Spring --- Validation

一） Validator接口
Spring的Validation功能设计很简单。使用Validator功能即可：

Java代码

1. public class Person {
2. private String name;
3. private int age;
4. // the usual getters and setters...
5. }
6. public class PersonValidatorimplements Validator {
7. /**
8. * This Validator validates just Person instances
9. */
10. public boolean supports(Class clazz) {
11. return Person.class.equals(clazz);
12. }
13. public void validate(Object obj, Errors e) {
14. ValidationUtils.rejectIfEmpty(e, "name", "name.empty");
15. Person p = (Person) obj;
16. if (p.getAge() < 0) {
17. e.rejectValue("age", "negativevalue");
18. } else if (p.getAge() >110) {
19. e.rejectValue("age", "too.darn.old");
20. }
21. }
22. }

public class Person {  private String name;  private int age;  // the usual getters and setters...}public class PersonValidator implements Validator {  /**  * This Validator validates just Person instances  */  public boolean supports(Class clazz) {   return Person.class.equals(clazz);  }  public void validate(Object obj, Errors e) {    ValidationUtils.rejectIfEmpty(e, "name", "name.empty");    Person p = (Person) obj;    if (p.getAge() < 0) {      e.rejectValue("age", "negativevalue");    } else if (p.getAge() > 110) {      e.rejectValue("age", "too.darn.old");    }  }}

Spring的Validate策略就是一个类（Person）对应一个校验类（PersonValidator）。至于校验类的绑定，可以代码中显式的调用，也可以是采用annotation。个人比较推荐用annotation的方法。而如果在一个类的校验中需要用到另一个类的校验，我们可以这样写：

Java代码

1. public class CustomerValidatorimplements Validator {
2. private final Validator addressValidator;
3. public CustomerValidator(Validator addressValidator) {
4. if (addressValidator == null) {
5. throw new IllegalArgumentException(
6. "The supplied [Validator] is required and must not be null.");
7. }
8. if (!addressValidator.supports(Address.class)) {
9. throw new IllegalArgumentException(
10. "The supplied [Validator] must support the validation of [Address] instances.");
11. }
12. this.addressValidator = addressValidator;
13. }
14. /**
15. * This Validator validates Customer instances, and any subclasses of Customer too
16. */
17. public boolean supports(Class clazz) {
18. return Customer.class.isAssignableFrom(clazz);
19. }
20. public void validate(Object target, Errors errors) {
21. ValidationUtils.rejectIfEmptyOrWhitespace(errors, "firstName","field.required");
22. ValidationUtils.rejectIfEmptyOrWhitespace(errors, "surname","field.required");
23. Customer customer = (Customer) target;
24. try {
25. errors.pushNestedPath("address");
26. ValidationUtils.invokeValidator(this.addressValidator,customer.getAddress(), errors);
27. } finally {
28. errors.popNestedPath();
29. }
30. }
31. }