SnippetException: Cannot document response fields as the response body is empty - spring

Question

Here is my Controller:
#PostMapping("post")
#PreAuthorize("hasAuthority('WRITE')")
public ResponseEntity<?> createPost(#RequestBody PostEntity postEntity) {
return new ResponseEntity<>(postService.createPost(postEntity), HttpStatus.CREATED);
}
Service :
#Override
public Post createPost(PostEntity postEntity) {
return postFactory.buildPost(postEntityRepository.save(postEntity));
}
//Post is Immutable class here
public Post buildPost(PostEntity entity) {
return new Post.Builder()
.groupId(entity.getGroupEntity().getGroupId())
.postedBy(entity.getPostedBy().getUsername())
.postType(entity.getType())
.postMedia(entity.getPostMedia())
.postId(entity.getPostId())
.build();
}
Here is my mockMvc:
#BeforeEach
public void setUp(WebApplicationContext webApplicationContext,
RestDocumentationContextProvider restDocumentation) {
this.mockMvc = MockMvcBuilders.webAppContextSetup(webApplicationContext)
.apply(documentationConfiguration(restDocumentation))
.alwaysDo(document("{method-name}",
preprocessRequest(prettyPrint()), preprocessResponse(prettyPrint())))
.build();
}
Here is my Test:
this.mockMvc.perform(post("/api/post")
.contentType(MediaTypes.HAL_JSON)
.contextPath("/api")
.content(this.objectMapper.writeValueAsString(postEntity)))
.andExpect(status().isCreated())
.andDo(
document("{method-name}", preprocessRequest(prettyPrint()),
preprocessResponse(prettyPrint()),
requestFields(describeCreatePostRequest()),
responseFields(describePostEntityResult())
));
Here is Post call:
#Value.Immutable
#JsonSerialize(as = ImmutablePost.class)
#JsonDeserialize(as = ImmutablePost.class)
#JsonInclude(JsonInclude.Include.NON_NULL)
#Relation(value = "post", collectionRelation = "posts")
public interface Post {
Long getPostId();
String getPostType();
String postedBy();
#Nullable
PostMedia postMedia();
Long groupId();
class Builder extends ImmutablePost.Builder {}
}
PostEntity #Entity class here is json format:
{
"type" : "text",
"postedBy" : {
"username": "sandeep"
},
"postMedia" : {
"mediaType": "text",
"mediaUrl": "null",
"content": "Hi this is testing media content",
"createdAt": 1234,
"updatedAt": 689
},
"groupEntity": {
"groupId": 4
}
}
And Post entity class:
#Entity
#Table(name = "POST")
#JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class PostEntity {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "POST_ID")
private Long postId;
#Column(name = "POST_TYPE")
private String type;
#ManyToOne
#JoinColumn(name = "username", referencedColumnName = "username")
private User postedBy;
#OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
#JoinColumn(name = "post_media_id", referencedColumnName = "id")
private PostMedia postMedia;
#ManyToOne(cascade = CascadeType.REMOVE, fetch = FetchType.LAZY)
#JoinColumn(name = "GROUP_ID", referencedColumnName = "GROUP_ID")
private GroupEntity groupEntity;
public PostEntity() {
}
}
I have tried
objectMapper.readValue(objectMapper.writeValueAsString(postEntity), ImmutablePost.class);
As well. but still its not working, I am facing same exception:
org.springframework.restdocs.snippet.SnippetException: Cannot document response fields as the response body is empty
at org.springframework.restdocs.payload.AbstractFieldsSnippet.verifyContent(AbstractFieldsSnippet.java:191)
at org.springframework.restdocs.payload.AbstractFieldsSnippet.createModel(AbstractFieldsSnippet.java:147)
at org.springframework.restdocs.snippet.TemplatedSnippet.document(TemplatedSnippet.java:78)
at org.springframework.restdocs.generate.RestDocumentationGenerator.handle(RestDocumentationGenerator.java:191)

Answer 1

The problem is with the "PostMedia" setters "PostMedia" and "GroupEntity". You need to accept strings in the setters parameter and convert them to the corresponding entity. Expecting the setter's arguments as the custom entity type is making the problem.
For example:
public class MyModel {
private CustomEnum myEnum;
public CustomEnum getMyEnum() {
return myEnum;
}
public void setMyEnum(String enumName) {
this.myEnum = CustomEnum.valueOf(enumName);
}
}