springboot(六)：如何优雅的使用mybatis

mybatis-spring-boot-starter

官方说明：MyBatis Spring-Boot-Starter will help you use MyBatis with Spring Boot
其实就是myBatis看spring boot这么火热也开发出一套解决方案来凑凑热闹,但这一凑确实解决了很多问题，使用起来确实顺畅了许多。mybatis-spring-boot-starter主要有两种解决方案，一种是使用注解解决一切问题，一种是简化后的老传统。

当然任何模式都需要首先引入mybatis-spring-boot-starter的pom文件,现在最新版本是1.1.1（刚好快到双11了 :)）

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

好了下来分别介绍两种开发模式

无配置文件注解版

就是一切使用注解搞定。

1 添加相关maven文件

<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包这里就不贴了，大家直接看源码

2、application.properties 添加相关配置

mybatis.type-aliases-package=com.neo.entityspring.datasource.driverClassName = com.mysql.jdbc.Driverspring.datasource.url = jdbc:mysql://localhost:3306/test1?useUnicode=true&characterEncoding=utf-8spring.datasource.username = rootspring.datasource.password = root

springboot会自动加载spring.datasource.*相关配置，数据源就会自动注入到sqlSessionFactory中，sqlSessionFactory会自动注入到Mapper中，对了你一切都不用管了，直接拿起来使用就行了。

在启动类中添加对mapper包扫描@MapperScan

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

或者直接在Mapper类上面添加注解@Mapper,建议使用上面那种，不然每个mapper加个注解也挺麻烦的

3、开发Mapper

第三步是最关键的一块，sql生产都在这里

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);}

为了更接近生产我特地将user_sex、nick_name两个属性在数据库加了下划线和实体类属性名不一致，另外user_sex使用了枚举

• @Select 是查询类的注解，所有的查询均使用这个
• @Result 修饰返回的结果集，关联实体类属性和数据库字段一一对应，如果实体类属性和数据库属性名保持一致，就不需要这个属性来修饰。
• @Insert 插入数据库使用，直接传入实体类会自动解析属性到对应的值
• @Update 负责修改，也可以直接传入对象
• @delete 负责删除

了解更多属性参考这里

注意，使用#符号和$符号的不同：

// 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关dao层开发，使用的时候当作普通的类注入进入就可以了

@RunWith(SpringRunner.class)@SpringBootTestpublic class UserMapperTest {@Autowiredprivate UserMapper UserMapper;@Testpublic 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());}@Testpublic void testQuery() throws Exception {List<UserEntity> users = UserMapper.getAll();System.out.println(users.toString());}@Testpublic 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())));}}

源码中controler层有完整的增删改查，这里就不贴了

极简xml版本

极简xml版本保持映射文件的老传统，优化主要体现在不需要实现dao的是实现层，系统会自动根据方法名在映射文件中找对应的sql.

1、配置

pom文件和上个版本一样，只是application.properties新增以下配置

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

指定了mybatis基础配置文件和实体类映射文件的地址

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>

这里也可以添加一些mybatis基础的配置

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>

其实就是把上个版本中mapper的sql搬到了这里的xml中了

3、编写Dao层的代码

public interface UserMapper {List<UserEntity> getAll();UserEntity getOne(Long id);void insert(UserEntity user);void update(UserEntity user);void delete(Long id);}

对比上一步这里全部只剩了接口方法

4、使用

使用和上个版本没有任何区别，大家就看代码吧