mybatis学习笔记

简单示例代码目录结构如下：

1 编写实体

public class Blog {
private Integer id;
private String title;
private Integer authorId;

//get/set方法

}

2 创建数据库及实体对应表

3 config.xml配置文件

<?xml version = "1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd" >


<configuration>
<properties resource="cn/yue/mybatis/demo/date/sqlconfig.properties" />
<typeAliases>
<typeAlias alias="Author" type="cn.yue.mybatis.demo.model.Author" />
<typeAlias alias="Blog" type="cn.yue.mybatis.demo.model.Blog" />
<typeAlias alias="Comment" type="cn.yue.mybatis.demo.model.Comment" />
<typeAlias alias="Post" type="cn.yue.mybatis.demo.model.Post" />
<typeAlias alias="Tag" type="cn.yue.mybatis.demo.model.Tag" />
</typeAliases>
<environments default="development">
<environment id="development">

<!-- mybatis有两种事物管理类型jdbc和managed-->
<transactionManager type="JDBC" />

<!-- 缓存了jdbc连接对象，加快程序响应速度 -->
<dataSource type="POOLED">
<property name="driver" value="${driver}" />
<property name="url" value="${url}" />
<property name="username" value="${username}" />
<property name="password" value="${password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="cn/yue/mybatis/demo/date/BlogMapper.xml" />
</mappers>
</configuration>

4 mapper.xml文件

<?xml version = "1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd" >


<mapper namespace="cn.yue.mybatis.demo.date.BlogMapper">
<select id="selectBlog_by_id" parameterType="int" resultType="Blog">
select * from Blog where id =#{id}
</select>
<select id="selectBlog_by_id_map" parameterType="HashMap"
resultType="Blog">
select * from Blog where id = #{id}
</select>
<select id="selectBlog_by_bean" parameterType="Blog" resultType="Blog">
select * from Blog where id = #{id}
</select>
</mapper>

5 xml配置管理器

public class SqlMapperManager {
private static SqlSessionFactory factory = null;
private static String fileName = "cn/yue/mybatis/demo/date/sqlconfig.xml";


/**
* 初始化方法
* 
* @param sqlMapperFileName
*/
public static void initMapper(String sqlMapperFileName) {
fileName = sqlMapperFileName;
}


/**
* 
* @return
*/
public static SqlSessionFactory getFactory() {


try {
if (null == factory) {

  //根一下代码可以发现

// getResourceAsReader()===>new InputStreamReader(getResourceAsStream(resource));

//getResourceAsStream() ===> classLoaderWrapper.getResourceAsStream(resource, loader);

//getResourceAsStream===>getResourceAsStream(resource, getClassLoaders(classLoader))

//InputStream getResourceAsStream(String resource, ClassLoader[] classLoader) {
                                   //        for (ClassLoader cl : classLoader) {
                                   //         if (null != cl) {


                                                       // try to find the resource as passed

//这一句是关键
                                  //                    InputStream returnValue = cl.getResourceAsStream(resource);


                                                     // now, some class loaders want this leading "/", so we'll add it and try again if we didn't find the resource
                                //                    if (null == returnValue) returnValue = cl.getResourceAsStream("/" + resource);


                               //                      if (null != returnValue) return returnValue;
                             //                         }
                                //            }
                               //                 return null;
                               //        }

//getClassLoaders===>return new ClassLoader[]{
      //   classLoader, 
        //    defaultClassLoader, 
        //   Thread.currentThread().getContextClassLoader(), 
                              //                                                                                                    getClass().getClassLoader(), 
                               //                                                                                                   systemClassLoader}; 
                               //                                                                                           }

Reader reader = Resources.getResourceAsReader(fileName);

//一但factory创建就没有必要保留builder了
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();

//此处得到的factory 就是xml中配置的blogMapper.xml

//factory的作用范围最好是一个应用的生命周期,所以这里使用单例模式
factory = builder.build(reader);
builder = null;
}
} catch (IOException e) {
e.printStackTrace();
return null;
}
return factory;


}
}

6 测试

/*
 * @version 1.0
 * @Date  2013-8-8
 * @author retacn yue
 *   
 */
// ~ Package Information
package cn.yue.mybatis.demo.test;


import java.util.HashMap;


import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.log4j.BasicConfigurator;


import cn.yue.mybatis.demo.model.Blog;
import cn.yue.mybatis.demo.service.SqlMapperManager;


/**
 * 测试类
 * 
 * @time 下午09:58:26
 * @author retacn yue
 * @Email zhenhuayue@sina.com
 */
public class SimpleMapperTest {
public static void main(String[] args) {
BasicConfigurator.configure();
SqlSession session = null;
Blog blog = null;


try {

                       
SqlSessionFactory factory = SqlMapperManager.getFactory();
if (null == factory) {
System.out.println("get SqlSessionFactory failed.");
return;
}

//session是不被共享的且线程不安全的
session = factory.openSession();
HashMap<String, Integer> paramMap = new HashMap<String, Integer>();
paramMap.put("id", 2);


Blog blog2 = new Blog();
blog2.setId(3);
// 按id查询
blog = session.selectOne("selectBlog_by_id", 1);
showBlog(blog);
// 按map条件查询
blog = session.selectOne("selectBlog_by_id_map", paramMap);
showBlog(blog);
// 按对象查询
blog = session.selectOne("selectBlog_by_bean", blog2);
showBlog(blog);
} catch (Exception e) {
e.printStackTrace();
} finally {
session.close();
}


}


public static void showBlog(Blog blog) {
if (null != blog) {
System.out.println("ID:" + blog.getId());
System.out.println("Title:" + blog.getTitle());
System.out.println("AuthorID:" + blog.getAuthorId());
} else {
System.out.println("blog is null!");
}
}
}