MyBatis框架的基本使用

MyBatis框架的基本使用

1 导包

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.4</version></dependency>

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.38</version></dependency>

2 配置mybatis.cfg.xml配置文件

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE configurationPUBLIC "-//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=""/><property name="url" value=""/><property name="username" value=""/><property name="password" value=""/></dataSource></environment></environments><mappers><mapper resource=""/></mappers></configuration>

3 写DTO 和 映射文件

映射文件的配置有两种方式

第一种

<select id="getAuthorById" parameterType="int" resultMap="authorResultMap"> select author_id,author_name from tb_author  where author_id = #{author_id}</select>  <resultMap type="mybatis.dto.AuthorDTO" id="authorResultMap"><id column="author_id" property="author_id"/><result column="author_name" property="author_name"/><collection property="bookList" column="author_id" ofType="mybatis.dto.BookDTO" select="getBookById"></collection> </resultMap><select id="getBookById" parameterType="int" resultType="mybatis.dto.BookDTO">select * from tb_book where book_author_id = #{author_id}</select>

第二种

<!-- 第二种实现,和多对多的配置一样 --><select id="getAuthorById2" parameterType="int" resultMap="authorResultMap2">select * from tb_author a join tb_book b on a.author_id = b.book_author_id and a.author_id = #{author_id}</select><resultMap type="mybatis.dto.AuthorDTO" id="authorResultMap2"><id column="author_id" property="author_id"/><result column="author_name" property="author_name"/><collection property="bookList" ofType="mybatis.dto.BookDTO" ><id column="book_id" property="book_id"/><result column="book_name" property="book_name"/></collection> </resultMap>

4 加载配置文件并获取sessionFactory和session

InputStream is = AppTest.class.getClassLoader().getResourceAsStream("mybatis.cfg.xml");SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);SqlSession session = sessionFactory.openSession();AuthorDTO author = session.selectOne("mybatis.dto.AuthorMapper.getAuthorById2", 1);System.out.println(author.getAuthor_name());List<BookDTO> bookList = author.getBookList();for(BookDTO book:bookList){ System.out.println(book.getBook_name()); }session.close();