代码优雅

1. 功能复用，写成公共方法。

2.mybatis 不应该用 select * 

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.hengxin.qianee.mapper.DictBankingMapper" >
  <resultMap id="BaseResultMap" type="com.hengxin.qianee.model.DictBanking" >
    <id column="id" property="id" jdbcType="INTEGER" />
    <result column="name" property="name" jdbcType="VARCHAR" />
    <result column="bank_code" property="bankCode" jdbcType="VARCHAR" />
    <result column="amount_day_limit" property="amount_day_limit" jdbcType="DECIMAL" />
    <result column="amount_single_limit" property="amount_single_limit" jdbcType="DECIMAL" />
    <result column="amount_month_limit" property="amount_month_limit" jdbcType="DECIMAL" />
    <result column="is_use" property="is_use" jdbcType="INTEGER" />
    <result column="images_path" property="images_path" jdbcType="VARCHAR" />
    <result column="images_path_wx" property="imagesPathWx" jdbcType="VARCHAR" />
    <result column="images_path_wx" property="imagesPathWx" jdbcType="VARCHAR" />
  </resultMap>
  <sql id="Base_Column_List" >
    id, name, images_path,amount_single_limit,amount_day_limit,amount_month_limit,is_use,images_path_wx
  </sql>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    select 
    <include refid="Base_Column_List" />
    from t_dict_banking
    where id = #{id,jdbcType=INTEGER}
  </select>
  
  <!-- 查询所有银行信息/图标、图片地址 -->
  <select id="selectBankingAll" resultMap="BaseResultMap">
    select 
    <include refid="Base_Column_List" />
    from t_dict_banking
  </select>
  
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    delete from t_dict_banking
    where id = #{id,jdbcType=INTEGER}
  </delete>
  
  <!-- 增加银行 -->
  <insert id="insert" parameterType="com.hengxin.qianee.model.DictBanking" >
    insert into t_dict_banking (id, name, images_path,amount_day_limit,amount_single_limit,amount_month_limit,is_use
      )
    values (#{id,jdbcType=INTEGER}, #{name,jdbcType=VARCHAR}, #{images_path,jdbcType=VARCHAR},#{amount_day_limit,jdbcType=DECIMAL},
            #{amount_single_limit,jdbcType=DECIMAL},#{amount_month_limit,jdbcType=DECIMAL},#{is_use,jdbcType=INTEGER}
      )
  </insert>
  
  <insert id="insertSelective" parameterType="com.hengxin.qianee.model.DictBanking" >
    insert into t_dict_banking
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        id,
      </if>
      <if test="name != null" >
        name,
      </if>
      <if test="images_path != null" >
        images_path,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="id != null" >
        #{id,jdbcType=INTEGER},
      </if>
      <if test="name != null" >
        #{name,jdbcType=VARCHAR},
      </if>
      <if test="images_path != null" >
        #{images_path,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <update id="updateByPrimaryKeySelective" parameterType="com.hengxin.qianee.model.DictBanking" >
    update t_dict_banking
    <set >
      <if test="name != null" >
        name = #{name,jdbcType=VARCHAR},
      </if>
      <if test="images_path != null" >
        images_path = #{images_path,jdbcType=VARCHAR},
      </if>
    </set>
    where id = #{id,jdbcType=INTEGER}
  </update>
  
  <!-- 保存修改银行卡信息 -->
  <update id="updateByPrimaryKey" parameterType="com.hengxin.qianee.model.DictBanking" >
    update t_dict_banking
    set name = #{name,jdbcType=VARCHAR},
    images_path = #{images_path,jdbcType=VARCHAR},
    amount_day_limit = #{amount_day_limit,jdbcType=DECIMAL},
    amount_single_limit = #{amount_single_limit,jdbcType=DECIMAL},
    amount_month_limit = #{amount_month_limit,jdbcType=DECIMAL},
    is_use = #{is_use,jdbcType=INTEGER}
    where id = #{id,jdbcType=INTEGER}
  </update>
  <!-- 微信用：根据银行编码获得银行信息 -->
  <select id="selectByBankCode" resultMap="BaseResultMap" parameterType="string" >
    select 
    <include refid="Base_Column_List" />
    from t_dict_banking
    where bank_code = #{bankCode} and type = 2 and is_use = 1
  </select>
</mapper>

3.不确定 查询语句是否能返回对象 而是有可能返回null时，要先判断该对象是否为null，再去取对象中的值。

4.金额等 double（Double）值相减的时候会丢失精度，转成“字符串”再转成BigDecimal

　　BigDecimal amountBG = new BigDecimal(amount.toString());

　　BigDecimal hasInvestedAmountBG = new BigDecimal(hasInvestedAmount.toString());

　　double money = amountBG.subtract(hasInvestedAmountBG).doubleValue();