Mybatis各种参数用法

1.只传单个String对象

<select id="findUser" parameterType="String" resultType="com.example.User">
select * from user_data where sex='M'
<choose>
<when test="_parameter != null "> AND user_id=#{userId} </when>
<otherwise> AND user_id=''</otherwise>
</choose>
and rownum <= 200
</select>

2.传多个String对象

<select id="findUser" resultType="User">
　　select * from user_data where user_id = #{0} and user_name = #{1}

</select>

3.传list对象

<select id="findUsers" parameterType="java.util.List" resultType="com.example.User">
select * from user_data where sex='M'  AND user_id in
<foreach collection="list" item="user_id" index="index" open="("
close=")" separator=",">
#{user_id}
</foreach>
and rownum <= 200
</select>

4.传普通对象

<select id="findUsers" parameterType="com.example.User"
resultType="com.example.User">
Select* from user_data
<where>
<if test="user_id !=null "> user_id=#{user_id} </if>
</where>

</select>

User类:

public class User extends BaseResult{
public String user_id;
public String user_name;
public String e_mail;
public String password;

}

其中test后的和大括号里的user_id都是对应User类中的字段，“=#”前面那个user_id对应user_data中的栏位

5.resultMap用法

我们平常返回的resultType为POJO类，但是有时我们只需要部分字段，那就用到resultMap替代resultType

<resultMap id="userResultMap" type="com.example.User">
<result property="user_id" column="user_id"/>
<result property="user_name" column="user_name"/>
</resultMap

上面的property后的user_id是对应User类中的字段，column中的user_id对应user_data中的栏位

select标签:

<select id="findUsers" parameterType="com.example.User"
resultMap="userResultMap">
Select* from user_data
<where>
<if test="user_id !=null "> user_id=#{user_id} </if>
</where>

</select>