oracle 用mybatis生成主键

oracle主键是不能像mysql一样自动管理的，需要自己手动管理，先生成，再插入。

<selectKey keyProperty="id" resultType="String" order="BEFORE">
     SELECT SEQ_GWFROZEN.nextval AS ID FROM DUAL
</selectKey>

<insert id="haha" parameterType="com.xx" >
    insert into xx
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        ID,
      </if>
      <if test="orderId != null" >
        ORDER_ID,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        #{id,jdbcType=VARCHAR},
      </if>
      <if test="orderId != null" >
        #{orderId,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>