Spring集成Mybatis配置与源码分析

1.配置

在spring配置文件中添加如下配置：
<!– SqlSessionFactory bean配置。
configuration与configLocation可以选择其中一个配置，若都配置了则使用configuration配置，若都不配置使用默认配置–>
<bean id=”sqlSessionFactory” class=”org.mybatis.spring.SqlSessionFactoryBean”>
<property name=”dataSource” ref=”dataSource”/>
<!–配置方式：setter注入–>
<property name=”configuration” ref=”configuration”/>
<!–配置方式：配置文件–>
<property name=”configLocation” value=”classpath:config/mybatis-config.xml”/>
<property name=”mapperLocations” value=”classpath:com/wxyh/study/dao/*/.xml”/>
<!–注入其他属性–>
</bean>
<!– spring与mybatis整合配置，扫描所有dao –>
<bean class=”org.mybatis.spring.mapper.MapperScannerConfigurer”>
<property name=”basePackage” value=”com.wxyh.study.dao.**.mapper”/>
<property name=”sqlSessionFactoryBeanName” value=”sqlSessionFactory”/>
</bean>
下面对主要源码进行分析讲解，源码版本mybatis-3.4.4，mybatis-spring-1.3.1。

2.SqlSessionFactoryBean源码分析

public class SqlSessionFactoryBean implements FactoryBean<SqlSessionFactory>, InitializingBean,     ApplicationListener<ApplicationEvent> {  // 核心字段，这些属性都提供了setter注入方法  private Resource configLocation;  private Configuration configuration;  private Resource[] mapperLocations;  private DataSource dataSource;  private TransactionFactory transactionFactory;  private SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();  private SqlSessionFactory sqlSessionFactory;  private String environment = SqlSessionFactoryBean.class.getSimpleName();  private boolean failFast;  private Interceptor[] plugins;  private TypeHandler<?>[] typeHandlers;  private String typeHandlersPackage;  private Class<?>[] typeAliases;  private String typeAliasesPackage;  private Class<?> typeAliasesSuperType;  private DatabaseIdProvider databaseIdProvider;  private Class<? extends VFS> vfs;  private Cache cache;  private ObjectFactory objectFactory;  private ObjectWrapperFactory objectWrapperFactory;  @Override  public void afterPropertiesSet() throws Exception {    notNull(dataSource, "Property 'dataSource' is required");    notNull(sqlSessionFactoryBuilder, "Property 'sqlSessionFactoryBuilder' is required");    state((configuration == null && configLocation == null) || !(configuration != null && configLocation != null),              "Property 'configuration' and 'configLocation' can not specified with together");    this.sqlSessionFactory = buildSqlSessionFactory();  }   protected SqlSessionFactory buildSqlSessionFactory() throws IOException {    Configuration configuration;    XMLConfigBuilder xmlConfigBuilder = null;    if (this.configuration != null) {      // 注入了configuration bean，优先使用      configuration = this.configuration;      if (configuration.getVariables() == null) {        configuration.setVariables(this.configurationProperties);      } else if (this.configurationProperties != null) {        configuration.getVariables().putAll(this.configurationProperties);      }    } else if (this.configLocation != null) {      // 有配置文件，后面会解析配置文件，把相关配置保存在configuration中      xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);      configuration = xmlConfigBuilder.getConfiguration();    } else {      if (LOGGER.isDebugEnabled()) {        LOGGER.debug("Property 'configuration' or 'configLocation' not specified, using default MyBatis Configuration");      }      // 没有配置configuration与configLocation，使用默认配置      configuration = new Configuration();      if (this.configurationProperties != null) {       configuration.setVariables(this.configurationProperties);      }    }    // 略去设置或解析setter注入属性代码    // ......    if (xmlConfigBuilder != null) {      try {        // 解析配置文件mybatis-config.xml，详细源码解析见：http://blog.csdn.net/u011424653/article/details/78202010        xmlConfigBuilder.parse();        if (LOGGER.isDebugEnabled()) {          LOGGER.debug("Parsed configuration file: '" + this.configLocation + "'");        }      } catch (Exception ex) {        throw new NestedIOException("Failed to parse config resource: " + this.configLocation, ex);      } finally {        ErrorContext.instance().reset();      }    }    if (this.transactionFactory == null) {      this.transactionFactory = new SpringManagedTransactionFactory();    }    configuration.setEnvironment(new Environment(this.environment, this.transactionFactory, this.dataSource));    // 解析mapperLocations指定mapper配置文件    if (!isEmpty(this.mapperLocations)) {      for (Resource mapperLocation : this.mapperLocations) {        if (mapperLocation == null) {          continue;        }        try {          // 逐个解析mapper配置文件，解析源码见：http://blog.csdn.net/u011424653/article/details/78202010#t3          XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(mapperLocation.getInputStream(),              configuration, mapperLocation.toString(), configuration.getSqlFragments());          xmlMapperBuilder.parse();        } catch (Exception e) {          throw new NestedIOException("Failed to parse mapping resource: '" + mapperLocation + "'", e);        } finally {          ErrorContext.instance().reset();        }        if (LOGGER.isDebugEnabled()) {          LOGGER.debug("Parsed mapper file: '" + mapperLocation + "'");        }      }    } else {      if (LOGGER.isDebugEnabled()) {        LOGGER.debug("Property 'mapperLocations' was not specified or no matching resources found");      }    }    // 构建sqlSessionFactory对象    return this.sqlSessionFactoryBuilder.build(configuration);  }  @Override  public SqlSessionFactory getObject() throws Exception {    if (this.sqlSessionFactory == null) {      afterPropertiesSet();    }    return this.sqlSessionFactory;  }}

SqlSessionFactoryBean是SqlSessionFactory的工厂bean。
启动项目时spring首先会创建SqlSessionFactoryBean对象，然后会把getObject()的返回值DefaultSqlSessionFactory对象作为bean注册到容器中。

3.MapperScannerConfigurer源码分析

public class MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor,     InitializingBean, ApplicationContextAware, BeanNameAware {  // 核心字段，这些属性都提供了setter注入方法  private String basePackage;  private boolean addToConfig = true;  private SqlSessionFactory sqlSessionFactory;  private SqlSessionTemplate sqlSessionTemplate;  private String sqlSessionFactoryBeanName;  private String sqlSessionTemplateBeanName;  // mapper接口使用的注解类型  private Class<? extends Annotation> annotationClass;  // mapper接口的父接口类型  private Class<?> markerInterface;  private ApplicationContext applicationContext;  private String beanName;  private boolean processPropertyPlaceHolders;  private BeanNameGenerator nameGenerator;  @Override  public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {    if (this.processPropertyPlaceHolders) {      processPropertyPlaceHolders();    }    ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);    scanner.setAddToConfig(this.addToConfig);    // 设置mapper接口使用的注解或父类型    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);    // 配置过滤basePackage包中mapper接口的规则，源码分析见4    scanner.registerFilters();    // 扫描basePackage包中mapper接口，将其封装为MapperFactoryBean<T>    scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));  }  ......}

4.ClassPathMapperScanner源码分析

public class ClassPathMapperScanner extends ClassPathBeanDefinitionScanner {  // 核心字段，这些属性都提供了setter注入方法  private boolean addToConfig = true;  private SqlSessionFactory sqlSessionFactory;  private SqlSessionTemplate sqlSessionTemplate;  private String sqlSessionTemplateBeanName;  private String sqlSessionFactoryBeanName;  private Class<? extends Annotation> annotationClass;  private Class<?> markerInterface;  private MapperFactoryBean<?> mapperFactoryBean = new MapperFactoryBean<Object>();  /**   * 配置扫描器以注册basePackage包中正确的接口为mapper   */  public void registerFilters() {    boolean acceptAllInterfaces = true;    // 把basePackage包中有annotationClass类型注解的所有接口注册为mapper    if (this.annotationClass != null) {      addIncludeFilter(new AnnotationTypeFilter(this.annotationClass));      acceptAllInterfaces = false;    }    // 把basePackage包中派生自markerInterface类型接口的所有接口注册为mapper，    // 重写matchClassName方法，以免注册markerInterface接口为mapper    if (this.markerInterface != null) {      addIncludeFilter(new AssignableTypeFilter(this.markerInterface) {        @Override        protected boolean matchClassName(String className) {          return false;        }      });      acceptAllInterfaces = false;    }    if (acceptAllInterfaces) {      // 如果没有设置annotationClass和markerInterface，则注册basePackage包中所有类为mapper      // default include filter that accepts all classes      addIncludeFilter(new TypeFilter() {        @Override        public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {          return true;        }      });    }    // exclude package-info.java    addExcludeFilter(new TypeFilter() {      @Override      public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {        String className = metadataReader.getClassMetadata().getClassName();        return className.endsWith("package-info");      }    });  }  /**   * Calls the parent search that will search and register all the candidates.   * Then the registered objects are post processed to set them as   * MapperFactoryBeans   */  @Override  public Set<BeanDefinitionHolder> doScan(String... basePackages) {    // 调用父类方法，扫描basePackages包中的mapper接口，返回BeanDefinitionHolder集合    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 {      processBeanDefinitions(beanDefinitions);    }    return beanDefinitions;  }  /**   * 定义mapper的工厂bean MapperFactoryBean   */  private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {    GenericBeanDefinition definition;    for (BeanDefinitionHolder holder : beanDefinitions) {      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      // 通过构造函数传参设置MapperFactoryBean所生产bean的类型      definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); // issue #59      definition.setBeanClass(this.mapperFactoryBean.getClass());      definition.getPropertyValues().add("addToConfig", this.addToConfig);      // 往MapperFactoryBean注入sqlSessionFactory      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;      }      // 往MapperFactoryBean注入sqlSessionTemplate.      // 如果已注入sqlSessionFactory则忽略该配置，使用sqlSessionTemplate，详见源码      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);      }    }  }}

5.MapperFactoryBean源码分析

public class MapperFactoryBean<T> extends SqlSessionDaoSupport implements FactoryBean<T> {  // mapper bean的类型  private Class<T> mapperInterface;  // true，添加mapper到MapperRegistry  private boolean addToConfig = true;  public MapperFactoryBean() {    //intentionally empty   }  public MapperFactoryBean(Class<T> mapperInterface) {    this.mapperInterface = mapperInterface;  }  @Override  protected void checkDaoConfig() {    super.checkDaoConfig();    notNull(this.mapperInterface, "Property 'mapperInterface' is required");    Configuration configuration = getSqlSession().getConfiguration();    if (this.addToConfig && !configuration.hasMapper(this.mapperInterface)) {      try {        // 添加mapper到MapperRegistry，源码分析见xxxxxxxxxxx        configuration.addMapper(this.mapperInterface);      } catch (Exception e) {        logger.error("Error while adding the mapper '" + this.mapperInterface + "' to configuration.", e);        throw new IllegalArgumentException(e);      } finally {        ErrorContext.instance().reset();      }    }  }  @Override  public T getObject() throws Exception {    // getSqlSession()返回的是一个SqlSessionTemplate对象    // getMapper方法从MapperRegistry中获取的是MapperProxyFactory对象    return getSqlSession().getMapper(this.mapperInterface);  }}public abstract class SqlSessionDaoSupport extends DaoSupport {  // 通过sqlSessionFactory或sqlSessionTemplate，生成的sqlSession对象都是SqlSessionTemplate类型，  // 实际上是SqlSession的代理对象  private SqlSession sqlSession;  private boolean externalSqlSession;  public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {    if (!this.externalSqlSession) {      // 如果设置了sqlSessionTemplate，则不再使用sqlSessionFactory了      this.sqlSession = new SqlSessionTemplate(sqlSessionFactory);    }  }  public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {    this.sqlSession = sqlSessionTemplate;    this.externalSqlSession = true;  }  /**   * Users should use this method to get a SqlSession to call its statement methods   * This is SqlSession is managed by spring. Users should not commit/rollback/close it   * because it will be automatically done.   *   * @return Spring managed thread safe SqlSession   */  public SqlSession getSqlSession() {    return this.sqlSession;  }  @Override  protected void checkDaoConfig() {    notNull(this.sqlSession, "Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required");  }}

6.SqlSessionTemplate源码分析

public class SqlSessionTemplate implements SqlSession, DisposableBean {  private final SqlSessionFactory sqlSessionFactory;  private final ExecutorType executorType;  // SqlSession的代理对象  private final SqlSession sqlSessionProxy;  private final PersistenceExceptionTranslator exceptionTranslator;  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;    // 创建sqlSession的代理对象，调用sqlSession的所有方法，都被SqlSessionInterceptor的invoke方法拦截    this.sqlSessionProxy = (SqlSession) newProxyInstance(        SqlSessionFactory.class.getClassLoader(),        new Class[] { SqlSession.class },        new SqlSessionInterceptor());  }  /**   * 内部类   * jdk动态代理拦截器类   */  private class SqlSessionInterceptor implements InvocationHandler {    @Override    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {      SqlSession sqlSession = getSqlSession(          SqlSessionTemplate.this.sqlSessionFactory,          SqlSessionTemplate.this.executorType,          SqlSessionTemplate.this.exceptionTranslator);      try {        Object result = method.invoke(sqlSession, args);        if (!isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)) {          // force commit even on non-dirty sessions because some databases require          // a commit/rollback before calling close()          sqlSession.commit(true);        }        return result;      } catch (Throwable t) {        Throwable unwrapped = unwrapThrowable(t);        if (SqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) {          // release the connection to avoid a deadlock if the translator is no loaded. See issue #22          closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);          sqlSession = null;          Throwable translated = SqlSessionTemplate.this.exceptionTranslator.translateExceptionIfPossible((PersistenceException) unwrapped);          if (translated != null) {            unwrapped = translated;          }        }        throw unwrapped;      } finally {        if (sqlSession != null) {          closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);        }      }    }  }}