MyBatis之MyBatis初体验

1 MyBatis是什么？

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。(摘自：MyBatis中文官网)

2 MyBatis环境搭建及简单案例

2.1 新建工程，添加Maven依赖

为了MyBatis系列文章讲解方便，我直接在Eclipse中新建一个名为“demo_mybatis”的war工程，并且使用强大的Maven工具来管理jar包。初学者如果对Maven不熟悉，也可以直接建一个普通工程，将jar包下载好之后放到 lib 目录下。

<!-- 添加junit -->
<dependency>
	<groupId>junit</groupId>
	<artifactId>junit</artifactId>
	<version>4.11</version>
	<scope>test</scope>
</dependency>

<!-- 添加mybatis -->
<dependency>
	<groupId>org.mybatis</groupId>
	<artifactId>mybatis</artifactId>
	<version>3.2.8</version>
</dependency>

<!-- 添加mysql -->
<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
	<version>5.1.33</version>
</dependency>

<!-- 添加log4j -->
<dependency>
	<groupId>log4j</groupId>
	<artifactId>log4j</artifactId>
	<version>1.2.16</version>
</dependency>

2.2 配置configuration.xml

<?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>
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url" value="jdbc:mysql://localhost:3306/tinytime_demo" />
				<property name="username" value="root" />
				<property name="password" value="123456" />
			</dataSource>
		</environment>
	</environments>

	<!-- 映射文件 -->
	<mappers>
		<mapper resource="com/demo/mybatis/mapper/BlogMapper.xml" />
	</mappers>
</configuration>

2.3 创建一张Blog表

-- ----------------------------
-- Database
-- ----------------------------
CREATE DATABASE IF NOT EXISTS tinytime_demo DEFAULT CHARSET utf8 COLLATE utf8_general_ci;

-- ----------------------------
-- Table structure
-- ----------------------------
DROP TABLE IF EXISTS `t_mybatis_blog`;
CREATE TABLE `t_mybatis_blog` (
  `id` int(11) NOT NULL,
  `title` varchar(20) NOT NULL,
  `content` varchar(500) DEFAULT NULL,
  `author` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- 插入一条数据
insert into t_mybatis_blog(id,title,content,author) values(1,'Mybatis之Mybatis初体验','Mybatis之Mybatis初体验','demo_mybatis');

2.4 编写代码

首先，来看看整个目录结构：

2.4.1 实体类Blog.java，与t_blog表对应

public class Blog {
	private Integer id;
	private String title;
	private String content;
	private String author;
	
	//getter and setter
}

2.4.2 BlogMapper接口

public interface BlogMapper {
	Blog selectBlogByID(Integer id);
}

2.4.3 BlogMapper.xml

<?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="com.demo.mybatis.dao.BlogMapper">
	<select id="selectBlogByID" resultType="com.demo.mybatis.model.Blog" parameterType="java.lang.Integer">
		select id,title,content,author from t_mybatis_blog where id = #{id}
	</select>
</mapper>

2.4.4 编写Junit测试代码：BlogMapperTest

public class BlogMapperTest {
	@Test
	public void selectBlogByID() {
		SqlSession sqlSession = getSessionFactory().openSession();
		BlogMapper blogMapper = sqlSession.getMapper(BlogMapper.class);
		Blog blog = blogMapper.selectBlogByID(1);
		Assert.assertNotNull(blog);
	}
	private static SqlSessionFactory getSessionFactory() {
		SqlSessionFactory sessionFactory = null;
		String resource = "configuration.xml";
		try {
			sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream(resource));
		} catch (IOException e) {
			e.printStackTrace();
		}
		return sessionFactory;
	}
}

 

转载于:https://my.oschina.net/javagoboy/blog/861809