MyBatis 完整實戰案例：從配置到 CRUD 的企業級最佳實踐

MyBatis 企業級實戰：配置、映射、動態 SQL、分頁、插件全流程

項目結構

src/main/java
├── cn.happy.entity          # 實體類
├── cn.happy.dao             # Mapper 接口
├── cn.happy.dao.impl        # 實現類（可省略，接口綁定 XML）
├── cn.happy.util            # 工具類
└── cn.happy.service         # 業務層

src/main/resources
├── mybatis-config.xml       # 全局配置
├── cn/happy/dao/*.xml       # SQL 映射文件
└── log4j.properties         # 日志配置

核心配置文件

1. mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" 
  "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 類型別名：包掃描，免寫全限定名 -->
    <typeAliases>
        <package name="cn.happy.entity"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="oracle.jdbc.OracleDriver"/>
                <property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl"/>
                <property name="username" value="happy"/>
                <property name="password" value="1"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="cn/happy/dao/StudentMapper.xml"/>
        <!-- 生產建議：包掃描 -->
        <package name="cn.happy.dao"/>
    </mappers>
</configuration>

2. StudentMapper.xml（動態 SQL 精髓）

<mapper namespace="cn.happy.dao.StudentMapper">

    <resultMap id="studentMap" type="Student">
        <id property="stuno" column="stuno"/>
        <result property="stuname" column="stuname"/>
        <result property="stuage" column="stuage"/>
        <result property="studate" column="studate"/>
    </resultMap>

    <!-- 插入 + 返回主鍵 -->
    <insert id="insertStudent" useGeneratedKeys="true" keyProperty="stuno">
        INSERT INTO student(stuname, stuage, studate)
        VALUES(#{stuname}, #{stuage}, #{studate})
    </insert>

    <!-- 全量查詢 -->
    <select id="findAll" resultMap="studentMap">
        SELECT * FROM student
    </select>

    <!-- 模糊查詢：#{ } 預編譯防注入，${ } 字符串拼接 -->
    <select id="findByNameLike" resultMap="studentMap">
        SELECT * FROM student 
        WHERE stuname LIKE CONCAT('%', #{stuname}, '%')
    </select>

    <!-- 刪除 -->
    <delete id="deleteById">
        DELETE FROM student WHERE stuno = #{id}
    </delete>

    <!-- 動態更新：僅更新非空字段 -->
    <update id="updateStudent">
        UPDATE student
        <set>
            <if test="stuname != null">stuname = #{stuname},</if>
            <if test="stuage != null">stuage = #{stuage},</if>
            <if test="studate != null">studate = #{studate}</if>
        </set>
        WHERE stuno = #{stuno}
    </update>

</mapper>

實體類與 Mapper 接口

// Student.java
@Data @NoArgsConstructor @AllArgsConstructor
public class Student {
    private Integer stuno;
    private String stuname;
    private Integer stuage;
    private Date studate;
}

// StudentMapper.java
public interface StudentMapper {
    int insertStudent(Student student);
    List findAll();
    List findByNameLike(String name);
    int deleteById(Integer id);
    int updateStudent(Student student);
}

Spring 整合最佳實踐（推薦替代手動 SqlSession）

@Configuration
@MapperScan("cn.happy.dao")  // 掃描 Mapper 接口自動創建代理
public class MyBatisConfig {
    
    @Bean
    public DataSource dataSource() {
        DruidDataSource ds = new DruidDataSource();
        ds.setUrl("jdbc:oracle:thin:@localhost:1521:orcl");
        ds.setUsername("happy"); ds.setPassword("1");
        return ds;
    }
    
    @Bean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setMapperLocations(new PathMatchingResourcePatternResolver()
            .getResources("classpath:cn/happy/dao/*.xml"));
        bean.setTypeAliasesPackage("cn.happy.entity");
        return bean.getObject();
    }
    
    @Bean
    public DataSourceTransactionManager txManager(DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }
}

Service 層使用

@Service
@Transactional
public class StudentService {
    @Autowired StudentMapper studentMapper;

    public Student create(Student s) {
        studentMapper.insertStudent(s); // 回填主鍵
        return s;
    }

    public Page search(String name, int page, int size) {
        PageHelper.startPage(page, size); // 分頁插件
        return (Page) studentMapper.findByNameLike(name);
    }
}

進階特性速覽

避坑指南

• #{ } 預編譯參數化（防注入），${ } 字符串拼接（用於表名、排序字段等不可參數化處）
• 結果映射優先用 resultMap，避免列名與屬性名不匹配導致字段為 null
• 大結果集使用 ResultHandler 流式處理，避免 OOM
• 事務邊界在 Service 層，Mapper 僅執行單條 SQL
• 生產環境關閉 log4j.logger.cn.happy.dao=trace，改為 info/warn

MyBatis 以「SQL 掌控在手、映射靈活透明」著稱。掌握動態 SQL、結果映射、Spring 整合、分頁插件，即可應對 90% 企業級持久化場景。建議新項目直接上 MyBatis-Plus，內置 CRUD、分頁、代碼生成器，開發效率再提升一個檔次。