mybatis初期使用比較麻煩，需要各種設(shè)定檔、實(shí)體類別、dao層映射關(guān)聯(lián)、還有一大推其它配置。當(dāng)然mybatis也發(fā)現(xiàn)了這種弊端，初期開發(fā)了generator可以根據(jù)表結(jié)果自動(dòng)生產(chǎn)實(shí)體類、設(shè)定檔和dao層程式碼，可以減輕一部分開發(fā)量；後期也進(jìn)行了大量的優(yōu)化可以使用註解了，自動(dòng)管理dao層和設(shè)定檔等，發(fā)展到最頂端就是今天要講的這種模式了，mybatis-spring-boot-starter就是springboot+mybatis可以完全註解不用設(shè)定文件，也可以簡單設(shè)定輕鬆上手。

現(xiàn)在想想spring boot 就是牛鼻呀，任何東西只要關(guān)聯(lián)到spring boot都是化繁為簡。

mybatis-spring-boot-starter

官方說明：MyBatis Spring-Boot-Starter will help you use MyBatis with Spring Boot
其實(shí)就是myBatis看spring boot這麼火熱也開發(fā)出一套解決方案來湊熱鬧一湊確實(shí)解決了許多問題，使用起來確實(shí)順暢了許多。 mybatis-spring-boot-starter主要有兩種解決方案，一種是使用註解解決一切問題，一種是簡化後的老傳統(tǒng)。

當(dāng)然任何模式都需要先引入mybatis-spring-boot-starter的pom檔,現(xiàn)在最新版本是1.1.1

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>1.1.1</version></dependency>

好了下來分別介紹兩種開發(fā)模式

無設(shè)定檔使用註解搞定。

1 新增相關(guān)maven檔案

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>1.1.1</version>
    </dependency>
     <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
     <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
        <optional>true</optional>
    </dependency></dependencies>

完整的pom套件這裡就不貼了，大家直接看源碼

2、application.properties?新增相關(guān)設(shè)定

mybatis.type-aliases-package=com.neo.entity

spring.datasource.driverClassName = com.mysql.jdbc.Driver
spring.datasource.url = jdbc:mysql://localhost:3306/test1?useUnicode=true&characterEncoding=utf-8spring.datasource.username = root
spring.datasource.password = root

springbootoot會(huì)自動(dòng)載入spring.datasource.來源就會(huì)自動(dòng)注入到sqlSessionFactory中，sqlSessionFactory會(huì)自動(dòng)注入到Mapper中，對(duì)了你一切都不用管了，直接拿起來使用就行了。

在啟動(dòng)類別中加入對(duì)mapper套件掃描@MapperScan

@SpringBootApplication@MapperScan("com.neo.mapper")public class Application {    
public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

或直接在Mapper類別中加入註解@Mapper,建議使用上面那種，不然每個(gè)mapper加個(gè)註解也挺麻煩的

3、開發(fā)Mapper

第三步是最關(guān)鍵的一塊，sql生產(chǎn)都在這裡

public interface UserMapper {

    @Select("SELECT * FROM users")
    @Results({
        @Result(property = "userSex",  column = "user_sex", javaType = UserSexEnum.class),
        @Result(property = "nickName", column = "nick_name")
    })
    List<UserEntity> getAll();

    @Select("SELECT * FROM users WHERE id = #{id}")
    @Results({
        @Result(property = "userSex",  column = "user_sex", javaType = UserSexEnum.class),
        @Result(property = "nickName", column = "nick_name")
    })
    UserEntity getOne(Long id);

    @Insert("INSERT INTO users(userName,passWord,user_sex) VALUES(#{userName}, #{passWord}, #{userSex})")
    void insert(UserEntity user);

    @Update("UPDATE users SET userName=#{userName},nick_name=#{nickName} WHERE id =#{id}")
    void update(UserEntity user);

    @Delete("DELETE FROM users WHERE id =#{id}")
    void delete(Long id);

}

注意，使用#符號(hào)和$符號(hào)的不同：

// This example creates a prepared statement, something like select * from teacher where name = ?;
@Select("Select * from teacher where name = #{name}")
Teacher selectTeachForGivenName(@Param("name") String name);

// This example creates n inlined statement, something like select * from teacher where name = 'someName';
@Select("Select * from teacher where name = '${name}')
Teacher selectTeachForGivenName(@Param("name") String name);

4、使用

上面三步就基本完成了相關(guān)dao層開發(fā)，使用的時(shí)候當(dāng)作普通的類注入進(jìn)入就可以了

@RunWith(SpringRunner.class)@SpringBootTestpublic class UserMapperTest {    @Autowired
    private UserMapper UserMapper;    @Test
    public void testInsert() throws Exception {
        UserMapper.insert(new UserEntity("aa", "a123456", UserSexEnum.MAN));
        UserMapper.insert(new UserEntity("bb", "b123456", UserSexEnum.WOMAN));
        UserMapper.insert(new UserEntity("cc", "b123456", UserSexEnum.WOMAN));

        Assert.assertEquals(3, UserMapper.getAll().size());
    }    @Test
    public void testQuery() throws Exception {
        List<UserEntity> users = UserMapper.getAll();
        System.out.println(users.toString());
    }    @Test
    public void testUpdate() throws Exception {
        UserEntity user = UserMapper.getOne(3l);
        System.out.println(user.toString());
        user.setNickName("neo");
        UserMapper.update(user);
        Assert.assertTrue(("neo".equals(UserMapper.getOne(3l).getNickName())));
    }
}

極簡xml版本

極簡xml版本保持映射文件的老傳統(tǒng)，優(yōu)化主要體現(xiàn)在不需要實(shí)現(xiàn)dao的是實(shí)現(xiàn)層，系統(tǒng)會(huì)自動(dòng)根據(jù)方法名稱在映射檔中找對(duì)應(yīng)的sql.

1、配置

pom文件和上個(gè)版本一樣，只是application.properties新增以下配置

mybatis.config-locations=classpath:mybatis/mybatis-config.xm

mybatis.config-locations=classpath:mybatis/mybatis-config.xml
mybatis.mapper-locations=classpath:mybatis/mapper/*.xml

指定了mybatis基礎(chǔ)配置文件和實(shí)體類映射文件的地址

mybatis-config.xml 配置

<configuration>
    <typeAliases>
        <typeAlias alias="Integer" type="java.lang.Integer" />
        <typeAlias alias="Long" type="java.lang.Long" />
        <typeAlias alias="HashMap" type="java.util.HashMap" />
        <typeAlias alias="LinkedHashMap" type="java.util.LinkedHashMap" />
        <typeAlias alias="ArrayList" type="java.util.ArrayList" />
        <typeAlias alias="LinkedList" type="java.util.LinkedList" />
    </typeAliases></configuration>

這里也可以添加一些mybatis基礎(chǔ)的配置

2、添加User的映射文件

<mapper namespace="com.neo.mapper.UserMapper" >
    <resultMap id="BaseResultMap" type="com.neo.entity.UserEntity" >
        <id column="id" property="id" jdbcType="BIGINT" />
        <result column="userName" property="userName" jdbcType="VARCHAR" />
        <result column="passWord" property="passWord" jdbcType="VARCHAR" />
        <result column="user_sex" property="userSex" javaType="com.neo.enums.UserSexEnum"/>
        <result column="nick_name" property="nickName" jdbcType="VARCHAR" />
    </resultMap>

    <sql id="Base_Column_List" >
        id, userName, passWord, user_sex, nick_name    </sql>

    <select id="getAll" resultMap="BaseResultMap"  >
       SELECT 
       <include refid="Base_Column_List" />
       FROM users    </select>

    <select id="getOne" parameterType="java.lang.Long" resultMap="BaseResultMap" >
        SELECT 
       <include refid="Base_Column_List" />
       FROM users
       WHERE id = #{id}
    </select>

    <insert id="insert" parameterType="com.neo.entity.UserEntity" >
       INSERT INTO 
               users
               (userName,passWord,user_sex) 
           VALUES
               (#{userName}, #{passWord}, #{userSex})    </insert>

    <update id="update" parameterType="com.neo.entity.UserEntity" >
       UPDATE 
               users 
       SET 
           <if test="userName != null">userName = #{userName},</if>
           <if test="passWord != null">passWord = #{passWord},</if>
           nick_name = #{nickName}
       WHERE 
               id = #{id}
    </update>

    <delete id="delete" parameterType="java.lang.Long" >
       DELETE FROM
                users 
       WHERE 
                id =#{id}
    </delete></mapper>

其實(shí)就是把上個(gè)版本中mapper的sql搬到了這里的xml中了

3、編寫Dao層的代碼

public interface UserMapper {

    List<UserEntity> getAll();

    UserEntity getOne(Long id);

    void insert(UserEntity user);

    void update(UserEntity user);

    void delete(Long id);

}

對(duì)比上一步這里全部只剩了接口方法

如何選擇

兩種模式各有特點(diǎn)，注解版適合簡單快速的模式，其實(shí)像現(xiàn)在流行的這種微服務(wù)模式，一個(gè)微服務(wù)就會(huì)對(duì)應(yīng)一個(gè)自已的數(shù)據(jù)庫，多表連接查詢的需求會(huì)大大的降低，會(huì)越來越適合這種模式。

老傳統(tǒng)模式比適合大型項(xiàng)目，可以靈活的動(dòng)態(tài)生成SQL，方便調(diào)整SQL，也有痛痛快快，洋洋灑灑的寫SQL的感覺。