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Testing custom JsonDeserializer in Jackson / SpringBoot

I am trying to write a unit test to a custom deserializer that is instantiated using a constructor with an #Autowired parameter and my entity marked with #JsonDeserialize. It works fine in my integration tests where a MockMvc brings up spring serverside.
However with tests where objectMapper.readValue(...) is being called, a new instance of deserializer using default constructor with no parameters is instantiated. Even though
#Bean
public MyDeserializer deserializer(ExternalObject externalObject)
instantiates wired version of deserializer, real call is still passed to empty constructor and context is not being filled up.
I tried manually instantiating of a deserializer instance and registering it in ObjectMapper, but it only works if I remove #JsonDeserialize from my entity class (and it breaks my integration tests even if I do the same in my #Configuration class.) - looks related to this: https://github.com/FasterXML/jackson-databind/issues/1300
I can still test the deserializer behavior calling deserializer.deserialize(...) directly, but this approach doesn't work for me in tests that are not Deserializer's unit tests...
UPD: working code below
import com.fasterxml.jackson.annotation.JacksonInject;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.cfg.HandlerInstantiator;
import com.github.tomakehurst.wiremock.common.Json;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.json.JsonTest;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.web.context.support.SpringBeanAutowiringSupport;
import java.io.IOException;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.ArgumentMatchers.eq;
import static org.mockito.Mockito.doReturn;
import static org.mockito.Mockito.mock;
#JsonTest
#RunWith(SpringRunner.class)
public class JacksonInjectExample {
private static final String JSON = "{\"field1\":\"value1\", \"field2\":123}";
public static class ExternalObject {
#Override
public String toString() {
return "MyExternalObject";
}
}
#JsonDeserialize(using = MyDeserializer.class)
public static class MyEntity {
public String field1;
public String field2;
public String name;
public MyEntity(ExternalObject eo) {
name = eo.toString();
}
#Override
public String toString() {
return name;
}
}
#Component
public static class MyDeserializer extends JsonDeserializer<MyEntity> {
#Autowired
private ExternalObject external;
public MyDeserializer() {
SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
}
public MyDeserializer(#JacksonInject final ExternalObject external) {
this.external = external;
}
#Override
public MyEntity deserialize(JsonParser p, DeserializationContext ctxt) throws IOException,
JsonProcessingException {
return new MyEntity(external);
}
}
#Configuration
public static class TestConfiguration {
#Bean
public ExternalObject externalObject() {
return new ExternalObject();
}
#Bean
public MyDeserializer deserializer(ExternalObject externalObject) {
return new MyDeserializer(externalObject);
}
}
#Test
public void main() throws IOException {
HandlerInstantiator hi = mock(HandlerInstantiator.class);
MyDeserializer deserializer = new MyDeserializer();
deserializer.external = new ExternalObject();
doReturn(deserializer).when(hi).deserializerInstance(any(), any(), eq(MyDeserializer.class));
final ObjectMapper mapper = Json.getObjectMapper();
mapper.setHandlerInstantiator(hi);
final MyEntity entity = mapper.readValue(JSON, MyEntity.class);
Assert.assertEquals("MyExternalObject", entity.name);
}
}

I don't know how to set this particularly using Jackson injection, but you can test it using spring Json tests. I think this method is closer to the real scenario and much more simplier. Spring will load only related to serialization/deserialization beans, thus you have to provide only custom beans or mocks instead them.
#JsonTest
public class JacksonInjectExample {
private static final String JSON = "{\"field1\":\"value1\", \"field2\":123}";
#Autowired
private JacksonTester<MyEntity> jacksonTester;
#Configuration
public static class TestConfiguration {
#Bean
public ExternalObject externalObject() {
return new ExternalObject();
}
}
#Test
public void test() throws IOException {
MyEntity result = jacksonTester.parseObject(JSON);
assertThat(result.getName()).isEqualTo("MyExternalObject");
}
If you would like to use mocks use following snippet:
#MockBean
private ExternalObject externalObject;
#Test
public void test() throws IOException {
when(externalObject.toString()).thenReturn("Any string");
MyEntity result = jacksonTester.parseObject(JSON);
assertThat(result.getName()).isEqualTo("Any string");
}

Very interesting question, it made me wonder how autowiring into jackson deserializers actually works in a spring application. The jackson facility that is used seems to be the HandlerInstantiator interface, which is configured by spring to the SpringHandlerInstantiator implementation, which just looks up the class in the application context.
So in theory you could setup an ObjectMapper in your unit test with your own (mocked) HandlerInstantiator, returning a prepared instance from deserializerInstance(). It seems to be fine to return null for other methods or when the class parameter does not match, this will cause jackson to create the instance on its own.
However, I do not think this is a good way to unit test deserialization logic, as the ObjectMapper setup is necessarily different from what is used during actual application execution. Using the JsonTest annotation as suggested in Anton's answer would be a much better approach, as you are getting the same json configuration that would be used during runtime.

Unit tests should not depend upon or invoke other major classes or frameworks. This is especially true if there are also integration or acceptance tests covering the functioning of the application with a particular set of dependencies as you describe. So it would be best to write the unit test so that it has a single class as its subject i.e. calling deserializer.deserialize(...) directly.
In this case a unit test should consist of instanciating a MyDeserializer with a mocked or stubbed ExternalObject, then testing that its deserialize() method returns a MyEntity correctly for different states of the JsonParser and DeserializationContext arguments. Mockito is really good for setting up mock dependencies!
By using an ObjectMapper in the unit test, quite a lot of code from the Jackson framework is also being invoked in each run - so the test is not verifying the contract of MyDeserializer, it is verifying the behaviour of the combination of MyDeserializer and a particular release of Jackson. If there is a failure of the test it won't be immediatly clear which of all the components involved is at fault. And because setting up the environment of the two frameworks together is more difficult the test will prove brittle over time and fail more often due to issues with the setup in the test class.
The Jackson framework is responsible for writing unit tests of ObjectMapper.readValue and constructors using #JacksonInject. For the 'other unit tests that are not Deserializer's unit tests' - it would be best to mock/stub the MyDeserializer (or other dependencies) for that test. That way the other class's logic is being isolated from the logic in MyDeserializer - and the other class's contracts can be verified without being qualified by the behaviour of code outside of the unit under test.

Custom declarative spring pojo validation during deserialization of request

I am looking for annotation to annotate pojo class which I need to validate during request deserialization. I am searching for annotation to pass as parameter class which will validate my pojo.
Implementation can look like that:
#ValidateAnnotation(class = ExampleClassValidator.class)
public class ExampleClass {
private String name;
}
Has anyone know any of spring annotation for that approach or some dependency which offer that declarative validation ? I am asking because I cannot find any similar solution in documentation.

You can use #InitBinder to configure a validator based on the target of the method. Here's a simple example:
Annotation class:
package test.xyz;
import org.springframework.validation.Validator;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
#Retention(RetentionPolicy.RUNTIME)
public #interface ValidateAnnotation {
Class<? extends Validator> value();
}
The example class to be validated:
package test.xyz;
#ValidateAnnotation(ExampleClassValidator.class)
public class ExampleClass {
}
The validator class:
package test.xyz;
import org.springframework.validation.Errors;
public class ExampleClassValidator implements org.springframework.validation.Validator {
#Override
public boolean supports(Class<?> aClass) {
return ExampleClass.class.isAssignableFrom(aClass);
}
#Override
public void validate(Object o, Errors errors) {
}
}
And finally the controller class with the #InitBinder definition:
import org.springframework.stereotype.Controller;
import org.springframework.validation.Errors;
import org.springframework.validation.Validator;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import test.xyz.ExampleClass;
import test.xyz.ValidateAnnotation;
import javax.servlet.http.HttpServletRequest;
import javax.validation.Valid;
import java.util.Collections;
#Controller
public class ExampleController {
#RequestMapping(value="test-endpoint", method= RequestMethod.GET)
public #ResponseBody
Object testMethod(#Valid ExampleClass exampleClass, Errors errors) {
return Collections.singletonMap("success", true);
}
#InitBinder
public void initBinder(WebDataBinder binder, HttpServletRequest request) throws IllegalAccessException, InstantiationException {
Class<?> targetClass = binder.getTarget().getClass();
if(targetClass.isAnnotationPresent(ValidateAnnotation.class)) {
ValidateAnnotation annotation = targetClass.getAnnotation(ValidateAnnotation.class);
Class<? extends Validator> value = annotation.value();
Validator validator = value.newInstance();
binder.setValidator(validator);
}
}
}
Explanation:
You can use the WebDataBinder's getTarget method to access the target to be validated. From there it is straightforward to check the annotation on the class, get the validator class, and set it on the binder. I believe you can also use the #ControllerAdvice annotation to configure a global InitBinder. As a disclaimer, I don't know if it is recommended to access the binder target within the InitBinder, but I haven't had any issues the few times I've done so.

For normal validation you can annotate your class with the annotations from the javax.validation.constraints package, like javax.validation.constraints.NotEmpty. For custom validation, you can make your own annotation that will call a custom validator that you write.
For example, if you wanted to create a validator that makes sure a field is nine characters long you could do the following:
First, create your custom validation annotation.
#Documented
#Constraint(validatedBy = NineCharactersValidator.class)
#Target( { ElementType.METHOD, ElementType.FIELD })
#Retention(RetentionPolicy.RUNTIME)
public #interface NineCharactersOnly {
String message() default "This field must contain exactly nine characters";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
Next, create your custom validator:
public class NineCharactersValidator implements ConstraintValidator<NineCharactersOnly, String> {
#Override
public void initialize(NineCharactersOnly contactNumber) {
}
#Override
public boolean isValid(String contactField, ConstraintValidatorContext cxt) {
return contactField != null && contactField.length() == 9;
}
}
Next, use the annotation on fields that need to be constrained on your pojo.
public class ExampleClass {
#NineCharactersOnly
private String fieldThatMustBeNineCharacters;
}
Next, mark your method parameters in the controller with #Valid so they will be validated by Spring:
#RestController
public class CustomValidationController {
#PostMapping("/customValidationPost")
public ResponseEntity<String> customValidation(#Valid ExampleClass exampleClass, BindingResult result, Model m) {
// we know the data is valid if we get this far because Spring automatically validates the input and
// throws a MethodArgumentNotValidException if it's invalid and returns an HTTP response of 400 (Bad Request).
return ResponseEntity.ok("Data is valid");
}
}
Finally, if you want custom logic for handling validation errors instead of just sending a 400, you can create a custom validation handler method.
#ResponseStatus(HttpStatus.BAD_REQUEST)
#ExceptionHandler(MethodArgumentNotValidException.class)
public Map<String, String> handleValidationException(MethodArgumentNotValidException e) {
Map<String, String> errors = new HashMap<>();
d.getBindingResult().getAllErrors().forEach((error) -> {
String fieldName = ((FieldError) error).getField();
String errorMessage = error.getDefaultMessage();
errors.put(fieldName, errorMessage);
});
return errors;
}

Maybe writing your custom annotation and using Spring AOP will help you. Spring AOP is quite simple.

I found pretty good solution but in one place i used reflection :(
Please feel free to comment and rate this solution, is it good enough or something could be done better.
I had create own annotation
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.TYPE)
public #interface Validator {
Class<? extends org.springframework.validation.Validator> validator();
}
I next step I extend LocalValidatorFactoryBean to override validate method and here I was forced to use reflection to get class from annotation.
#Component
#RequiredArgsConstructor
class CustomLocalValidatorFactoryBean extends LocalValidatorFactoryBean {
private final Map<Class<? extends Validator>, Validator> validators;
#Override
public void validate(Object target, Errors errors, Object... validationHints) {
Class<? extends Validator> validatorKey = target.getClass().getAnnotation(com.validation.validator.Validator.class).validator();
Optional.ofNullable(validators.get(validatorKey)).ifPresentOrElse(
validator ->
validator.validate(target, errors),
() -> super.validate(target, errors, validationHints)
);
}
}
I annotate pojo with my annotation to specify validator.
#Data
#Validator(validator = PersonValidator.class)
public class PersonDto {
private final String name;
private final String surname;
private final Integer age;
}
As you can see in my CustomLocalValidatorFactoryBean I injected a map of validators, in this map i store validators assigned to key which is the class of this validator. This class i specify in annotation in pojo to fetch suitable validator for currect validate target. And this is my configuration of validatos map.
#Configuration
class ValidatorConfig {
#Bean
Map<Class<? extends Validator>, Validator> validators() {
var validators = new HashMap<Class<? extends Validator>, Validator>();
validators.put(PersonValidator.class, new PersonValidator());
return validators;
}
}
I specify custom #RestControllerAdvice and override method handleMethodArgumentNotValid.
#RestControllerAdvice
class GlobalExceptionHandler extends ResponseEntityExceptionHandler {
#Override
protected ResponseEntity<Object> handleMethodArgumentNotValid(MethodArgumentNotValidException ex, HttpHeaders headers,
HttpStatus status, WebRequest request) {
Map<String, String> errors = new HashMap<>();
ex.getBindingResult().getAllErrors().forEach((error) -> {
String fieldName = error.getCode();
String errorMessage = error.getDefaultMessage();
errors.put(fieldName, errorMessage);
});
return new ResponseEntity<>(errors, HttpStatus.BAD_REQUEST);
}
}
And this is my validator, it could be bean with dao acces but it could also be simple pojo.
public class PersonValidator implements Validator {
#Override
public boolean supports(Class<?> aClass) {
return PersonDto.class.isAssignableFrom(aClass);
}
#Override
public void validate(Object object, Errors errors) {
Optional.of(object).map(obj -> (PersonDto) obj).ifPresent(person -> {
Optional.ofNullable(person.getName())
.filter(name -> Strings.isNotBlank(name) && name.length() >= 3)
.ifPresentOrElse(name -> doNothing(), () -> errors.reject("person.name", "name of person is invalid!"));
});
}
}
What do you think about that configuration, is it cannon on sparrow or you just like that solution ?

Autowire dependency in builder class with static instantiation method

I'm pondering this builder class that should calculate a hash from the field values. Maybe this in itself is wrong for starters, but at the moment it seems to me that it belongs there because I'm striving to an immutable Article.
I would like to autowire/inject ArticleMD5HashCalculator but when I put #Autowired on the field, IntelliJ complains: field injection is not recommended. Constructor injection is not possible because it's a builder pattern class, which means it has a private constructor without parameters and a static method for instantiation where it would be awkward to pass in hashCalculator.
The builder is injected into a scraper. The scraper will reuse the same builder for many articles. When Spring creates the builder with prototype scope, the builder will carry old values when the next article doesn't overwrite the old values.
New'ing the hashCalculator results is a hard dependency, making it impractical to inject mocks. What is the best way to handle this situation?
Here's the code of how it is now:
import org.observer.media.utils.ArticleMD5HashCalculator;
import org.observer.media.utils.MD5HashCalculator;
import java.time.ZonedDateTime;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
public class ArticleBuilder {
private ArticleMD5HashCalculator hashCalculator;
private String headline;
private String subheading;
private String lead;
// other article fields...
private ArticleBuilder() {
// This seems wrong.
this.hashCalculator = new ArticleMD5HashCalculator(new MD5HashCalculator());
}
public static ArticleBuilder article() {
return new ArticleBuilder();
}
public ArticleBuilder withHeadline(String headline) {
this.headline = headline;
return this;
}
//Other with-methods...
public Article build() {
// calculateHash() is called in the 9th argument.
return new Article(headline, subheading, lead, body, images, quotations, subArticles, url, calculateHash(), author, sources, category, subjects, index, medium, company, datePublished, dateFetched);
}
private String calculateHash() {
return hashCalculator.hash(headline, subheading, lead, body, quotations, datePublished, dateFetched);
}
}

Assumptions:
There is one to one relationship between ArticleBuilder and ArticleMD5HashCalculator. Meaning you don't plan to inject different instances of hashCalculator into ArticleBuilder at different places in the project (essentially having multiple instances of ArticleBuilder)
You can change the ArticleBuilder impl as follows
public class ArticleBuilder {
private ArticleMD5HashCalculator hashCalculator;
public ArticleBuilder(ArticleMD5HashCalculator hashCalculator) {
this.hashCalculator = hashCalculator;
}
}
You can create a spring bean of type ArticleMD5HashCalculator and have this injected into a spring bean of type ArticleBuilder the following way.
#Configuration
public class ArticleConfig {
#Bean
public ArticleMD5HashCalculator articleMD5HashCalculator() {
return new ArticleMD5HashCalculator(new MD5HashCalculator());
}
#Bean
public ArticleBuilder() {
return new ArticleBuilder(articleMD5HashCalculator());
}
}
You can autowire ArticleBuilder elsewhere in your project and use it as a builder.
I am not sure why you made a private constructor and a static method to invoke that. I assume it is because you want a singleton ArticleBuilder. That can be achieved with the above approach. Correct me if I am wrong about this.
Update 1:
Based on the information you provided in the comments, you are injecting ArticleBuilder in a Scraper object and you want to have a way of getting a new instance of ArticleBuilder every time. You can use spring #Lookup annotation for that.
Stub implementation of Scraper class.
public class Scraper {
//assuming this is the method where you want to use ArticleBuilder
public void scrape() {
getArticleBuilder();
}
//You can even pass constructor arguments to this method.
//They will be used to match a constructor on the target bean and that gets invoked
#Lookup
public ArticleBuilder getArticleBuilder() {
//Spring creates a runtime implementation of this method.
return null;
}
}
You can call getArticleBuilder anytime you want a new instance of the bean. If it is declared prototype, you will always get a new instance of the bean.
But the only caveat with this is that Lookup annotation is not going to work with beans created with #Bean annotation. You alternate config may look like this.
#Component
#Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class ArticleBuilder {
#Autowired
private ArticleMD5HashCalculator hashCalculator;
public ArticleBuilder(ArticleMD5HashCalculator hashCalculator) {
this.hashCalculator = hashCalculator;
}
}
#Component
public class ArticleMD5HashCalculator {
public ArticleMD5HashCalculator(MD5HashCalculator hashCalculator) {
this.hashCalculator = hashCalculator;
}
}
beans.xml:
<beans>
<bean class="MD5HashCalculator" />
<!-- Fully qualified class name is needed -->
</beans>

Also due to convention used in Spring documentation please use constructor-based injection when possible.
The Spring team generally advocates constructor injection as it enables one to implement application components as immutable objects and to ensure that required dependencies are not null.
Full info (scroll a little): Spring DOCS

I brewed up this alternative approach to pull out the new'ing and to open a window for injecting mocks. The solution implies that the builder has to be instantiated and recreated by a factory.
The factory:
import org.observer.media.hash.ArticleHashCalculator;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.time.ZonedDateTime;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
#Component
public class ArticleBuilderFactory {
private ArticleHashCalculator articleHashCalculator;
#Autowired
public ArticleBuilderFactory(ArticleHashCalculator articleHashCalculator) {
this.articleHashCalculator = articleHashCalculator;
}
public ArticleBuilder create() {
return new ArticleBuilder(articleHashCalculator);
}
public class ArticleBuilder {
private ArticleHashCalculator articleHashCalculator;
private String headline;
private String subheading;
//...
private ArticleBuilder(ArticleHashCalculator articleHashCalculator) {
this.articleHashCalculator = articleHashCalculator;
}
public ArticleBuilderFactory.ArticleBuilder withIndex(int index) {
this.index = index;
return this;
}
public ArticleBuilderFactory.ArticleBuilder withHeadline(String headline) {
this.headline = headline;
return this;
}
//...
public Article build() {
return new Article(headline, subheading, lead, body, images, quotations, subArticles, url, calculateHash(), author, sources, category, subjects, index, medium, company, datePublished, dateFetched);
}
private String calculateHash() {
return articleHashCalculator.hash(headline, subheading, lead, body, quotations, datePublished, dateFetched);
}
}
}
Usage of the factory:
import org.junit.Test;
import org.junit.runner.RunWith;
import org.observer.media.hash.ArticleMD5HashCalculator;
import org.observer.media.hash.MD5HashCalculator;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringRunner;
import static org.assertj.core.api.Java6Assertions.assertThat;
#RunWith(SpringRunner.class)
#ContextConfiguration(classes = {
ArticleBuilderFactory.class,
MD5HashCalculator.class,
ArticleMD5HashCalculator.class
})
public class ArticleBuilderFactoryTest {
private static final String HEADLINE = "headline";
private static final String LEAD = "lead";
private static final String BODY = "body";
#Autowired
private ArticleBuilderFactory articleBuilderFactory;
#Autowired
private ArticleMD5HashCalculator hashCalculator;
#Test
public void build() {
ArticleBuilderFactory.ArticleBuilder articleBuilder = articleBuilderFactory.create();
Article article = articleBuilder
.withHeadline(HEADLINE)
.withLead(LEAD)
.withBody(BODY)
.build();
assertThat(article.getHeadline()).isEqualTo(HEADLINE);
assertThat(article.getLead()).isEqualTo(LEAD);
assertThat(article.getBody()).isEqualTo(BODY);
assertThat(article.getHash()).isEqualTo(hashCalculator.hash(HEADLINE, null, LEAD, BODY, null, null, null));
}
}
ArticleMD5HashCalculator has #Component:
#Component
public class ArticleMD5HashCalculator {
}

How to confirgure swagger to handle custom Controller-level PathVariable annotations?

In my Spring (4.3.2) project I'm using Swagger (2.7.0) to automatically generate docs and swagger-ui for my project. This worked great so far.
But now I determined that I need to be able to declare Path Variables at the Controller level (not method level). And I need to teach swagger to discover these path variables and add them to docs and swagger-ui.
I've created custom annotation
#Target(ElementType.TYPE)
#Retention(RetentionPolicy.RUNTIME)
public #interface HasCommonPathVariable {
/**
* The URI template variable to bind to.
*/
String name();
Class<?> type();
String defaultValue() default "";
}
And I'm using it like this:
#RestController
#Secured(SecurityConstants.ROLE_USER)
#RequestMapping(path = "/rest/api/v1/env/{envId}/asset-type")
#HasCommonPathVariable(name = "envId", type = Long.class)
public class AssetTypeRestController extends CustomRestControllerBase<Long, AssetTypeRow, AssetTypeService> {
// ... contorller code
}
I do not have controller methods that mentions parameters with Spring's PathVariable annotation, and the point is I'm not allowed to do so (it's due to the fact that I'm building micro-framework).
So question is: how to teach swagger to discover path variables described using custom annotation HasCommonPathVariable applied at the controller level?

Ok, I've figured it out. Here is the solution. This bean needs to be registered in the context. Swagger will discover this bean and use it as one of the plugins to enrich operations
import java.util.ArrayList;
import java.util.List;
import org.apache.log4j.Logger;
import org.springframework.core.annotation.Order;
import com.fasterxml.classmate.TypeResolver;
import com.google.common.base.Optional;
import springfox.documentation.builders.ParameterBuilder;
import springfox.documentation.schema.ModelRef;
import springfox.documentation.service.Parameter;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spi.service.OperationBuilderPlugin;
import springfox.documentation.spi.service.contexts.OperationContext;
import springfox.documentation.swagger.common.SwaggerPluginSupport;
#Order(SwaggerPluginSupport.SWAGGER_PLUGIN_ORDER + 1000)
public class CommonPathVariableOperationBuilderPlugin implements OperationBuilderPlugin {
protected Logger log = Logger.getLogger(getClass());
private TypeResolver typeResolver;
public CommonPathVariableOperationBuilderPlugin(TypeResolver typeResolver) {
this.typeResolver = typeResolver;
}
#Override
public boolean supports(DocumentationType delimiter) {
return true;
}
#Override
public void apply(OperationContext opCtx) {
List<Parameter> ret = new ArrayList<Parameter>();
Optional<HasCommonPathVariable> annSingle = opCtx.findControllerAnnotation(HasCommonPathVariable.class);
if (annSingle.isPresent()) {
ret.add(addParameter(annSingle.get()));
}
Optional<HasCommonPathVariables> annPlural = opCtx.findControllerAnnotation(HasCommonPathVariables.class);
if (annPlural.isPresent()) {
for (HasCommonPathVariable ann : annPlural.get().value()) {
ret.add(addParameter(ann));
}
}
opCtx.operationBuilder().parameters(ret);
}
private Parameter addParameter(HasCommonPathVariable ann) {
ParameterBuilder pb = new ParameterBuilder();
pb.parameterType("path").name(ann.name()).type(typeResolver.resolve(ann.type()));
pb.modelRef(new ModelRef("string"));
pb.required(true);
if (!"".equals(ann.defaultValue())) {
pb.defaultValue(ann.defaultValue());
}
return pb.build();
}
}

Use #Validated and #Valid with spring validator

I have a java bean being used to send JSON messages to a spring #RestController and I have bean validation setup and running just fine using #Valid. But I want to move to Protobuf/Thrift and move away from REST. It is an internal API and a lot of big companies have done away with REST internally. What this really means is that I no longer have control of the message objects - they are generated externally. I can't put annotations on them anymore.
So now my validation has to be programmatic. How do I do this? I have coded up a Validator and it works just great. But it doesn't use the nice #Valid annotation. I have to do the following:
#Service
public StuffEndpoint implements StuffThriftDef.Iface {
#Autowired
private MyValidator myValidator;
public void things(MyMessage msg) throws BindException {
BindingResult errors = new BeanPropertyBindingResult(msg, msg.getClass().getName());
errors = myValidator.validate(msg);
if (errors.hasErrors()) {
throw new BindException(errors);
} else {
doRealWork();
}
}
}
This stinks. I have to do this in every single method. Now, I can put a lot of that into one method that throws BindException and that makes it one line of code to add to every method. But that's still not great.
What I want is to see it look like this:
#Service
#Validated
public StuffEndpoint implements StuffThriftDef.Iface {
public void things(#Valid MyMessage msg) {
doRealWork();
}
}
And still get the same result. Remember, my bean has no annotations. And yes, I know I can use the #InitBinder annotation on a method. But that only works for web requests.
I don't mind injecting the correct Validator into this class, but I would prefer if my ValidatorFactory could pull the correct one based on the supports() method.
Is this possible? Is there a way to configure bean validation to actually use Spring validation instead? Do I have to hijack a Aspect somewhere? Hack into the LocalValidatorFactory or the MethodValidationPostProcessor?
Thanks.

Its pretty complicated thing to combine Spring validation and JSR-303 constrains. And there is no 'ready to use' way. The main inconvenience is that Spring validation uses BindingResult, and JSR-303 uses ConstraintValidatorContext as result of validation.
You can try to make your own validation engine, using Spring AOP. Let's consider, what we need to do for it. First of all, declare AOP dependencies (if you didn't yet):
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>4.2.4.RELEASE</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.8.8</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.8.8</version>
</dependency>
I'm using Spring of version 4.2.4.RELEASE, but of cause you can use your own. AspectJ needed for use aspect annotation. Next step, we have to create simple validator registry:
public class CustomValidatorRegistry {
private List<Validator> validatorList = new ArrayList<>();
public void addValidator(Validator validator){
validatorList.add(validator);
}
public List<Validator> getValidatorsForObject(Object o) {
List<Validator> result = new ArrayList<>();
for(Validator validator : validatorList){
if(validator.supports(o.getClass())){
result.add(validator);
}
}
return result;
}
}
As you see it is very simple class, which allow us to find validator for object. Now lets create annotation, that will be mark methods, that need to be validated:
package com.mydomain.validation;
#Target({ElementType.METHOD})
#Retention(RetentionPolicy.RUNTIME)
public #interface CustomValidation {
}
Because of standard BindingException class is not RuntimeException, we can't use it in overriden methods. This means we need define our own exception:
public class CustomValidatorException extends RuntimeException {
private BindingResult bindingResult;
public CustomValidatorException(BindingResult bindingResult){
this.bindingResult = bindingResult;
}
public BindingResult getBindingResult() {
return bindingResult;
}
}
Now we are ready to create an aspect that will do most of the work. Aspect will execute before methods, which marked with CustomValidation annotation:
#Aspect
#Component
public class CustomValidatingAspect {
#Autowired
private CustomValidatorRegistry registry; //aspect will use our validator registry
#Before(value = "execution(public * *(..)) && annotation(com.mydomain.validation.CustomValidation)")
public void doBefore(JoinPoint point){
Annotation[][] paramAnnotations =
((MethodSignature)point.getSignature()).getMethod().getParameterAnnotations();
for(int i=0; i<paramAnnotations.length; i++){
for(Annotation annotation : paramAnnotations[i]){
//checking for standard org.springframework.validation.annotation.Validated
if(annotation.annotationType() == Validated.class){
Object arg = point.getArgs()[i];
if(arg==null) continue;
validate(arg);
}
}
}
}
private void validate(Object arg) {
List<Validator> validatorList = registry.getValidatorsForObject(arg);
for(Validator validator : validatorList){
BindingResult errors = new BeanPropertyBindingResult(arg, arg.getClass().getSimpleName());
validator.validate(arg, errors);
if(errors.hasErrors()){
throw new CustomValidatorException(errors);
}
}
}
}
execution(public * *(..)) && #annotation(com.springapp.mvc.validators.CustomValidation) means, that this aspect will applied to any public methods of beans, which marked with #CustomValidation annotation. Also note, that to mark validated parameters we are using standard org.springframework.validation.annotation.Validated annotation. But of cause we could make our custom. I think other code of aspect is very simple and does not need any comments. Further code of example validator:
public class PersonValidator implements Validator {
#Override
public boolean supports(Class<?> aClass) {
return aClass==Person.class;
}
#Override
public void validate(Object o, Errors errors) {
Person person = (Person)o;
if(person.getAge()<=0){
errors.rejectValue("age", "Age is too small");
}
}
}
Now we have make tune the configuration and all ready to use:
#Configuration
#ComponentScan(basePackages = "com.mydomain")
#EnableAspectJAutoProxy(proxyTargetClass = true)
public class AppConfig{
.....
#Bean
public CustomValidatorRegistry validatorRegistry(){
CustomValidatorRegistry registry = new CustomValidatorRegistry();
registry.addValidator(new PersonValidator());
return registry;
}
}
Note, proxyTargetClass is true because we will use cglib class proxy.
Example of target method in service class:
#Service
public class PersonService{
#CustomValidation
public void savePerson(#Validated Person person){
....
}
}
Because of #CustomValidation annotation aspect will be applied, and because of #Validated annotation person will be validated. And example of usage of service in controller(or any other class):
#Controller
public class PersonConroller{
#Autowired
private PersonService service;
public String savePerson(#ModelAttribute Person person, ModelMap model){
try{
service.savePerson(person);
}catch(CustomValidatorException e){
model.addAttribute("errors", e.getBindingResult());
return "viewname";
}
return "viewname";
}
}
Keep in mind, that if you will invoke #CustomValidation from methods of PersonService class, validation will not work. Because it will invoke methods of original class, but not proxy. This means, that you can invoke this methods only from outside of class (from other classes), if you want validation to be working (eg #Transactional works same way).
Sorry for long post. My answer is not about 'simple declarative way', and possible you will do not need it. But I was curious resolve this problem.

I marked #Ken's answer as correct because it is. But I have taken it a little further and wanted to post what I have made. I hope anybody coming to this page will find it interesting. I might try to get it in front of the Spring folks to see if it might be something included in future releases.
The idea is to have a new annotation to replace #Valid. So I called it #SpringValid. Using this annotation would kick off the system put together above. Here are all the pieces:
SpringValid.java
package org.springframework.validation.annotation;
import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
#Target({METHOD, FIELD, CONSTRUCTOR, PARAMETER})
#Retention(RUNTIME)
public #interface SpringValid {
}
SpringValidationAspect.java
package org.springframework.validation;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.util.List;
#Aspect
#Component
public class SpringValidationAspect {
private SpringValidatorRegistry springValidatorRegistry;
#Autowired
public SpringValidationAspect(final SpringValidatorRegistry springValidatorRegistry) {
this.springValidatorRegistry = springValidatorRegistry;
}
public SpringValidatorRegistry getSpringValidatorRegistry() {
return springValidatorRegistry;
}
#Before("#target(org.springframework.validation.annotation.Validated) "
+ "&& execution(public * *(#org.springframework.validation.annotation.SpringValid (*), ..)) "
+ "&& args(validationTarget)")
public void beforeMethodThatNeedsValidation(Object validationTarget) {
validate(validationTarget);
}
private void validate(Object arg) {
List<Validator> validatorList = springValidatorRegistry.getValidatorsForObject(arg);
for (Validator validator : validatorList) {
BindingResult errors = new BeanPropertyBindingResult(arg, arg.getClass().getSimpleName());
validator.validate(arg, errors);
if (errors.hasErrors()) {
throw new SpringValidationException(errors);
}
}
}
}
Spring's examples show classes annotated with #Validated so I wanted to keep that. The above aspect only targets classes with #Validated at the class-level. And, just like when you use #Valid, it looks for the #SpringValid annotation stuck to a method parameter.
SpringValidationException.java
package org.springframework.validation;
import org.springframework.validation.BindingResult;
public class SpringValidationException extends RuntimeException {
private static final long serialVersionUID = 1L;
private BindingResult bindingResult;
public SpringValidationException(final BindingResult bindingResult) {
this.bindingResult = bindingResult;
}
public BindingResult getBindingResult() {
return bindingResult;
}
}
SpringValidatorRegistry.java
package org.springframework.validation;
import org.springframework.validation.Validator;
import java.util.ArrayList;
import java.util.List;
public class SpringValidatorRegistry {
private List<Validator> validatorList = new ArrayList<>();
public void addValidator(Validator validator) {
validatorList.add(validator);
}
public List<Validator> getValidatorsForObject(Object o) {
List<Validator> result = new ArrayList<>();
for (Validator validator : validatorList) {
if (validator.supports(o.getClass())) {
result.add(validator);
}
}
return result;
}
}
Just like the first answer, a place to register all classes that implement Spring's org.springframework.validation.Validator interface.
SpringValidator.java
package org.springframework.validation.annotation;
import org.springframework.stereotype.Component;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
#Target(ElementType.TYPE)
#Retention(RetentionPolicy.RUNTIME)
#Documented
#Component
public #interface SpringValidator {
}
This is just extra sauce to make it easier to register/find Validators. You could register all your Validators by hand, or you could find them via reflection. So this part is not required, I just thought it made things easier.
MyConfig.java
package com.example.config;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.validation.SpringValidationAspect;
import org.springframework.validation.SpringValidatorRegistry;
import org.springframework.validation.annotation.SpringValidator;
import java.util.Map;
import javax.validation.Validator;
#Configuration
public class MyConfig {
#Autowired
private ApplicationContext applicationContext;
#Bean
public SpringValidatorRegistry validatorRegistry() {
SpringValidatorRegistry registry = new SpringValidatorRegistry();
Map<String, Object> validators =
applicationContext.getBeansWithAnnotation(SpringValidator.class);
validators.values()
.forEach(v -> registry.addValidator((org.springframework.validation.Validator) v));
return registry;
}
#Bean
public SpringValidationAspect springValidationAspect() {
return new SpringValidationAspect(validatorRegistry());
}
}
See, scan your classpath and look for #SpringValidator classes and register them. Then register the Aspect and away you go.
Here is an example of such a Validator:
MyMessageValidator.java
package com.example.validators;
import com.example.messages.MyMessage;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;
import org.springframework.validation.annotation.SpringValidator;
#SpringValidator
public class MyMessageValidator implements Validator {
#Override
public boolean supports(Class<?> clazz) {
return MyMessage.class.isAssignableFrom(clazz);
}
#Override
public void validate(Object target, Errors errors) {
ValidationUtils.rejectIfEmpty(errors, "firstField", "{javax.validation.constraints.NotNull}",
"firstField cannot be null");
MyMessage obj = (MyMessage) target;
if (obj.getSecondField != null && obj.getSecondField > 100) {
errors.rejectField(errors, "secondField", "{javax.validation.constraints.Max}", "secondField is too big");
}
}
}
And here is the service class that uses the #SpringValid annotation:
MyService.java
package com.example.services;
import com.example.messages.MyMessage;
import org.springframework.validation.annotation.SpringValid;
import org.springframework.validation.annotation.Validated;
import javax.inject.Inject;
#Validated
public class MyService {
public String doIt(#SpringValid final MyMessage msg) {
return "we did it!";
}
}
Hope this makes sense for someone at some point. I personally think it is quite useful. A lot of companies are starting to move their internal APIs away from REST and to something like Protobuf or Thrift. You can still use Bean Validation but you have to use XML, and it isn't all that nice. So I hope this will be helpful to people who want to still do programmatic validation.

Hope it helps someone. I've got it working by adding the following configuration:
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
#Configuration
public class ValidatorConfiguration {
#Bean
public MethodValidationPostProcessor getMethodValidationPostProcessor(){
MethodValidationPostProcessor processor = new MethodValidationPostProcessor();
processor.setValidator(this.validator());
return processor;
}
#Bean
public LocalValidatorFactoryBean validator(){
return new LocalValidatorFactoryBean();
}
}
The service is then annotated the same way (#Validated on the class and #Valid on the parameter) and can be injected into another bean where the method can be called directly and validation happens.