如何在 MyBatis 中将方法应用于参数

发布于 2025-01-04 00:07:03 字数 1351 浏览 4 评论 0原文

在阅读了 Mapper XMLs 后，我不禁想知道人们会如何去关于对参数应用一些常见的转换。例如...

<select id="selectPerson" parameterType="String" resultType="hashmap">
  <!-- #{name} should always be upper case and have a trailing % -->
  SELECT * FROM PERSON WHERE FIRST_NAME like #{name} 
</select>

阅读此和<一个href="https://stackoverflow.com/questions/7491291/how-can-i-use-like-in-sql-queries-with-mybatis-safely-and-db-agnostic">这个我可以进行一些观察。

使用 upper 或 concat 或 '||' 或 '+' 等 SQL 函数进行转换会降低性能在 DB2 中，
我总是可以包装映射器或在服务层中公开详细信息，但这看起来很混乱

我想要的是能够做类似的事情...

<select id="selectPerson" parameterType="String" resultType="hashmap">
  <!-- #{name} should always be upper case and have a trailing % -->
  SELECT * FROM PERSON WHERE FIRST_NAME like #{name.upperCase() + '%'} 
</select>

这样的事情可能吗？或者第二个最佳解决方案是什么？

更新：看来 MyBatis 使用 OGNL 进行某些表达式求值。例如，if 和 ${} 表达式使用 OGNL，但 #{} 似乎不会，除非有某种方法可以欺骗它。< /em>

原文

After reading about Mapper XMLs I can't help to wonder how one might go about appling some common transforms to a parameter. For example...

<select id="selectPerson" parameterType="String" resultType="hashmap">
  <!-- #{name} should always be upper case and have a trailing % -->
  SELECT * FROM PERSON WHERE FIRST_NAME like #{name} 
</select>

After reading this and this I can make some observations.

Using SQL functions such as upper or concat or '||' or '+' to do transforms kills performance in DB2
I could always wrap the the mapper or expose the details in the service layer but that seems messy

What I want is to be able to do something like...

<select id="selectPerson" parameterType="String" resultType="hashmap">
  <!-- #{name} should always be upper case and have a trailing % -->
  SELECT * FROM PERSON WHERE FIRST_NAME like #{name.upperCase() + '%'} 
</select>

Is something like this possible or what is the second best solution?

Update: it appears that MyBatis uses OGNL for some expression evaluation. For example, if and ${} expressions use OGNL but #{} does NOT appear to unless there is some way to trick it.

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独﹏钓一江月 2025-01-11 00:07:03

Bind

MyBatis 允许使用。

Bind 在当前语句的范围内创建一个新变量。绑定值的 OGNL 语句可以使用传入的 _parameter 对象来计算新的绑定值，然后 MyBatis 可以使用该值来构造准备好的语句。

示例

使用绑定的示例：

<select id="selectPerson" parameterType="String" resultType="hashmap">
  <!-- #{name} should always be upper case and have a trailing % -->
  <bind name="nameStartsWith" value="_parameter.getName().upperCase() + '%'"/>
  SELECT * FROM PERSON WHERE FIRST_NAME like #{nameStartsWith} 
</select>

来源

MyBatis 动态 SQL 文档

Bind

MyBatis allows for creating values from method and properties in the context using <bind/>.

Bind creates a new variable in the scope of the current statement. The OGNL statement that binds the value can use the passed in _parameter object to compute a new bound value that can then used by MyBatis to construct the prepared statement.

Example

Your example using bind:

<select id="selectPerson" parameterType="String" resultType="hashmap">
  <!-- #{name} should always be upper case and have a trailing % -->
  <bind name="nameStartsWith" value="_parameter.getName().upperCase() + '%'"/>
  SELECT * FROM PERSON WHERE FIRST_NAME like #{nameStartsWith} 
</select>