Test Spring REST API. How to save entity with subobject in JUnit test? - spring

Question

I have two classes: Course and Lesson. Course is #OneToMany relationship with Lesson. Using Spring Boot I've created a simple REST API to manage the classes. I've tested the API manually with postman and it looks like everything is working.
Next, I've writen simple JUnite to test the API automatically. When the test finishes, Course entity was saved correctly in the database but Lesson throws an error:
2014-10-15 20:19:15.162 ERROR 5812 --- [nio-8080-exec-2] s.d.r.w.AbstractRepositoryRestController : Could not read JSON: Template must not be null or empty! (through reference chain: com.mbury.elearning.domain.Lesson["course"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Template must not be null or empty! (through reference chain: com.mbury.elearning.domain.Lesson["course"])
Looks like #OneToMany relationship was not correctly mapped but I don't know how to handle this. Does anyone have an idea how to configure Spring REST with an entity that contains subobject to work correctly?
Bellow I've attached all my code:
LessonTest.java
package com.mbury.elearning;
import static org.hamcrest.Matchers.equalTo;
import static org.springframework.test.util.MatcherAssertionErrors.assertThat;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.IntegrationTest;
import org.springframework.boot.test.SpringApplicationConfiguration;
import org.springframework.boot.test.TestRestTemplate;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;
import org.springframework.web.client.RestTemplate;
import com.mbury.elearning.domain.Course;
import com.mbury.elearning.domain.Lesson;
#RunWith(SpringJUnit4ClassRunner.class)
#SpringApplicationConfiguration(classes = Application.class)
#WebAppConfiguration
#IntegrationTest
public class LessonTest {
final String BASE_URL_COURSE = "http://localhost:8080/courses/";
final String BASE_URL_LESSON = "http://localhost:8080/lessons/";
#Test
public void shouldCreateNewLesson() {
final String COURSE_TITLE = "test";
final String COURSE_DESCRIPTION = "test";
final String LESSON_TOPIC = "test";
Course course = new Course();
course.setTitle(COURSE_TITLE);
course.setDescription(COURSE_DESCRIPTION);
Lesson lesson = new Lesson();
lesson.setTopic(LESSON_TOPIC);
lesson.setCourse(course);
RestTemplate rest = new TestRestTemplate();
ResponseEntity<Course> response = rest.postForEntity(BASE_URL_COURSE, course,
Course.class);
assertThat(response.getStatusCode(), equalTo(HttpStatus.CREATED));
ResponseEntity<Lesson> response1 = rest.postForEntity(BASE_URL_LESSON, lesson,
Lesson.class);
assertThat(response1.getStatusCode(), equalTo(HttpStatus.CREATED));
}
}
Course.java
package com.mbury.elearning.domain;
import java.util.List;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
#Entity
#Table(name = "course")
public class Course {
#Column(name = "description")
private String description;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private Integer id;
#OneToMany(mappedBy = "course")
private List<Lesson> lesson;
#Column(name = "title")
private String title;
public String getDescription() {
return description;
}
public Integer getId() {
return id;
}
public List<Lesson> getLesson() {
return lesson;
}
public String getTitle() {
return title;
}
public void setDescription(String description) {
this.description = description;
}
public void setId(Integer id) {
this.id = id;
}
public void setLesson(List<Lesson> lesson) {
this.lesson = lesson;
}
public void setTitle(String title) {
this.title = title;
}
}
Lesson.java
package com.mbury.elearning.domain;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
#Entity
#Table(name = "lesson")
public class Lesson {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
private int id;
#Column(name = "topic")
private String topic;
#ManyToOne(optional = false)
#JoinColumn(name = "ID_COURSE")
Course course;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTopic() {
return topic;
}
public void setTopic(String topic) {
this.topic = topic;
}
public Course getCourse() {
return course;
}
public void setCourse(Course course) {
this.course = course;
}
}
CourseRepository.java
package com.mbury.elearning.repository;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.rest.core.annotation.RepositoryRestResource;
import com.mbury.elearning.domain.Course;
#RepositoryRestResource
public interface CourseRepository extends CrudRepository<Course, Integer> {
}
LessonRepository .java
package com.mbury.elearning.repository;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.rest.core.annotation.RepositoryRestResource;
import com.mbury.elearning.domain.Lesson;
#RepositoryRestResource
public interface LessonRepository extends CrudRepository<Lesson, Integer> {
}
Application .java
package com.mbury.elearning;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.data.rest.webmvc.config.RepositoryRestMvcConfiguration;
#Configuration
#ComponentScan
#EnableJpaRepositories
#Import(RepositoryRestMvcConfiguration.class)
#EnableAutoConfiguration
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}

Answer 1

The root of the problem is that you're trying to reuse your domain objects, Lesson and Course, to create the JSON payloads that you're sending to your REST API. This doesn't work as the REST API's view of a Lesson or Course is different from the implementation's JPA-based view of them. For example, on the server, the id of a Lesson or Course is an int, whereas in the REST API the id is a URI.
Given that Course and Lession are both quite simple types, it's probably easiest to use a Map when you're sending a request to the REST API. For example, you can create a course like this:
Map<String, Object> course = new HashMap<String, Object>();
course.put("title", "test");
course.put("description", "test");
I mentioned above that, in the REST API, a URI is used to identify a course. This means that when you create a lesson, you need the URI of the course to which it belongs. You get that URI from the Location header of the response that's returned when you create the course:
ResponseEntity<Void> courseResponse = rest.postForEntity(BASE_URL_COURSE, course, Void.class);
assertThat(courseResponse.getStatusCode(), equalTo(HttpStatus.CREATED));
URI courseLocation = courseResponse.getHeaders().getLocation();
You can then use this URI to create the Map for the lesson and make the API call to create it:
Map<String, Object> lesson = new HashMap<String, Object>();
lesson.put("topic", "test");
lesson.put("course", courseLocation);
ResponseEntity<Void> lessonResponse = rest.postForEntity(BASE_URL_LESSON, lesson, Void.class);
assertThat(lessonResponse.getStatusCode(), equalTo(HttpStatus.CREATED));
Putting this all together gives you this test method:
#Test
public void shouldCreateNewLesson() {
Map<String, Object> course = new HashMap<String, Object>();
course.put("title", "test");
course.put("description", "test");
RestTemplate rest = new TestRestTemplate();
ResponseEntity<Void> courseResponse = rest.postForEntity(BASE_URL_COURSE, course, Void.class);
assertThat(courseResponse.getStatusCode(), equalTo(HttpStatus.CREATED));
URI courseLocation = courseResponse.getHeaders().getLocation();
Map<String, Object> lesson = new HashMap<String, Object>();
lesson.put("topic", "test");
lesson.put("course", courseLocation);
ResponseEntity<Void> lessonResponse = rest.postForEntity(BASE_URL_LESSON, lesson, Void.class);
assertThat(lessonResponse.getStatusCode(), equalTo(HttpStatus.CREATED));
}

Answer 2

I am getting a 404 error. It looks like the issue could be with calling the BASE_URL_LESSON.