Spring MVC binding parameters to backing object

Question

I am using Spring MVC and in my controller, I want to be able to automatically bind incoming parameters to my Java object. It seems like this should be pretty easy to do. The only wrinkle is that the incoming parameter names (e.g. "username") may not match up exactly with the field name in the java object (e.g. "name").

From the Spring documentation (http://static.springsource.org/spring/docs/2.5.6/reference/mvc.html):

"Spring Web MVC allows you to use any object as a command or form object.... All this means that you don't need to duplicate your business objects' properties as simple, untyped strings in your form objects just to be able to handle invalid submissions, or to convert the Strings properly. Instead, it is often preferable to bind directly to your business objects. "

How do I actually do this? Any code or links appreciated.

For example, my business object

public class User {
  private String username;
  private String password;

  //getters and setter
}

The request my controller is handling:

example.com/login?name=Steve&pw=1234

I would like to bind "Steve" to User.username and "1234" to User.password.

Thanks.

Answer 1

example.com/login?username=Steven&password=1234

You can't expect spring MVC to do automatic binding when the property names don't match up. That's just not logical.

Answer 2

EDIT: Do what Kaleb said, overriding formBackingObject is cleaner.

I'll leave this note though:

However, if you have any control over both sides, I strongly recommend making the name consistent. Convention over configuration.

Answer 3

If I remember correctly, you can override public Object formBackingObject(HttpServletRequest request) and manually setup your command POJO.

Answer 4

If you want to bind request to the POJO you may need to extend AbstractCommandController or if you have a form - SimpleFormController. I believe you will need the servlet version from org.springframework.web.servlet.mvc package.

• use setCommandClass() to setup the correct type of your backing bean in controller constructor, ie POJO:

  setCommandClass(User.class);

• formBackingBean() used to create new instance of the POJO, that would be used by controller.

• controller is responsible for mapping request parameters to the POJO fields.
• if mapping is not working good for you, than override formBackingBean() or onBind() methods to read request paratemers and put values to POJO.