使用Mybatis 连接数据库 项目示例
建一个使用 MyBatis 连接数据库的项目涉及多个步骤。以下是一个简单的示例，展示如何创建一个 Maven 项目，配置 MyBatis，并编写相关的类、方法和测试用例
1.创建Maven项目
首先，创建一个 Maven 项目。你可以使用 IDE（如 IntelliJ IDEA 或 Eclipse）来创建项目，或者在命令行中使用以下命令：
mvn archetype:generate -DgroupId=com.example -DartifactId=mybatis-demo -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false2. 添加依赖
在 pom.xml 文件中添加 MyBatis 和数据库驱动的依赖：
<dependencies>
<!-- MyBatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.7</version>
</dependency>
<!-- MySQL 驱动 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.26</version>
</dependency>
<!-- 测试依赖 -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.2</version>
<scope>test</scope>
</dependency>
</dependencies>3. 配置 MyBatis
在 src/main/resources 目录下创建 mybatis-config.xml 文件，配置 MyBatis：
<?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.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis_demo"/>
<property name="username" value="root"/>
<property name="password" value="password"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/example/mapper/UserMapper.xml"/>
</mappers>
</configuration>4. 创建实体类
创建一个简单的 User 实体类：
package com.example.model;
public class User {
private int id;
private String name;
private String email;
// Getters and Setters
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
", email='" + email + '\'' +
'}';
}
}5. 创建 Mapper 接口
创建一个 UserMapper 接口：
package com.example.mapper;
import com.example.model.User;
import java.util.List;
public interface UserMapper {
User selectUserById(int id);
List<User> selectAllUsers();
void insertUser(User user);
void updateUser(User user);
void deleteUser(int id);
}6. 创建 Mapper XML 文件
在 src/main/resources/com/example/mapper 目录下创建 UserMapper.xml 文件：
<?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">
<select id="selectUserById" resultType="com.example.model.User">
SELECT * FROM users WHERE id = #{id}
</select>
<select id="selectAllUsers" resultType="com.example.model.User">
SELECT * FROM users
</select>
<insert id="insertUser" parameterType="com.example.model.User">
INSERT INTO users (name, email) VALUES (#{name}, #{email})
</insert>
<update id="updateUser" parameterType="com.example.model.User">
UPDATE users SET name = #{name}, email = #{email} WHERE id = #{id}
</update>
<delete id="deleteUser" parameterType="int">
DELETE FROM users WHERE id = #{id}
</delete>
</mapper>7. 创建 MyBatis 工具类
创建一个工具类来获取 SqlSession：
package com.example.util;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class MyBatisUtil {
private static SqlSessionFactory sqlSessionFactory;
static {
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession() {
return sqlSessionFactory.openSession();
}
}8. 编写测试用例
在 src/test/java 目录下创建一个测试类 UserMapperTest：
package com.example;
import com.example.mapper.UserMapper;
import com.example.model.User;
import com.example.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {
@Test
public void testSelectUserById() {
try (SqlSession session = MyBatisUtil.getSqlSession()) {
UserMapper mapper = session.getMapper(UserMapper.class);
User user = mapper.selectUserById(1);
System.out.println(user);
}
}
@Test
public void testSelectAllUsers() {
try (SqlSession session = MyBatisUtil.getSqlSession()) {
UserMapper mapper = session.getMapper(UserMapper.class);
List<User> users = mapper.selectAllUsers();
users.forEach(System.out::println);
}
}
@Test
public void testInsertUser() {
try (SqlSession session = MyBatisUtil.getSqlSession()) {
UserMapper mapper = session.getMapper(UserMapper.class);
User user = new User();
user.setName("John Doe");
user.setEmail("john.doe@example.com");
mapper.insertUser(user);
session.commit();
}
}
@Test
public void testUpdateUser() {
try (SqlSession session = MyBatisUtil.getSqlSession()) {
UserMapper mapper = session.getMapper(UserMapper.class);
User user = mapper.selectUserById(1);
user.setName("Jane Doe");
mapper.updateUser(user);
session.commit();
}
}
@Test
public void testDeleteUser() {
try (SqlSession session = MyBatisUtil.getSqlSession()) {
UserMapper mapper = session.getMapper(UserMapper.class);
mapper.deleteUser(1);
session.commit();
}
}
}9. 运行测试
运行 UserMapperTest 类中的测试方法，确保 MyBatis 正确连接数据库并执行相应的操作。
10. 数据库表结构
确保数据库中有一个 users 表，表结构如下：
CREATE TABLE users (
id INT AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(100) NOT NULL,
email VARCHAR(100) NOT NULL
);总结：
以上步骤展示了如何创建一个使用 MyBatis 连接数据库的简单项目。你可以根据需要扩展这个项目，添加更多的功能和复杂性。