– a single shared
controller instance handles a particular request type
- controllers,
interceptors run in the IoC container
- allows multiple
DispatcherServlets that can share an “application context”
- Interface based not
class-based
Provides a good alternative to EJB for most applications
Provides end-to-end framework for applications.
Inversion
of Control has already been referred to as Dependency Injection. The basic principle is that beans define their
dependencies (i.e. the other objects
they work with) only through constructor arguments or properties. Then, it is the job of the container to
actually inject those dependencies
when it creates the bean. This is fundamentally the inverse (hence the name Inversion of Control) of the bean
instantiating or locating its
dependencies on its own using direct construction of classes, or something like the Service Locator pattern. While we will not elaborate too much on the advantages of Dependency Injection, it
becomes evident upon usage that code
gets much cleaner and reaching a higher grade of decoupling is much easier when beans do not look up their
dependencies, but are provided them,
and additionally do not even know where the dependencies are located and of what actual type they
are.
As touched on in the
previous paragraph, Inversion of Control/Dependency
Injection exists in two major variants:
•setter-based dependency injection is realized by calling setters on
your beans after invoking a
no-argument constructor to instantiate your bean. Beans defined in the BeanFactory that use setter-based
dependency injection are true JavaBeans. Spring generally advocates usage of setter-based dependency injection, since a large number
of constructor arguments can get
unwieldy, especially when some properties are optional.
•constructor-based dependency injection is realized by invoking a constructor with a number of arguments, each
representing a collaborator or
property. Although Spring generally advocates usage of setter-based dependency injection as much as possible, it does
fully support the constructor-based
approach as well, since you may wish to use it with pre-existing beans which provide only multi-argument
constructors, and no setters.
Additionally, for simpler beans, some people prefer the constructor approach as a means of ensuring beans can not
be constructed in an invalid
state.
Inversion
of Control has already been referred to as Dependency Injection. The basic principle is that beans define their
dependencies (i.e. the other objects
they work with) only through constructor arguments or properties. Then, it is the job of the container to
actually inject those dependencies
when it creates the bean. This is fundamentally the inverse (hence the name Inversion of Control) of the bean
instantiating or locating its
dependencies on its own using direct construction of classes, or something like the Service Locator pattern. While we will not elaborate too much on the advantages of Dependency Injection, it
becomes evident upon usage that code
gets much cleaner and reaching a higher grade of decoupling is much easier when beans do not look up their
dependencies, but are provided them,
and additionally do not even know where the dependencies are located and of what actual type they
are.
As touched on in the
previous paragraph, Inversion of Control/Dependency
Injection exists in two major variants:
•setter-based dependency injection is realized by calling setters on
your beans after invoking a
no-argument constructor to instantiate your bean. Beans defined in the BeanFactory that use setter-based
dependency injection are true JavaBeans. Spring generally advocates usage of setter-based dependency injection, since a large number
of constructor arguments can get
unwieldy, especially when some properties are optional.
•constructor-based dependency injection is realized by invoking a constructor with a number of arguments, each
representing a collaborator or
property. Although Spring generally advocates usage of setter-based dependency injection as much as possible, it does
fully support the constructor-based
approach as well, since you may wish to use it with pre-existing beans which provide only multi-argument
constructors, and no setters.
Additionally, for simpler beans, some people prefer the constructor approach as a means of ensuring beans can not
be constructed in an invalid
state.
The DAO would be injected with a
Session/Connection object
The DAO would be injected with a
Session/Connection object
The DAO would be injected with a
Session/Connection object
The DAO would be injected with a
Session/Connection object
The DAO would be injected with a
Session/Connection object
The DAO would be injected with a
Session/Connection object
The DAO would be injected with a
Session/Connection object
For example WebSphere initializes
Listeners after Servlets are loaded which is a bad thing in this case.