MyBatis:使用动态查询比较String值

Question

我正在使用MyBatis映射一些我需要比较String参数(myString)的查询.

我的Mapper 界面是:

public Map<Integer, String> findSomething(@Param("myString") String myString);

我的XML如下:

<select id="findSomething" parameterType="String" resultType="Map">
    SELECT column1 as key,
           column2 as value
    FROM my_table
    <where>
         <choose>
            <when test="myString == 'xxx'">
                column3 = 1
            </when>
            <when test="myString == 'yyy'">
                myColumn  = 2
            </when>
            <when test="myString == 'zzz'">
                myColumn  = 3
            </when>
        </choose>
    </where>
    ORDER BY value;
</select>

当我执行此语句时,抛出以下错误:

ERROR [stderr] Caused by: org.apache.ibatis.exceptions.PersistenceException: 
ERROR [stderr] ### Error querying database.  Cause: org.apache.ibatis.reflection.ReflectionException: There is no getter for property named 'myString' in 'class java.lang.String'

这样String比较,闻起来很糟糕.不幸的是,这是数据库建模的方式.

MyBatis版本: 3.2.2

Answer 1

用MyBatis 3.2.8测试

<select id="findSomething" parameterType="String" resultType="Map">
    SELECT column1 as key,
           column2 as value
    FROM my_table
    <where>
         <choose>
            <when test='"xxx".equals(myString)'>
                column3 = 1
            </when>
            <when test='"yyy".equals(myString)'>
                myColumn  = 2
            </when>
            <when test='"zzz".equals(myString)'>
                myColumn  = 3
            </when>
        </choose>
    </where>
    ORDER BY value;
</select>

请注意测试周围的单引号和de常量值周围的双引号.诀窍是使用equals,你可以看到.

Answer 2

当然，我必须经历一个复杂的方法。

更改了映射器方法签名：

public Map<Integer, String> findSomething(@Param("myPojo") MyPojo myPojo);

XML必须是：

<select id="findSomething" resultType="Map">
SELECT column1 as key,
       column2 as value
FROM my_table
<where>
     <choose>
        <when test="myPojo == 'xxx'">
            column3 = 1
        </when>
        <when test="myPojo == 'yyy'">
            myColumn  = 2
        </when>
        <when test="myPojo == 'zzz'">
            myColumn  = 3
        </when>
    </choose>
</where>
ORDER BY value;

只是不要忘记，作为 POJO，参数类必须具有其各自的 getter 和 setter。