之前文章介绍过了Fluent基本框架等，其中有几个重要的方法用到了IQuery和IUpdate对象。 这2个对象是FluentMybatis实现复杂和动态sql的构造类，通过这2个对象fluent mybatis可以不用写具体的xml文件， 直接通过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。下面接着介绍如何通过IQuery和IUpdate定义强大的动态SQL语句。
表结构 假如有学生成绩表结构如下:
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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;
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统计2000年到2019年, 三门学科(‘英语', ‘数学', ‘语文')分数按学期,学科统计最低分，最高分和平均分,统计结果按学期和学科排序
SQL：
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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 ('英语', '数学', '语文')
and is_deleted = 0
group by school_term, subject
order by school_term, subject
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- 通过FluentMybatis来具体实现
- 在StudentScoreDao类上定义接口
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@Data
public class ScoreStatistics {
private int schoolTerm;
private String subject;
private long count;
private Integer minScore;
private Integer maxScore;
private BigDecimal avgScore;
}
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public interface StudentScoreDao extends IBaseDao<StudentScoreEntity> {
/**
* 统计从fromYear到endYear年间学科subjects的统计数据
*
* @param fromYear 统计年份区间开始
* @param endYear 统计年份区间结尾
* @param subjects 统计的学科列表
* @return 统计数据
*/
List<ScoreStatistics> statistics(int fromYear, int endYear, String[] subjects);
}
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在StudentScoreDaoImpl上实现业务逻辑
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@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()
);
}
}
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- DaoImpl实现中，除了根据条件返回统计结果，还讲结果按照下划线转驼峰的规则自动转换为ScoreStatistics对象返回。
- 测试
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@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[]{"语文", "数学", "英语"});
System.out.println(list);
}
}
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查看控制台输出结果：
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), 语文(String), 数学(String), 英语(String)
DEBUG - <== Total: 30
[ScoreStatistics(schoolTerm=2000, subject=数学, count=17, minScore=1, maxScore=93, avgScore=36.0588),
...
ScoreStatistics(schoolTerm=2009, subject=语文, count=24, minScore=3, maxScore=100, avgScore=51.2500)]
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原文链接：https://blog.csdn.net/qq_27933251/article/details/115378245