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Fluent Mybatis實際開發(fā)中的優(yōu)勢對比

更新時間：2021年08月04日 15:28:36 作者：夜慬涼

本文給大家介紹如何通過IQuery和IUpdate定義強大的動態(tài)SQL語句，給大家分享Fluent Mybatis實際開發(fā)中的優(yōu)勢講解，感興趣的朋友一起看看吧

之前文章介紹過了Fluent基本框架等，其中有幾個重要的方法用到了IQuery和IUpdate對象。這2個對象是FluentMybatis實現(xiàn)復(fù)雜和動態(tài)sql的構(gòu)造類，通過這2個對象fluent mybatis可以不用寫具體的xml文件，直接通過java api可以構(gòu)造出比較復(fù)雜的業(yè)務(wù)sql語句，做到代碼邏輯和sql邏輯的合一。下面接著介紹如何通過IQuery和IUpdate定義強大的動態(tài)SQL語句。

表結(jié)構(gòu) 假如有學(xué)生成績表結(jié)構(gòu)如下:

create table `student_score`
(
    id           bigint auto_increment comment '主鍵ID' primary key,
    student_id   bigint            not null comment '學(xué)號',
    gender_man   tinyint default 0 not null comment '性別, 0:女; 1:男',
    school_term  int               null comment '學(xué)期',
    subject      varchar(30)       null comment '學(xué)科',
    score        int               null comment '成績',
    gmt_create   datetime          not null comment '記錄創(chuàng)建時間',
    gmt_modified datetime          not null comment '記錄最后修改時間',
    is_deleted   tinyint default 0 not null comment '邏輯刪除標(biāo)識'
) engine = InnoDB default charset=utf8;

統(tǒng)計2000年到2019年, 三門學(xué)科(‘英語', ‘?dāng)?shù)學(xué)', ‘語文')分?jǐn)?shù)按學(xué)期,學(xué)科統(tǒng)計最低分，最高分和平均分,統(tǒng)計結(jié)果按學(xué)期和學(xué)科排序
SQL：

select school_term, subject, count(score), min(score), max(score), avg(score)
from student_score
where school_term between 2000 and 2019
  and subject in ('英語', '數(shù)學(xué)', '語文')
  and is_deleted = 0
group by school_term, subject
order by school_term, subject

通過FluentMybatis來具體實現(xiàn)
在StudentScoreDao類上定義接口

@Data
public class ScoreStatistics {
    private int schoolTerm;
    private String subject;
    private long count;
    private Integer minScore;
    private Integer maxScore;
    private BigDecimal avgScore;
}

public interface StudentScoreDao extends IBaseDao<StudentScoreEntity> {
    /**
     * 統(tǒng)計從fromYear到endYear年間學(xué)科subjects的統(tǒng)計數(shù)據(jù)
     *
     * @param fromYear 統(tǒng)計年份區(qū)間開始
     * @param endYear  統(tǒng)計年份區(qū)間結(jié)尾
     * @param subjects 統(tǒng)計的學(xué)科列表
     * @return 統(tǒng)計數(shù)據(jù)
     */
    List<ScoreStatistics> statistics(int fromYear, int endYear, String[] subjects);
}

在StudentScoreDaoImpl上實現(xiàn)業(yè)務(wù)邏輯

@Repository
public class StudentScoreDaoImpl extends StudentScoreBaseDao implements StudentScoreDao {
    @Override
    public List<ScoreStatistics> statistics(int fromSchoolTerm, int endSchoolTerm, String[] subjects) {
        return super.listPoJos(ScoreStatistics.class, super.query()
            .select.schoolTerm().subject()
            .count("count")
            .min.score("min_score")
            .max.score("max_score")
            .avg.score("avg_score")
            .end()
            .where.isDeleted().isFalse()
            .and.schoolTerm().between(fromSchoolTerm, endSchoolTerm)
            .and.subject().in(subjects)
            .end()
            .groupBy.schoolTerm().subject().end()
            .orderBy.schoolTerm().asc().subject().asc().end()
        );
    }
}

DaoImpl實現(xiàn)中，除了根據(jù)條件返回統(tǒng)計結(jié)果，還講結(jié)果按照下劃線轉(zhuǎn)駝峰的規(guī)則自動轉(zhuǎn)換為ScoreStatistics對象返回。
測試

@RunWith(SpringRunner.class)
@SpringBootTest(classes = QuickStartApplication.class)
public class StudentScoreDaoImplTest {
    @Autowired
    private StudentScoreDao dao;

    @Test
    public void statistics() {
        List<ScoreStatistics> list = dao.statistics(2000, 2019, new String[]{"語文", "數(shù)學(xué)", "英語"});
        System.out.println(list);
    }
}

查看控制臺輸出結(jié)果：

DEBUG - ==> Preparing: SELECT school_term, subject, count(*) AS count, MIN(score) AS min_score, MAX(score) AS max_score, AVG(score) AS avg_score
    FROM student_score
    WHERE is_deleted = ?
    AND school_term BETWEEN ? AND ?
    AND subject IN (?, ?, ?)
    GROUP BY school_term, subject
    ORDER BY school_term ASC, subject ASC
DEBUG - ==> Parameters: false(Boolean), 2000(Integer), 2019(Integer), 語文(String), 數(shù)學(xué)(String), 英語(String)
DEBUG - <==      Total: 30
[ScoreStatistics(schoolTerm=2000, subject=數(shù)學(xué), count=17, minScore=1, maxScore=93, avgScore=36.0588),
...
ScoreStatistics(schoolTerm=2009, subject=語文, count=24, minScore=3, maxScore=100, avgScore=51.2500)]

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