mybatis(springboot 集成mybatis)

在这漫长的岁月里，一个人敲敲代码也是一件不容易的事情啊

入门

maven构建classpath:

<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>x.x.x</version>
</dependency>

mybatis-config.xml：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="org/mybatis/example/BlogMapper.xml"/>
  </mappers>
</configuration>

构建SqlSessionFactory:

方法一：

String resource = "org/mybatis/example/mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

方法二：

DataSource dataSource = BlogDataSourceFactory.getBlogDataSource();
TransactionFactory transactionFactory = new JdbcTransactionFactory();
Environment environment = new Environment("development", transactionFactory, dataSource);
Configuration configuration = new Configuration(environment);
configuration.addMapper(BlogMapper.class);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

从SqlSessionFactory中构建SqlSession:

方法一：

SqlSession session = sqlSessionFactory.openSession();
try {
  Blog blog = (Blog) session.selectOne("org.mybatis.example.BlogMapper.selectBlog", 101);
} finally {
  session.close();
}

方法二：

SqlSession session = sqlSessionFactory.openSession();
try {
  BlogMapper mapper = session.getMapper(BlogMapper.class);
  Blog blog = mapper.selectBlog(101);
} finally {
  session.close();
}

xml Sql语句编写

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.mybatis.example.BlogMapper">
  <select id="selectBlog" resultType="Blog">
    select * from Blog where id = #{id}
  </select>
</mapper>

然后使用Sqlsession进行调用：
方法一：

Blog blog = (Blog) session.selectOne("org.mybatis.example.BlogMapper.selectBlog", 101);

这个命名可以直接映射到在命名空间中同名的 Mapper 类，并将已映射的 select 语句中的名字、参数和返回类型匹配成方法。
方法二：

BlogMapper mapper = session.getMapper(BlogMapper.class);
Blog blog = mapper.selectBlog(101);

可以将xml sql语句改为：

public interface BlogMapper {
  @Select("SELECT * FROM blog WHERE id = #{id}")
  Blog selectBlog(int id);
}

技术实战

//使用@Configuration实现配置
@Configuration
@MapperScan(basePackages = {"xxxx.mapper"}, sqlSessionFactoryRef = "sqlSessionFactory1")
public class MybatisCsmerConfig {
    @Autowired
    @Qualifier("dataSourceCsmer")
    private DataSource dataSource;

    @Bean
    public SqlSessionFactory sqlSessionFactory1() throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        factoryBean.setDataSource(dataSource);
        factoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
                .getResources("classpath*:mybatis/mapper/*.xml"));
        factoryBean.setConfigLocation(new PathMatchingResourcePatternResolver()
                .getResource("classpath:mybatis/mybatis-config.xml"));
        return factoryBean.getObject();
    }

    @Bean
    public SqlSessionTemplate sqlSessionTemplate1() throws Exception {
        SqlSessionTemplate template = new SqlSessionTemplate(sqlSessionFactory1()); // 使用上面配置的Factory
        return template;
    }
}

spring boot集成mybatis

pom.xml中引入依赖：

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>1.3.2.RELEASE</version>
  <relativePath/> <!-- lookup parent from repository -->
</parent>

<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.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>
    <version>5.1.21</version>
  </dependency>
</dependencies>

在application.properties中配置mysql的连接配置

spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

然后写一个例子：

//使用@Mapper注解，告诉spring boot自动扫描这个类为mapper
import org.apache.ibatis.annotations.*;

@Mapper
public interface UserMapper {

    @Select("SELECT * FROM USER WHERE NAME = #{name}")
    User findByName(@Param("name") String name);

    @Insert("INSERT INTO USER(NAME, AGE) VALUES(#{name}, #{age})")
    int insert(@Param("name") String name, @Param("age") Integer age);

}

相应的实体：

public class User {

    private Long id;
    private String name;
    private Integer age;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

}

springboot整合mybatis会自动配置完所有信息，用户只需要在写的时候加入@Mapper注解，会自动进行扫描。

原理：

mybatis-spring-boot-starter就是springboot+mybatis可以完全注解不用配置文件，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。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。
首先，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);
  }
}

方式一：
直接在Mapper类上面添加注解@Mapper。
####Mapper的写法

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);
 
}

注解解释

@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

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);

方式二：极简xml
application.properties新增以下配置

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

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>

添加映射文件：

<mapper namespace="com.neo.mapper.UserMapper" >
    <resultMap id="BaseResultMap" type="com.neo.entity.UserEntity" >
        <id column="id" property="id" jdbcType="BIGINT" />
        <result column="user_name" property="userName" jdbcType="VARCHAR" />
        <result column="pass_word" 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。

我们的结构原本是按照第二种模式动态生成sqlnode，为了增强代码的可维护性，我们使用了mybatis的拦截器方法将动态生成改为更加简单的通过java语言来控制，而不需要去修改xml语句。​​见下文​​