[Springframework-developer] Type 3 IoC support

[<jue...@we...>]

Everybody,
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I'm pleased to announce that a Spring bean factory is now capable of =
handling Type 3 IoC components! As the most important feature, I've =
introduced autowire=3D"constructor" for autowiring constructor arguments =
by type, just like autowire=3D"byType" does for bean properties.=20
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Furthermore, there is a "constructor-arg" tag within the "bean" tag now, =
to pass specific beans or values to constructor arguments. =
"constructor-arg" can specify generic values that get matched by type, =
or values for a specific argument via its "index" attribute. This means =
that we can handle any kind of constructor, be it with bean references, =
simple values, lists, maps, etc. We can also easily handle multiple =
constructor arguments of the same type, i.e. 2 DataSource arguments or 2 =
String values (in contrast to the current Pico version)!
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The only limitation is that constructor-wired components are just =
allowed to have one single constructor. This is also what Pico =
recommends, although they have some heuristic kind of constructor choice =
in case of multiple constructors now. I guess we can limit this to one =
single constructor for the time being. Of course, standard beans defined =
without autowire=3D"constructor" or "constructor-arg" tags can still =
have any number of constructors, the only requirement being that they =
must provide a no-arg constructor.
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As an example, the XML bean definition from the test case:
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<beans>
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 <bean id=3D"rod1" =
class=3D"org.springframework.beans.factory.xml.ConstructorDependenciesBea=
n">
  <constructor-arg><ref bean=3D"other"/></constructor-arg>
  <constructor-arg><ref bean=3D"kerry2"/></constructor-arg>
 </bean>
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 <bean id=3D"rod2" =
class=3D"org.springframework.beans.factory.xml.ConstructorDependenciesBea=
n">
  <constructor-arg index=3D"1"><ref bean=3D"kerry1"/></constructor-arg>
  <constructor-arg index=3D"0"><ref bean=3D"kerry2"/></constructor-arg>
  <constructor-arg><ref bean=3D"other"/></constructor-arg>
 </bean>
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 <bean id=3D"rod3" =
class=3D"org.springframework.beans.factory.xml.ConstructorDependenciesBea=
n"
  autowire=3D"constructor">
  <constructor-arg><ref bean=3D"kerry2"/></constructor-arg>
 </bean>
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 <bean id=3D"rod4" =
class=3D"org.springframework.beans.factory.xml.DerivedConstructorDependen=
ciesBean">
  <constructor-arg index=3D"1"><ref bean=3D"kerry1"/></constructor-arg>
  <constructor-arg index=3D"3"><value>99</value></constructor-arg>
  <constructor-arg><ref bean=3D"other"/></constructor-arg>
  <constructor-arg index=3D"4"><value>myname</value></constructor-arg>
  <constructor-arg index=3D"0"><ref bean=3D"kerry2"/></constructor-arg>
 </bean>
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 <bean id=3D"kerry1" class=3D"org.springframework.beans.TestBean">
  <property name=3D"name">
   <value>Kerry</value>
  </property>
 </bean>
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 <bean id=3D"kerry2" class=3D"org.springframework.beans.TestBean">
  <property name=3D"name">
   <value>Kerry</value>
  </property>
 </bean>
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 <bean id=3D"other" =
class=3D"org.springframework.beans.factory.LifecycleBean"/>
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</beans>

Juergen