How to implement correct data binding in controller?

Question

I have a jsp page which combines User object using forms. On the last form I'm trying to get Collection<Permission>. But when I'm trying to pass data to controller I'm getting 400 Error because of:

Field error in object 'user' on field 'permissions':
rejected value [add,view];
codes [typeMismatch.user.permissions,typeMismatch.permissions,typeMismatch.java.util.Collection,typeMismatch];
arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [user.permissions,permissions];
arguments [];
default message [permissions]];
default message [Failed to convert property value of type 'java.lang.String[]' to required type 'java.util.Collection' for property 'permissions'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [it.marco.javaproject.domain.Permission] for property 'permissions[0]': no matching editors or conversion strategy found]

Here is my jsp form:

<form:form action="/user/permission" method="POST" modelAttribute="user">
   <form:checkboxes path="permissions" items="${permissions}" delimiter=<br>"/>
   <form:hidden path="email"/>
   <form:hidden path="password"/>
   <form:hidden path="name"/>
   <input type="submit" value="Next" name="next"/>
</form:form>

Part of controller:

public String processRoleForm(@ModelAttribute("user") User user, ModelMap model) {
    model.addAttribute("permissions", userService.getPermissions());
    return "user/form/permissionForm";
}

Permission class:

@Entity
@Table(name = "permission")
public class Permission implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "name")
    private String name;

If I'm not mistaken I need to use some kind of data binder in my controller. How to implement it? How to properly translate String[] to Collection of Permission?

user3279337 · Accepted Answer · 2014-03-12 19:13:51Z

1

I find simple solution. Here it is:

@InitBinder
public void initBinder(WebDataBinder binder) {
    binder.registerCustomEditor(Permission.class, new PropertyEditorSupport() {
        @Override
        public void setAsText(String id) throws IllegalArgumentException {
            setValue(userService.getPermission(Integer.parseInt(id)));
        }
    });
}

answered Mar 12, 2014 at 19:13

user3279337

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1 Comment

CodeChimp Over a year ago

This would be my preferred way, but you could have also referenced each permission individually by indexing them like path="permissions[0].value". However, doing that would mean that you would need to do a LOT of cleanup on the backend to "clean" unchecked items. I'd say your are WAY better off writing a proper binding for it and let it be handled that way so you get a complete list without having to do cleanup.

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