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？

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’, 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_scorefrom student_scorewhere school_term >= 2000 and subject in (’英語’, ’數(shù)學(xué)’, ’語文’) and score >= 60 and is_deleted = 0group by school_term, subjecthaving count(score) > 1order 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。

使用fluent mybatis 來實(shí)現(xiàn)上面的功能

我們可以看到fluent api的能力，以及IDE對(duì)代碼的渲染效果。

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

1. 定義Mapper接口

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

2. 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<String> subjects; private Integer score; private Integer minCount;}

3. 定義實(shí)現(xiàn)業(yè)務(wù)邏輯的mapper xml文件

<select 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. 實(shí)現(xiàn)業(yè)務(wù)接口(這里是測試類, 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() {SummaryQuery paras = new SummaryQuery() .setSchoolTerm(2000) .setSubjects(Arrays.asList('英語', '數(shù)學(xué)', '語文')) .setScore(60) .setMinCount(1); List<Map<String, Object>> 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)姆爆崳侍汀Ｄ菗Q成mybatis plus的效果怎樣呢？

mybatis plus的實(shí)現(xiàn)比mybatis會(huì)簡單比較多，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)：

1. 字段名稱的記憶和敲碼困難

2. 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。

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(); }}

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。

作者：稻草江南

鏈接：juejin.cn/post/6886019929519177735

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