mybatis_读取千万级数据（不分页）的两种方法

流式查询-ResultHandler

        ①数据库URL链接中添加-----&useCursorFetch=true

        ②mapper接口定义

方法名(ResultHandler<返回实体对象或者HashMap<String, Object>> handler);

         ③xml定义

<select id="" resultType="返回实体对象或者HashMap<String, Object>" parameterType="参数"     
     resultSetType="FORWARD_ONLY" fetchSize="每批返回的数量">

</select>

         ④service调用

 

mapper.方法名(new ResultHandler<返回实体对象或者HashMap<String, Object>>() {
    @Override
	public void handleResult(ResultContext<? extends 返回实体对象或者HashMap<String, Object>> resultContext) {
        返回实体对象或者HashMap<String, Object> map = (返回实体对象或者HashMap<String, Object>) resultContext.getResultObject();
       .......
    }
});

流式查询-Cursor

 ①mapper接口定义

Cursor<返回实体对象或者HashMap<String, Object>> 方法名(返回实体对象或者HashMap<String, Object> obj);

②xml定义

<select id="" resultType="返回实体对象或者HashMap<String, Object>" parameterType="参数"     
     resultSetType="FORWARD_ONLY" fetchSize="每批返回的数量">

</select>

③service调用

SqlSession sqlSession = SpringUtils.getBean(SqlSessionFactory.class).openSession();

try {
    Cursor<返回实体对象或者HashMap<String, Object>> data= sqlSession.getMapper(mapper类).方法();
    Iterator<返回实体对象或者HashMap<String, Object>> dataIterator = data.iterator();
            while (dataIterator.hasNext()) {
        返回实体对象或者HashMap<String, Object> dataObj = dataIterator.next();
				if(dataObj!=null) {
                    .....
                }
    }
} catch (Exception e) {

} finally {
     sqlSession.close();
}

import com.macha.scwz.security.utils.StringUtils;
import org.springframework.aop.framework.AopContext;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * spring工具类 方便在非spring管理环境中获取bean
 * 
 */
@Component
public final class SpringUtils implements BeanFactoryPostProcessor, ApplicationContextAware
{
    /** Spring应用上下文环境 */
    private static ConfigurableListableBeanFactory beanFactory;

    private static ApplicationContext applicationContext;

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException
    {
        SpringUtils.beanFactory = beanFactory;
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
    {
        SpringUtils.applicationContext = applicationContext;
    }

    /**
     * 获取对象
     *
     * @param name
     * @return Object 一个以所给名字注册的bean的实例
     * @throws BeansException
     *
     */
    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) throws BeansException
    {
        return (T) beanFactory.getBean(name);
    }

    /**
     * 获取类型为requiredType的对象
     *
     * @param clz
     * @return
     * @throws BeansException
     *
     */
    public static <T> T getBean(Class<T> clz) throws BeansException
    {
        T result = (T) beanFactory.getBean(clz);
        return result;
    }

    /**
     * 如果BeanFactory包含一个与所给名称匹配的bean定义，则返回true
     *
     * @param name
     * @return boolean
     */
    public static boolean containsBean(String name)
    {
        return beanFactory.containsBean(name);
    }

    /**
     * 判断以给定名字注册的bean定义是一个singleton还是一个prototype。 如果与给定名字相应的bean定义没有被找到，将会抛出一个异常（NoSuchBeanDefinitionException）
     *
     * @param name
     * @return boolean
     * @throws NoSuchBeanDefinitionException
     *
     */
    public static boolean isSingleton(String name) throws NoSuchBeanDefinitionException
    {
        return beanFactory.isSingleton(name);
    }

    /**
     * @param name
     * @return Class 注册对象的类型
     * @throws NoSuchBeanDefinitionException
     *
     */
    public static Class<?> getType(String name) throws NoSuchBeanDefinitionException
    {
        return beanFactory.getType(name);
    }

    /**
     * 如果给定的bean名字在bean定义中有别名，则返回这些别名
     *
     * @param name
     * @return
     * @throws NoSuchBeanDefinitionException
     *
     */
    public static String[] getAliases(String name) throws NoSuchBeanDefinitionException
    {
        return beanFactory.getAliases(name);
    }

    /**
     * 获取aop代理对象
     * 
     * @param invoker
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> T getAopProxy(T invoker)
    {
        return (T) AopContext.currentProxy();
    }

    /**
     * 获取当前的环境配置，无配置返回null
     *
     * @return 当前的环境配置
     */
    public static String[] getActiveProfiles()
    {
        return applicationContext.getEnvironment().getActiveProfiles();
    }

    /**
     * 获取当前的环境配置，当有多个环境配置时，只获取第一个
     *
     * @return 当前的环境配置
     */
    public static String getActiveProfile()
    {
        final String[] activeProfiles = getActiveProfiles();
        return StringUtils.isNotEmpty(activeProfiles) ? activeProfiles[0] : null;
    }
}