原生mybatis使用方法：
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
try {
Employee employee = new Employee(null, "doubi", "1", "ddd@sys.com");
EmployeeMapper mapper = session.getMapper(EmployeeMapper.class);
mapper.addEmp(employee);
session.commit();
} finally {
session.close();
}
複製程式碼@Autowired
EmployeeMapper employeeMapper複製程式碼那麼spring為我們做了什麼？下面研究一下mybatis-spring.jar這個jar包
首先來看一下如何使用spring整合mybatis，下面是使用spring-mybatis的四種方法：
方法一：（使用MapperFactoryBean）
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="configLocation" value="classpath:mybatis-config.xml"></property>
<!-- 自動掃描mapping.xml檔案 -->
<property name="mapperLocations" value="classpath:mapper/*.xml"></property>
</bean>
<!--上面生成sqlSessionFactory的幾個方法基本相同-->
<bean id="userMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
<property name="mapperInterface" value="org.mybatis.spring.sample.mapper.UserMapper" />
<property name="sqlSessionFactory" ref="sqlSessionFactory" />
</bean>複製程式碼這樣做的缺點是每一個mapper介面都要在xml裡配置一下
方法二：採用介面org.apache.ibatis.session.SqlSession的實現類org.mybatis.spring.SqlSessionTemplate
mybatis中, sessionFactory可由SqlSessionFactoryBuilder.來建立。MyBatis-Spring
中，使用了SqlSessionFactoryBean來替代。SqlSessionFactoryBean有一個必須屬性dataSource，另外其還有一個通用屬性configLocation（用來指定mybatis的xml配置檔案路徑）。
SqlSessionFactoryBean即相當於原生mybatis中的SqlSessionFactoryBuilder
<!-- spring和MyBatis完美整合，不需要mybatis的配置對映檔案 -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="configLocation" value="classpath:sqlMapConfig.xml"/>
<!-- 自動掃描mapping.xml檔案，**表示迭代查詢,也可在sqlMapConfig.xml中單獨指定xml檔案-->
<property name="mapperLocations" value="classpath:com/hua/saf/**/*.xml" />
</bean>
<!-- mybatis spring sqlSessionTemplate,使用時直接讓spring注入即可 -->
<bean id="sqlSessionTemplate" class="org.mybatis.spring.SqlSessionTemplate">
<constructor-arg index="0" ref="sqlSessionFactory"></constructor-arg>
</bean>複製程式碼//使用方法：
@Repositorypublic class UserDao{ @Resource private SqlSessionTemplate sqlSessionTemplate; public User getUser(int id) { return sqlSessionTemplate.selectOne(this.getClass().getName() + ".getUser", 1); } }複製程式碼為什麼可以這樣寫，來看一下SqlSessionTemplate
public class SqlSessionTemplate implements SqlSession { private final SqlSessionFactory sqlSessionFactory; private final ExecutorType executorType; private final SqlSession sqlSessionProxy; private final PersistenceExceptionTranslator exceptionTranslator; /** * Constructs a Spring managed SqlSession with the {@code SqlSessionFactory} * provided as an argument. * * @param sqlSessionFactory */ public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory) { this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType()); }
........省略......
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()); }
}複製程式碼如上面程式碼所示，SqlSessionTemplate類實現了原生Mybatis中的SqlSession介面，實際上它就是原生mybatis中的SqlSession
方法三：採用抽象類org.mybatis.spring.support.SqlSessionDaoSupport提供SqlSession
<!-- spring和MyBatis完美整合，不需要mybatis的配置對映檔案 -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="configLocation" value="classpath:sqlMapConfig.xml"/>
<!-- 自動掃描mapping.xml檔案，**表示迭代查詢,也可在sqlMapConfig.xml中單獨指定xml檔案-->
<property name="mapperLocations" value="classpath:com/hua/saf/**/*.xml" />
</bean>複製程式碼public class BaseDao extends SqlSessionDaoSupport{ //使用sqlSessionFactory @Autowired private SqlSessionFactory sqlSessionFactory; @Autowired public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) { super.setSqlSessionFactory(sqlSessionFactory); } /** * 執行insert操作 * @param statement * @return */ public int insert(String statement) { return getSqlSession().insert(statement); } /** * 執行insert操作 * @param statement * @param parameter * @return */ public int insert(String statement, Object parameter) { return getSqlSession().insert(statement, parameter); } public int update(String statement) { return getSqlSession().update(statement); } public int update(String statement, Object parameter) { return getSqlSession().update(statement, parameter); } public int delete(String statement) { return getSqlSession().delete(statement); } public int delete(String statement, Object parameter) { return getSqlSession().delete(statement, parameter); } /** * 獲取一個list集合 * @param statement * @return */ public List<?> selectList(String statement) { return getSqlSession().selectList(statement); } /** * 根據引數 獲取一個list集合 * @param statement * @param parameter * @return */ public List<?> selectList(String statement, Object parameter) { return getSqlSession().selectList(statement, parameter); } public Map<?, ?> selectMap(String statement, String mapKey) { return getSqlSession().selectMap(statement, mapKey); } public Map<?, ?> selectMap(String statement, Object parameter, String mapKey) { return getSqlSession().selectMap(statement, parameter, mapKey); } /** * 獲取Object物件 * @param statement * @return */ public Object selectOne(String statement) { return getSqlSession().selectOne(statement); } /** * 獲取connection, 以便執行較為複雜的用法 * @return */ public Connection getConnection() { return getSqlSession().getConnection(); } }複製程式碼如上程式碼，一個Dao類繼承了SqlSessionDaoSupport類後，就可以在類中注入SessionFactory，進而通過getSqlSession()獲取當前SqlSession
下面是SqlSessionDaoSupport的原始碼，它是一個抽象類，並擁有sqlSession屬性，在setSqlSessionFactory方法中例項化了該sqlSession：
public abstract class SqlSessionDaoSupport extends DaoSupport { private SqlSession sqlSession; private boolean externalSqlSession; public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) { if (!this.externalSqlSession) { this.sqlSession = new SqlSessionTemplate(sqlSessionFactory); } } public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) { this.sqlSession = sqlSessionTemplate; this.externalSqlSession = true; } public SqlSession getSqlSession() { return this.sqlSession; } protected void checkDaoConfig() { notNull(this.sqlSession, "Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required"); }}複製程式碼方法四：（也是最常見的使用方法，使用MapperScannerConfigurer，它將會查詢類路徑下的對映器並自動將它們建立成MapperFactoryBean）
由於直接使用MapperFactoryBean會在配置檔案中配置大量mapper，因此這裡使用包掃描的方式通過註解獲取該bean
<!-- spring和MyBatis完美整合，不需要mybatis的配置對映檔案 -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<!-- 自動掃描mapping.xml檔案，**表示迭代查詢 -->
<property name="mapperLocations" value="classpath:com/hua/saf/**/*.xml" />
</bean>
<!-- DAO介面所在包名，Spring會自動查詢其下的類 ,包下的類需要使用@MapperScan註解,否則容器注入會失敗 -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.hua.saf.*" />
<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
</bean>
//使用如下程式碼，即可完成注入
@Resource
private UserDao userDao;複製程式碼下面看一下MapperScannerConfigurer這個類：
public class MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware { private String basePackage; private boolean addToConfig = true; private SqlSessionFactory sqlSessionFactory; private SqlSessionTemplate sqlSessionTemplate; private String sqlSessionFactoryBeanName; private String sqlSessionTemplateBeanName; private Class<? extends Annotation> annotationClass; private Class<?> markerInterface; private ApplicationContext applicationContext; private String beanName; private boolean processPropertyPlaceHolders; private BeanNameGenerator nameGenerator;
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException { if (this.processPropertyPlaceHolders) { processPropertyPlaceHolders(); } ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry); scanner.setAddToConfig(this.addToConfig); scanner.setAnnotationClass(this.annotationClass); scanner.setMarkerInterface(this.markerInterface); scanner.setSqlSessionFactory(this.sqlSessionFactory); scanner.setSqlSessionTemplate(this.sqlSessionTemplate); scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName); scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName); scanner.setResourceLoader(this.applicationContext); scanner.setBeanNameGenerator(this.nameGenerator); scanner.registerFilters(); scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS)); }複製程式碼ClassPathMapperScanner ：
public Set<BeanDefinitionHolder> doScan(String... basePackages) { Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages); if (beanDefinitions.isEmpty()) { logger.warn("No MyBatis mapper was found in '" + Arrays.toString(basePackages) + "' package. Please check your configuration."); } else { for (BeanDefinitionHolder holder : beanDefinitions) { GenericBeanDefinition definition = (GenericBeanDefinition) holder.getBeanDefinition(); if (logger.isDebugEnabled()) { logger.debug("Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + definition.getBeanClassName() + "' mapperInterface"); } // the mapper interface is the original class of the bean // but, the actual class of the bean is MapperFactoryBean definition.getPropertyValues().add("mapperInterface", definition.getBeanClassName()); definition.setBeanClass(MapperFactoryBean.class); definition.getPropertyValues().add("addToConfig", this.addToConfig); boolean explicitFactoryUsed = false; if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) { definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName)); explicitFactoryUsed = true; } else if (this.sqlSessionFactory != null) { definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory); explicitFactoryUsed = true; } if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) { if (explicitFactoryUsed) { logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored."); } definition.getPropertyValues().add("sqlSessionTemplate", new RuntimeBeanReference(this.sqlSessionTemplateBeanName)); explicitFactoryUsed = true; } else if (this.sqlSessionTemplate != null) { if (explicitFactoryUsed) { logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored."); } definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate); explicitFactoryUsed = true; } if (!explicitFactoryUsed) { if (logger.isDebugEnabled()) { logger.debug("Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'."); } definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE); } } } return beanDefinitions; }複製程式碼總結：spring-mybatis與原生Mybatis相比，如下概念：
1）SqlSessionFactory類在兩者中都存在
2）前者用SqlSessionFactoryBean生成SqlSessionFactory，後者則使用SqlSessionFactoryBuilder;
3）前者使用SqlSessionTemplate，後者使用SqlSession，實際上前者實現了後者
4）MapperFactoryBean中實現了原生mybatis中下面的步驟，因此通過該類可以直接獲取到一個mapper介面的實現物件
EmployeeMapper mapper = session.getMapper(EmployeeMapper.class); 複製程式碼以上是個人總結，如有錯誤，歡迎指正