标签：初始化 构造 bat exception one orm cond eal nbsp
在使用 mybatis 时, 还需要对mapper进行配置:
mybatis: mapper-locations: classpath:mapper/**Mapper.xml
这些配置其实是映射到 mybatis-spring-boot-autoconfigure 包下的 MybatisProperties 文件中的.
@ConfigurationProperties(prefix = MybatisProperties.MYBATIS_PREFIX) public class MybatisProperties { public static final String MYBATIS_PREFIX = "mybatis"; /** * Location of MyBatis xml config file. */ private String configLocation; /** * Locations of MyBatis mapper files. */ private String[] mapperLocations; /** * Packages to search type aliases. (Package delimiters are ",; \t\n") */ private String typeAliasesPackage; /** * Packages to search for type handlers. (Package delimiters are ",; \t\n") */ private String typeHandlersPackage; /** * Indicates whether perform presence check of the MyBatis xml config file. */ private boolean checkConfigLocation = false; /** * Execution mode for {@link org.mybatis.spring.SqlSessionTemplate}. */ private ExecutorType executorType; /** * Externalized properties for MyBatis configuration. */ private Properties configurationProperties; /** * A Configuration object for customize default settings. If {@link #configLocation} * is specified, this property is not used. */ @NestedConfigurationProperty private Configuration configuration; ...... }
MybatisAutoConfiguration 是 mybatis-spring-boot-autoconfigure 中的一个配置类.
在这个配置类中, 主要加入了两个组件: SqlSessionFactory 和 SqlSessionTemplate
@Bean @ConditionalOnMissingBean public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception { SqlSessionFactoryBean factory = new SqlSessionFactoryBean(); factory.setDataSource(dataSource); factory.setVfs(SpringBootVFS.class); if (StringUtils.hasText(this.properties.getConfigLocation())) { factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation())); } Configuration configuration = this.properties.getConfiguration(); if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) { configuration = new Configuration(); } if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) { for (ConfigurationCustomizer customizer : this.configurationCustomizers) { customizer.customize(configuration); } } factory.setConfiguration(configuration); if (this.properties.getConfigurationProperties() != null) { factory.setConfigurationProperties(this.properties.getConfigurationProperties()); } if (!ObjectUtils.isEmpty(this.interceptors)) { factory.setPlugins(this.interceptors); } if (this.databaseIdProvider != null) { factory.setDatabaseIdProvider(this.databaseIdProvider); } if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) { factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage()); } if (StringUtils.hasLength(this.properties.getTypeHandlersPackage())) { factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage()); } if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) { factory.setMapperLocations(this.properties.resolveMapperLocations()); } return factory.getObject(); }
(从名字可以看出来, SqlSessionFactory 是 SqlSession的一个工厂类. SqlSession 这个类很重要, 里面定义了 数据库的一套增删改查操作的规范.)
MybatisProperties 中的配置会在这个方法中进行解析.
1. 创建了 Configuration 配置类(后面会用到, 这个类也很重要)的实例
2. 通过 factory.getObject() 方法创建了 SqlSessionFactory 类的实例
创建的过程中, 又调用了 protected SqlSessionFactory buildSqlSessionFactory() 方法进行创建, 创建过程比较多, 留给后面在解析.
@Bean @ConditionalOnMissingBean public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) { ExecutorType executorType = this.properties.getExecutorType(); if (executorType != null) { return new SqlSessionTemplate(sqlSessionFactory, executorType); } else { return new SqlSessionTemplate(sqlSessionFactory); } }
SqlSessionTemplate 这个类 实现了 SqlSession 接口, 也就是说, 他也有一套 数据库的 增删改查的方法. 先看一下构造过程:
public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory) { this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType()); } | | \|/ public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType) { this(sqlSessionFactory, executorType, new MyBatisExceptionTranslator( sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(), true)); } | | \|/ public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType, PersistenceExceptionTranslator exceptionTranslator) { notNull(sqlSessionFactory, "Property ‘sqlSessionFactory‘ is required"); notNull(executorType, "Property ‘executorType‘ is required"); this.sqlSessionFactory = sqlSessionFactory; this.executorType = executorType; this.exceptionTranslator = exceptionTranslator; this.sqlSessionProxy = (SqlSession) newProxyInstance( SqlSessionFactory.class.getClassLoader(), new Class[] { SqlSession.class }, new SqlSessionInterceptor()); }
这里初始化了一个很重要的属性: sqlSessionProxy.
sqlSessionProxy 是为 SqlSession 创建了一个代理类, 且代理方法为: SqlSessionInterceptor
看一个 实现了 SqlSession 接口中的 selectOne 方法:
@Override public <T> T selectOne(String statement, Object parameter) { return this.sqlSessionProxy.<T> selectOne(statement, parameter); }
可以看到, 在调用 selectOne 方法的时候, 其实就是调用了 SqlSessionInterceptor 的 invoke 方法.
mybatis - MybatisAutoConfiguration
标签：初始化 构造 bat exception one orm cond eal nbsp
原文地址：https://www.cnblogs.com/elvinle/p/12297104.html
