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《SpringBoot整合MyBatis连接数据库及常见问题》MyBatis是一个优秀的持久层框架,支持定制化SQL、存储过程以及高级映射,下面详细介绍如何在SpringBoot项目中整合My...
MyBATis 是一个优秀的持久层框架，支持定制化 SQL、存储过程以及高级映射。下面详细介绍如何在 Spring Boot 项目中整合 MyBatis 并连接数据库。
一、基本配置
1. 添加依赖
在pom.xml中添加以下依赖：
<!-- Spring Boot Starter Web -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- MyBatis Spring Boot Starter -->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.2.0</version> <!-- 使用最新版本 -->
</dependency>
<!-- 数据库驱动，根据你的数据库选择 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-Java</artifactId>javascript;
<scope>runtime</scope>
</dependency>
<!-- 其他可能需要的依赖 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid-spring-boot-starter</artifactId>
<version>1.2.6</version> <!-- Druid 连接池 -->
</dependency>2. 配置数据库连接
在application.yml或application.properties中配置数据库连接：
# application.yml 配置示例
spring:
datasource:
url: jdbc:mysql://localhost:3306/your_database?useSSL=false&serverTimezone=UTC&characterEncoding=utf8
username: your_username
password: your_password
driver-class-name: com.mysql.cj.jdbc.Driver
type: com.alibaba.druid.pool.DruidDataSource # 使用Druid连接池
# MyBatis 配置
mybatis:
mapper-locations: classpath:mapper/*.xml # mapper.xml文件位置
type-aliases-package: com.example.model # 实体类所在包
configuration:
map-underscore-to-camel-case: true # 开启驼峰命名转换二、项目结构
典型的项目结构如下：
src/main/java
└── com.example.demo
├── DemoApplication.java # 启动类
├── config
│ └── MyBatisConfig.java # MyBatis配置类(可选)
├── controller
│ └── UserController.java # 控制器
├── service
│ ├── UserService.java # 服务接口
│ └── impl
│ └── UserServiceImpl.java # 服务实现
├── mapper
│ └── UserMapper.java # Mapper接口
└── model
└── User.java # 实体类
src/main/resources
├── application.yml # 配置文件
└── mapper
└── UserMapper.xml # SQL映射文件三、核心组件实现（示例）
1. 实体类
package com.example.model;
public class User {
private Long id;
private String username;
private String password;
private String email;
// getters and setters
// toString()
}2. Mapper 接口
package com.example.mapper;
import com.example.model.User;
import org.apache.ibatis.annotations.*;
import java.util.List;
@Mapper // 重要：标识这是一个MyBatis的Mapper接口
public interface UserMapper {
@Select("SELECT * FROM user WHERE id = #{id}")
User findById(Long id);
@Insert("INSERT INTO user(username, password, email) VALUES(#{username}, #{password}, #{email})")
@Options(useGeneratedKeys = true, keyProperty = "id")
int insert(User user);
@Update("UPDATE user SET username=#{username}, password=#{password}, email=#{email} WHERE id=#{id}")
int update(User user);
@Delete("DELETE FROM user WHERE id=#{id}")
int delete(Long id);
// XML配置方式
List<User> findAll();
}3. Mapper XML 文件
src/main/resources/mapper/UserMapper.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.example.mapper.UserMapper">
<resultMap id="userResultMap" type="User">
<id property="id" column="id"/>
<result property="username" column="username"/>
<result property="password" column="password"/>
<result property="email" column="email"/>
</resultMap>
<select id="findAll" resultMap="userResultMap">
SELECT * FROM user
</select>
</mapper>4. Service 层
package com.example.service; import com.example.model.Usjser; import java.util.List; public interface UserService { User findById(Long id)android; List<User> findAll(); int save(User user); int update(User user); int delete(Long id); }
service层实现类：
package com.example.service.impl;
import com.example.mapper.UserMapper;
import com.example.model.User;
import com.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class UserServiceImpl implements UserService {
@Autowired
private UserMapper userMapper;
@Override
public User findById(Long id) {
return userMapper.findById(id);
}
@Override
public List<User> findAll() {
return userMapper.findAll();
}
@Override
public int save(User user) {
return userMapper.insert(user);
}
@Override
public int update(User user) {
return userMapper.update(user);
}
@Override
public int delete(Long id) {
return userMapper.delete(id);
}
}5. Controller 层：
package com.example.controller;
import com.example.model.User;
import com.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;
@RestController
@RequestMapping("/users")
public class UserController {
@Autowired
private UserService userService;
@GetMapping("/{id}")
public User getUser(@PathVariable Long id) {
return userService.findById(id);
}
@GetMapping
public List<User> getAllUsers() {
return userService.findAll();
}
@PostMapping
public int createUser(@RequestBody User user) {
return userService.save(user);
}
@PutMapping
public int updateUser(@RequestBody User user) {
return userService.update(user);
}
@DeleteMapping("/{id}")
public int deleteUser(@PathVariable Long id) {
return userService.delete(id);
}
}四、高级特性
1. 动态SQL
在XML中使用动态SQL：
<select id="findByCondition" parameterType="map" resultMap="userResultMap">
SELECT * FROM user
<where>
<if test="username != null and username != ''">
AND username LIKE CONCAT('%', #{username}, '%')
</if>
<if test="email != null and email != ''">
AND email = #{email}
</if>
</where>
</select>2. 分页查询
使用PageHelper插件：
添加依赖：
<select id="findByCondition" parameterType="map" resultMap="userResultMap">
SELECT * FROM user
<where>
<if test="username != null and username != ''">
AND username LIKE CONCAT('%', #{username}, '%')
</if>
<if test="email != null and email != ''">
AND email = #{email}
</if>
</where>
</select>使用示例：
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.4.1</version>
</dependency>3. 多数据源配置
配置多个数据源：
spring:
datasource:
primary:
url: jdbc:mysql://localhost:3306/db1
username: root
password: root
driver-class-name: com.mysql.cj.jdbc.Driver
secondary:
url: jdbc:mysql://localhost:3306/DB2
username: root
password: root
driver-class-name: com.mysql.cj.jdbc.Driver创建配置类：
@Configuration
@MapperScan(basePackages = "com.example.mapper.primary", sqlSessionFactoryRef = "primarySqlSessionFactory")
public class PrimaryDataSourceConfig {
@Bean(name = "primaryDataSource")
@ConfigurationProperties(prefix = "spring.datasource.primary")
public DataSource primaryDataSource() {
return DataSourceBuilder.create().build();
}
@Bean(name = "primarySqlSessionFactory")
public SqlSessionFactory primarySqlSessionFactory(@Qualifier("primaryDataSource") DataSource dataSource) throws Exception {
SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
bean.setDataSource(dataSource);
bean.setMapperlocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/primary/*.xml"));
return bean.getObject();
}
@Bean(name = "primaryTransactionManager")
public DataSourceTransactionManager primaryTransactionManager(@Qualifier("primaryDataSource") DataSource dataSource) {
return new DataSourceTransactionManager(dataSource);
}
}
// 类似地创建SecondaryDataSourceConfig五、常www.chinasem.cn见问题解决
Mapper接口无法注入：
- 确保启动类上有
@MapperScan("com.example.mapper")注解 - 或者每个Mapper接口上有
@Mapper注解
XML文件找不到：
- 检查
mybatis.mapper-locations配置是否正确 - 确保XML文件在resources目录下正确位置
驼峰命名不生效：
- 确认配置
mybatis.configuration.map-underscore-to-camel-case=true
连接池配置：
- 推荐使用Druid连接池，并配置合理的连接参数
事务管理：
- 在Service方法上添加
@Transactional注解
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