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更新 MyBatis 快速入门笔记。
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jacky committed Feb 21, 2025
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34 changes: 23 additions & 11 deletions .obsidian/workspace.json
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86 changes: 69 additions & 17 deletions docs/Java/MyBatis 快速入门.md
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MyBatis 官网：https://mybatis.org/mybatis-3/zh_CN/index.html

## 准备数据
DDL
```sql
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`username` varchar(100) NOT NULL COMMENT '姓名',
`age` int NOT NULL COMMENT '年龄',
`create_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '数据创建时间'
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci COMMENT='用户信息表';
) ENGINE=InnoDB COMMENT='用户信息表';

INSERT INTO `user` VALUES ('jacky',22,'2025-02-14 10:52:01'),('otto',18,'2025-02-14 10:52:01'),('zhangsan',25,'2025-02-14 10:52:01');
INSERT INTO `user`
VALUES
('jacky',22,'2025-02-14 10:52:01'),
('otto',18,'2025-02-14 10:52:01'),
('zhangsan',25,'2025-02-14 10:52:01');
```


实体类
```java
package com.jacky.mybatis.entity;
package com.otto.mybatis.entity;

import java.time.LocalDateTime;

Expand All @@ -32,8 +36,6 @@ public class User {

```
## 直接使用 JDBC 查询数据
直接使用 JDBC 查询数据。

添加依赖
```
<dependency>
Expand Down Expand Up @@ -69,7 +71,6 @@ public class JDBCTest {
```

## 使用 MyBatis

添加依赖
```xml
<dependency>
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<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://192.168.199.129:3306/test"/>
<property name="username" value="test"/>
<property name="password" value="Chxy@122619"/>
<property name="username" value="xxx"/>
<property name="password" value="xxxxxx"/>
</dataSource>
</environment>
</environments>
Expand All @@ -123,13 +124,12 @@ public class JDBCTest {
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="UserMapper">
<select id="selectAll" resultType="com.jacky.mybatis.entity.User">
<select id="selectAll" resultType="com.otto.mybatis.entity.User">
select username, age, create_at as createAt from user where username = #{username} and age = #{age}
</select>
</mapper>
```


查询数据代码
```java

Expand Down Expand Up @@ -159,7 +159,6 @@ public class MyBatisTest {
>
> 示例代码中参数如果有多个占位符参数的话，可以使用 Map 传递参数，使用占位符名称作为键，实际的参数作为值。

### 使用 Mapper 代理开发
配置 Maven 打包代码包里面的 xml 文件。
```xml
Expand All @@ -184,25 +183,25 @@ public class MyBatisTest {
```xml
<mappers>
<mapper resource="mapper/UserMapper.xml"/>
<package name="com.jacky.mybatis.mapper"/>
<package name="com.otto.mybatis.mapper"/>
</mappers>
```

新增 com.jacky.mybatis.mapper.UserMapper.java 文件
新增 com.otto.mybatis.mapper.UserMapper.java 文件
```java
public interface UserMapper {
List<User> selectAll(@Param("username") String username, @Param("age") Integer age);
}
```

新增 com.jacky.mybatis.mapper.UserMapper.xml 文件
新增 com.otto.mybatis.mapper.UserMapper.xml 文件
```xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.jacky.mybatis.mapper.UserMapper">
<select id="selectAll" resultType="com.jacky.mybatis.entity.User">
<mapper namespace="com.otto.mybatis.mapper.UserMapper">
<select id="selectAll" resultType="com.otto.mybatis.entity.User">
select username, age, create_at as createAt from user where username = #{username} and age = #{age}
</select>
</mapper>
Expand All @@ -213,4 +212,57 @@ public interface UserMapper {
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = userMapper.selectAll("jacky", 22);
System.out.println("query result: ==> " + userList);
```

### 不使用 XML 构建 SqlSessionFactory
使用单例模式构建 SqlSessionFactory
```java
public class MyBatisConfig {

private static SqlSessionFactory FACTORY_INSTANCE = null;

public static SqlSessionFactory sqlSessionFactory() {
if (FACTORY_INSTANCE == null) {
synchronized (MyBatisConfig.class) {
if (FACTORY_INSTANCE == null) {
// 配置数据源
PooledDataSource dataSource = new PooledDataSource();
dataSource.setDriver("com.mysql.cj.jdbc.Driver");
dataSource.setUrl("jdbc:mysql://192.168.199.129:3306/test_db");
dataSource.setUsername("xxx");
dataSource.setPassword("xxxxx");
// 配置事务管理器
JdbcTransactionFactory transactionFactory = new JdbcTransactionFactory();
// 配置环境
Environment environment = new Environment("development", transactionFactory, dataSource);
// 配置 MyBatis
Configuration configuration = new Configuration(environment);
// 设置日志实现为标准输出
configuration.setLogImpl(org.apache.ibatis.logging.stdout.StdOutImpl.class);
// 如果 Mapper 接口都在同一个包下，可以使用包扫描
configuration.addMappers("com.otto.mybatis.mapper");
// 构建 SqlSessionFactory
FACTORY_INSTANCE = new SqlSessionFactoryBuilder().build(configuration);
}
}
}
return FACTORY_INSTANCE;
}
}
```

进一步简化调用代码
```java
public class App {
public static void main(String[] args) throws IOException {
// 从 SqlSessionFactory 中获取 SqlSession
try(SqlSession sqlSession = MyBatisConfig.sqlSessionFactory().openSession()) {

UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

List<User> userList = userMapper.selectAll("jacky", 22);
System.out.println("query result: ==> " + userList);
}
}
}
```
7 changes: 6 additions & 1 deletion mkdocs.yml
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