干掉 XML Mapper，新出的 Fluent Mybatis 真香！
來源：juejin.cn/post/6886019929519177735
使用fluent mybatis可以不用寫具體的xml文件，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。
不再需要在Dao中組裝查詢或更新操作，在xml或mapper中再組裝參數(shù)。那對(duì)比原生Mybatis, Mybatis Plus或者其他框架，F(xiàn)luentMybatis提供了哪些便利呢？
需求場(chǎng)景設(shè)置
我們通過一個(gè)比較典型的業(yè)務(wù)需求來具體實(shí)現(xiàn)和對(duì)比下，假如有學(xué)生成績(jī)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(hào)',
????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(jī)',
????gmt_create???datetime??????????not?null?comment?'記錄創(chuàng)建時(shí)間',
????gmt_modified?datetime??????????not?null?comment?'記錄最后修改時(shí)間',
????is_deleted???tinyint?default?0?not?null?comment?'邏輯刪除標(biāo)識(shí)'
)?engine?=?InnoDB?default?charset=utf8;
現(xiàn)在有需求:
統(tǒng)計(jì)2000年三門學(xué)科('英語', '數(shù)學(xué)', '語文')及格分?jǐn)?shù)按學(xué)期,學(xué)科統(tǒng)計(jì)最低分，最高分和平均分, 且樣本數(shù)需要大于1條,統(tǒng)計(jì)結(jié)果按學(xué)期和學(xué)科排序
我們可以寫SQL語句如下
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?('英語',?'數(shù)學(xué)',?'語文')
??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，分別用fluent mybatis, 原生mybatis 和 Mybatis plus來實(shí)現(xiàn)一番。
三者實(shí)現(xiàn)對(duì)比
使用fluent mybatis 來實(shí)現(xiàn)上面的功能
具體代碼
我們可以看到fluent api的能力，以及IDE對(duì)代碼的渲染效果。
換成mybatis原生實(shí)現(xiàn)效果
定義Mapper接口
public?interface?MyStudentScoreMapper?{
????List>?summaryScore(SummaryQuery?paras);
}
定義接口需要用到的參數(shù)實(shí)體 SummaryQuery
@Data
@Accessors(chain?=?true)
public?class?SummaryQuery?{
????private?Integer?schoolTerm;
????private?List?subjects;
????private?Integer?score;
????private?Integer?minCount;
}
定義實(shí)現(xiàn)業(yè)務(wù)邏輯的mapper xml文件
"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
????"subjects"?item="item"?open="("?close=")"?separator=",">
????????#{item}
????
????and?score?>=?#{score}
????and?is_deleted?=?0
????group?by?school_term,?subject
????having?count(score)?>?#{minCount}
????order?by?school_term,?subject
實(shí)現(xiàn)業(yè)務(wù)接口(這里是測(cè)試類, 實(shí)際應(yīng)用中應(yīng)該對(duì)應(yīng)Dao類)
@RunWith(SpringRunner.class)
@SpringBootTest(classes?=?QuickStartApplication.class)
public?class?MybatisDemo?{
????@Autowired
????private?MyStudentScoreMapper?mapper;
????@Test
????public?void?mybatis_demo()?{
????????//?構(gòu)造查詢參數(shù)
????????SummaryQuery?paras?=?new?SummaryQuery()
????????????.setSchoolTerm(2000)
????????????.setSubjects(Arrays.asList("英語",?"數(shù)學(xué)",?"語文"))
????????????.setScore(60)
????????????.setMinCount(1);
????????List>?summary?=?mapper.summaryScore(paras);
????????System.out.println(summary);
????}
}
總之，直接使用mybatis，實(shí)現(xiàn)步驟還是相當(dāng)?shù)姆爆?，效率太低。那換成mybatis plus的效果怎樣呢？
換成mybatis plus實(shí)現(xiàn)效果
mybatis plus的實(shí)現(xiàn)比mybatis會(huì)簡(jiǎn)單比較多，實(shí)現(xiàn)效果如下
如紅框圈出的，寫mybatis plus實(shí)現(xiàn)用到了比較多字符串的硬編碼（可以用Entity的get lambda方法部分代替字符串編碼）。字符串的硬編碼，會(huì)給開發(fā)同學(xué)造成不小的使用門檻，個(gè)人覺的主要有2點(diǎn)：
字段名稱的記憶和敲碼困難 Entity屬性跟隨數(shù)據(jù)庫字段發(fā)生變更后的運(yùn)行時(shí)錯(cuò)誤
其他框架，比如TkMybatis在封裝和易用性上比mybatis plus要弱，就不再比較了。
生成代碼編碼比較
fluent mybatis生成代碼設(shè)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(
????????/**?數(shù)據(jù)庫連接信息?**/
????????url?=?url,?username?=?"root",?password?=?"password",
????????/**?Entity類parent?package路徑?**/
????????basePack?=?"cn.org.fluent.mybatis.springboot.demo",
????????/**?Entity代碼源目錄?**/
????????srcDir?=?"spring-boot-demo/src/main/java",
????????/**?Dao代碼源目錄?**/
????????daoDir?=?"spring-boot-demo/src/main/java",
????????/**?如果表定義記錄創(chuàng)建，記錄修改，邏輯刪除字段?**/
????????gmtCreated?=?"gmt_create",?gmtModified?=?"gmt_modified",?logicDeleted?=?"is_deleted",
????????/**?需要生成文件的表?(?表名稱:對(duì)應(yīng)的Entity名稱?)?**/
????????tables?=?@Table(value?=?{"student_score"})
????)
????static?class?Abc?{
????}
}
mybatis plus代碼生成設(shè)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();
????}
}
FluentMybatis特性一覽
三者對(duì)比總結(jié)
看完3個(gè)框架對(duì)同一個(gè)功能點(diǎn)的實(shí)現(xiàn), 各位看官肯定會(huì)有自己的判斷，筆者這里也總結(jié)了一份比較。
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