SPRINGMVC @ModelAttribute Study

SPRINGMVC @ModelAttribute Study Blog Category:

• Spring

@ModelAttribute binding request parameters to a Command object

@ModelAttribute one has the following three functions:

① bind request parameter to command object: When placed on the parameter of a function processing method, it is used to bind multiple request parameters to a command object, thus simplifying the binding

and automatically exposed to model data for use in view page presentations;

② exposing a form reference object to model data: when placed on a processor's general method (non-functional processing method), prepares the form reference to be presented for the form

object, such as the city in which you want to select when registering, and automatically add a function before you perform a functional processing method (@RequestMapping annotation)

To the model object for use when the view page is displayed;

③ Exposure @requestmapping method returns a value of model data: when placed on the return value of a function processing method, the return value of the exposed function processing method is

Model data for use when the view page is displayed.

binding request parameters to a specified object

Java code

1. Public String test1 (@ModelAttribute ("user") Usermodel user)

It's just that there's one more annotation @modelattribute ("user"), whose purpose is to add the bound command object to the model object with a name of "user" for use in the View page display. We can now use ${user.username} on the view page to get the properties of the bound Command object.

If the request parameter contains "? USERNAME=ZHANG&PASSWORD=123&WORKINFO.CITY=BJ", it is automatically bound to the city property of the Workinfo property in user.

Java code

1. @RequestMapping (value="/model2/{username}")
2. Public String test2 (@ModelAttribute ("model") Databindertestmodel model)

URI template variables can also be automatically bound to the Command object when you request a URL that contains "bool=yes&schooinfo.specialty=computer&hobbylist[0]=program& Hobbylist[1]=music&map[key1]=value1&map[key2]=value2&state=blocked "is automatically bound to the Command object. The URI template variable has a high priority when the URI template variable and the request parameter have the same name.

second, exposing the form reference object as model data

Java code

2. /**
4. * After setting this annotation you can use the HB object (List) collection directly on the front page
6. * @return
8. */
10. @ModelAttribute ("HB")
12. Public list<string> hobbieslist () {
14. list<string> hobbise = new linkedlist<string> ();
16. Hobbise.add ("basketball");
18. Hobbise.add ("Football");
20. Hobbise.add ("tennis");
22. return hobbise;
24. }

JSP pages show up

Java code

2. <br>
4. Initialized data: ${HB}
6. <br>
10. <c:foreach items="${HB}" var="hobby" varstatus="vs" >
12. <c:choose>
14. <c:when test="${hobby = = ' basketball '}" >
16. Basketball <input type="checkbox" Name="Hobbies" value="basketball" >
18. </c:when>
20. <c:when test="${hobby = = ' Football '}" >
22. Football <input type="checkbox" Name="Hobbies" value="Football" >
24. </c:when>
26. <c:when test="${hobby = = ' tennis '}" >
28. Tennis <input type="checkbox" Name="Hobbies" value= "Tennis" >
30. </c:when>
32. </c:choose>
34. </c:forEach>

Note:

1. The contents of a set can be displayed in this way

2, the above JSP code is using JSTL, need to import JSTL related jar package

<% @taglib prefix= "C" uri= "Http://java.sun.com/jsp/jstl/core"%>

Iii. Exposure @requestmapping method return value is model data

Java code

1. Public @ModelAttribute ("user2") Usermodel test3 (@ModelAttribute ("user2") Usermodel user)

You can see that the return value type is a command object type, and through @modelattribute ("user2") annotations, the return value is exposed to the model data (named User2) for use in the view display

The return value of the @ModelAttribute annotation overrides the command object with the same name as the @modelattribute annotation in the @requestmapping annotation method

SPRINGMVC @ModelAttribute Study