來(lái)源：juejin.cn/post/6886019929519177735

使用fluent mybatis也可以不用寫具體的 xml 文件，通過(guò) java api 可以構(gòu)造出比較復(fù)雜的業(yè)務(wù) sql 語(yǔ)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，或在 xml 與 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(guò)一個(gè)比較典型的業(yè)務(wù)需求來(lái)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(yǔ)', '數(shù)學(xué)', '語(yǔ)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(yǔ)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(yǔ)', '數(shù)學(xué)', '語(yǔ)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(lái)實(shí)現(xiàn)一番。

三者實(shí)現(xiàn)對(duì)比

使用fluent mybatis 來(lái)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。

換成mybatis原生實(shí)現(xiàn)效果

定義Mapper接口
public interface MyStudentScoreMapper {    ListString, Object>> 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<String> subjects;
    private Integer score;
    private Integer minCount;}

定義實(shí)現(xiàn)業(yè)務(wù)邏輯的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, subjectselect>

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(yǔ)", "數(shù)學(xué)", "語(yǔ)文"))            .setScore(60)            .setMinCount(1);
        ListString, 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?，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(kù)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(kù)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。

對(duì) Fluent Mybatis 感興趣的網(wǎng)友，支持大家去閱讀官方源碼，發(fā)現(xiàn)更多新大陸！
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