MyBatis实现注册及获取Mapper_Java教程

MyBatis实现注册及获取Mapper

2022-10-28 11:38Integer_Double Java教程

本文主要介绍了MyBatis实现注册及获取Mapper，文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值，需要的朋友们下面随着小编来一起学习学习吧

一、搭建环境

1.1 pom.xml

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									<dependency>

									           <groupId>mysql</groupId>

									           <artifactId>mysql-connector-java</artifactId>

									       </dependency>

									       <dependency>

									           <groupId>com.baomidou</groupId>

									           <artifactId>mybatis-plus-boot-starter</artifactId>

									       </dependency>

1.2 BlogMapper.java

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									public interface BlogMapper {

									    List<Blog> selectBlog(String id);

									}

1.3 BlogMapper.xml

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									<?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="mybatis.source.study.BlogMapper">

									    <select id="selectBlog" resultType="mybatis.source.study.Blog">

									    select * from t_blog where id= #{id}

									  </select>

									</mapper>

BlogMapper.xml放在resource目录下与BlogMapper.java包路径相同的路径下

1.4 MyBatisDemo.java

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									public class MyBatisDemo {

									    public static void main(String[] args) {

									        //创建数据源

									        DataSource dataSource = getDataSource();

									        TransactionFactory transactionFactory = new JdbcTransactionFactory();

									        //创建sql运行环境

									        Environment environment = new Environment("development", transactionFactory, dataSource);

									        //创建mybatis的所有配置

									        Configuration configuration = new Configuration(environment);

									        //注册mapper

									        configuration.addMapper(BlogMapper.class);

									//        configuration.addInterceptor(new PaginationInterceptor());

									        //根据配置创建sql会话工厂

									        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

									        SqlSession sqlSession = sqlSessionFactory.openSession();

									        BlogMapper mapper = sqlSession.getMapper(BlogMapper.class);

									        System.out.println(mapper.selectBlog("001"));

									    }

									    private static DataSource getDataSource() {

									        DruidDataSource druidDataSource = new DruidDataSource();

									        druidDataSource.setUrl("jdbc:mysql://localhost:3306/demo?characterEncoding=utf-8&serverTimezone=Asia/Shanghai");

									        druidDataSource.setUsername("root");

									        druidDataSource.setPassword("root");

									        return druidDataSource;

									    }

二、addMapper详细分析

2.1 MapperRegistry

MyBatis实现注册及获取Mapper

这块就是判断这个mapper.xml解析过没有，解析是在 parser.parse();中做的，来看

MyBatis实现注册及获取Mapper

loadXmlResource();根据xml解析每个mapper接口的方法，将得到的MapperStatement放进了configuration，然后记录该xml的namespace表示已经处理过。具体调用链：

loadXmlResource()–>xmlParser.parse()–>configurationElement(parser.evalNode("/mapper"))–> buildStatementFromContext(context.evalNodes(“select|insert|update|delete”))–> buildStatementFromContext(list, null)–>statementParser.parseStatementNode()–>builderAssistant.addMappedStatement–>configuration.addMappedStatement(statement);

MyBatis实现注册及获取Mapper