MyBatis动态插入的实现

mybatis通过定义前缀后缀和分割字符来拼接sql语句，实现动态插入的功能

<insert id="insertSelective" parameterType="com.bootdo.system.domain.LogDO">
    insert into sys_log
    <trim prefix="(" suffix=")" suffixOverrides=",">
      <if test="id != null">
        id,
      </if>
      <if test="userId != null">
        user_id,
      </if>
      <if test="username != null">
        username,
      </if>
      <if test="operation != null">
        operation,
      </if>
      <if test="time != null">
        time,
      </if>
      <if test="method != null">
        method,
      </if>
      <if test="params != null">
        params,
      </if>
      <if test="ip != null">
        ip,
      </if>
      <if test="gmtCreate != null">
        gmt_create,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides=",">
      <if test="id != null">
        #{id,jdbcType=BIGINT},
      </if>
      <if test="userId != null">
        #{userId,jdbcType=BIGINT},
      </if>
      <if test="username != null">
        #{username,jdbcType=VARCHAR},
      </if>
      <if test="operation != null">
        #{operation,jdbcType=VARCHAR},
      </if>
      <if test="time != null">
        #{time,jdbcType=INTEGER},
      </if>
      <if test="method != null">
        #{method,jdbcType=VARCHAR},
      </if>
      <if test="params != null">
        #{params,jdbcType=VARCHAR},
      </if>
      <if test="ip != null">
        #{ip,jdbcType=VARCHAR},
      </if>
      <if test="gmtCreate != null">
        #{gmtCreate,jdbcType=TIMESTAMP},
      </if>
    </trim>
  </insert>