mybatis入门

mybatis解决的问题

xml或者配置映射sql，执行sql，返回对象

mybatis的xml方式

定义resultMap

    <resultMap id="userMap" type="tk.mybatis.simple.model.SysUser">
        <id property="id" column="id"/>
        <result property="userName" column="user_name"/>
        <result property="userPassword" column="user_password"/>
        <result property="userEmail" column="user_email"/>
        <result property="userInfo" column="user_info"/>
        <result property="headImg" column="head_img" jdbcType="BLOB"/>
        <result property="createTime" column="create_time" jdbcType="TIMESTAMP"/>
    </resultMap>

xml支持select，insert，update，delete

    <select id="selectById" resultMap="userMap">
        select * from sys_user where id = #{id}
    </select>

<insert id="insert2" useGeneratedKeys="true" keyProperty="id">
        insert into sys_user(
            user_name, user_password, 
            <if test="userEmail != null">
                <if test="userEmail != ''">
                user_email, 
                </if>
            </if>
            user_info, head_img, create_time)
        values(
            #{userName}, #{userPassword}, 
            <if test="userEmail != null">
                <if test="userEmail != ''">
                #{userEmail}, 
                </if>
            </if>
            #{userInfo}, #{headImg, jdbcType=BLOB}, #{createTime, jdbcType=TIMESTAMP})
    </insert>

<update id="updateById">
        update sys_user 
        set user_name = #{userName},
            user_password = #{userPassword},
            user_email = #{userEmail},
            user_info = #{userInfo},
            head_img = #{headImg, jdbcType=BLOB},
            create_time = #{createTime, jdbcType=TIMESTAMP}
        where id = #{id}
    </update>

    <delete id="deleteById">
        delete from sys_user where id = #{id}
    </delete>

mybatis的注解方式

注解方式写sql和provider注解

@Results(id = "roleResultMap", value = {
        @Result(property = "id", column = "id", id = true),
        @Result(property = "roleName", column = "role_name"),
        @Result(property = "enabled", column = "enabled"),
        @Result(property = "createBy", column = "create_by"),
        @Result(property = "createTime", column = "create_time")
    })
    @Select("select id,role_name, enabled, create_by, create_time from sys_role where id = #{id}")

@Insert({"insert into sys_role(role_name, enabled, create_by, create_time)", 
    "values(#{roleName}, #{enabled}, #{createBy}, #{createTime, jdbcType=TIMESTAMP})"})
    @Options(useGeneratedKeys = true, keyProperty = "id")

@Update({"update sys_role",
             "set role_name = #{roleName},",
                 "enabled = #{enabled},",
                 "create_by = #{createBy},",
                 "create_time = #{createTime, jdbcType=TIMESTAMP}",
             "where id = #{id}"
        })

@Delete("delete from sys_role where id = #{id}")



    public String selectById(final Long id){
        return new SQL(){
            {
                SELECT("id, privilege_name, privilege_url");
                FROM("sys_privilege");
                WHERE("id = #{id}");
            }
        }.toString();
    }

mybatis的动态SQL

if choose(when, otherwise,trim,where,set,foreach,bind)

mybaits的代码生成器

支持生成代码

mybatis的高级查询

一对一使用join和association标签

一对多collection标签

mybatis的缓存

一级缓存：单个sqlsession有效

二级缓存：各类插件

ehcache和redis

mybatis的插件开发

拦截器接口

public interface Interceptor {

 # 拦截器方法调用
  Object intercept(Invocation invocation) throws Throwable;

  #要拦截的对象
  Object plugin(Object target);

  #设置配置
  void setProperties(Properties properties);
}

#拦截器前面
@Intercepts(
    @Signature(
        type = Executor.class, 
        method = "query", 
        args = {MappedStatement.class, Object.class, 
                RowBounds.class, ResultHandler.class}
    )
)

拦截4类接口：Executor，ParameterHandler，ResultSetHandler，StatementHandler

spring集成mybatis

<dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
</dependency>

springboot集成mybatis

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