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Using depends-on
If a bean is a dependency of another bean, that usually means that one bean is set as a
property of another. Typically you accomplish this with the <ref/>
element in XML-based configuration metadata. However, sometimes dependencies between
beans are less direct. An example is when a static initializer in a class needs to be
triggered, such as for database driver registration. The depends-on
attribute can
explicitly force one or more beans to be initialized before the bean using this element
is initialized. The following example uses the depends-on
attribute to express a
dependency on a single bean:
<bean id="beanOne" class="ExampleBean" depends-on="manager"/>
<bean id="manager" class="ManagerBean" />
To express a dependency on multiple beans, supply a list of bean names as the value of
the depends-on
attribute (commas, whitespace, and semicolons are valid
delimiters):
<bean id="beanOne" class="ExampleBean" depends-on="manager,accountDao">
<property name="manager" ref="manager" />
</bean>
<bean id="manager" class="ManagerBean" />
<bean id="accountDao" class="x.y.jdbc.JdbcAccountDao" />
The depends-on attribute can specify both an initialization-time dependency and,
in the case of singleton beans only, a corresponding
destruction-time dependency. Dependent beans that define a depends-on relationship
with a given bean are destroyed first, prior to the given bean itself being destroyed.
Thus, depends-on can also control shutdown order.
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