Java_myBatis_动态SQL

主要是设计到映射文件的编写：

SELECT:

<sql id="query_user_where">
    <!-- test里面可以编写OGNL表达式 -->
    <!-- 判断字符串不为空的标准写法 -->
    <if test=" user.username != null and user.username !='' ">
         AND username like '%${user.username}%'
    </if>
</sql>

<!-- 分页查询之查询记录 -->
<select id="findUserList" parameterType="UserQueryVO"
    resultType="user">
    SELECT * FROM user
    <where>
        <include refid="query_user_where" />
    </where>
</select>

if语句前面必须带AND，where会自己判断什么时候该去除

UPDATE:

<update id="testDSQL" parameterType="User">
    UPDATE user 
    <set>
        <if test="username != null and username != ''">
            username = #{username},
        </if>
        <if test="address != null and address != ''">
            address = #{address},
        </if>
    </set>
    WERE id = 36
</update>

if最后的逗号是必须写的，set会自己判断什么时候去除

INSERT:

<insert id="insertSelective" parameterType="com.kkb.mybatis.pojo.Account" >
  <selectKey resultType="java.lang.Integer" keyProperty="id" order="AFTER" >
    SELECT LAST_INSERT_ID()
  </selectKey>
  INSERT INTO account
  <trim prefix="(" suffix=")" suffixOverrides="," >
    <if test="name != null" >
      name,
    </if>
    <if test="money != null" >
      money,
    </if>
  </trim>
  <trim prefix="values (" suffix=")" suffixOverrides="," >
    <if test="name != null" >
      #{name,jdbcType=VARCHAR},
    </if>
    <if test="money != null" >
      #{money,jdbcType=DOUBLE},
    </if>
  </trim>
</insert>

if最后的逗号是必须写的，trim会自己判断什么时候去除