How to autowire service in ConstraintValidator

问题

I'm writting my application using Spring MVC. I want to validate is e-mail exists in database when user is registering. I've written my own annotation constraint named UniqueEmail.

My User entity User.java:

@Entity
@Table(name="users")
public class User {

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

    @Column(name = "email", length = 100, nullable = false, unique = true)
    @NotEmpty
    @Email
    @UniqueEmail(message = "E-mail is not unique")
    private String email;

    @Column(name = "password", nullable = false)
    @NotEmpty
    @Size(min = 5, message = "size must be more 5")
    private String password;
}

My annotation constraint UniqueEmail.java:

@Target({FIELD})
@Retention(RUNTIME)
@Constraint(validatedBy = UniqueEmailValidator.class)
@Documented
public @interface UniqueEmail {
    String message() default "Email is exist";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};
}

My validator UniqueEmailValidator.java:

@Component
public class UniqueEmailValidator implements ConstraintValidator<UniqueEmail, String> {

    @Autowired
    private UserService userService;

    @Override
    public void initialize(UniqueEmail uniqueEmail) {
    }

    @Override
    public boolean isValid(String s, ConstraintValidatorContext constraintValidatorContext) {
        try {
            return userService.isExistEmail(s);
        } catch (Exception e) {
            System.out.println(e);
            return false;
        }
    }
}

This code works in application.

When I run my test code its return NullPointerException. In my validation class userService is null.

I've read http://docs.spring.io/spring/docs/3.0.0.RC3/reference/html/ch05s07.html but cannot any solution.

Any idea?

Update

I use JUnit. UserClassTest.java

@ContextConfiguration("file:src/main/webapp/WEB-INF/mvc-dispatcher-servlet.xml")
public class UserClass {

    private static Validator validator;

    @BeforeClass
    public static void setup() {
        ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
        validator = factory.getValidator();
    }

    @Test
    public void emailIsUnique() {

        User user = new User();
        user.setEmail("mail@example.com"); // I've written exist email in DB.

        Set<ConstraintViolation<User>> constraintViolations = validator.validateProperty(user, "email");

        assertEquals(1, constraintViolations.size());
        assertEquals("E-mail is not unique", constraintViolations.iterator().next().getMessage());
    }
}

Update

<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:context="http://www.springframework.org/schema/context"
   xmlns:mvc="http://www.springframework.org/schema/mvc"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">

<context:component-scan base-package="ru.yadoka"/>

<import resource="db/db-config.xml"/>

<!-- Apache tiles -->
<bean id="tilesConfigurer"
      class="org.springframework.web.servlet.view.tiles3.TilesConfigurer">
    <property name="definitions">
        <list>
            <value>/WEB-INF/tiles.xml</value>
        </list>
    </property>
</bean>

<bean id="viewResolver"
      class="org.springframework.web.servlet.view.UrlBasedViewResolver">
    <property name="viewClass" value="org.springframework.web.servlet.view.tiles3.TilesView"/>
</bean>

<!-- Mapping resources from theme -->
<mvc:resources mapping="/css/**" location="/resources/css/"/>
<mvc:resources mapping="/js/**" location="/resources/js/"/>
<mvc:resources mapping="/fonts/**" location="/resources/
<mvc:annotation-driven/>

回答1:

Don't you have a Validator configured in your bean context. If you are bootstrapping Validator via Validation.buildDefaultValidatorFactory(); you are bypassing the Spring mechanism and you get a Validator which is not aware of Spring beans and components. Hence injection is not working. In your test you want to get hold of the Spring provided Validator.

回答2:

If your main code is working, then it should be straight forward to get your test working. You need to use @ContextConfiguration on your test class, see this for more details: http://docs.spring.io/spring/docs/3.2.x/spring-framework-reference/html/testing.html

In general, there are 2 ways to test this:

• unit test
• integration test

For unit test, you need to create an instance of the UniqueEmailValidator and set a UserService on that instance (normally a mock UserServer).

For integration test, you need to have the spring context initialized as I mentioned above.

回答3:

You can call injection all @Autowired service:

@Override
public void initialize(UniqueEmail uniqueEmail) {
   org.springframework.web.context.support.SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
}

来源：https://stackoverflow.com/questions/21338883/how-to-autowire-service-in-constraintvalidator