trim, set, where label add notEmpty attr.

[abel533]

trim, set, where label add notEmpty attr.

When notempty is set, an exception is thrown if the content of the element is empty. The settings here can avoid dangerous SQL.

Example:

<select id="getUserIfNode" resultType="org.apache.ibatis.submitted.ognlstatic.User">
   select * from users
  <where notEmpty="query criteria cannot be blank">
   <if test="value not in {null, ''}">
   name = #{value}
   </if>
   </where>
</select>

<delete id="deleteAuthor" parameterType="int">
    delete from Author
    <where notEmpty="Dangerous: clear the table!">
    <if test="id!=null">
    id = #{id}
    </if>
    </where>
</delete>

If it is useful, I will add some tests.

[coveralls]

Coverage decreased (-0.02%) to 87.237% when pulling a176431 on abel533:notEmpty into e257a1d on mybatis:master.