How do you state "No Response Fields" with Spring Rest Docs? - spring

Question

I am building an API from scratch and documenting it using Spring Rest Docs (1.0.1) and at present there are no Response Fields for a specific API.
I realize I could manually document this in the .adoc file but if later on, we advance the API and response fields come into play, I want the unit test to kick in and alert me that I need to update.
When I try:
getDocument().snippets(PayloadDocumentation.responseFields());
or
getDocument().snippets(PayloadDocumentation.responseFields(Collections.emptyMap()));
I get the following error:
org.springframework.restdocs.payload.PayloadHandlingException: com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input
at [Source: [B#7f3e9acc; line: 1, column: 1]
at org.springframework.restdocs.payload.JsonContentHandler.readContent(JsonContentHandler.java:84)
at org.springframework.restdocs.payload.JsonContentHandler.findMissingFields(JsonContentHandler.java:49)
at org.springframework.restdocs.payload.AbstractFieldsSnippet.validateFieldDocumentation(AbstractFieldsSnippet.java:112)
at org.springframework.restdocs.payload.AbstractFieldsSnippet.createModel(AbstractFieldsSnippet.java:73)
at org.springframework.restdocs.snippet.TemplatedSnippet.document(TemplatedSnippet.java:64)
at org.springframework.restdocs.mockmvc.RestDocumentationResultHandler.handle(RestDocumentationResultHandler.java:101)
at org.springframework.test.web.servlet.MockMvc.applyDefaultResultActions(MockMvc.java:195)
at org.springframework.test.web.servlet.MockMvc.perform(MockMvc.java:163)
at com.cafex.services.web.SchedEventControllerTest.createNewEvent(SchedEventControllerTest.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.restdocs.RestDocumentation$1.evaluate(RestDocumentation.java:59)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input
at [Source: [B#7f3e9acc; line: 1, column: 1]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148)
at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3781)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3721)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2819)
at org.springframework.restdocs.payload.JsonContentHandler.readContent(JsonContentHandler.java:81)
... 40 more

Answer 1

As you've seen, REST Docs doesn't support that at the moment. As an alternative, I'd recommend using standard MockMvc expectations to assert that there response has no body such as MockMvcResultMatchers.content().bytes(new byte[0]).
I've opened an issue to consider enhancing REST Docs so that you could use the snippet in the way that you have tried.