spring mvc add common fields in json response - spring

Question

Before the result is sent, we want to add common fields (timestamp, version etc) in JSON response. We don't want to do this in every Controller. Is there any elegant way to do this in spring mvc?
Another similar question is if the parameter validation is failed, how to return the same JSON response.

Answer 1

Yes there is. You can use Spring AOP. You can intercept every service you write and add parameters from one place. For example, using Spring Around Advice. Note you need to write yourself addParameters function that return JsonNode. Good luck!
public class DoAroundMethod implements MethodInterceptor {
private static final Logger LOG = LoggerFactory.getLogger(DoAroundMethod.class);
#Autowired
ObjectMapper mapper;
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
LOG.debug("****SPRING AOP**** DoAroundMethod: Method name : "
+ methodInvocation.getMethod().getName());
LOG.debug("****SPRING AOP**** DoAroundMethod: Method name : "
+ methodInvocation.getMethod().getName());
LOG.debug("****SPRING AOP**** DoAroundMethod: Method arguments : "
+ Arrays.toString(methodInvocation.getArguments()));
// same with MethodBeforeAdvice
LOG.debug("****SPRING AOP**** DoAroundMethod: Before method executing!");
try {
// proceed to original method call
Object result = methodInvocation.proceed();
// same with AfterReturningAdvice
if(result!=null){
//LOG.debug("Return value "+result.toString());
try{
JsonNode jN = mapper.readTree(result.toString());
result=addParameters(jN);
}catch(JsonParseException e){
LOG.debug("****SPRING AOP**** DoAroundMethod: When JsonParse throws Exception!");
return result;
}
}
LOG.debug("****SPRING AOP**** DoAroundMethod: After method executing!");
return result;
} catch (IllegalArgumentException e) {
// same with ThrowsAdvice
LOG.debug("****SPRING AOP**** DoAroundMethod: When method throws Exception!");
throw e;
}
}
Then to assign this Advice to all services you have, assuming they all end in *Service.java
<bean class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
<property name="beanNames">
<list>
<value>*Service</value>
</list>
</property>
<property name="interceptorNames">
<list>
<value>regexAdvisor</value>
</list>
</property>
</bean>

Answer 2

Maybe a custom Jackson plugin, or a ResponseBodyAdvice? (see this blog post for more details).