mybatis学习总结

   今天对mybatis进行了学习并写了个demo，总结如下

   该例子直接和spring集成数据库mysql，缓存用ehcache，在写demo遇到的一些问题记下来：

   1.mybatis映射domain的两种方法：

      （1）通过MapperFactoryBean来实现：

      

<bean id="userMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
        <property name="mapperInterface" value="org.guarx.dao.UserDao" />
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    </bean>

UserDao就是一个接口：

  

* @(#)UserMapper.java 2011-8-29 下午1:01:44
package org.guarx.dao;

import java.util.List;

/**
 * Description:
 * Company:
 * @author: gang.xu
 * @version: 1.0
 * Create at: 2011-8-29 下午1:01:44
 *
 * Modification History:
 * Date Author Version Description
 * ------------------------------------------------------------------
 * 2011-8-29 gang.xu 1.0 1.0 Version
 */
public interface UserDao {
 User getUser(String userId);
 List<User> getUsers();
}

2.通过继承SqlSessionDaoSupport并实现UserDao的方式：

UserDaoImpl：

* @(#)UserDaoImpl.java    2011-8-29 下午1:28:34
package org.guarx.dao;

import java.util.List;

import org.guarx.domain.User;
import org.mybatis.spring.mapper.MapperFactoryBean;
import org.mybatis.spring.support.SqlSessionDaoSupport;

/**
 * Description:
 * Company:
 * @author: gang.xu
 * @version: 1.0
 * Create at: 2011-8-29 下午1:28:34
 *
 * Modification History:
 * Date Author Version Description
 * ------------------------------------------------------------------
 * 2011-8-29 gang.xu 1.0 1.0 Version
 */
public class UserDaoImpl extends SqlSessionDaoSupport implements UserDao {

    public User getUser(String userId) {
        return (User) getSqlSession().selectOne("org.guarx.dao.UserDao.getUser", userId);
    }

    @SuppressWarnings("unchecked")
    @Override
    public List<User> getUsers() {
        // TODO Auto-generated method stub

        return (List<User>) getSqlSession().selectList("org.guarx.dao.UserDao.getUsers", new User());
    }
}

对应的配置文件如下：

UserService是service层代码.

<bean id="userService" class="org.guarx.service.UserService">
        <property name="userDao" ref="userDao" />
    </bean>
 <bean id="userDao" class="org.guarx.dao.UserDaoImpl">
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    </bean>

UserDao.xml配置文件如下：

 

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "">

<mapper namespace="org.guarx.dao.UserDao">
    <cache type="org.mybatis.caches.ehcache.EhcacheCache" size="2048" eviction="LRU">
    </cache>
    <select id="getUser" resultType="org.guarx.domain.User" parameterType="java.lang.String">
        select * from users where id=#{value}
    </select>

    <select id="getUsers" resultType="org.guarx.domain.User">
        select * from users
    </select>

</mapper>

  2.mybatis对ehcache集成的一点说明：

  配置UserDao.xmlde 标签部分；

  size属性是配置内存块大小默认为1024k；

  查看org.mybatis.caches.ehcache.EhcacheCache的源码：

  public EhcacheCache(final String id) {
        if (id == null) {
            throw new IllegalArgumentException("Cache instances require an ID");
        }
        this.id = id;
        if (!CACHE_MANAGER.cacheExists(this.id)) {
            CACHE_MANAGER.addCache(this.id);
        }
    }

这样的话，addCache的时候用的是defaultCache的配置