MyBatis - 定义全局参数

发布于 2024-12-19 19:06:11 字数 451 浏览 1 评论 0原文

首先是问题：我使用 XML 定义的查询，并且 SQL 包含数据库名称作为表名称的一部分。例如：从 mydb.bar 中选择 *。不幸的是，数据库是在各处创建/命名的，而 mudb 部分实际上是动态的，可以随时更改。所以我想用一个属性替换它，这样它看起来像 SELECT * FROM ${dbname}.bar 然后我在 mybatis-config.xml 中定义了以下部分：

<properties>
    <property name="dbname" value="mydb"/>
</properties>

但是当我运行查询时${dbname} 计算结果为 null。如果我在属性文件中定义此属性，也会发生同样的情况。我不想将其作为每个调用参数的一部分传递，因为这确实是一个全局属性。这可以做到吗？如果是的话——怎么办？

原文

First the problem: I'm using XML-defined queries and the SQL contains database name as part of a table name. For example: SELECT * from mydb.bar. Unfortunately, databases are created/named all over the place and mudb part is really dynamic and can change at any moment. So I wanted to replace it with a property so it would look like SELECT * FROM ${dbname}.bar and then I defined the following section in mybatis-config.xml:

<properties>
    <property name="dbname" value="mydb"/>
</properties>

But when I run the query ${dbname} evaluates to null. Same happens if I define this property in the properties file. I would hate to pass this as part of the each call parameters since this is truly a global property. Can this be done? And if yes - how?

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听你说爱我 2024-12-26 19:06:11

是的，你可以！这可能是一个奇怪的未记录的功能。构建配置对象时，请执行以下操作。 (org.apache.ibatis.session.Configuration)

configuration.getVariables().put("global_param", "123");

然后在你的XML映射中，你可以引用。

    select * from ${global_param}

Yes, you can! This is kind of a weird undocumented feature maybe. When building your Configuration object, do something like this. (org.apache.ibatis.session.Configuration)

configuration.getVariables().put("global_param", "123");

Then in your XML map, you can reference.

    select * from ${global_param}

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笨死的猪 2024-12-26 19:06:11

我在使用 Spring+MyBatis 时遇到了同样的问题，并通过使用我的 sqlSessionFactory 的 Spring XML 定义设置“configurationProperties”来解决它。下面的示例展示了如何设置名为“encryptionKey”的自定义全局属性，您可以在 XML 文件中硬编码该值，也可以使用 context:property-placeholder 标记从外部文件加载该值（如下所示）。

<context:property-placeholder location="/WEB-INF/spring/config-datasource.properties" />

<beans:bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <beans:property name="dataSource" ref="dataSource" />
    <beans:property name="typeAliasesPackage" value="com.example.model" />
    <beans:property name="configurationProperties">
        <beans:props>
            <beans:prop key="encryptionKey">${jdbc.encryptionKey}</beans:prop>
        </beans:props>
    </beans:property>
</beans:bean>

I had the same issue using Spring+MyBatis, and solved it by setting 'configurationProperties' using my Spring XML definition for sqlSessionFactory. My example below shows how to set a custom global property named 'encryptionKey', with a value which you can either hard-code in the XML file, or load from an external file using the context:property-placeholder tag (as below).

<context:property-placeholder location="/WEB-INF/spring/config-datasource.properties" />

<beans:bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <beans:property name="dataSource" ref="dataSource" />
    <beans:property name="typeAliasesPackage" value="com.example.model" />
    <beans:property name="configurationProperties">
        <beans:props>
            <beans:prop key="encryptionKey">${jdbc.encryptionKey}</beans:prop>
        </beans:props>
    </beans:property>
</beans:bean>

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不寐倦长更 2024-12-26 19:06:11

我使用的是 XML 配置，而不是 Spring，并在 Configuration 对象内设置了一个属性，但发现必须在加载映射器文件之前完成（请参阅此处）。我放弃了配置对象方法并采用了这种对我有用的方法：

  Reader reader = Resources.getResourceAsReader("..../mybatis-config.xml");
  Properties properties = new Properties();
  properties.setProperty("dbname", "mydb");
  SqlSessionFactory.factory = new SqlSessionFactoryBuilder().build(reader, "development", properties);

然后，正如 Andy Pryor 发布的那样，在 XML 映射器中使用 select * from ${dbname} 。

I was using an XML configuration but not Spring and set a property inside the Configuration object but discovered that had to be done before the mapper files are loaded (see here). I abandoned the Configuration object approach and went with this approach, which worked for me:

  Reader reader = Resources.getResourceAsReader("..../mybatis-config.xml");
  Properties properties = new Properties();
  properties.setProperty("dbname", "mydb");
  SqlSessionFactory.factory = new SqlSessionFactoryBuilder().build(reader, "development", properties);

Then, as Andy Pryor posted, use select * from ${dbname} in the XML mapper.

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