I am trying to implement pagination to my Spring Data JPA repository in Spring Boot but I am stuck with the following exception when running uni tests:
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.domain.Pageable]: Specified class is an interface
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:982)
...
Could someone point out to me what am I missing here? This is my repository:
#Repository
public interface VenueRepository extends PagingAndSortingRepository<Venue, Long> {
public Page<Venue> findAll(Pageable pageable);
}
and controller:
#RestController
#RequestMapping("/venues")
public class VenueController {
#Autowired
private VenueRepository venueRepo;
#RequestMapping(method = RequestMethod.GET)
public ResponseEntity<Page<Venue>> getVenues(Pageable pageable) {
return new ResponseEntity<>(venueRepo.findAll(pageable), HttpStatus.OK);
}
}
and finally my test:
#Test
public void responseOkVenuesTest() throws Exception {
mvc.perform(get("/venues").accept(MediaType.APPLICATION_JSON_VALUE)).andExpect(status().isOk());
}
I spent couple of hours trying to make this work and am running out of ideas. Thank you for any tips!
Change your method getVenues in the way that you can pass the parameters to instantiate a PageRequest instead of passing Pageable :
#RequestMapping(method = RequestMethod.GET)
public ResponseEntity<List<Venue>> getVenues(int from,int to) {
return new ResponseEntity<>(
venueRepo.findAll((new PageRequest(from, to)), HttpStatus.OK).getContent();
}
In addition to #SEY_91's answer you might also like to use the following solution inspired with How to remove redundant Spring MVC method by providing POST-only #Valid? and used in my Spring Boot-driven application for long time.
In short, here is an annotation to annotate controller method parameters:
#Target(PARAMETER)
#Retention(RUNTIME)
public #interface PlainModelAttribute {
}
Now, just a method processor that would scan for parameters annotated with #PlainModelAttribute:
public final class PlainModelAttributeMethodProcessor
extends ModelAttributeMethodProcessor {
private final Map<TypeToken<?>, Converter<? super NativeWebRequest, ?>> index;
private PlainModelAttributeMethodProcessor(final Map<TypeToken<?>, Converter<? super NativeWebRequest, ?>> index) {
super(true);
this.index = index;
}
public static HandlerMethodArgumentResolver plainModelAttributeMethodProcessor(final Map<TypeToken<?>, Converter<? super NativeWebRequest, ?>> index) {
return new PlainModelAttributeMethodProcessor(index);
}
#Override
public boolean supportsParameter(final MethodParameter parameter) {
return parameter.hasParameterAnnotation(PlainModelAttribute.class) || super.supportsParameter(parameter);
}
#Override
protected Object createAttribute(final String attributeName, final MethodParameter parameter, final WebDataBinderFactory binderFactory,
final NativeWebRequest request) {
final TypeToken<?> typeToken = TypeToken.of(parameter.getGenericParameterType());
final Converter<? super NativeWebRequest, ?> converter = index.get(typeToken);
if ( converter == null ) {
throw new IllegalArgumentException("Cannot find a converter for " + typeToken.getType());
}
return converter.convert(request);
}
#Override
protected void bindRequestParameters(final WebDataBinder binder, final NativeWebRequest request) {
final HttpServletRequest servletRequest = request.getNativeRequest(HttpServletRequest.class);
if ( !isSafe(resolve(servletRequest.getMethod())) ) {
((ServletRequestDataBinder) binder).bind(servletRequest);
}
}
private static HttpMethod resolve(final String name) {
return HttpMethod.valueOf(name.toUpperCase());
}
private static boolean isSafe(final HttpMethod method)
throws UnsupportedOperationException {
switch ( method ) {
case GET:
case HEAD:
case OPTIONS:
return true;
case POST:
case PUT:
case PATCH:
case DELETE:
return false;
case TRACE:
throw new UnsupportedOperationException();
default:
throw new AssertionError(method);
}
}
}
I don't really remember, but a resolve() method equivalent should be present in Spring Framework somewhere. Note that I use Google Guava TypeToken in order to let the processor be compatible with generic types (since I use models like IQuery<Foo> and IQuery<Bar> in controllers). Now just register the processor:
#Configuration
#EnableWebMvc
public class MvcConfiguration
extends WebMvcConfigurerAdapter {
#Override
public void addArgumentResolvers(final List<HandlerMethodArgumentResolver> argumentResolvers) {
argumentResolvers.add(createModelAttributeMethodProcessor());
}
private static HandlerMethodArgumentResolver createModelAttributeMethodProcessor() {
return plainModelAttributeMethodProcessor(ImmutableMap.of(pageableTypeToken, MvcConfiguration::toPageable));
}
private static final TypeToken<Pageable> pageableTypeToken = new TypeToken<Pageable>() {
};
private static Pageable toPageable(final WebRequest request) {
return new PageRequest(
ofNullable(request.getParameter("page")).map(Integer::parseInt).orElse(0),
ofNullable(request.getParameter("size")).map(Integer::parseInt).orElse(1)
);
}
}
Here is a web request to a Pageable DTO conversion, and the converter must be registered as an argument resolver. So now it's ready to use:
#RestController
#RequestMapping("/")
public class Controller {
#RequestMapping(method = GET)
public String get(#PlainModelAttribute final Pageable pageable) {
return toStringHelper(pageable)
.add("offset", pageable.getOffset())
.add("pageNumber", pageable.getPageNumber())
.add("pageSize", pageable.getPageSize())
.add("sort", pageable.getSort())
.toString();
}
}
A few examples:
/ ⇒ PageRequest{offset=0, pageNumber=0, pageSize=1, sort=null}
/?page=43 ⇒ PageRequest{offset=43, pageNumber=43, pageSize=1, sort=null}
/?size=32 ⇒ PageRequest{offset=0, pageNumber=0, pageSize=32, sort=null}
/?page=22&size=32 ⇒ PageRequest{offset=704, pageNumber=22, pageSize=32, sort=null}
Related
In my Spring Boot application (2.5.5) I get a large JSON body in the POST request to a specific endpoint. On that request I need to get both the parsed object and that whole object as a string to do some validation. The JSON object contains a lot of information that I don't need so that is not included in the Object so I can't convert it to a string.
#RestController
#RequestMapping("/example")
public class ExampleController {
#PostMapping("")
public void example(
#RequestBody String stringBody,
#RequestBody ExampleRequest exampleRequest
) {
// Validate request with 'stringBody'
// Do things with 'exampleRequest'
}
}
The best idea I had so far is to just use #RequestBody String stringBody and then convert that string to a JSON object but that is really not the ideal solution.
I know that you can't have two #RequestBody but I really need to somehow have both.
I believe that a custom HandlerMethodArgumentResolver is your best option.
For that I suggest you create a custom annotation as follows:
#Target({ElementType.PARAMETER})
#Retention(RetentionPolicy.RUNTIME)
public #interface ValidJsonSignature { }
Now you need to implement the custom HandlerMethodArgumentResolver:
public class JsonSignatureValidationArgumentResolver implements HandlerMethodArgumentResolver {
private final ObjectMapper objectMapper;
public JsonSignatureValidationArgumentResolver(ObjectMapper objectMapper) {
this.objectMapper = objectMapper;
}
#Override
public boolean supportsParameter(MethodParameter methodParameter) {
return methodParameter.getParameterAnnotation(ValidJsonSignature.class) != null;
}
#Override
public Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer, NativeWebRequest nativeWebRequest, WebDataBinderFactory webDataBinderFactory) throws Exception {
HttpServletRequest httpServletRequest = nativeWebRequest.getNativeRequest(HttpServletRequest.class);
String jsonPayload = StreamUtils.copyToString(httpServletRequest.getInputStream(), StandardCharsets.UTF_8);
// Do actual validation here
if (// Valid) {
// If valid, then convert String to method parameter type and return it
return objectMapper.treeToValue(objectMapper.readTree(jsonPayload), methodParameter.getParameterType());
} else {
// Throw exception if validation failed
}
}
}
Next, you need to register JsonSignatureValidationArgumentResolver as an argument resolver:
#Configuration
public class JsonSignatureValidationConfiguraion implements WebMvcConfigurer {
#Autowired
private ObjectMapper objectMapper;
#Override
public void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
resolvers.add(new JsonSignatureValidationArgumentResolver(objectMapper));
}
}
Last but not the least, you need to annotate the Controller attribute with #ValidJsonSignature as follows:
#RestController
#RequestMapping("/example")
public class ExampleController {
#PostMapping("")
public void example(#ValidJsonSignature ExampleRequest exampleRequest) {
}
}
I have a Java Spring controller.
I want to escape all quotes in my request (sanitize it for using it in SQL queries for example).
Is there a way to do that with Spring ?
Example :
#RequestMapping(method = RequestMethod.POST)
public List<String[]> myEndpoint(#RequestBody Map<String, String> params, #AuthenticationPrincipal Account connectedUser) throws Exception{
return myService.runQuery(params, connectedUser);
}
If you want to validate all your request parameters in controllers, you can use custom validators. For Complete info, check Complete Example
Brief Overview:
Validator Implementation
#Component
public class YourValidator implements Validator {
#Override
public boolean supports(Class<?> clazz) {
return clazz.isAssignableFrom(YourPojoType.class);
}
#Override
public void validate(Object target, Errors errors) {
if (target instanceof YourPojoType) {
YourPojoType req = (YourPojoType) target;
Map<String, String> params = req.getParams();
//Do your validations.
//if any validation failed,
errors.rejectValue("yourFieldName", "YourCustomErrorCode", "YourCustomErrorMessage");
}
}
}
Controller
#RestController
public class YourController{
#Autowired
private YourValidator validator;
#RequestMapping(method = RequestMethod.POST)
public List<String[]> myEndpoint(#Valid YourPojoType req, BindingResult result, #AuthenticationPrincipal Account connectedUser) throws Exception{
if (result.hasErrors()) {
//throw exception
}
return myService.runQuery(params, connectedUser);
}
#InitBinder
private void initBinder(WebDataBinder binder) {
binder.setValidator(validator);
}
}
I'm trying to use the Spring Validator and #Validated annotation to validate a Get Request parameter but cannot get the validator to run. I'm using a ModelAttribute to try and get the validator to run on the Path Variable instead of the Request Body. Is it possible to run a validator on a Get Request Path Variable?
Here is my controller class and method
#RestController
public class ProfileController {
#RequestMapping(value = "/profile/{param}", method = RequestMethod.GET)
public IVRProfile getProfile(#Validated(ParamValidator.class) #ModelAttribute("param") String param) {
return sampleProfile();
}
#ModelAttribute("param")
public String paramAsModelAttribute(#PathVariable String param) {
return param;
}
}
And the Validator class
#Component
public class ParamValidator implements Validator
{
#Override
public boolean supports(Class<?> clazz)
{
System.out.println("Validator supports test");
return String.class.isAssignableFrom(clazz);
}
#Override
public void validate(Object target, Errors errors)
{
System.out.println("Validator Test");
// Validation code
}
}
Neither prints statements are executed when hitting the endpoint.
Any help on what I could be missing or do differently would be greatly appreciated, thanks!
You can implement desired validation functionality as following.
public class ParamValidator implements ConstraintValidator<ParamConstraint, String> {
#Override
public void initialize(ParamConstraint paramConstraint) {
}
#Override
public boolean isValid(String paramField, ConstraintValidatorContext cxt) {
//Perform paramField validation
return true;
}
}
-
#Documented
#Constraint(validatedBy = ParamValidator.class)
#Target( { ElementType.PARAMETER })
#Retention(RetentionPolicy.RUNTIME)
public #interface ParamConstraint {
String message() default "Default validation message";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
-
#RequestMapping(value = "/profile/{param}", method = RequestMethod.GET)
public IVRProfile getProfile(#Valid #ParamConstraint #ModelAttribute("param") String param) {
return sampleProfile();
}
And finally don't forget to annotate Controller with #Validated.
#RestController
#Validated
public class ProfileController {
//...
}
More details you can find in the example as mentioned here.
You can create the answer you want by using the fields in the ConstraintViolationException with the following method;
#ExceptionHandler(ConstraintViolationException.class)
protected ResponseEntity<Object> handlePathVariableError(final ConstraintViolationException exception) {
log.error(exception.getMessage(), exception);
final List<SisSubError> subErrors = new ArrayList<>();
exception.getConstraintViolations().forEach(constraintViolation -> subErrors.add(generateSubError(constraintViolation)));
final SisError error = generateErrorWithSubErrors(VALIDATION_ERROR, HttpStatus.BAD_REQUEST, subErrors);
return new ResponseEntity<>(error, HttpStatus.BAD_REQUEST);
}
You need to added an #Validated annotation to Controller class and any validation annotation before path variable field
If you want to get single RequestParams like status, you can force it by following the code below.
#RestController
public class ProfileController {
#RequestMapping(value = "/profile/{param}", method = RequestMethod.GET)
public IVRProfile getProfile(#RequestParam(name = "status", required = true) String status, #ModelAttribute("param") String param) {}
}
if you want to force PathVariable, then do this.
#RestController
public class ProfileController {
#RequestMapping(value = "/profile/{param}", method = RequestMethod.GET)
public IVRProfile getProfile(#PathVariable(name = "param", required = true) String param, #ModelAttribute("param") String param) {}
}
Hope this work!!!
I am updating an application from Spring Platform version 1.1.3.RELEASE to 2.0.1.RELEASE, which bumps the Spring Framework version from 4.1.7 to 4.2.4, and Jackson from 2.4.6 to 2.6.4. There does not seem to have been any significant changes in Spring or Jackson's handling of custom HttpMessageConverter implementations, but my custom JSON serialization is failing to occur, and I have not been able to determine why. The following works fine in the previous Spring Platform release:
Model
#JsonFilter("fieldFilter")
public class MyModel {
/*model fields and methods*/
}
Model wrapper
public class ResponseEnvelope {
private Set<String> fieldSet;
private Set<String> exclude;
private Object entity;
public ResponseEnvelope(Object entity) {
this.entity = entity;
}
public ResponseEnvelope(Object entity, Set<String> fieldSet, Set<String> exclude) {
this.fieldSet = fieldSet;
this.exclude = exclude;
this.entity = entity;
}
public Object getEntity() {
return entity;
}
#JsonIgnore
public Set<String> getFieldSet() {
return fieldSet;
}
#JsonIgnore
public Set<String> getExclude() {
return exclude;
}
public void setExclude(Set<String> exclude) {
this.exclude = exclude;
}
public void setFieldSet(Set<String> fieldSet) {
this.fieldSet = fieldSet;
}
public void setFields(String fields) {
Set<String> fieldSet = new HashSet<String>();
if (fields != null) {
for (String field : fields.split(",")) {
fieldSet.add(field);
}
}
this.fieldSet = fieldSet;
}
}
Controller
#Controller
public class MyModelController {
#Autowired MyModelRepository myModelRepository;
#RequestMapping(value = "/model", method = RequestMethod.GET, produces = { MediaType.APPLICATION_JSON_VALUE })
public HttpEntity find(#RequestParam(required=false) Set<String> fields, #RequestParam(required=false) Set<String> exclude){
List<MyModel> objects = myModelRepository.findAll();
ResponseEnvelope envelope = new ResponseEnvelope(objects, fields, exclude);
return new ResponseEntity<>(envelope, HttpStatus.OK);
}
}
Custom HttpMessageConverter
public class FilteringJackson2HttpMessageConverter extends MappingJackson2HttpMessageConverter {
private boolean prefixJson = false;
#Override
public void setPrefixJson(boolean prefixJson) {
this.prefixJson = prefixJson;
super.setPrefixJson(prefixJson);
}
#Override
protected void writeInternal(Object object, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
ObjectMapper objectMapper = getObjectMapper();
JsonGenerator jsonGenerator = objectMapper.getFactory().createGenerator(outputMessage.getBody());
try {
if (this.prefixJson) {
jsonGenerator.writeRaw(")]}', ");
}
if (object instanceof ResponseEnvelope) {
ResponseEnvelope envelope = (ResponseEnvelope) object;
Object entity = envelope.getEntity();
Set<String> fieldSet = envelope.getFieldSet();
Set<String> exclude = envelope.getExclude();
FilterProvider filters = null;
if (fieldSet != null && !fieldSet.isEmpty()) {
filters = new SimpleFilterProvider()
.addFilter("fieldFilter", SimpleBeanPropertyFilter.filterOutAllExcept(fieldSet))
.setFailOnUnknownId(false);
} else if (exclude != null && !exclude.isEmpty()) {
filters = new SimpleFilterProvider()
.addFilter("fieldFilter", SimpleBeanPropertyFilter.serializeAllExcept(exclude))
.setFailOnUnknownId(false);
} else {
filters = new SimpleFilterProvider()
.addFilter("fieldFilter", SimpleBeanPropertyFilter.serializeAllExcept())
.setFailOnUnknownId(false);
}
objectMapper.setFilterProvider(filters);
objectMapper.writeValue(jsonGenerator, entity);
} else if (object == null){
jsonGenerator.writeNull();
} else {
FilterProvider filters = new SimpleFilterProvider().setFailOnUnknownId(false);
objectMapper.setFilterProvider(filters);
objectMapper.writeValue(jsonGenerator, object);
}
} catch (JsonProcessingException e){
e.printStackTrace();
throw new HttpMessageNotWritableException("Could not write JSON: " + e.getMessage());
}
}
}
Configuration
#Configuration
#EnableWebMvc
public class WebServicesConfig extends WebMvcConfigurerAdapter {
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
FilteringJackson2HttpMessageConverter jsonConverter = new FilteringJackson2HttpMessageConverter();
jsonConverter.setSupportedMediaTypes(MediaTypes.APPLICATION_JSON);
converters.add(jsonConverter);
}
// Other configurations
}
Now I am getting this exception (which is caught by Spring and logged) and a 500 error when making any sort of request:
[main] WARN o.s.w.s.m.s.DefaultHandlerExceptionResolver - Failed to write HTTP message:
org.springframework.http.converter.HttpMessageNotWritableException: Could not write content:
Can not resolve PropertyFilter with id 'fieldFilter';
no FilterProvider configured (through reference chain:
org.oncoblocks.centromere.web.controller.ResponseEnvelope["entity"]->java.util.ArrayList[0]);
nested exception is com.fasterxml.jackson.databind.JsonMappingException:
Can not resolve PropertyFilter with id 'fieldFilter';
no FilterProvider configured (through reference chain:
org.oncoblocks.centromere.web.controller.ResponseEnvelope["entity"]->java.util.ArrayList[0])
The configureMessageConverters method executes, but it does not look like custom converter is ever utilized during requests. Is it possible that another message converter could be preventing this one from reaching my response? My understanding was that overriding configureMessageConverters would prevent converters other than the manually registered ones from being used.
No changes have been made between the working and non-working versions of this code, besides updating dependency versions via the Spring Platform. Has there been any change in the JSON serialization that I am just missing in the documentation?
Edit
Further testing yields strange results. I wanted to test to check the following things:
Is my custom HttpMessageConverter actually being registered?
Is another converter overriding/superseding it?
Is this a problem with my test setup only?
So, I added an extra test and took a look at the output:
#Autowired WebApplicationContext webApplicationContext;
#Before
public void setup(){
mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext).build();
}
#Test
public void test() throws Exception {
RequestMappingHandlerAdapter adapter = (RequestMappingHandlerAdapter) webApplicationContext.getBean("requestMappingHandlerAdapter");
List<EntrezGene> genes = EntrezGene.createDummyData();
Set<String> exclude = new HashSet<>();
exclude.add("entrezGeneId");
ResponseEnvelope envelope = new ResponseEnvelope(genes, new HashSet<String>(), exclude);
for (HttpMessageConverter converter: adapter.getMessageConverters()){
System.out.println(converter.getClass().getName());
if (converter.canWrite(ResponseEnvelope.class, MediaType.APPLICATION_JSON)){
MockHttpOutputMessage message = new MockHttpOutputMessage();
converter.write((Object) envelope, MediaType.APPLICATION_JSON, message);
System.out.println(message.getBodyAsString());
}
}
}
...and it works fine. My the envelope object and its contents are serialized and filtered correctly. So either there is an issue with the request handling before it reaches the message converters, or there has been a change in how MockMvc is testing requests.
Your configuration is ok. The reason why writeInternal() is not called from your custom converter is because you are overriding the wrong method.
Looking at the source code of 4.2.4.RELEASE
AbstractMessageConverterMethodProcessor#writeWithMessageConverters
protected <T> void writeWithMessageConverters(T returnValue, MethodParameter returnType,
ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
...
((GenericHttpMessageConverter<T>) messageConverter).write(returnValue, returnValueType, selectedMediaType, outputMessage);
...
}
AbstractGenericHttpMessageConverter#write
public final void write(final T t, final Type type, MediaType contentType, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
...
writeInternal(t, type, outputMessage);
...
}
The method writeInternal(...) called from within AbstractGenericHttpMessageConverter#write(...) has three arguments - (T t, Type type, HttpOutputMessage outputMessage). You are overriding the overloaded version of writeInternal(...) that has only 2 arguments - (T t, HttpOutputMessage outputMessage).
However, in version 4.1.7.RELEASE, it is not the case, hence the root cause of your problem. The writeInternal(...) used in this version is the other overloaded method (the method with 2 arguments) that you have overriden. This explains why it is working fine in 4.1.7.RELEASE.
#Override
public final void write(final T t, MediaType contentType, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
...
writeInternal(t, outputMessage);
...
}
So, to solve your problem, instead of overriding writeInternal(Object object, HttpOutputMessage outputMessage), override writeInternal(Object object, Type type, HttpOutputMessage outputMessage)
I've got multiple controllers for RESTful endpoints which currently return null if there's no resource at the endpoint. For instance,
#RequestMapping(method = ReqeustMethod.GET, value = "{id}")
#ResponseBody
public MyResource get(#PathVariable final Long id) {
return this.myService.get(id); // returns null if bad id
}
I want to return a specific, different resource to the client (ErrorResource) when there's no MyResource with the given id. I know I can do that with a separate method with #ExceptionHandler, such as:
#RequestMapping(method = RequestMethod.GET, value = "{id}")
#ResponseBody
public MyResource get(#PathVariable final Long id) {
final MyResource myResource = this.myService.get(id);
if (myResource == null) {
throw new NotFoundException();
}
return myResource;
}
#ExceptionHandler(NotFoundException.class)
#ResponseStatus(value = HttpStatus.NOT_FOUND)
#ResponseBody
public ErrorResource notFoundException(
final HttpServletRequest request,
final NotFoundException exception) {
final ErrorResource errorResource = new ErrorResource();
errorResource.setStatus(HttpStatus.NOT_FOUND.value());
errorResource.setDeveloperMessage("No resource found at " + request.getRequestURL());
return errorResource;
}
And that's nice. But what I'd really like to be able to do is have some kind of interceptor that figures out for me that whenever an API method is returning a null #ResponseBody, it should instead run the logic in my notFoundException() method. That will make all my controller methods a little cleaner. Is there any way to do that?
It sounds like a job for Spring's HttpMessageConverter.
You can write your own converter by implementing HttpMessageConverter<T> interface.
In your case I would implement a converter of HttpMessageConverter<MyResource> with a null check on the MyResource instance in the write method. If the MyResource instance is null, then build and write your ErrorResource instance.
Here is an example:
import java.io.IOException;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
public class MyResourceConverter implements HttpMessageConverter<MyResource> {
// a real message converter that will respond to ancillary methods and do the actual work
private HttpMessageConverter<Object> delegateConverter;
public MyResourceConverter(HttpMessageConverter<Object> delegateConverter){
this.delegateConverter = delegateConverter;
}
#Override
public boolean canRead(Class<?> clazz, MediaType mediaType) {
return delegateConverter.canRead(clazz, mediaType) && MyResource.class.equals(clazz);
}
#Override
public boolean canWrite(Class<?> clazz, MediaType mediaType) {
return delegateConverter.canWrite(clazz, mediaType) && MyResource.class.equals(clazz);
}
#Override
public MyResource read(Class<? extends MyResource> clazz,
HttpInputMessage inputMessage) throws IOException,
HttpMessageNotReadableException {
return (MyResource) delegateConverter.read(clazz, inputMessage);
}
#Override
public void write(MyResource t, MediaType contentType,
HttpOutputMessage outputMessage) throws IOException,
HttpMessageNotWritableException {
Object result = null;
if(t == null){
result = // build your ErrorResource here
}else{
result = t;
}
delegateConverter.write(result, contentType, outputMessage);
}
}
Note that this converter needs to be registered in your Spring configuration.
The configuration class must extend WebMvcConfigurerAdapter and override the configureMessageConverters method, like:
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
// Here we add our custom-configured HttpMessageConverters.
// yourDelegateConverter may be a MappingJackson2HttpMessageConverter instance for example
converters.add(new EmployeeConverter(yourDelegateConverter));
super.configureMessageConverters(converters);
}
References (from official Spring documentation):
HTTP Message conversion
HttpMessageConverter
WebMvcConfigurerAdapter