MyBatis笔记_赵庆轩

SqlSessionFactory的创建

String resource = "org/mybatis/example/SqlMapConfig.xml"; 
Reader reader = Resources.getResourceAsReader(resource); 
SqlSessionFactory　sqlMapper = new SqlSessionFactoryBuilder().build(reader);

Mybatis的配置：

SqlMapConfig.xml

 

<?xml version="1.0"encoding="UTF-8" ?>

<!DOCTYPE configuration

PUBLIC "-//mybatis.org//DTD Config3.0//EN"

"http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

         <typeAliases>

                   <typeAliastype="cn.itcast.mybatis.domain.User" alias="User"/>

                   <typeAliastype="cn.itcast.mybatis.domain.Person" alias="Person"/>

                   <typeAliastype="cn.itcast.mybatis.domain.Order" alias="Order"/>

         </typeAliases>

         <environmentsdefault="development">

                   <environmentid="development">

                            <transactionManagertype="JDBC" />

                            <dataSourcetype="POOLED">

                                     <propertyname="driver" value="com.mysql.jdbc.Driver" />

                                     <propertyname="url" value="jdbc:mysql://localhost/mybatis" />

                                     <propertyname="username" value="root" />

                                     <propertyname="password" value="root" />

                            </dataSource>

                   </environment>

         </environments>

         <mappers>

                   <!--映射文件的位置 -->

                   <mapperresource="cn/itcast/mybatis/domain/User.xml" />

                   <mapperresource="cn/itcast/mybatis/domain/Person.xml" />

                   <mapperresource="cn/itcast/mybatis/domain/Order.xml" />

         </mappers>

</configuration>

 

 

User.xml

 

<?xml version="1.0"encoding="UTF-8" ?>

<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="cn.itcast.mybatis.domain.User">

 

         <resultMaptype="User" id="userMap">

                   <idcolumn="id" property="id"/>

                   <resultcolumn="name" property="userName"/>

                   <resultcolumn="address" property="address"/>

         </resultMap>

        

         <sqlid="mysql">

                   id,name,address

         </sql>

        

         <!--根据id查询User -->

         <!--id:当前sql语句的唯一标示  parameterType：参数类型resultType:结果类型(返回值类型)-->

         <selectid="selectUserById" parameterType="string"resultMap="userMap">

                   select<include refid="mysql"/> from user where id = #{userid}

         </select>

        

         <!--查询所有User -->

         <selectid="selectAllUsers" resultType="User">

                   selectid,name as userName ,address from user

         </select>

        

         <!--根据id查询User，返回值为：Map -->

         <selectid="selectUserByIdForMap" parameterType="string"resultType="hashmap">

                   selectid,name,address from user where id = #{userid}

         </select>

        

         <!--动态sql -->

         <selectid="selectUserByCondition" parameterType="User"resultType="User">

                   selectid,name as userName ,address from user where 1=1

                   <iftest="id != null">

                            andid = #{id}

                   </if>

                   <!--userName指的是实体的属性 -->

                   <iftest="userName != null">

                            andname = #{userName}

                   </if>

                   <iftest="address != null">

                            andaddress = #{address}

                   </if>

         </select>

        

         <!--动态sql -->

         <selectid="selectUserByCondition2" parameterType="User"resultType="User">

                   selectid,name as userName ,address from user

                   <where>

                            <iftest="id != null">

                               id = #{id}

                            </if>

                            <!--userName指的是实体的属性 -->

                            <iftest="userName != null">

                                     andname = #{userName}

                            </if>

                            <iftest="address != null">

                                     andaddress = #{address}

                            </if>

                   </where>

         </select>

        

         <!--插入User -->

         <insertid="insertUser" parameterType="User">

                   insertinto user (id,name,address) values (#{id},#{userName},#{address});

         </insert>

        

         <!--插入User 参数为hashmap-->

         <insertid="insertUserForMap" parameterType="hashmap">

                   insertinto user (id,name,address) values (#{id},#{name},#{address});

         </insert>

        

         <!--根据id删除User -->

         <deleteid="deleteUserById" parameterType="string">

                   deletefrom user where id = #{id}

         </delete>

        

         <!--根据id更新User -->

         <updateid="updateUserById" parameterType="User">

                   updateuser set name = #{userName},address = #{address} where id = #{id}

         </update>

        

         <!--根据id更新User 参数为map-->

         <updateid="updateUserByIdForMap" parameterType="hashmap">

                   updateuser set name = #{userName},address = #{address} where id = #{id}

         </update>

        

</mapper>

 

 

mybatis一对多映射:

Person.xml(Person和Order的一对多映射)

<?xml version="1.0"encoding="UTF-8" ?>

<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mappernamespace="cn.itcast.mybatis.domain.Person">

         <resultMaptype="Person" id="personMap">

                   <idcolumn="personId" property="id"/>

                   <resultcolumn="personName" property="name"/>

                   <resultcolumn="personAddress" property="address"/>

                   <resultcolumn="personTel" property="tel"/>

                  

                   <!--一对多 -->

                   <!--property:指的是集合属性的值 ofType：集合中元素的类型-->

                   <collectionproperty="orders" ofType="Order">

                            <idcolumn="orderId" property="id"/>

                            <resultcolumn="orderNumber" property="number"/>

                            <resultcolumn="orderPrice" property="price"/>

                   </collection>

         </resultMap>

        

         <selectid="selectPersonById" parameterType="string"resultMap="personMap">

                   selectp.*,o.* from person p,orders o where p.personId = o.pid and p.personId = #{id}

         </select>

</mapper>

 

 

Mybatis多对一关联映射：

 

<?xml version="1.0"encoding="UTF-8" ?>

<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mappernamespace="cn.itcast.mybatis.domain.Order">

         <resultMaptype="Order" id="orderMap">

                            <idcolumn="orderId" property="id"/>

                            <resultcolumn="orderNumber" property="number"/>

                            <resultcolumn="orderPrice" property="price"/>

                           

                            <!--多对一的关系 -->

                            <associationproperty="p" javaType="Person">

                                     <idcolumn="personId" property="id"/>

                                     <resultcolumn="personName" property="name"/>

                                     <resultcolumn="personAddress" property="address"/>

                                     <resultcolumn="personTel" property="tel"/>

                            </association>

         </resultMap>

        

         <!--根据id查询Order，关联将Person查询出来 -->

         <selectid="selectOrderById" parameterType="string"resultMap="orderMap">

                   selectp.*,o.* from person p,orders o where p.personId = o.pid and o.orderId = #{id}

         </select>

</mapper>

 

Include Sql语句

1,定义 sql语句模板：

 

<sql id="mysql">

         id,name,address

</sql>

 

2,引用sql模板：

 

<!-- 根据id查询User -->

<!-- id:当前sql语句的唯一标示  parameterType：参数类型 resultType:结果类型(返回值类型)-->

<select id="selectUserById"parameterType="string" resultMap="userMap">

         select<include refid="mysql"/> from user where id = #{userid}

</select>

 

 

实体属性与数据库字段不一致时的解决方案：

1,使用as:select id, nameas username, address from user;(用的不是很多)

2,使用resultMap

<resultMap type="User"id="userMap">

         <idcolumn="id" property="id"/>

         <resultcolumn="name" property="userName"/>

         <resultcolumn="address" property="address"/>

</resultMap>

 

<!-- 根据id查询User -->

<!-- id:当前sql语句的唯一标示  parameterType：参数类型 resultType:结果类型(返回值类型)-->

<select id="selectUserById"parameterType="string" resultMap="userMap">

         select<include refid="mysql"/> from user where id = #{userid}

</select>