MyBatis-Plus实战：Spring Boot数据库操作效率提升10倍

一、引入依赖

<!-- pom.xml -->
<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.5</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
</dependency>

# application.yml
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb?useUnicode=true&characterEncoding=utf8
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  global-config:
    db-config:
      logic-delete-field: deleted
      logic-delete-value: 1
      logic-not-delete-value: 0

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二、实体类

@Data
@TableName("user")
public class User {

    @TableId(type = IdType.AUTO)
    private Long id;

    @TableField("username")
    private String username;

    private String email;

    private Integer age;

    @TableLogic  // 逻辑删除
    private Integer deleted;

    @TableField(fill = FieldFill.INSERT)
    private LocalDateTime createTime;

    @TableField(fill = FieldFill.INSERT_UPDATE)
    private LocalDateTime updateTime;
}

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三、Mapper 接口

@Mapper
public interface UserMapper extends BaseMapper<User> {
    // 继承 BaseMapper 后，自动拥有以下方法：
    // - insert(entity)
    // - deleteById(id)
    // - updateById(entity)
    // - selectById(id)
    // - selectList(wrapper)
    // - selectPage(page, wrapper)
    // 无需编写 XML！
}

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四、条件构造器

// 查询年龄大于18且邮箱不为空的用户
List<User> users = userMapper.selectList(
    new LambdaQueryWrapper<User>()
        .gt(User::getAge, 18)
        .isNotNull(User::getEmail)
        .orderByDesc(User::getCreateTime)
);

// 模糊查询
List<User> users = userMapper.selectList(
    new LambdaQueryWrapper<User>()
        .likeRight(User::getUsername, "张")
        .between(User::getAge, 20, 30)
);

// 更新：年龄大于30的用户状态改为1
userMapper.update(null,
    new LambdaUpdateWrapper<User>()
        .set(User::getStatus, 1)
        .gt(User::getAge, 30)
);

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五、分页查询

// 分页配置类
@Configuration
public class MyBatisPlusConfig {
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
        return interceptor;
    }
}

// 分页查询
Page<User> page = new Page<>(1, 10);  // 第1页，每页10条
userMapper.selectPage(page,
    new LambdaQueryWrapper<User>()
        .gt(User::getAge, 18)
);

List<User> records = page.getRecords();  // 当前页数据
long total = page.getTotal();           // 总记录数
long pages = page.getPages();           // 总页数

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六、代码生成器

// AutoGenerator 一键生成 Entity、Mapper、Service、Controller
AutoGenerator generator = new AutoGenerator();

// 全局配置
GlobalConfig globalConfig = new GlobalConfig();
globalConfig.setOutputDir(System.getProperty("user.dir") + "/src/main/java");
globalConfig.setAuthor("myname");
globalConfig.setOpen(false);
generator.setGlobalConfig(globalConfig);

// 数据源配置
DataSourceConfig dataSourceConfig = new DataSourceConfig.Builder(
    "jdbc:mysql://localhost:3306/mydb",
    "root", "123456"
).build();
generator.setDataSource(dataSourceConfig);

// 策略配置
StrategyConfig strategyConfig = new StrategyConfig.Builder()
    .addInclude("user", "order")  // 表名
    .entityBuilder().enableLombok()
    .controllerBuilder().enableRestStyle()
    .build();
generator.setStrategy(strategyConfig);

generator.execute();