Mybatis中的mapper.xml文件學習和使用

Mybatis中的mapper.xml文件學習和使用

本文是基於Windows 10系統環境，進行Mybatis中的mapper.xml的學習和使用

• Windows 10
• Mybatis

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一、mapper.xml書寫規範

(1) select語句

<select id="getUserByMap" parameterType="java.util.Map" resultType="java.util.Map">
        select * from user
        <where>
            1=1
            <if test="parameter != null and parameter.username != null and parameter.username != ''">
                and username like concat('%',#{parameter.username},'%')
            </if>
            <if test="parameter != null and parameter.age != null">
                and age = #{parameter.age}
            </if>
            <if test="filters != null and filters.authority != null">
                and authority in
                <foreach item="item" index="index" collection="filters.authority" open="(" separator="," close=")">
                    #{item}
                </foreach>
            </if>
            <if test="filters != null and filters.nickname != null">
                and nickname in
                <foreach item="item" index="index" collection="filters.nickname" open="(" separator="," close=")">
                    #{item}
                </foreach>
            </if>
            <choose>
            <when test="type != null and mobile != null and type=='mobile'" >
                and mobile = #{mobile}
            </when>
            <otherwise>
                and account = #{account}
            </otherwise>
        </choose>
        </where>
        <if test="sorter != null and sorter.field != null and sorter.order != null">
            order by ${sorter.field} ${sorter.order}
        </if>
        <if test="pagination != null and pagination.pageSize != null and pagination.offset != null">
            limit #{pagination.offset},#{pagination.pageSize}
        </if>
    </select>

二、注意事項

(1) order by後面的參數不生效

在mybatis中使用下面的語句，不會生效

select XXXX from table order by #{column} #{order}

mybatis會將上面的語句翻譯爲

select XXXX from table order by "authority" "desc"

將#{ }改爲${ }，語句生效

select XXXX from table order by ${column} ${order}

mybatis會將上面的語句翻譯爲

select XXXX from table order by authority desc

三、Mybatis中javaType和jdbcType對應關係

JDBC Type           Java Type  
CHAR                String  
VARCHAR             String  
LONGVARCHAR         String  
NUMERIC             java.math.BigDecimal  
DECIMAL             java.math.BigDecimal  
BIT             	boolean  
BOOLEAN             boolean  
TINYINT             byte  
SMALLINT            short  
INTEGER             int  
BIGINT              long  
REAL                float  
FLOAT               double  
DOUBLE              double  
BINARY              byte[]  
VARBINARY           byte[]  
LONGVARBINARY       byte[]  
DATE                java.sql.Date  
TIME                java.sql.Time  
TIMESTAMP           java.sql.Timestamp  
CLOB                Clob  
BLOB                Blob  
ARRAY               Array  
DISTINCT            mapping of underlying type  
STRUCT              Struct  
REF                 Ref  
DATALINK            java.net.URL[color=red][/color]  

<resultMap type="java.util.Map" id="resultjcm">  
  <result property="FLD_NUMBER" column="FLD_NUMBER"  javaType="double" jdbcType="NUMERIC"/>  
  <result property="FLD_VARCHAR" column="FLD_VARCHAR" javaType="string" jdbcType="VARCHAR"/>  
  <result property="FLD_DATE" column="FLD_DATE" javaType="java.sql.Date" jdbcType="DATE"/>  
  <result property="FLD_INTEGER" column="FLD_INTEGER"  javaType="int" jdbcType="INTEGER"/>  
  <result property="FLD_DOUBLE" column="FLD_DOUBLE"  javaType="double" jdbcType="DOUBLE"/>  
  <result property="FLD_LONG" column="FLD_LONG"  javaType="long" jdbcType="INTEGER"/>  
  <result property="FLD_CHAR" column="FLD_CHAR"  javaType="string" jdbcType="CHAR"/>  
  <result property="FLD_BLOB" column="FLD_BLOB"  javaType="[B" jdbcType="BLOB" />  
  <result property="FLD_CLOB" column="FLD_CLOB"  javaType="string" jdbcType="CLOB"/>  
  <result property="FLD_FLOAT" column="FLD_FLOAT"  javaType="float" jdbcType="FLOAT"/>  
  <result property="FLD_TIMESTAMP" column="FLD_TIMESTAMP"  javaType="java.sql.Timestamp" jdbcType="TIMESTAMP"/>  
 </resultMap>

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