Learn to create HTTP POST REST APIs using Spring boot 2 framework which accept JSON request and return JSON response to client. In this Spring Boot 2 REST POST API tutorial, we will create a REST API which returns list of employees after adding a new employee to collection.
1. Maven dependencies
At first, create a simple maven web project and update following spring boot dependencies in pom.xml file.
The important dependencies are spring-boot-starter-parent (read more) and spring-boot-starter-web (read more).
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.howtodoinjava.demo</groupId> <artifactId>springbootdemo</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>SpringBootDemo</name> <description>Spring Boot2 REST API Demo for http://howtodoinjava.com</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.5.RELEASE</version> <relativePath /> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
2. REST Controller
In Spring, a controller class, which is capable of serving REST API requests, is called rest controller. It should be annotated with @RestController annotation. In given rest controller, we have two API methods. Feel free to add more methods as needed.
2.1. HTTP POST API
- It adds an employee in the employees collection.
- It accept employee data in
Employeeobject. - It accepts and creates JSON meda type.
- It accepts two HTTP headers i.e. X-COM-PERSIST and X-COM-LOCATION. First header is required and second header is optional.
- It returns the location of resource created.
package com.howtodoinjava.rest.controller;
import java.net.URI;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
import com.howtodoinjava.rest.dao.EmployeeDAO;
import com.howtodoinjava.rest.model.Employee;
import com.howtodoinjava.rest.model.Employees;
@RestController
@RequestMapping(path = "/employees")
public class EmployeeController
{
@Autowired
private EmployeeDAO employeeDao;
@GetMapping(path="/", produces = "application/json")
public Employees getEmployees()
{
return employeeDao.getAllEmployees();
}
@PostMapping(path= "/", consumes = "application/json", produces = "application/json")
public ResponseEntity<Object> addEmployee(
@RequestHeader(name = "X-COM-PERSIST", required = true) String headerPersist,
@RequestHeader(name = "X-COM-LOCATION", required = false, defaultValue = "ASIA") String headerLocation,
@RequestBody Employee employee)
throws Exception
{
//Generate resource id
Integer id = employeeDao.getAllEmployees().getEmployeeList().size() + 1;
employee.setId(id);
//add resource
employeeDao.addEmployee(employee);
//Create resource location
URI location = ServletUriComponentsBuilder.fromCurrentRequest()
.path("/{id}")
.buildAndExpand(employee.getId())
.toUri();
//Send location in response
return ResponseEntity.created(location).build();
}
}
3. Custom error handler
A good designed resi api must have consistent error messages as well. One way to achieve it in spring boot applications is using controller advice. Inside @ControllerAdvice class, use @ExceptionHandler annotated methods to return consistent responses in invalid scenarios.
package com.howtodoinjava.rest.exception;
import java.util.ArrayList;
import java.util.List;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.ServletRequestBindingException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.request.WebRequest;
@SuppressWarnings({"unchecked","rawtypes"})
@ControllerAdvice
public class CustomExceptionHandler
{
@ExceptionHandler(ServletRequestBindingException.class)
public final ResponseEntity<Object> handleHeaderException(Exception ex, WebRequest request)
{
List<String> details = new ArrayList<>();
details.add(ex.getLocalizedMessage());
ErrorResponse error = new ErrorResponse("Bad Request", details);
return new ResponseEntity(error, HttpStatus.BAD_REQUEST);
}
@ExceptionHandler(Exception.class)
public final ResponseEntity<Object> handleAllExceptions(Exception ex, WebRequest request)
{
List<String> details = new ArrayList<>();
details.add(ex.getLocalizedMessage());
ErrorResponse error = new ErrorResponse("Server Error", details);
return new ResponseEntity(error, HttpStatus.INTERNAL_SERVER_ERROR);
}
}
4. @SpringBootApplication
Run the application in embedded tomcat application by executing main() method of SpringBootDemoApplication class.
package com.howtodoinjava.rest;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class SpringBootDemoApplication {
public static void main(String[] args) {
SpringApplication.run(SpringBootDemoApplication.class, args);
}
}
5. Model classes and DAO
These classes are not directly related to REST. Still lets take a look how they have been written.
package com.howtodoinjava.rest.model;
public class Employee {
public Employee() {
}
public Employee(Integer id, String firstName, String lastName, String email) {
super();
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
this.email = email;
}
private Integer id;
private String firstName;
private String lastName;
private String email;
//Getters and setters
@Override
public String toString() {
return "Employee [id=" + id + ", firstName=" + firstName + ",
lastName=" + lastName + ", email=" + email + "]";
}
}
package com.howtodoinjava.rest.model;
import java.util.ArrayList;
import java.util.List;
public class Employees
{
private List<Employee> employeeList;
public List<Employee> getEmployeeList() {
if(employeeList == null) {
employeeList = new ArrayList<>();
}
return employeeList;
}
public void setEmployeeList(List<Employee> employeeList) {
this.employeeList = employeeList;
}
}
DAO class uses a static list to store data. Here we need to implement actual database interaction.
package com.howtodoinjava.rest.dao;
import org.springframework.stereotype.Repository;
import com.howtodoinjava.rest.model.Employee;
import com.howtodoinjava.rest.model.Employees;
@Repository
public class EmployeeDAO
{
private static Employees list = new Employees();
static
{
list.getEmployeeList().add(new Employee(1, "Lokesh", "Gupta", "howtodoinjava@gmail.com"));
list.getEmployeeList().add(new Employee(2, "Alex", "Kolenchiskey", "abc@gmail.com"));
list.getEmployeeList().add(new Employee(3, "David", "Kameron", "titanic@gmail.com"));
}
public Employees getAllEmployees()
{
return list;
}
public void addEmployee(Employee employee) {
list.getEmployeeList().add(employee);
}
}
6. Spring Boot 2 REST POST API – Demo
To start the application, run the main() method in SpringBootDemoApplication class. It will start the embedded tomcat server. In server logs, you will see that API have been registered in spring context.
s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/employees/],methods=[GET],produces=[application/json]}" onto public com.howtodoinjava.rest.model.Employees com.howtodoinjava.rest.controller. EmployeeController.getEmployees()
s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/employees/],methods=[POST], consumes=[application/json], produces=[application/json]}" onto public org.springframework.http.ResponseEntity <java.lang.Object> com.howtodoinjava.rest. controller. EmployeeController.addEmployee( java.lang.String, java.lang.String, com.howtodoinjava.rest.model.Employee) throws java.lang.Exception
6.1. HTTP POST – Validate missing header
Once server is UP, access the API using some rest client. Do not pass the request headers.
{
"message": "Bad Request",
"details": [
"Missing request header 'X-COM-PERSIST' for method parameter of type String"
],
}
6.2. HTTP POST – Valid response
location: http://localhost:8080/employees/4 content-length: 0 date: Sat, 06 Oct 2018 04:33:37 GMT
Hit the GET request and this time we will get the added employee as well.
Let me know if you have query in this spring boot post request example.
Happy Learning !!
References:
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