What is @ModelAttribute in Spring MVC?
Spring MVC中@ModelAttribute的用途和用途是什么？
@ModelAttribute refers to a property of the Model object (the M in MVC ;) so let's say we have a form with a form backing object that is called "Person" Then you can have Spring MVC supply this object to a Controller method by using the @ModelAttribute annotation:
public String processForm(@ModelAttribute("person") Person person){
person.getStuff();
}
Check here for an example (Spring 2.5), also see "Using @ModelAttribute on a method argument" (Spring 3.1).
On the other hand the annotation is used to define objects which should be part of a Model. So if you want to have a Person object referenced in the Model you can use the following method:
@ModelAttribute("person")
public Person getPerson(){
return new Person();
}
This annotated method will allow access to the Person object in your View, since it gets automatically added to the Models by Spring.
See "Using @ModelAttribute on a method" (Spring 3.1).
Hope this helped.
I know this is an old thread, but I thought I throw my hat in the ring and see if I can muddy the water a little bit more :)
I found my initial struggle to understand @ModelAttribute was a result of Spring's decision to combine several annotations into one. It became clearer once I split it into several smaller annotations:
For parameter annotations, think of @ModelAttribute as the equivalent of @Autowired + @Qualifier ie it tries to retrieve a bean with the given name from the Spring managed model. If the named bean is not found, instead of throwing an error or returning null , it implicitly takes on the role of @Bean ie Create a new instance using the default constructor and add the bean to the model.
For method annotations, think of @ModelAttribute as the equivalent of @Bean + @Before , ie it puts the bean constructed by user's code in the model and it's always called before a request handling method.
Figuratively, I see @ModelAttribute as the following (please don't take it literally!!):
@Bean("person")
@Before
public Person createPerson(){
return new Person();
}
@RequestMapping(...)
public xxx handlePersonRequest( (@Autowired @Qualifier("person") | @Bean("person")) Person person, xxx){
...
}
As you can see, Spring made the right decision to make @ModelAttribute an all-encompassing annotation; no one wants to see an annotation smorgasbord.
For my style, I always use @ModelAttribute to catch object from spring form jsp. for example, I design form on jsp page, that form exist with commandName
<form:form commandName="Book" action="" methon="post">
<form:input type="text" path="title"></form:input>
</form:form>
and I catch the object on controller with follow code
public String controllerPost(@ModelAttribute("Book") Book book)
and every field name of book must be match with path in sub-element of form
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