Mybatis-Spring（2）MapperFactoryBean

接上一节，BeanDefiniton设置

//1、BeanDefiniton将自己的构造器设置为自己的className

definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName());

//2、BeanDefiniton将自己的BeanClass设置为：MapperFactoryBean.class

definition.setBeanClass(this.mapperFactoryBean.getClass());

//3、BeanDefiniton设置属性sqlSessionFactory

definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName));

实例化Bean

1、调用构造方法实例化MapperFactoryBean

public MapperFactoryBean(Class<T> mapperInterface) {
  this.mapperInterface = mapperInterface;
}

2、设置属性，MapperFactoryBean的父类SqlSessionDaoSupport.setSqlSessionFactory方法

public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
    if (!this.externalSqlSession) {
      this.sqlSession = new SqlSessionTemplate(sqlSessionFactory);
    }
}

2、调用afterPropertiesSet

@Override
public final void afterPropertiesSet() throws IllegalArgumentException, BeanInitializationException {
	// Let abstract subclasses check their configuration.
	checkDaoConfig();
	// Let concrete implementations initialize themselves.
	try {
		initDao();
	}
	catch (Exception ex) {
		throw new BeanInitializationException("Initialization of DAO failed", ex);
	}
}

调用  checkDaoConfig，将mapperInterface放入configuration中，

configuration.addMapper(this.mapperInterface) 会解析 mapperInterface （mapperInterface）对应的XML和注解。

protected void checkDaoConfig() {
    super.checkDaoConfig();

    notNull(this.mapperInterface, "Property 'mapperInterface' is required");

    Configuration configuration = getSqlSession().getConfiguration();
    if (this.addToConfig && !configuration.hasMapper(this.mapperInterface)) {
      try {
        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();
      }
    }
  }

因为是FactoryBean，用到的是FactoryBean.getObject()返回的数据。

public T getObject() throws Exception {
   return getSqlSession().getMapper(this.mapperInterface);
}

最终返回的是一个代理对象：mapperProxyFactory.newInstance(sqlSession);

public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
        MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory)this.knownMappers.get(type);
        if (mapperProxyFactory == null) {
            throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
        } else {
            try {
                return mapperProxyFactory.newInstance(sqlSession);
            } catch (Exception var5) {
                throw new BindingException("Error getting mapper instance. Cause: " + var5, var5);
            }
        }
}

　总结：

　　对于一个MapperInterface，在Spring中会存在一个BeanDifition，两个实例：MapperFactory<MapperInterface.class> 和 ProxyBean。