultSqlSessionFactory的实例。