Fluent Mybatis如何做到代码逻辑和sql逻辑的合一

来源：jb51　　时间：2021/8/4 17:55:53　　对本文有异议

使用fluent mybatis可以不用写具体的xml文件，通过java api可以构造出比较复杂的业务sql语句，做到代码逻辑和sql逻辑的合一。不再需要在Dao中组装查询或更新操作，在xml或mapper中再组装参数。那对比原生Mybatis, Mybatis Plus或者其他框架，FluentMybatis提供了哪些便利呢？

场景需求设置

我们通过一个比较典型的业务需求来具体实现和对比下，假如有学生成绩表结构如下:

create table `student_score`
(
    id           bigint auto_increment comment '主键ID' primary key,
    student_id bigint            not null comment '学号',
    gender_man tinyint default 0 not null comment '性别, 0:女; 1:男',
    school_term int               null comment '学期',
    subject varchar(30) null comment '学科',
    score int               null comment '成绩',
    gmt_create datetime not null comment '记录创建时间',
    gmt_modified datetime not null comment '记录最后修改时间',
    is_deleted tinyint default 0 not null comment '逻辑删除标识'
) engine = InnoDB default charset=utf8;

现在有需求:

统计2000年三门学科('英语', '数学', '语文')及格分数按学期,学科统计最低分，最高分和平均分, 且样本数需要大于1条,统计结果按学期和学科排序

我们可以写SQL语句如下:

select school_term,
       subject,
       count(score) as count,
       min(score) as min_score,
       max(score) as max_score,
       avg(score) as max_score
from student_score
where school_term >= 2000
  and subject in ('英语', '数学', '语文')
  and score >= 60
  and is_deleted = 0
group by school_term, subject
having count(score) > 1
order by school_term, subject;

那上面的需求，分别用fluent mybatis, 原生mybatis 和 Mybatis plus来实现一番。

三者对比

使用fluent mybatis 来实现上面的功能

我们可以看到fluent api的能力，以及IDE对代码的渲染效果。

代码：https://gitee.com/fluent-mybatis/fluent-mybatis-docs/tree/master/spring-boot-demo/

换成mybatis原生实现效果

1. 定义Mapper接口

public interface MyStudentScoreMapper {
    List<Map<String, Object>> summaryScore(SummaryQuery paras);
}

2. 定义接口需要用到的参数实体 SummaryQuery

@Data
@Accessors(chain = true)
public class SummaryQuery {
    private Integer schoolTerm;
    private List<String> subjects;
    private Integer score;
    private Integer minCount;
}

3. 定义实现业务逻辑的mapper xml文件

<select id="summaryScore" resultType="map" parameterType="cn.org.fluent.mybatis.springboot.demo.mapper.SummaryQuery">
    select school_term,
    subject,
    count(score) as count,
    min(score) as min_score,
    max(score) as max_score,
    avg(score) as max_score
    from student_score
    where school_term >= #{schoolTerm}
    and subject in
    <foreach collection="subjects" item="item" open="(" close=")" separator=",">
        #{item}
    </foreach>
    and score >= #{score}
    and is_deleted = 0
    group by school_term, subject
    having count(score) > #{minCount}
    order by school_term, subject
</select>

4. 实现业务接口(这里是测试类, 实际应用中应该对应Dao类)

@RunWith(SpringRunner.class)
@SpringBootTest(classes = QuickStartApplication.class)
public class MybatisDemo {
    @Autowired
    private MyStudentScoreMapper mapper;
 
    @Test
    public void mybatis_demo() {
        
        SummaryQuery paras = new SummaryQuery()
            .setSchoolTerm(2000)
            .setSubjects(Arrays.asList("英语", "数学", "语文"))
            .setScore(60)
            .setMinCount(1);
 
        List<Map<String, Object>> summary = mapper.summaryScore(paras);
        System.out.println(summary);
    }
}

总之，直接使用mybatis，实现步骤还是相当的繁琐，效率太低。那换成mybatis plus的效果怎样呢？

换成mybatis plus实现效果

mybatis plus的实现比mybatis会简单比较多，实现效果如下:

如红框圈出的，写mybatis plus实现用到了比较多字符串的硬编码（可以用Entity的get lambda方法部分代替字符串编码）。字符串的硬编码，会给开发同学造成不小的使用门槛，个人觉的主要有2点：

1. 字段名称的记忆和敲码困难

2. Entity属性跟随数据库字段发生变更后的运行时错误

其他框架，比如TkMybatis在封装和易用性上比mybatis plus要弱，就不再比较了。

生成代码编码比较

fluent mybatis生成代码设置

public class AppEntityGenerator {
    static final String url = "jdbc:mysql://localhost:3306/fluent_mybatis_demo?useSSL=false&useUnicode=true&characterEncoding=utf-8";
 
    public static void main(String[] args) {
        FileGenerator.build(Abc.class);
    }
 
    @Tables(
        /** 数据库连接信息 **/
        url = url, username = "root", password = "password",
        /** Entity类parent package路径 **/
        basePack = "cn.org.fluent.mybatis.springboot.demo",
        /** Entity代码源目录 **/
        srcDir = "spring-boot-demo/src/main/java",
        /** Dao代码源目录 **/
        daoDir = "spring-boot-demo/src/main/java",
        /** 如果表定义记录创建，记录修改，逻辑删除字段 **/
        gmtCreated = "gmt_create", gmtModified = "gmt_modified", logicDeleted = "is_deleted",
        /** 需要生成文件的表 ( 表名称:对应的Entity名称 ) **/
        tables = @Table(value = {"student_score"})
    )
    static class Abc {
    }
}

mybatis plus代码生成设置

public class CodeGenerator {
 
    static String dbUrl = "jdbc:mysql://localhost:3306/fluent_mybatis_demo?useSSL=false&useUnicode=true&characterEncoding=utf-8";
 
    @Test
    public void generateCode() {
        GlobalConfig config = new GlobalConfig();
        DataSourceConfig dataSourceConfig = new DataSourceConfig();
        dataSourceConfig.setDbType(DbType.MYSQL)
            .setUrl(dbUrl)
            .setUsername("root")
            .setPassword("password")
            .setDriverName(Driver.class.getName());
        StrategyConfig strategyConfig = new StrategyConfig();
        strategyConfig
            .setCapitalMode(true)
            .setEntityLombokModel(false)
            .setNaming(NamingStrategy.underline_to_camel)
            .setColumnNaming(NamingStrategy.underline_to_camel)
            .setEntityTableFieldAnnotationEnable(true)
            .setFieldPrefix(new String[]{"test_"})
            .setInclude(new String[]{"student_score"})
            .setLogicDeleteFieldName("is_deleted")
            .setTableFillList(Arrays.asList(
                new TableFill("gmt_create", FieldFill.INSERT),
                new TableFill("gmt_modified", FieldFill.INSERT_UPDATE)));
 
        config
            .setActiveRecord(false)
            .setIdType(IdType.AUTO)
            .setOutputDir(System.getProperty("user.dir") + "/src/main/java/")
            .setFileOverride(true);
 
        new AutoGenerator().setGlobalConfig(config)
            .setDataSource(dataSourceConfig)
            .setStrategy(strategyConfig)
            .setPackageInfo(
                new PackageConfig()
                    .setParent("com.mp.demo")
                    .setController("controller")
                    .setEntity("entity")
            ).execute();
    }
}