Spring Rest Docs error - "No content to map due to end-of-input" - spring-restdocs

Question

I have a test case on the Get method with Spring Rest Docs. It runs fine. With the same fashion of code on the Post method as the following:
Foo foo = new Foo(...);
this.mockMvc.perform(post("/foos")
.contentType(APPLICATION_JSON_UTF8)
.content(objectMapper.writeValueAsString(foo)))
.andExpect(status().isCreated())
.andExpect(header().string("Location", notNullValue()))
.andDo(document("foo-post", preprocessResponse(prettyPrint()),
links(
halLinks(),
linkWithRel("self").description("..."),
linkWithRel("foo").description("...")),
responseFields(
fieldWithPath("attr1").description("..."),
fieldWithPath("attr2").description("..."),
...
fieldWithPath("_links").description("<<resource-book-links,links>> to other resources")
)
));
I get an error, however.
org.springframework.restdocs.snippet.ModelCreationException: com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input at [Source: [B#47fca3cc; line: 1, column: 0]
at org.springframework.restdocs.hypermedia.LinksSnippet.createModel(LinksSnippet.java:131)
at org.springframework.restdocs.snippet.TemplatedSnippet.document(TemplatedSnippet.java:64)
at org.springframework.restdocs.generate.RestDocumentationGenerator.handle(RestDocumentationGenerator.java:196)
at org.springframework.restdocs.mockmvc.RestDocumentationResultHandler.handle(RestDocumentationResultHandler.java:55)
at org.springframework.test.web.servlet.MockMvc$1.andDo(MockMvc.java:177)
at com.example.SpringDataSampleApplicationTests.createBookRest(SpringDataSampleApplicationTests.java:173)
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:483)
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.JUnitRestDocumentation$1.evaluate(JUnitRestDocumentation.java:55)
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:252)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
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$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:51)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:237)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
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:483)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: com.fasterxml.jackson.databind.JsonMappingException: No content to map due to end-of-input at [Source: [B#47fca3cc; line: 1, column: 0]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3838)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3783)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2929)
at org.springframework.restdocs.hypermedia.AbstractJsonLinkExtractor.extractLinks(AbstractJsonLinkExtractor.java:41)
at org.springframework.restdocs.hypermedia.LinksSnippet.createModel(LinksSnippet.java:127)
... 41 more
If I comment out anything after "andDo(..)", it is fine. That means the problem is in the document section.
What is missing?

Answer 1

Your tests using MockMvc are not setting an Accept header in the POST request. That means that, by default, Spring Data REST does not include a body in its 201 Created response. You either need to configure Spring Data REST to always return a body for create requests or you need to change your tests to send an Accept header.