在Spring 4中从另一个xml文件访问xml中定义的bean

Question

In a Spring web app I have some common beans such as dataSource , transactionManager , mailSender etc. defined in an xml file. I also have many other xml files which I am using to start some tasks, and I am importing them in here:

servlet.xml:

<bean id="dataSource"
        class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"
        p:driverClassName="${jdbc.driverClassName}"
        p:url="${jdbc.databaseurl}" p:username="${jdbc.username}"
        p:password="${jdbc.password}"
        p:initialSize="1"
        p:maxWait="30000"
        p:maxIdle="-1"
        p:maxActive="-1" />

<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
</bean>
<import resource="aTaskStarter.xml"/>

Now in the aTaskStarter.xml file I would like to access those beans and pass them to the java class:

aTaskStarter.xml:

<bean id="dailyReportTask" class="com.package.task.MyTask">
    <property name="dataSource" ref="dataSource" />
</bean>

How can I do this?

Answer 1

将常见内容放入第三个xml文件中，并将其包含在其他两个文件中：

<import resource="common.xml" />

Answer 2

You should just move up the import to before the bean definitions and all should function as you expect...

The documentation states

It's often useful to split up container definitions into multiple XML files. One way to then load an application context which is configured from all these XML fragments is to use the application context constructor which takes multiple Resource locations. With a bean factory, a bean definition reader can be used multiple times to read definitions from each file in turn.

Generally, the Spring team prefers the above approach, since it keeps container configurations files unaware of the fact that they are being combined with others. However, an alternate approach is to from one XML bean definition file, use one or more instances of the import element to load definitions from one or more other files. Any import elements must be placed before bean elements in the file doing the importing. Let's look at a sample:

<beans>

  <import resource="services.xml"/>

  <import resource="resources/messageSource.xml"/>

  <import resource="/resources/themeSource.xml"/>

  <bean id="bean1" class="..."/>

  <bean id="bean2" class="..."/>
  . . .

In this example, external bean definitions are being loaded from 3 files, services.xml, messageSource.xml, and themeSource.xml. All location paths are considered relative to the definition file doing the importing, so services.xml in this case must be in the same directory or classpath location as the file doing the importing, while messageSource.xml and themeSource.xml must be in a resources location below the location of the importing file. As you can see, a leading slash is actually ignored, but given that these are considered relative paths, it is probably better form not to use the slash at all.

The contents of the files being imported must be fully valid XML bean definition files according to the DTD, including the top level beans element.