Mybatis详解(一)

<dependency>
	<groupId>org.mybatis</groupId>
	<artifactId>mybatis</artifactId>
	<version>3.5.1</version>
</dependency>

<?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>
    <!-- 导入外部配置文件 -->
    <properties resource="jdbc.properties"/>
</configuration>

<settings>
        <!-- 覆盖JDBC驱动中默认查询结果集的数量。默认值：null(未设置) -->
        <setting name="defaultFetchSize" value="10"/>
        <!-- 是否自动将数据库字段映射成小驼峰样式的POJO属性名，如数据库中是create_time，会自动映射成createTime。 默认值: false -->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <!-- 一级缓存生效范围： SESSION（一次会话）、STATEMENT（一次statement）。默认值：SESSION -->
        <setting name="localCacheScope" value="SESSION"/>
        <!-- 全局的开启、关闭所有Mapper文件中配置的二级缓存。默认值：true -->
        <setting name="cacheEnabled" value="true" />
        <!-- 发现无法映射字段时如何处理： NONE（不做处理）、WARNING(输出警告日志)、FAILING（抛出SQLException异常）。 默认值：NONE -->
        <setting name="autoMappingUnknownColumnBehavior" value="WARNING"/>
        <!-- 指定 MyBatis 应如何自动映射列到字段或属性。NONE(不自动映射)、PARTIAL(只映射单表查询)、FULL(级联映射多表查询结果集)。默认值：PARTIAL -->
        <setting name="autoMappingBehavior" value="NONE" />
        <!-- 全局延迟加载开关（针对关联对象），可在具体Mapper中通过fetchType覆盖这里的全局开关状态。默认值:false -->
        <setting name="lazyLoadingEnabled" value="true" />
        <!-- 是否使用数据库自动生成主键值，默认值：false -->
        <setting name="useGeneratedKeys" value="true" />
</settings>

<typeAliases>
  <typeAlias alias="Author" type="domain.blog.Author"/>
  <typeAlias alias="Blog" type="domain.blog.Blog"/>
  <typeAlias alias="Comment" type="domain.blog.Comment"/>
  <typeAlias alias="Post" type="domain.blog.Post"/>
  <typeAlias alias="Section" type="domain.blog.Section"/>
  <typeAlias alias="Tag" type="domain.blog.Tag"/>
</typeAliases>

<typeAliases>
  <package name="domain.blog"/>
</typeAliases>

SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(reader, environment);

<!-- 多环境配置根节点，并设置默认启用的环境 -->
<environments default="development">
  <!-- 定义development环境参数 -->
  <environment id="development">
     <!-- 指定事务配置 -->
     <transactionManager type="JDBC">
      <property name="..." value="..."/>
    </transactionManager>
    <!-- 配置数据源 -->
    <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>

<transactionManager type="MANAGED">
  <property name="closeConnection" value="false"/>
</transactionManager>

<!-- 使用相对于类路径的资源引用 -->
<mappers>
  <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
  <mapper resource="org/mybatis/builder/BlogMapper.xml"/>
  <mapper resource="org/mybatis/builder/PostMapper.xml"/>
</mappers>

<!-- 使用完全限定资源定位符（URL） -->
<mappers>
  <mapper url="file:///var/mappers/AuthorMapper.xml"/>
  <mapper url="file:///var/mappers/BlogMapper.xml"/>
  <mapper url="file:///var/mappers/PostMapper.xml"/>
</mappers>


<!-- 导入基于注解配置的Mapper -->
<mappers>
  <mapper class="org.mybatis.builder.AuthorMapper"/>
  <mapper class="org.mybatis.builder.BlogMapper"/>
  <mapper class="org.mybatis.builder.PostMapper"/>
</mappers>


<!-- 将包内的映射器接口实现全部注册为映射器 -->
<mappers>
  <package name="org.mybatis.builder"/>
</mappers>

<?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="com.spring.mapper.StudentMapper">
    <select id="queryAll" resultType="Student">
    select * from student
  </select>
</mapper>

public interface StudentMapper {

    List<Student> queryAll();

}

<insert id="insertAuthor">
  insert into Author (id,username,password,email,bio)
  values (#{id},#{username},#{password},#{email},#{bio})
</insert>

<update id="updateAuthor">
  update Author set
    username = #{username},
    password = #{password},
    email = #{email},
    bio = #{bio}
  where id = #{id}
</update>

<delete id="deleteAuthor">
  delete from Author where id = #{id}
</delete>

<!-- 获取数据库（如mysql、sqlserver）自增的id -->
<insert id="insertAuthor" useGeneratedKeys="true"
    keyProperty="id">
  insert into Author (username,password,email,bio)
  values (#{username},#{password},#{email},#{bio})
</insert>


<!-- 批量插入，并获取自增的id -->
<insert id="insertAuthor" useGeneratedKeys="true"
    keyProperty="id">
  insert into Author (username, password, email, bio) values
  <foreach item="item" collection="list" separator=",">
    (#{item.username}, #{item.password}, #{item.email}, #{item.bio})
  </foreach>
</insert>

<select id="selectPerson" parameterType="int" resultType="hashmap">
  SELECT * FROM PERSON WHERE ID = #{id}
</select>

// 近似的 JDBC 代码，非 MyBatis 代码...
String selectPerson = "SELECT * FROM PERSON WHERE ID=?";
PreparedStatement ps = conn.prepareStatement(selectPerson);
ps.setInt(1,id);

<sql id="userColumns"> ${alias}.id,${alias}.username,${alias}.password </sql>

<select id="selectUsers" resultType="map">
  select
    <include refid="userColumns"><property name="alias" value="t1"/></include>,
    <include refid="userColumns"><property name="alias" value="t2"/></include>
  from some_table t1
    cross join some_table t2
</select>

<cache />

<cache
  eviction="FIFO"
  flushInterval="60000"
  size="512"
  readOnly="true"/>

<cache-ref namespace="com.someone.application.data.SomeMapper"/>

<resultMap id="userResultMap" type="User">
  <id property="id" column="user_id" />
  <result property="username" column="user_name"/>
  <result property="password" column="hashed_password"/>
</resultMap>

<select id="selectUsers" resultMap="userResultMap">
  select user_id, user_name, hashed_password
  from some_table
  where id = #{id}
</select>

<select id="selectUsers" resultType="map">
  select id, username, hashedPassword
  from some_table
  where id = #{id}
</select>

<select id="selectUsers" resultType="com.someapp.model.User">
  select id, username, hashedPassword
  from some_table
  where id = #{id}
</select>

<select id="selectUsers" resultType="User">
  select
    user_id             as "id",
    user_name           as "userName",
    hashed_password     as "hashedPassword"
  from some_table
  where id = #{id}
</select>

<select id="selectUsers" resultType="User" parameterType="int">
  select id, username, password
  from users
  where id = #{id}
</select>

<insert id="insertUser" parameterType="User">
  insert into users (id, username, password)
  values (#{id}, #{username}, #{password})
</insert>

ORDER BY ${columnName}

@Select("select * from user where id = #{id}")
User findById(@Param("id") long id);

@Select("select * from user where name = #{name}")
User findByName(@Param("name") String name);

@Select("select * from user where email = #{email}")
User findByEmail(@Param("email") String email);

@Select("select * from user where ${column} = #{value}")
User findByColumn(@Param("column") String column, @Param("value") String value);

<select id="queryByIdAndAge" resultType="Teacher">
	select * from teacher where id = #{param1} and age &lt;= #{param2};
</select>

List<Teacher> queryByIdAndAge(@Param("tid") int id, @Param("age") int age);

<select id="queryByIdAndAge" parameterType="int" resultType="Teacher">
	select * from teacher where id = #{tid} and age <= #{age};
</select>

javac -parameters xxx.java

<plugin>
    <artifactId>maven-compiler-plugin</artifactId>                
    <version>3.8.0</version>
    <configuration>                  
        <compilerArgument>-parameters</compilerArgument>
        <encoding>UTF-8</encoding>                    
        <source>1.8</source>                 
        <target>1.8</target>
     </configuration>
</plugin>

public interface TeacherMapper {

    @Insert("insert into teacher(tname) values (#{tname})")
    int insertTeacher(Teacher teacher);
}

BlogMapper mapper = session.getMapper(BlogMapper.class);
// 调用mapper中的查询一个blog对象的方法
Blog blog = mapper.selectBlog(101);