spring mvc nested model validation

Question

I have two models : User,Project

public class Project{
    private int id;
    @NotEmpty(message="Project Name can not be empty")
    private String name;
    private User manager;
    private User operator;
    //getter/setter omitted
}

public class User{
    private int id;
    private String name;
    //omit other properties and getter/setter
}

Now, when I create a new Project, I will submit the following parameters to ProjectController:

projects?name=jhon&manager.id=1&operator.id=2...

Then I will create a new Project object and insert it to db.

However I have to validate the id of the manager and operator is valid,that's to say I will validate that if there is matched id in the user table.

So I want to know how to implement this kind of validation?

---

update1:using validator

This is the form for create new project:

<sf:form method="${project.id==0?'post':'put'}" commandName="project" action="${context}${action}">
    Manager:<sf:input path="manager.id" />  <sf:errors path="manager.id" /> <br />
    Operator:<sf:input path="operator.id" />    <sf:errors path="operator.id" />    <br />
    Name:<sf:input path="name" />   <sf:errors path="name" />   <br />
    <input type="submit" value="Submit" />
</sf:form>


@Override
public void validate(Object obj, Errors errors) {
    User user = (User) obj;
    int id=user.getId();
    User u=userDao.query(id);
    if(u==null){
        errors.rejectValue("id", "user does not exist!");
    }
}

It seems that this validator works.

However,the error message can not be displayed in the form.

Then though debug I inspect the result object and I found this:

org.springframework.validation.BeanPropertyBindingResult: 2 errors
Field error in object 'project' on field 'id': rejected value [0]; codes [user does not exist!.project.id,user does not exist!.id,user does not exist!.int,user does not exist!]; arguments []; default message [null]
Field error in object 'project' on field 'id': rejected value [0]; codes [user does not exist!.project.id,user does not exist!.id,user does not exist!.int,user does not exist!]; arguments []; default message [null]

It seems that the result does have errors,but it's path is project.id while in my form it is project.manager.id

How to fix?

Answer 1

I did what Jerome Dalbert suggested and in addition added a custom BeanValidator for delegating the actual work of validating to a JSR 303 implementation.

The prefix is used to denote the path of the property in the form.

@Component
public class BeanValidator implements org.springframework.validation.Validator, InitializingBean {    

 private Validator validator;
 public void afterPropertiesSet() throws Exception {
  ValidatorFactory validatorFactory = Validation.buildDefaultValidatorFactory();
  validator = validatorFactory.usingContext().getValidator();
 }

 public boolean supports(Class clazz) {
  return true;
 }

 public void validate(Object target, Errors errors, String prefix) {
  Set<ConstraintViolation<Object>> constraintViolations = validator.validate(target);
  for (ConstraintViolation<Object> constraintViolation : constraintViolations) {
   String propertyPath = constraintViolation.getPropertyPath().toString();
   String message = constraintViolation.getMessage();
   errors.rejectValue(prefix + "." + propertyPath, "", message);
  }
 }

 public void validate(Object target, Errors errors) {
  validate(target, errors, "");
 }
}

and here how I used it in the UserValidator:

@Component
public class UserValidator implements Validator {

 @Autowired
 BeanValidator beanValidator;

 @Override
 public boolean supports(Class<?> clazz) {
  return User.class.equals(clazz);
 }

 @Override
 public void validate(Object target, Errors errors) {
  User user = (User) target;
  beanValidator.validate(user.getAddress(), errors, "address");
 }
}

References:

• http://blog.trifork.com/2009/08/04/bean-validation-integrating-jsr-303-with-spring/

Answer 2

Actually what you need to do is add @Valid on

private User manager;
private User operator;

like this

@Valid
private User manager;
@Valid
private User operator;

Answer 3

Here's one possible solution.

Create the class below :

...
import org.springframework.validation.Validator;
...

@Component
public class ProjectValidator implements Validator {

    @Override
    public boolean supports(Class<?> clazz) {
        return Project.class.equals(clazz);
    }

    @Override
    public void validate(Object target, Errors errors) {
        Project project = (Project) target;

        /* Do your checks here */
        ...

        if (managerIdDoesNotMatch) {
            errors.rejectValue("manager.id", "your_error_code");
        }

        ...

        if (operatorIdDoesNotMatch) {
            errors.rejectValue("operator.id", "your_error_code");
        }

        ...
    }
}

And in your controller do something like :

...
public class ProjectController {

    @Autowired
    ProjectValidator projectValidator;

    ...

    @RequestMapping(...)
    public String yourCreateMethod(..., @ModelAttribute @Valid Project project, BindingResult result) {
        projectValidator.validate(project, result);           

        if (result.hasErrors()){
          // do something
        }
        else {
          // do something else
        }
    }

}

This should get you started. You could instantiate/set the validator differently, have a a user sub-validator, but you get the general idea.

References :

• Latest Spring validation documentation
• This Stack Overflow post about how to perform validation

Answer 4

In your Controller you can add a custom validator:

@InitBinder
protected void initBinder(WebDataBinder binder) {
    binder.setValidator(new ProjectValidator());
}

In this validator, you could check the User objects or delegate to a UserValidator, as done here in the last paragraph before section 6.3