I want to test the restTemplate.getForObject method using a mock but having issues. I'm new with Mockito, so I read some blogs about testing restTemplate using Mockito but still can not write a successful test.
The class to test is :
package rest;
#PropertySource("classpath:application.properties")
#Service
public class RestClient {
private String user;
// from application properties
private String password;
private RestTemplate restTemplate;
public Client getClient(final short cd) {
restTemplate.getInterceptors().add(new BasicAuthenticationInterceptor(user, password));
Client client = null;
try {
client = restTemplate.getForObject("http://localhost:8080/clients/findClient?cd={cd}",
Client.class, cd);
} catch (RestClientException e) {
println(e);
}
return client;
}
public RestTemplate getRestTemplate() {
return restTemplate;
}
public void setRestTemplate(final RestTemplate restTemplate) {
this.restTemplate = restTemplate;
}
}
My test class :
package test;
#PropertySource("classpath:application.properties")
#RunWith(MockitoJUnitRunner.class)
public class BatchRestClientTest {
#Mock
private RestTemplate restTemplate;
#InjectMocks
private RestClient restClient;
private MockRestServiceServer mockServer;
#Before
public void setUp() throws Exception {
}
#After
public void tearDown() throws Exception {
}
#Test
public void getCraProcessTest() {
Client client=new Client();
client.setId((long) 1);
client.setCd((short) 2);
client.setName("aaa");
Mockito
.when(restTemplate.getForObject("http://localhost:8080/clients/findClient?cd={cd},
Client.class, 2))
.thenReturn(client);
Client client2= restClient.getClient((short)2);
assertEquals(client, client2);
}
public RestTemplate getRestTemplate() {
return restTemplate;
}
public void setRestTemplate(RestTemplate restTemplate) {
this.restTemplate = restTemplate;
}
public RestClient getRestClient() {
return restClient;
}
public void setRestClient(RestClient restClient) {
this.restClient = restClient;
}
}
It is returning null and not the expected client, the restTemplate for Object class works fine. I want just to write the test . Am I missing something or doing the test wrong way?
Thanks for any guidance.
Use this instead:
Mockito.when(restTemplate.getForObject(
"http://localhost:8080/clients/findClient?cd={id}",
Client.class,
new Object[] {(short)2})
).thenReturn(client);
The third parameter is a varargs.
So you need to wrap into an Object[] in the test, otherwise Mockito is not able to match it. Note that this happens automatically in your implementation.
Also:
You forgot to terminate your url (missing closing ") in your examples in the question. Probably just a typo.
You used different url's in your implementation in your test: ...?cd={cd} instead of ...?cd={id}.(As previously pointed out by #ArnaudClaudel in the comments).
You did not define a behaviour for restTemplate.getInterceptors() so I would expect it to fail with a NullPointerException, when trying to add the BasicAuthenticationInterceptor.
Additionally you might want to check my answer here for another example of how to mock the getForObject method. Note that it does not include a case where any of the real parameters would be null.
Maybe the title is not the best to explain the problem, but I'll try to explain it as best as possible.
I have an Spring Boot Application using JPA and MySQL, so in order to check everything worked properly, I made a simple CRUD test for my database, and I found problems with autowiring which are explained in my previous question. The solution for those problems was just adding the #ComponentScan annotation to my Application.java.
It was the solution for the test because it run without problems, but then I find another problem. Apart from the test, I need my application to show a list of Proposals made by some Users and also some Comments. Before adding that annotation, the HTMLs showed the correct information, but after adding it shows information about the database in JSON format on the main page and if I try to navigate to "localhost:8080/viewProposal" p.e. it shows a WhiteLabel error page with error code 404. I have no idea why it is replacing the HTMLs because I have just one controller and is not a RESTController. These are my classes:
Application.java
#SpringBootApplication
#EntityScan("persistence.model")
#EnableJpaRepositories("persistence.repositories")
#ComponentScan("services.impl")
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
MainController.java
#Controller
#RequestMapping("/")
public class MainController {
private static final Logger logger = Logger.getLogger(MainController.class);
private List<SseEmitter> sseEmitters = Collections.synchronizedList(new ArrayList<>());
private Map<String, Proposal> proposals = generateProposals();
#RequestMapping({"/live","/"})
public String landing(Model model) {
return "index";
}
#RequestMapping("/viewProposal")
public String viewProposal(Model model, Long id) {
//put the object in the map
return "viewProposal";
}
#KafkaListener(topics = "newVote")
public void listen(String data) {
String[] contents = data.split(";");
if(contents.length!=2)
return;
Proposal p;
int newVote;
if (proposals.containsKey(contents[0]))
p = proposals.get(contents[0]);
else {
p = new Proposal();
p.setTitle(contents[0]);
proposals.put(p.getTitle(), p);
}
if (contents[1].equals("+"))
newVote = +1;
else if (contents[1].equals("-"))
newVote = -1;
else
newVote = 0;
p.setNumberOfVotes(p.getNumberOfVotes() + newVote);
logger.info("New message received: \"" + data + "\"");
}
private static Map<String, Proposal> generateProposals() {
Map<String, Proposal> lista = new HashMap<String, Proposal>();
Proposal p = new Proposal();
p.setTitle("tituloPrueba");
lista.put("tituloPrueba", p);
return lista;
}
#ModelAttribute("proposals")
public Map<String, Proposal> getProposals() {
return proposals;
}
public void setProposals(Map<String, Proposal> proposals) {
this.proposals = proposals;
}
}
MvcConfiguration
#Configuration
#EnableWebMvc
public class MvcConfiguration extends WebMvcConfigurerAdapter{
#Bean
public ViewResolver getViewResolver() {
InternalResourceViewResolver resolver = new InternalResourceViewResolver();
resolver.setPrefix("/resources/templates/");
resolver.setSuffix(".html");
return resolver;
}
#Override
public void configureDefaultServletHandling(
DefaultServletHandlerConfigurer configurer) {
configurer.enable();
}
#Override
public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
configurer.defaultContentType(MediaType.TEXT_HTML);
}
}
If you want to see the rest of the classes, please go to my previous question everything is in there.
Thanks in advance.
I'm working on a old Spring Application which contains lots of legacy code which needs to survive. Right now I'm working on a more modern approach of API usage and I've stumbled into a problem.
I've Added GSON for converting dates of different formats and front-ends (see below). But this causes a problem at runtime, the #ResponseBody objects become empty.
It all works fine in MockMVC which hooks up the config, but at runtime in Tomcat 8, it has problems. As I've been googling this for quite a while it seems that it could be a problem due to Jackson trying to parse the JSON as well.
Any idea's how I can ensure only GSON is used for JSON requests? (My requests contain only Simple Pojo's with Date, String and Long objects), but can have some nested objects.
Some code snippets:
WebConfig:
#EnableWebMvc
#Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
#Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new RestLoggingInterceptor());
}
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.add(new ExtendedGsonHttpMessageConverter());
}
}
ExtendedGsonHttpMessageConverter
public class ExtendedGsonHttpMessageConverter extends GsonHttpMessageConverter
{
private static final String[] DATE_FORMATS = new String[] {
"yyyy-MM-dd'T'HH:mm:ss.SSS'Z'",
"yyyy-MM-dd'T'HH:mm:ss.SSSZ",
"yyyy-MM-dd'T'HH:mmZ",
"yyyy-MM-dd'T'HH:mm:ssZ",
"yyyy-MM-dd'T'HH:mm:ss-'07:00'"
};
public ExtendedGsonHttpMessageConverter()
{
super();
super.setGson(buildGson());
}
protected static Gson buildGson() {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(Date.class, new DateDeserializer());
return gsonBuilder.create();
}
private static class DateDeserializer implements JsonDeserializer<Date> {
#Override
public Date deserialize(JsonElement jsonElement, Type typeOF,
JsonDeserializationContext context) throws JsonParseException {
for (String format : DATE_FORMATS) {
try {
return new SimpleDateFormat(format, Locale.GERMANY).parse(jsonElement.getAsString());
} catch (ParseException e) {
}
}
throw new JsonParseException("Unparseable date: \"" + jsonElement.getAsString()
+ "\". Supported formats: " + Arrays.toString(DATE_FORMATS));
}
}
}
The problem was using an interceptor which was logging the request.
Logging the request causes the requestBody to be null, so now I'll be using Springs AbstractRequestLoggingFilter as in the comments.
After extensive investigations, I wanted to share the problem and the resolution.
Problem
I have a RestController that works well, as long as I'm in charge of converting the JSON message. The moment I try to use an HttpMessageConverter to make the conversion more elegant, the client will start receiving HTTP 406.
So this works:
#RequestMapping(value = "/objects", method = RequestMethod.GET)
public Map<String, Object>[] getObjects(#RequestBody Object jsonQuery) {
MyQuery query = new MyConverter().convert(jsonQuery);
// do something with query
}
But, when I configure the converter, like this:
#Configuration
#EnableWebMvc
#ComponentScan
public class WebConfiguration extends WebMvcConfigurerAdapter {
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> httpMessageConverters) {
httpMessageConverters.add(new QueryMessageConverter(new MediaType("application", "json")));
}
}
This causes HTTP 406:
#RequestMapping(value = "/objects", method = RequestMethod.GET)
public Map<String, Object>[] getObjects(#RequestBody Query Query) {
// do something with query
}
My pom.xml only refers spring-boot, and doesn't mention jackson at all.
Solution
See below
The solution is really very simple, and it is to register the jackson handler explicitly:
#Configuration
#EnableWebMvc
#ComponentScan
public class WebConfiguration extends WebMvcConfigurerAdapter {
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> httpMessageConverters) {
httpMessageConverters.add(new QueryMessageConverter(new MediaType("application", "json")));
httpMessageConverters.add(new MappingJackson2HttpMessageConverter());
}
}
I am writing a rest service using spring MVC which produces JSON response. It should allow client to select only the given fields in response, means client can mention the fields he is interested in as url parameter like ?fields=field1,field2.
Using Jackson annotations does not provide what I am looking for as it is not dynamic also the filters in Jackson doesnt seem to be promising enough.
So far I am thinking to implement a custom message converter which can take care of this.
Is there any other better way to achieve this? I would like if this logic is not coupled with my services or controllers.
From Spring 4.2, #JsonFilter is supported in MappingJacksonValue
Issue : SPR-12586 : Support Jackson #JsonFilter
Commit : ca06582
You can directly inject PropertyFilter to MappingJacksonValue in a controller.
#RestController
public class BookController {
private static final String INCLUSION_FILTER = "inclusion";
#RequestMapping("/novels")
public MappingJacksonValue novel(String[] include) {
#JsonFilter(INCLUSION_FILTER)
class Novel extends Book {}
Novel novel = new Novel();
novel.setId(3);
novel.setTitle("Last summer");
novel.setAuthor("M.K");
MappingJacksonValue res = new MappingJacksonValue(novel);
PropertyFilter filter = SimpleBeanPropertyFilter.filterOutAllExcept(include);
FilterProvider provider = new SimpleFilterProvider().addFilter(INCLUSION_FILTER, filter);
res.setFilters(provider);
return res;
}
or you can declare global policy by ResponseBodyAdvice. The following example implements filtering policy by "exclude" parameter.
#ControllerAdvice
public class DynamicJsonResponseAdvice extends AbstractMappingJacksonResponseBodyAdvice {
public static final String EXCLUDE_FILTER_ID = "dynamicExclude";
private static final String WEB_PARAM_NAME = "exclude";
private static final String DELI = ",";
private static final String[] EMPTY = new String[]{};
#Override
protected void beforeBodyWriteInternal(MappingJacksonValue container, MediaType contentType,
MethodParameter returnType, ServerHttpRequest req, ServerHttpResponse res) {
if (container.getFilters() != null ) {
// It will be better to merge FilterProvider
// If 'SimpleFilterProvider.addAll(FilterProvider)' is provided in Jackson, it will be easier.
// But it isn't supported yet.
return;
}
HttpServletRequest baseReq = ((ServletServerHttpRequest) req).getServletRequest();
String exclusion = baseReq.getParameter(WEB_PARAM_NAME);
String[] attrs = StringUtils.split(exclusion, DELI);
container.setFilters(configFilters(attrs));
}
private FilterProvider configFilters(String[] attrs) {
String[] ignored = (attrs == null) ? EMPTY : attrs;
PropertyFilter filter = SimpleBeanPropertyFilter.serializeAllExcept(ignored);
return new SimpleFilterProvider().addFilter(EXCLUDE_FILTER_ID, filter);
}
}
IMHO, the simplest way to do that would be to use introspection to dynamically generate a hash containing selected fields and then serialize that hash using Json. You simply have to decide what is the list of usable fields (see below).
Here are two example functions able to do that, first gets all public fields and public getters, the second gets all declared fields (including private ones) in current class and all its parent classes :
public Map<String, Object> getPublicMap(Object obj, List<String> names)
throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {
List<String> gettedFields = new ArrayList<String>();
Map<String, Object> values = new HashMap<String, Object>();
for (Method getter: obj.getClass().getMethods()) {
if (getter.getName().startsWith("get") && (getter.getName().length > 3)) {
String name0 = getter.getName().substring(3);
String name = name0.substring(0, 1).toLowerCase().concat(name0.substring(1));
gettedFields.add(name);
if ((names == null) || names.isEmpty() || names.contains(name)) {
values.put(name, getter.invoke(obj));
}
}
}
for (Field field: obj.getClass().getFields()) {
String name = field.getName();
if ((! gettedFields.contains(name)) && ((names == null) || names.isEmpty() || names.contains(name))) {
values.put(name, field.get(obj));
}
}
return values;
}
public Map<String, Object> getFieldMap(Object obj, List<String> names)
throws IllegalArgumentException, IllegalAccessException {
Map<String, Object> values = new HashMap<String, Object>();
for (Class<?> clazz = obj.getClass(); clazz != Object.class; clazz = clazz.getSuperclass()) {
for (Field field : clazz.getDeclaredFields()) {
String name = field.getName();
if ((names == null) || names.isEmpty() || names.contains(name)) {
field.setAccessible(true);
values.put(name, field.get(obj));
}
}
}
return values;
}
Then you only have to get the result of one of this function (or of one you could adapt to your requirements) and serialize it with Jackson.
If you have custom encoding of you domain objects, you would have to maintain the serialization rules in two different places : hash generation and Jackson serialization. In that case, you could simply generate the full class serialization with Jackson and filter the generated string afterwards. Here is an example of such a filter function :
public String jsonSub(String json, List<String> names) throws IOException {
if ((names == null) || names.isEmpty()) {
return json;
}
ObjectMapper mapper = new ObjectMapper();
Map<String, Object> map = mapper.readValue(json, HashMap.class);
for (String name: map.keySet()) {
if (! names.contains(name)) {
map.remove(name);
}
}
return mapper.writeValueAsString(map);
}
Edit : integration in Spring MVC
As you are speaking of a web service and of Jackson, I assume that you use Spring RestController or ResponseBody annotations and (under the hood) a MappingJackson2HttpMessageConverter. If you use Jackson 1 instead, it should be a MappingJacksonHttpMessageConverter.
What I propose is simply to add a new HttpMessageConverter that could make use of one of the above filtering functions, and delegate actual work (and also ancilliary methods) to a true MappingJackson2HttpMessageConverter. In the write method of that new converter, it is possible to have access to the eventual fields request parameter with no need for an explicit ThreadLocal variable thanks to Spring RequestContextHolder. That way :
you keep a clear separation of roles with no modification on existing controllers
you have no modification in Jackson2 configuration
you need no new ThreadLocal variable and simply use a Spring class in a class already tied to Spring since it implements HttpMessageConverter
Here is an example of such a message converter :
public class JsonConverter implements HttpMessageConverter<Object> {
private static final Logger logger = LoggerFactory.getLogger(JsonConverter.class);
// a real message converter that will respond to ancilliary methods and do the actual work
private HttpMessageConverter<Object> delegate =
new MappingJackson2HttpMessageConverter();
// allow configuration of the fields name
private String fieldsParam = "fields";
public void setFieldsParam(String fieldsParam) {
this.fieldsParam = fieldsParam;
}
#Override
public boolean canRead(Class<?> clazz, MediaType mediaType) {
return delegate.canRead(clazz, mediaType);
}
#Override
public boolean canWrite(Class<?> clazz, MediaType mediaType) {
return delegate.canWrite(clazz, mediaType);
}
#Override
public List<MediaType> getSupportedMediaTypes() {
return delegate.getSupportedMediaTypes();
}
#Override
public Object read(Class<? extends Object> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
return delegate.read(clazz, inputMessage);
}
#Override
public void write(Object t, MediaType contentType, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
// is there a fields parameter in request
String[] fields = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes())
.getRequest().getParameterValues(fieldsParam);
if (fields != null && fields.length != 0) {
// get required field names
List<String> names = new ArrayList<String>();
for (String field : fields) {
String[] f_names = field.split("\\s*,\\s*");
names.addAll(Arrays.asList(f_names));
}
// special management for Map ...
if (t instanceof Map) {
Map<?, ?> tmap = (Map<?, ?>) t;
Map<String, Object> map = new LinkedHashMap<String, Object>();
for (Entry entry : tmap.entrySet()) {
String name = entry.getKey().toString();
if (names.contains(name)) {
map.put(name, entry.getValue());
}
}
t = map;
} else {
try {
Map<String, Object> map = getMap(t, names);
t = map;
} catch (Exception ex) {
throw new HttpMessageNotWritableException("Error in field extraction", ex);
}
}
}
delegate.write(t, contentType, outputMessage);
}
/**
* Create a Map by keeping only some fields of an object
* #param obj the Object
* #param names names of the fields to keep in result Map
* #return a map containing only requires fields and their value
* #throws IllegalArgumentException
* #throws IllegalAccessException
*/
public static Map<String, Object> getMap(Object obj, List<String> names)
throws IllegalArgumentException, IllegalAccessException {
Map<String, Object> values = new HashMap<String, Object>();
for (Class<?> clazz = obj.getClass(); clazz != Object.class; clazz = clazz.getSuperclass()) {
for (Field field : clazz.getDeclaredFields()) {
String name = field.getName();
if (names.contains(name)) {
field.setAccessible(true);
values.put(name, field.get(obj));
}
}
}
return values;
}
}
If you want the converter to be more versatile, you could define an interface
public interface FieldsFilter {
Map<String, Object> getMap(Object obj, List<String> names)
throws IllegalAccessException, IllegalArgumentException, InvocationTargetException;
}
and inject it with an implementation of that.
Now you must ask Spring MVC to use that custom message controller.
If you use XML config, you simply declare it in the <mvc:annotation-driven> element :
<mvc:annotation-driven >
<mvc:message-converters>
<bean id="jsonConverter" class="org.example.JsonConverter"/>
</mvc:message-converters>
</mvc:annotation-driven>
And if you use Java configuration, it is almost as simple :
#EnableWebMvc
#Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
#Autowired JsonConverter jsonConv;
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.add(jsonConv);
StringHttpMessageConverter stringConverter = new StringHttpMessageConverter();
stringConverter.setWriteAcceptCharset(false);
converters.add(new ByteArrayHttpMessageConverter());
converters.add(stringConverter);
converters.add(new ResourceHttpMessageConverter());
converters.add(new SourceHttpMessageConverter<Source>());
converters.add(new AllEncompassingFormHttpMessageConverter());
converters.add(new MappingJackson2HttpMessageConverter());
}
}
but here you have to explicitely add all the default message converters that you need.
I've never done this but after looking at this page http://wiki.fasterxml.com/JacksonFeatureJsonFilter it seems that it would be possible to do what you want this way:
1) Create a custom JacksonAnnotationIntrospector implementation (by extending default one) that will use a ThreadLocal variable to choose a filter for current request and also create a custom FilterProvider that would provide that filter.
2) Configure the message converter's ObjectMapper to use the custom introspector and filter provider
3) Create an MVC interceptor for REST service that detects fields request parameter and configures a new filter for current request via your custom filter provider (this should be a thread local filter). ObjectMapper should pick it up through your custom JacksonAnnotationIntrospector.
I'm not 100% certain that this solution would be thread safe (it depends on how ObjectMapper uses annotation introspector and filter provider internally).
- EDIT -
Ok I did a test implementation and found out that step 1) wouldn't work because Jackson caches the result of AnnotationInterceptor per class. I modified idea to apply dynamic filtering only on annotated controller methods and only if the object doesn't have anoter JsonFilter already defined.
Here's the solution (it's quite lengthy):
DynamicRequestJsonFilterSupport class manages the per-request fields to be filtered out:
public class DynamicRequestJsonFilterSupport {
public static final String DYNAMIC_FILTER_ID = "___DYNAMIC_FILTER";
private ThreadLocal<Set<String>> filterFields;
private DynamicIntrospector dynamicIntrospector;
private DynamicFilterProvider dynamicFilterProvider;
public DynamicRequestJsonFilterSupport() {
filterFields = new ThreadLocal<Set<String>>();
dynamicFilterProvider = new DynamicFilterProvider(filterFields);
dynamicIntrospector = new DynamicIntrospector();
}
public FilterProvider getFilterProvider() {
return dynamicFilterProvider;
}
public AnnotationIntrospector getAnnotationIntrospector() {
return dynamicIntrospector;
}
public void setFilterFields(Set<String> fieldsToFilter) {
filterFields.set(Collections.unmodifiableSet(new HashSet<String>(fieldsToFilter)));
}
public void setFilterFields(String... fieldsToFilter) {
filterFields.set(Collections.unmodifiableSet(new HashSet<String>(Arrays.asList(fieldsToFilter))));
}
public void clear() {
filterFields.remove();
}
public static class DynamicIntrospector extends JacksonAnnotationIntrospector {
#Override
public Object findFilterId(Annotated annotated) {
Object result = super.findFilterId(annotated);
if (result != null) {
return result;
} else {
return DYNAMIC_FILTER_ID;
}
}
}
public static class DynamicFilterProvider extends FilterProvider {
private ThreadLocal<Set<String>> filterFields;
public DynamicFilterProvider(ThreadLocal<Set<String>> filterFields) {
this.filterFields = filterFields;
}
#Override
public BeanPropertyFilter findFilter(Object filterId) {
return null;
}
#Override
public PropertyFilter findPropertyFilter(Object filterId, Object valueToFilter) {
if (filterId.equals(DYNAMIC_FILTER_ID) && filterFields.get() != null) {
return SimpleBeanPropertyFilter.filterOutAllExcept(filterFields.get());
}
return super.findPropertyFilter(filterId, valueToFilter);
}
}
}
JsonFilterInterceptor intercepts controller methods annotated with custom #ResponseFilter annotation.
public class JsonFilterInterceptor implements HandlerInterceptor {
#Autowired
private DynamicRequestJsonFilterSupport filterSupport;
private ThreadLocal<Boolean> requiresReset = new ThreadLocal<Boolean>();
#Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
if (handler instanceof HandlerMethod) {
HandlerMethod method = (HandlerMethod) handler;
ResponseFilter filter = method.getMethodAnnotation(ResponseFilter.class);
String[] value = filter.value();
String param = filter.param();
if (value != null && value.length > 0) {
filterSupport.setFilterFields(value);
requiresReset.set(true);
} else if (param != null && param.length() > 0) {
String filterParamValue = request.getParameter(param);
if (filterParamValue != null) {
filterSupport.setFilterFields(filterParamValue.split(","));
}
}
}
requiresReset.remove();
return true;
}
#Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
}
#Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
Boolean reset = requiresReset.get();
if (reset != null && reset) {
filterSupport.clear();
}
}
}
Here's the custom #ResponseFilter annotation. You can either define a static filter (via annotation's value property) or a filter based on request param (via annotation's param property):
#Target({ElementType.METHOD, ElementType.TYPE})
#Retention(RetentionPolicy.RUNTIME)
#Documented
public #interface ResponseFilter {
String[] value() default {};
String param() default "";
}
You will need to setup the message converter and the interceptor in the config class:
...
#Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
converters.add(converter());
}
#Bean
JsonFilterInterceptor jsonFilterInterceptor() {
return new JsonFilterInterceptor();
}
#Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(jsonFilterInterceptor);
}
#Bean
DynamicRequestJsonFilterSupport filterSupport() {
return new DynamicRequestJsonFilterSupport();
}
#Bean
MappingJackson2HttpMessageConverter converter() {
MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
ObjectMapper mapper = new ObjectMapper();
mapper.setAnnotationIntrospector(filterSupport.getAnnotationIntrospector());
mapper.setFilters(filterSupport.getFilterProvider());
converter.setObjectMapper(mapper);
return converter;
}
...
And finally, you can use the filter like this:
#RequestMapping("/{id}")
#ResponseFilter(param = "fields")
public Invoice getInvoice(#PathVariable("id") Long id) { ... }
When request is made to /invoices/1?fields=id,number response will be
filtered and only id and number properties will be returned.
Please note I haven't tested this thoroughly but it should get you started.
Would populating a HashMap from the object not suite the requirements? You could then just parse the HashMap. I have done something similar with GSON in the past where I had to provide a simple entity and ended up just populating a HashMap and then serializing it, it was far more maintainable than over engineering a whole new system.