I am testing out Grails static compilation, specifically GrailsCompileStatic. The documentation is limited in explaining what Grails dynamic features aren't supported. My test Controller is very simple, but I'm running into problems already.
#GrailsCompileStatic
class UserController {
UserService userService
def list() {
def model = [:]
def model = request.JSON
withFormat {
json {
render(model as JSON)
}
}
}
}
When compiling the application I get two compile time errors. The first about a missing property for JSON on the request object, and a second error about a missing method for json in the withFormat closure.
Seems to me I'm either doing something wrong or GrailsCompileStatic doesn't work with these features?
About request.JSON
The request object's getJSON() method is added via the ConvertersPluginSupport class. The exact lines are:
private static void enhanceRequest() {
// Methods for Reading JSON/XML from Requests
def getXMLMethod = { -> XML.parse((HttpServletRequest) delegate) }
def getJSONMethod = { -> JSON.parse((HttpServletRequest) delegate)}
def requestMc = GrailsMetaClassUtils.getExpandoMetaClass(HttpServletRequest)
requestMc.getXML = getXMLMethod
requestMc.getJSON = getJSONMethod
}
As you can see it uses the dynamic dispatch mechanism, but fortunately it's not such a big deal. You can simply replicate it by executing JSON.parse(request) anywhere in your controller.
Pay attention though! JSON.parse(HttpServletRequest) returns an Object, which is either a JSONObject or a JSONArray, so if you plan on using them explicitly, and you are compiling statically, you will have to cast it.
You might create a common base class for your controllers:
import org.codehaus.groovy.grails.web.json.JSONArray
import org.codehaus.groovy.grails.web.json.JSONObject
import grails.converters.JSON
#GrailsCompileStatic
class BaseController {
protected JSONObject getJSONObject() {
(JSONObject) JSON.parse(request)
}
protected JSONArray getJSONArray() {
(JSONArray) JSON.parse(request)
}
}
Then in your controller you can simpy invoke getJSONObject() or getJSONArray. It's a bit of a workaround, but results in a staticly compileable code.
About withFormat
This is a bit more complicated. The withFormat construct is really a method, which has a Closure as it's first parameter. The internal implementation then figures out based on the current request or response content type which part of the argument closure is to be used.
If you want to figure out how to do this statically, take a look at the source code.
You could extend this class, then use it's protected methods, but I don't know if it's worth all the hussle, you would loose much of Grails' conciseness. But if you really want to do it, you can. Don't you just love open source projects ? :)
Related
How to mock listAPiMetrics when my code looks like this
List<JSONObject> metrics = new ApiMetricsClient().listApiMetrics(new ApiIdList(apiIds));
You can not mock that behavior. Because you are initiate your object inside code. You need to inject dependencies via contrutor or somehow. Basically, you need to do dependency injection.
Some mock frameworks (like moq from c#) able to mock only interface or abstract types so you need to inject your dependencies as interface which this is the most common way in general. Some frameworks like mockito/powermock allow to mock concrete types too (powermock also can be able to mock private methods as I remember).
Change your code to work as below :
class YourClass {
private IApiMetricsClient apiMetricClient;
public YourClass(IApiMetricsClient apiMetricClient) {
this.apiMetricClient = apiMetricClient;
}
public [returnType] yourMethod() {
List<JSONObject> metrics = this.apiMetricClient.listApiMetrics(new ApiIdList(apiIds));
// other logics and return data or whatever
}
}
I am used to JAX-RS and would like to have similar comfort when sending requests using Spring MVC and working with the responses, i.e. on the client side inside my tests.
On the server (controller) side I'm quite happy with the automatic conversion, i.e. it suffices to just return an object instance and have JSON in the resulting HTTP response sent to the client.
Could you tell me how to work around the manual process of converting objectInstance to jsonString or vice versa in these snippets? If possible, I'd also like to skip configuring the content type manually.
String jsonStringRequest = objectMapper.writeValueAsString(objectInstance);
ResultActions resultActions = mockMvc.perform(post(PATH)
.contentType(MediaType.APPLICATION_JSON)
.content(jsonStringRequest)
)
String jsonStringResponse = resultActions.andReturn().getResponse().getContentAsString();
Some objectInstanceResponse = objectMapper.readValue(jsonStringResponse, Some.class);
For comparison, with JAX-RS client API I can easily send an object using request.post(Entity.entity(objectInstance, MediaType.APPLICATION_JSON_TYPE) and read the response using response.readEntity(Some.class);
if you have lot's of response objects, you could create some generic JsonToObject mapper-factory. It could be then used to detect the object type from a generic response (all response objects inherit from the same generic class) and respond/log properly from a bad mapping attempt.
I do not have a code example at hand, but as a pseudocode:
public abstract GenericResponse {
public String responseClassName = null;
// get/set
}
In the server code, add the name of the actual response object to this class.
The JsonToObject factory
public ConverterFactory<T> {
private T objectType;
public ConverterFactory(T type) {
objectType = type;
}
public T convert(String jsonString) {
// Type check
GenericResponse genResp = mapper.readValue(result.getResponse().getContentAsString(),
GenericResponse.class);
if (objectType.getClass().getSimpleName().equals(genResp.getResponseClassName())) {
// ObjectMapper code
return mapper.readValue(result.getResponse().getContentAsString(),
objectType.class);
} else {
// Error handling
}
}
}
I think this could be extended to be used with annotation to do more automation magic with the response. (start checking with BeanPostProcessor)
#Component
public class AnnotationWorker implements BeanPostProcessor {
#Override
public Object postProcessBeforeInitialization(final Object bean, String name) throws BeansException {
ReflectionUtils.doWithFields(bean.getClass(), field -> {
// make the field accessible if defined private
ReflectionUtils.makeAccessible(field);
if (field.getAnnotation(MyAnnotation.class) != null) {
field.set(bean, log);
}
});
return bean;
}
}
The above code snippet is copied from my current project and it injects to fields, you need to change it so, that it works for methods, eg ... where you may need it.
Having this all implemented may be tricky and can't say it necessarily works even, but it's something to try if you don't mind a bit of educative work.
The problem is as follows: I want to handle a POST request with JSON body. The body consists of an array of JSON Objects, without further nesting, i.e. simple HashMaps. All of these objects represent JSON-serialized domain classes from an Android Application, which will have their counterpart in my Grails app. I am thinking of parsing the JSON body, iterating through every element and saving each node as its corresponding domain class instance.
a) How should I save the instance? I am quite new to Grails/Groovy so please excuse any huge mistakes. Code so far is
public static Object JSONArray2Instances(String json, Class type) {
def slurper = new JsonSlurper()
def result = slurper.parseText(json)
//we only want to parse JSON Arrays
if (!(result instanceof JSONArray))
return null
result.each {
def instance = it.asType(type)
// now I need to save to domain class!
}
}
b) where do I place the corresponding code? Currently it is in /grails-app/src/groovy. Where do the tests go? (Since it is not a 'real' Grails component)
c) Is an intermediate command object more appropriate?
Your code should go in to the controller which is handling the request. Please take a look at
gson-grails plugin which has examples of how to serialize and deserialze objects and map them to domain objects. Please take a look at the grails basics where they talk about the conventions used in the grails application and the layout. There are good examples at grails site. Hope this helps
I solved my problem as follows, based on help provided by the comment from allthenutsandbolts. : (Grails-Gson plugin was not needed)
Let N2696AdminAction be the name of a Domain Class
in my controller:
class N2696AdminActionController extends RestfulController{
static responseFormats = ['json', 'xml']
def JSONHandlerService
N2696AdminActionController() {
super(N2696AdminAction)
}
#Override
#Transactional
def save(){
if (request!=null)
JSONHandlerService.instancesfromJSON(request.JSON)
}
}
then I delegate persisting to my service as follows
class JSONHandlerService {
def instancesfromJSON(Object request){
//we only want to parse JSON Arrays
if (!(request instanceof JSONArray))
return null
request.each {
def domainClass = Class.forName("${it.type}",
true, Thread.currentThread().getContextClassLoader())
def newDomainObject = domainClass.newInstance(it)
newDomainObject.save(failOnError:true, flush:true, insert: true)
}
}
}
type is a Json attribute which holds the full (package inclusive) name for my class. This way, I can save to multiple Domain Classes with the same POST request.
Suppose I have two sets of controllers in Spring:
/jsonapi1/*
/jsonapi2/*
both of which return objects that are to be interpretted as JSON text.
I'd like some kind of filter to wrap the responses from one set of these controllers so that:
the original response is contained within another object.
For example, if /jsonapi1/count returns:
{"num_humans":123, "num_androids":456}
then the response should be wrapped and returned as follows:
{ "status":0,
"content":{"num_humans":123, "num_androids":456}
}
if an exception happens in the controller, then filter should catch the exception and report it as follows
{ "status":5,
"content":"Something terrible happened"
}
The responses from the other controllers are returned unchanged.
We're currently customizing a MappingJackson2HttpMessageConverter passed to WebMvcConfigurerAdapter.configureMessageConverters in order to perform the above tasks. Works great except that it doesn't seem possible for this approach to be selective about the URLs (or controller classes) it applies to.
Is it possible to apply these kinds of wrappers to individual controller classes or URLs?
Update: Servlet filters look like a solution. Is it possible chose which filter gets applied to which controller methods, or which URLs?
I was struggling on this for multiple days. The solution by #Misha didn't work for me. I was able to finally get this working using ControllerAdvice and ResponseBodyAdvice.
ResponseBodyAdvice allows to inject custom transformation logic on the response returned by a controller but before it is converted to HttpResponse and committed.
This is how my controller method looks:
#RequestMapping("/global/hallOfFame")
public List<HallOfFame> getAllHallOfFame() {
return hallOfFameService.getAllHallOfFame();
}
Now i wanted to add some standard fields around the response like devmessage and usermessage. That logic goes into the ResponseAdvice:
#ControllerAdvice
public class TLResponseAdvice implements ResponseBodyAdvice<Object> {
#Override
public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
return true;
}
#Override
public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType,
Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request,
ServerHttpResponse response) {
// TODO Auto-generated method stub
final RestResponse<Object> output = new RestResponse<>();
output.setData(body);
output.setDevMessage("ResponseAdviceDevMessage");
output.setHttpcode(200);
output.setStatus("Success");
output.setUserMessage("ResponseAdviceUserMessage");
return output;
}
}
The entity classes look like this:
#Setter // All lombok annotations
#Getter
#ToString
public class RestResponse<T> {
private String status;
private int httpcode;
private String devMessage;
private String userMessage;
private T data;
}
#Entity
#Data // Lombok
public class HallOfFame {
#Id
private String id;
private String name;
}
To handle exceptions, simply create another ControllerAdvice with ExceptionHandler. Use the example in this link.
Advantages of this solution:
It keeps your controllers clean. You can support any return type from your controller methods.
Your controller return type class does not need to extend some base class as required by the AOP approach.
You do not need to hack your way through Spring filters by using HttpServletResponseWrappers. They come up with a performance penalty.
EDIT - 17th September 2019
To handle exceptions use #ExceptionHandler. Refer code below.
#ExceptionHandler(Exception.class)
#ResponseBody
public MyResponseEntity<Object> handleControllerException(HttpServletRequest request, Throwable ex) {
// default value
int httpCode = HttpStatus.INTERNAL_SERVER_ERROR.value();
if(ex instanceof ResourceNotFoundException) {
httpCode = HttpStatus.NOT_FOUND.value();
}
...
}
The way I understand your question, you have exactly three choices.
Option #1
Manually wrap your objects in simple SuccessResponse, ErrorResponse, SomethingSortOfWrongResponse, etc. objects that have the fields you require. At this point, you have per-request flexibility, changing the fields on one of the response wrappers is trivial, and the only true drawback is code repetition if many of the controller's request methods can and should be grouped together.
Option #2
As you mentioned, and filter could be designed to do the dirty work, but be wary that Spring filters will NOT give you access to request or response data. Here's an example of what it might look like:
#Component
public class ResponseWrappingFilter extends GenericFilterBean {
#Override
public void doFilter(
ServletRequest request,
ServletResponse response,
FilterChain chain) {
// Perform the rest of the chain, populating the response.
chain.doFilter(request, response);
// No way to read the body from the response here. getBody() doesn't exist.
response.setBody(new ResponseWrapper(response.getStatus(), response.getBody());
}
}
If you find a way to set the body in that filter, then yes, you could easily wrap it up. Otherwise, this option is a dead end.
Option #3
A-ha. So you got this far. Code duplication is not an option, but you insist on wrapping responses from your controller methods. I'd like to introduce the true solution - aspect-oriented programming (AOP), which Spring supports fondly.
If you're not familiar with AOP, the premise is as follows: you define an expression that matches (like a regular expression matches) points in the code. These points are called join points, while the expressions that match them are called pointcuts. You can then opt to execute additional, arbitrary code, called advice, when any pointcut or combination of pointcuts are matched. An object that defines pointcuts and advice is called an aspect.
It's great for expressing yourself more fluently in Java. The only drawback is weaker static type checking. Without further ado, here's your response-wrapping in aspect-oriented programming:
#Aspect
#Component
public class ResponseWrappingAspect {
#Pointcut("within(#org.springframework.stereotype.Controller *)")
public void anyControllerPointcut() {}
#Pointcut("execution(* *(..))")
public void anyMethodPointcut() {}
#AfterReturning(
value = "anyControllerPointcut() && anyMethodPointcut()",
returning = "response")
public Object wrapResponse(Object response) {
// Do whatever logic needs to be done to wrap it correctly.
return new ResponseWrapper(response);
}
#AfterThrowing(
value = "anyControllerPointcut() && anyMethodPointcut()",
throwing = "cause")
public Object wrapException(Exception cause) {
// Do whatever logic needs to be done to wrap it correctly.
return new ErrorResponseWrapper(cause);
}
}
The final result will be the non-repeating response wrapping that you seek. If you only want some or one controller receive this effect, then update the pointcut to match methods only within instances of that controller (rather than any class holding the #Controller annotation).
You'll need to include some AOP dependencies, add the AOP-enabling annotation in a configuration class, and make sure something component-scans the package this class is in.
Simplest way i manage custom responses from controllers is by utilising the Map variable.
so your code ends up looking like:
public #ResponseBody Map controllerName(...) {
Map mapA = new HashMap();
mapA.put("status", "5");
mapA.put("content", "something went south");
return mapA;
}
beauty of is is that you can configure it any thousand ways.
Currently i use for object transmition, custom exception handling and data reporting, too easy.
Hope this helps
I am also using AOP with #Around. Developed a custom annotation and using that for point cut. I am using a global Response. It has the status, Message and data which is of type List of type
List <? extends parent> dataList
( which can solve your class cast exception). All the entities extends this Parent class. This way I can set all the data into my List.
Also I am using the message key as param with the custom annotation and setting it in action.
Hope this helps.
I have successfully set up a quick test of creating a "REST-like" service that returns an object serialized to JSON, and that was quite easy and quick (based on this article).
But while returning JSON-ified objects was easy as peach, I have yet to see any examples dealing with input parameters that are not primitives. How can I pass in a complex object as an argument? I am using Apache CXF, but examples using other frameworks like Jackson are welcome too :)
Client side would probably be something like building a javascript object, pass it into JSON.stringify(complexObj), and pass that string as one of the parameters.
The service would probably look something like this
#Service("myService")
class RestService {
#GET
#Produces("application/json")
#Path("/fooBar")
public Result fooBar(#QueryParam("foo") double foo, #QueryParam("bar") double bar,
#QueryParam("object") MyComplex object) throws WebServiceException {
...
}
}
Sending serialized objects as parameters would probably quickly touch the 2KB URL-limit imposed by Internet Explorer. Would you recommend using POST in these cases, and would I need to change much in the function definitions?
After digging a bit I quickly found out there are basically two options:
Option 1
You pass a "wrapper object" containing all the other parameters to the service. You might need to annotate this wrapper class with JAXB annotations like #XmlRootElement in order for this to work with the Jettison based provider, but if you use Jackson in stead there is no need. Just set the content type to the right type and the right message body reader will be invoked.
This will only work for POST type services of course (AFAIK).
Example
This is just an example of turning the service mentioned in the original question into one using a wrapper object.
#Service("myService")
class RestService {
#POST
#Produces("application/json")
#Path("/fooBar")
public Result fooBar(
/**
* Using "" will inject all form params directly into a ParamsWrapper
* #see http://cxf.apache.org/docs/jax-rs-basics.html
*/
#FormParam("") FooBarParamsWrapper wrapper
) throws WebServiceException {
doSomething(wrapper.foo);
}
}
class ParamsWrapper {
double foo, bar;
MyComplexObject object;
}
Option 2
You can provide some special string format that you pack your objects into and then implement either a constructor taking a string, a static valueOf(String s) or a static fromString(String s) in the class that will take this string and create an object from it. Or quite similar, create a ParameterHandler that does exactly the same.
AFAIK, only the second version will allow you to call your services from a browser using JSONP (since JSONP is a trick restricted to GET). I chose this route to be able to pass arrays of complex objects in the URI.
As an example of how this works, take the following domain class and service
Example
#GET
#Path("myService")
public void myService(#QueryParam("a") MyClass [] myVals) {
//do something
}
class MyClass {
public int foo;
public int bar;
/** Deserializes an Object of class MyClass from its JSON representation */
public static MyClass fromString(String jsonRepresentation) {
ObjectMapper mapper = new ObjectMapper(); //Jackson's JSON marshaller
MyClass o= null;
try {
o = mapper.readValue(jsonRepresentation, MyClass.class );
} catch (IOException e) {
throw new WebApplicationException()
}
return o;
}
}
A URI http://my-server.com/myService?a={"foo":1, "bar":2}&a={"foo":100, "bar":200} would in this case be deserialized into an array composed of two MyClass objects.
2019 comment:
Seeing that this answer still gets some hits in 2019, I feel I should comment. In hindsight, I would not recomment option 2, as going through these steps just to be able to be able to do GET calls adds complexity that's probably not worth it. If your service takes such complex input, you will probably not be able to utilize client side caching anyway, due to the number of permutations of your input. I'd just go for configuring proper Cross-Origin-Sharing (CORS) headers on the server and POST the input. Then focus on caching whatever you can on the server.
The accepted answer is missing #BeanParam. See
https://docs.jboss.org/resteasy/docs/3.0-rc-1/javadocs/javax/ws/rs/BeanParam.html
for further details. It allows you to define query params inside a wrapper object.
E.g.
public class TestPOJO {
#QueryParam("someQueryParam")
private boolean someQueryParam;
public boolean isSomeQueryParam() {
return someQueryParam;
}
public boolean setSomeQueryParam(boolean value) {
this.someQueryParam = value;
}
}
... // inside the Resource class
#GET
#Path("test")
public Response getTest(#BeanParam TestPOJO testPOJO) {
...
}
the best and simplest solution is to send your object as a json string and in server side implement a method which will decode that json and map to the specified object as per your need.. and yes it`s better to use POST.