MyBatis学习笔记(四) 注解

    使用MyBatis注解开发，可以省去类配置文件，简洁方便。但是比较复杂的SQL和动态SQL还是建议书写类配置文件。

注解还是不推荐使用的。只是了解了解！简单的CRUD可以使用注解。简单写写。

    把之前的例子改成使用注解的。

 

UserMapper.java

 package com.cy.mybatis.mapper;

 import java.util.List;
 import java.util.Map;

 import org.apache.ibatis.annotations.Delete;
 import org.apache.ibatis.annotations.Insert;
 import org.apache.ibatis.annotations.Options;
 import org.apache.ibatis.annotations.Param;
 import org.apache.ibatis.annotations.Result;
 import org.apache.ibatis.annotations.ResultMap;
 import org.apache.ibatis.annotations.Results;
 import org.apache.ibatis.annotations.Select;
 import org.apache.ibatis.annotations.Update;

 import com.cy.mybatis.beans.UserBean;

 public interface UserMapper {
     // 简单的增删改查可以使用注解
     // 注解+配置文件

     /**
      * 新增用戶
      * @param user
      * @return
      * @throws Exception
      */
     @Insert("insert into t_user value (null,user.username,user.password,user.account)")
     @Options(useGeneratedKeys=true,keyProperty="user.id")
     public int insertUser(@Param("user")UserBean user) throws Exception;

     /**
      * 修改用戶
      * @param user
      * @param id
      * @return
      * @throws Exception
      */
     @Update(" update t_user set username=#{u.username},password=#{u.password},account=#{u.account} where id=#{id}")
     public int updateUser (@Param("u")UserBean user,@Param("id")int id) throws Exception;

      /**
       * 刪除用戶
       * @param id
       * @return
       * @throws Exception
       */
     @Delete(" delete from t_user where id=#{id}  ")
     public int deleteUser(int id) throws Exception;

     /**
      * 根据id查询用户信息
      * @param id
      * @return
      * @throws Exception
      */

     @Select(" select * from t_user where id=#{id}")
     @Results({

         @Result(id=true,property="id",column="id",javaType=Integer.class),
         @Result(property="username",column="username",javaType=String.class),
         @Result(property="password",column="password",javaType=String.class),
         @Result(property="account",column="account",javaType=Double.class)
     })
     public UserBean selectUserById(int id) throws Exception;
      /**
       * 查询所有的用户信息
       * @return
       * @throws Exception
       */

     @Select(" select * from t_user")
     @ResultMap("userMap")
     public List<UserBean> selectAllUser() throws Exception;

     /**
      * 批量增加
      * @param user
      * @return
      * @throws Exception
      */
    public int batchInsertUser(@Param("users")List<UserBean> user) throws Exception;

    /**
     * 批量删除
     * @param list
     * @return
     * @throws Exception
     */
    public int batchDeleteUser(@Param("list")List<Integer> list) throws Exception;

    /**
     * 分页查询数据
     * @param parma
     * @return
     * @throws Exception
     */
    public List<UserBean> pagerUser(Map<String, Object> parmas) throws Exception;

    /**
     *
     * 分页统计数据
     * @param parma
     * @return
     * @throws Exception
     */
     public int countUser(Map<String, Object> parmas) throws Exception;  

 }

UserMapper.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper 3.0" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 <mapper namespace="com.cy.mybatis.mapper.UserMapper">
 <!-- 自定义返回结果集 -->
    <resultMap id="userMap" type="UserBean">
         <id property="id" column="id" javaType="java.lang.Integer"></id>
         <result property="username" column="username" javaType="java.lang.String"></result>
         <result property="password" column="password" javaType="java.lang.String"></result>
         <result property="account" column="account" javaType="java.lang.Double"></result>
     </resultMap>

     <!-- 批量操作和foreach标签 -->

     <insert id="batchInsertUser" parameterType="java.util.List">
        insert into t_user values
         <foreach collection="users" item="users" separator=",">
          (null,#{users.username},#{users.password},#{users.account})
         </foreach>
     </insert>

     <delete id="batchDeleteUser">
        delete from t_user where id in (
          <foreach collection="list" item="list" separator=",">
           #{id}
          </foreach>
        )
     </delete>

     <!--collection 为用于遍历的元素（必选），支持数组、List、Set  -->
     <!-- item 表示集合中每一个元素进行迭代时的别名. -->
     <!--separator表示在每次进行迭代之间以什么符号作为分隔 符.  -->

     <!--#在生成SQL时，对于字符类型参数，会拼装引号
          $在生成SQL时，不会拼装引号，可用于order by之类的参数拼装
       -->
     <select id="pagerUser" parameterType="java.util.Map" resultMap="userMap">
       select * from t_user where 1=1
       <if test="username!=null">
        and username like '%${username}%'
       </if>
        limit ${index},${pageSize}
     </select>

     <select id="countUser" parameterType="java.util.Map" resultType="int">
         select count(*) from t_user where 1=1
         <if test="username != null">
             and username like '%${username}%'
         </if>
     </select>    

 </mapper>    

 简单的一个一对一的使用注解的。

 package com.lovo.mybatis.mapper;

 import org.apache.ibatis.annotations.Insert;
 import org.apache.ibatis.annotations.One;
 import org.apache.ibatis.annotations.Options;
 import org.apache.ibatis.annotations.Param;
 import org.apache.ibatis.annotations.Result;
 import org.apache.ibatis.annotations.ResultType;
 import org.apache.ibatis.annotations.Results;
 import org.apache.ibatis.annotations.Select;

 import com.lovo.mybatis.beans.HusbandBean;
 import com.lovo.mybatis.beans.WifeBean;

 public interface HusbandMapper {

     /**
      * 保存丈夫
      * @param husband
      * @return
      */
     @Insert("insert into t_husband values (null,#{h.name})")
     @Options(useGeneratedKeys=true,keyProperty="h.id")
     public int saveHusband(@Param("h")HusbandBean husband);

     /**
      * 根据ID查询丈夫资料
      * @param id
      * @return
      */
     @Select("select * from t_husband where id=#{id}")
     @ResultType(HusbandBean.class)
     public HusbandBean findHusbandById(int id);

     /**
      * 根据ID查询丈夫与妻子资料
      * @param id
      * @return
      */
     @Select("select * from t_husband where id=#{id}")
     @Results({
         @Result(id=true,property="id",column="id",javaType=Integer.class),
         @Result(property="name",column="name",javaType=String.class),
         @Result(property="wife",column="id",javaType=WifeBean.class,one=@One(select="com.lovo.mybatis.mapper.WifeMapper.findWifeByHusbandId"))
     })
     public HusbandBean findHusbandAndWife(int id);

 }

 package com.cy.mybatis.mapper;

 import org.apache.ibatis.annotations.ResultType;
 import org.apache.ibatis.annotations.Select;

 import com.cy.mybatis.beans.WifeBean;

 public interface WifeMapper {

     @Select("select * from t_wife where fk_husband_id = #{id}")
     @ResultType(WifeBean.class)
     public WifeBean selectWifeByHusbandId(int id)throws Exception;

 }

注意：使用resultType时，一定要保证，你属性名与字段名相同；如果不相同，就使用resultMap 。