In the tutorial, we show how to expose CRUD RestAPIs Post/Get/Put/Delete to interact with Hibernate Spring JPA One-to-Many association models using SpringBoot and PostgreSQL database.
Previous post:
– Expose CRUD RestAPIs Spring JPA One-to-One Association
Related articles:
– Spring JPA – Many to Many relationship
– How to configure Spring JPA One to One Relationship – SpringBoot
– Spring Data Rest – JPA One-to-Many relational entities | SpringBoot + MySql + HAL Browser
– Kotlin SpringJPA Hibernate One-To-Many relationship
Related pages:
Contents
Technologies
- Java 8
- Maven 3.5.4
- SpringToolSuite version 3.9.4.RELEASE
- SpringBoot 2.0.4.RELEASE
Demo
Overview
We have 2 models Student & Assignment with One-to-Many association relationship:
We create a SpringBoot project as below:
Hibernate JPA configuration for 2 models Student & Assignment:
– Student model ->
@Entity @Table(name = "students") @JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) public class Student implements Serializable{ private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "name") private String name; @Column(name = "age") private int age; @OneToMany(mappedBy = "student", cascade = CascadeType.ALL, fetch = FetchType.LAZY) private Set<Assignment> assignments; public Student() {} public Student(String name, int age) { this.name = name; this.age = age; } // Getter & Setter methods // ... |
– Assignment model ->
@Entity @Table(name = "assignments") @JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) public class Assignment implements Serializable{ private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "name") private String name; @Column(name = "grade") private int grade; @ManyToOne(fetch = FetchType.LAZY, optional = false) @JoinColumn(name = "student_id", nullable = false) @JsonIgnore private Student student; public Assignment() {} public Assignment(String name, int grade) { this.name = name; this.grade = grade; } // Getter & Setter methods // ... |
We exposes RestAPIs for Post/Get/Put/Delete Students & Assignments:
– Student ->
@GetMapping("/api/students"): get all Students@GetMapping("/api/students/{id}"): get a Student by ID@PostMapping("/api/students"): post a Student@PutMapping("/api/students/{id}"): update a Student@DeleteMapping("/api/students/{id}"): delete a Student
– Assignments ->
@GetMapping("/students/{studentId}/assignments"): get a Assignment by Student’s ID@PostMapping("/students/{studentId}/assignments"): add an Assignment@PutMapping("/students/{studentId}/assignments/{assignmentId}"): update an Assignment@DeleteMapping("/students/{studentId}/assignments/{assignmentId}"): delete an Assignment by ID
Now we’ll create a project from scratch ->
Practice
Create SpringBoot project
We use SpringToolSuite to create a Java 8 SpringBoot project with below dependencies:
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>org.postgresql</groupId> <artifactId>postgresql</artifactId> <scope>runtime</scope> </dependency> |
OneToMany Models
– Student model ->
package com.grokonez.springrestapi.onetomany.model; import java.io.Serializable; import java.util.Set; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.OneToMany; import javax.persistence.Table; import com.fasterxml.jackson.annotation.JsonIgnoreProperties; @Entity @Table(name = "students") @JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) public class Student implements Serializable{ private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "name") private String name; @Column(name = "age") private int age; @OneToMany(mappedBy = "student", cascade = CascadeType.ALL, fetch = FetchType.LAZY) private Set<Assignment> assignments; public Student() {} public Student(String name, int age) { this.name = name; this.age = age; } public void setId(Long id) { this.id = id; } public Long getId() { return this.id; } public void setName(String name) { this.name = name; } public String getName() { return this.name; } public void setAge(int age) { this.age = age; } public int getAge() { return this.age; } public void setAssignments(Set<Assignment> assignments) { this.assignments = assignments; } public Set<Assignment> getAssignments(){ return this.assignments; } } |
– Assignment model ->
package com.grokonez.springrestapi.onetomany.model; import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table; import com.fasterxml.jackson.annotation.JsonIgnore; import com.fasterxml.jackson.annotation.JsonIgnoreProperties; @Entity @Table(name = "assignments") @JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) public class Assignment implements Serializable{ private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "name") private String name; @Column(name = "grade") private int grade; @ManyToOne(fetch = FetchType.LAZY, optional = false) @JoinColumn(name = "student_id", nullable = false) @JsonIgnore private Student student; public Assignment() {} public Assignment(String name, int grade) { this.name = name; this.grade = grade; } public void setId(Long id) { this.id = id; } public Long getId() { return this.id; } public void setName(String name) { this.name = name; } public String getName() { return this.name; } public void setGrade(int grade) { this.grade = grade; } public int getGrade() { return this.grade; } public void setStudent(Student student) { this.student = student; } public Student getStudent() { return this.student; } } |
JPA Repositories
– StudentRepository ->
package com.grokonez.springrestapi.onetomany.jpa; import org.springframework.data.jpa.repository.JpaRepository; import com.grokonez.springrestapi.onetomany.model.Student; public interface StudentRepository extends JpaRepository<Student, Long> { } |
– AssignmentRepository ->
package com.grokonez.springrestapi.onetomany.jpa; import java.util.List; import org.springframework.data.jpa.repository.JpaRepository; import com.grokonez.springrestapi.onetomany.model.Assignment; public interface AssignmentRepository extends JpaRepository<Assignment, Long> { List<Assignment> findByStudentId(Long studentId); } |
Add datasource configurations in application.properties file ->
spring.datasource.url=jdbc:postgresql://localhost/testdb spring.datasource.username=postgres spring.datasource.password=123 spring.jpa.generate-ddl=true #spring.jackson.serialization.fail-on-empty-beans=false |
Expose Rest APIs
– Create NotFoundException ->
package com.grokonez.springrestapi.onetomany.exception; import org.springframework.http.HttpStatus; import org.springframework.web.bind.annotation.ResponseStatus; @ResponseStatus(code = HttpStatus.NOT_FOUND, reason = "NotFoundException not found") public class NotFoundException extends RuntimeException { private static final long serialVersionUID = 1L; public NotFoundException(String message) { super(message); } public NotFoundException(String message, Throwable cause) { super(message, cause); } } |
– StudentController APIs ->
package com.grokonez.springrestapi.onetomany.rest; import java.util.List; import java.util.Optional; import javax.validation.Valid; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.DeleteMapping; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.PutMapping; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import com.grokonez.springrestapi.onetomany.exception.NotFoundException; import com.grokonez.springrestapi.onetomany.jpa.StudentRepository; import com.grokonez.springrestapi.onetomany.model.Student; @RestController @RequestMapping("/api") public class StudentController { @Autowired private StudentRepository studentRepository; @GetMapping("/students") public List<Student> getAllStudents() { return studentRepository.findAll(); } @GetMapping("/students/{id}") public Student getStudentByID(@PathVariable Long id) { Optional<Student> optStudent = studentRepository.findById(id); if(optStudent.isPresent()) { return optStudent.get(); }else { throw new NotFoundException("Student not found with id " + id); } } @PostMapping("/students") public Student createStudent(@Valid @RequestBody Student student) { return studentRepository.save(student); } @PutMapping("/students/{id}") public Student updateStudent(@PathVariable Long id, @Valid @RequestBody Student studentUpdated) { return studentRepository.findById(id) .map(student -> { student.setName(studentUpdated.getName()); student.setAge(studentUpdated.getAge()); return studentRepository.save(student); }).orElseThrow(() -> new NotFoundException("Student not found with id " + id)); } @DeleteMapping("/students/{id}") public String deleteStudent(@PathVariable Long id) { return studentRepository.findById(id) .map(student -> { studentRepository.delete(student); return "Delete Successfully!"; }).orElseThrow(() -> new NotFoundException("Student not found with id " + id)); } } |
– AssignmentController APIs ->
package com.grokonez.springrestapi.onetomany.rest; import java.util.List; import javax.validation.Valid; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.DeleteMapping; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.PutMapping; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import com.grokonez.springrestapi.onetomany.exception.NotFoundException; import com.grokonez.springrestapi.onetomany.jpa.AssignmentRepository; import com.grokonez.springrestapi.onetomany.jpa.StudentRepository; import com.grokonez.springrestapi.onetomany.model.Assignment; @RestController @RequestMapping("/api") public class AssignmentController { @Autowired private AssignmentRepository assignmentRepository; @Autowired private StudentRepository studentRepository; @GetMapping("/students/{studentId}/assignments") public List<Assignment> getContactByStudentId(@PathVariable Long studentId) { if(!studentRepository.existsById(studentId)) { throw new NotFoundException("Student not found!"); } return assignmentRepository.findByStudentId(studentId); } @PostMapping("/students/{studentId}/assignments") public Assignment addAssignment(@PathVariable Long studentId, @Valid @RequestBody Assignment assignment) { return studentRepository.findById(studentId) .map(student -> { assignment.setStudent(student); return assignmentRepository.save(assignment); }).orElseThrow(() -> new NotFoundException("Student not found!")); } @PutMapping("/students/{studentId}/assignments/{assignmentId}") public Assignment updateAssignment(@PathVariable Long studentId, @PathVariable Long assignmentId, @Valid @RequestBody Assignment assignmentUpdated) { if(!studentRepository.existsById(studentId)) { throw new NotFoundException("Student not found!"); } return assignmentRepository.findById(assignmentId) .map(assignment -> { assignment.setName(assignmentUpdated.getName()); assignment.setGrade(assignmentUpdated.getGrade()); return assignmentRepository.save(assignment); }).orElseThrow(() -> new NotFoundException("Assignment not found!")); } @DeleteMapping("/students/{studentId}/assignments/{assignmentId}") public String deleteAssignment(@PathVariable Long studentId, @PathVariable Long assignmentId) { if(!studentRepository.existsById(studentId)) { throw new NotFoundException("Student not found!"); } return assignmentRepository.findById(assignmentId) .map(assignment -> { assignmentRepository.delete(assignment); return "Deleted Successfully!"; }).orElseThrow(() -> new NotFoundException("Contact not found!")); } } |
Run & Check Results
– Run the SpringBoot project with commandline mvn spring-boot:run.
2 tables is created in PostgreSQL ->
– Add Students ->
– Add Assignments ->
– Get All Students ->
– Get All Assignments of a Student->
– Update Student ->
– Update Assignment ->
– Delete a Student -> image
– Delete an Assignment ->
Note: PostgreSQL commandline ->
PostgreSQL\9.6\bin>psql.exe --username="postgres" -W: connect to PostgreSQL ->
C:\Program Files\PostgreSQL\9.6\bin>psql.exe --username="postgres" -W Password for user postgres: psql (9.6.9) WARNING: Console code page (437) differs from Windows code page (1252) 8-bit characters might not work correctly. See psql reference page "Notes for Windows users" for details. Type "help" for help. |
– \l: List of databases
– \c testdb: connect to “testdb”
– \d: List of relations ->
testdb=# \d List of relations Schema | Name | Type | Owner --------+--------------------+----------+---------- public | assignments | table | postgres public | assignments_id_seq | sequence | postgres public | students | table | postgres public | students_id_seq | sequence | postgres (4 rows) |
– \d assignments: Get Schema of a table assignments ->
testdb=# \d assignments; Table "public.assignments" Column | Type | Modifiers ------------+------------------------+---------------------------------------------------------- id | bigint | not null default nextval('assignments_id_seq'::regclass) grade | integer | name | character varying(255) | student_id | bigint | not null Indexes: "assignments_pkey" PRIMARY KEY, btree (id) Foreign-key constraints: "fkn1mo9c6bajjx15gthydqdnv4b" FOREIGN KEY (student_id) REFERENCES students(id) |
Nice article.
I reproduce the code (not download your codes).
I added the data. It was successfully.
But, when I try to get the data via client it goes error :
{
"timestamp": "2019-03-12T16:04:43.868+0000",
"status": 500,
"error": "Internal Server Error",
"message": "Could not write JSON: Infinite recursion (StackOverflowError); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: com.hendisantika.springbootrestapionetomany.entity.Student[\"assignments\"])",
"path": "/api/students/1"
}
Any suggets?
Thanks