Spring Boot (2) RESTful Service

Developing a RESTful service

This section describes how to develop a pure RESTful service based on Spring Boot.

1. Creating the POM

<?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.my.study.springboot</groupId>
	<artifactId>restful-service</artifactId>
	<version>0.0.1-RELEASE</version>
	<properties>
		<!-- Generic properties -->
		<java.version>1.8</java.version>
		<maven.compiler.source>1.8</maven.compiler.source>
		<maven.compiler.target>1.8</maven.compiler.target>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
	</properties>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>1.5.14.RELEASE</version>
	</parent>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
	</dependencies>
	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>
</project>

2. Writing the Code

package com.my.study.restful;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Main {
	public static void main(String[] args) {
		SpringApplication.run(Main.class, args);
	}
}

package com.my.study.restful.controller;

import java.util.List;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.util.UriComponentsBuilder;

import com.my.study.restful.entity.Employee;
import com.my.study.restful.mockdb.EmployeeDB;

@RestController
@CrossOrigin(origins = "*", methods = { RequestMethod.GET, RequestMethod.POST, RequestMethod.PUT,
		RequestMethod.DELETE })
public class EmployeeController {

	// Query all employees
	@RequestMapping(value = "/employee/", method = RequestMethod.GET)
	public ResponseEntity<List<Employee>> listAllEmployees() {
		List<Employee> employees = EmployeeDB.findAllEmployees();
		if (employees.isEmpty()) {
			// You many decide to return HttpStatus.NOT_FOUND
			return new ResponseEntity<List<Employee>>(HttpStatus.NO_CONTENT);
		}
		return new ResponseEntity<List<Employee>>(employees, HttpStatus.OK);
	}

	// Query one employee by ID
	@RequestMapping(value = "/employee/{id}", method = RequestMethod.GET)
	public ResponseEntity<Employee> findEmployee(@PathVariable("id") int id) {
		Employee employee = EmployeeDB.findEmployee(id);
		if (null == employee) {
			return new ResponseEntity<Employee>(HttpStatus.NOT_FOUND);
		}
		return new ResponseEntity<Employee>(employee, HttpStatus.OK);
	}

	// Add one employee
	@RequestMapping(value = "/employee/", method = RequestMethod.POST)
	public ResponseEntity<Void> createEmployee(@RequestBody Employee employee, UriComponentsBuilder ucBuilder) {
		if (null != EmployeeDB.findEmployee(employee.getId())) {
			return new ResponseEntity<Void>(HttpStatus.CONFLICT);
		}
		EmployeeDB.addEmployee(employee);
		HttpHeaders headers = new HttpHeaders();
		// This is to send client a URL of how to get added employee
		headers.setLocation(ucBuilder.path("/employee/{id}").buildAndExpand(employee.getId()).toUri());
		return new ResponseEntity<Void>(headers, HttpStatus.CREATED);
	}

	// Update employee by ID
	@RequestMapping(value = "/employee/{id}", method = RequestMethod.PUT)
	public ResponseEntity<Employee> updateEmployee(@PathVariable("id") long id, @RequestBody Employee employee) {
		Employee currentEmployee = EmployeeDB.findEmployee(employee.getId());
		if (null == currentEmployee) {
			return new ResponseEntity<Employee>(HttpStatus.NOT_FOUND);
		}
		EmployeeDB.updateEmployee(employee);
		return new ResponseEntity<Employee>(employee, HttpStatus.OK);
	}

	// Delete employee by ID
	@RequestMapping(value = "/employee/{id}", method = RequestMethod.DELETE)
	public ResponseEntity<Void> deleteEmployee(@PathVariable("id") int id) {
		Employee currentEmployee = EmployeeDB.findEmployee(id);
		if (null == currentEmployee) {
			return new ResponseEntity<Void>(HttpStatus.NOT_FOUND);
		}
		EmployeeDB.deleteEmployee(id);
		return new ResponseEntity<Void>(HttpStatus.NO_CONTENT);
	}

	// Delete all employees
	@RequestMapping(value = "/employee/", method = RequestMethod.DELETE)
	public ResponseEntity<Void> deleteAllEmployees() {
		EmployeeDB.deleteAll();
		return new ResponseEntity<Void>(HttpStatus.NO_CONTENT);
	}
}

package com.my.study.restful.entity;

/**
 * Entity Object
 */
public class Employee {
	private int id;
	private String name;
	private int age;
	private String desc;

	public Employee() {
	}

	public Employee(int id, String name, int age, String desc) {
		this.id = id;
		this.name = name;
		this.age = age;
		this.desc = desc;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getDesc() {
		return desc;
	}

	public void setDesc(String desc) {
		this.desc = desc;
	}
}

package com.my.study.restful.mockdb;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.my.study.restful.entity.Employee;

/**
 * Employee mock DB
 */
public class EmployeeDB {
	private static final List<Employee> EMPLOYEES = new ArrayList<>();
	static {
		for (int i = 0; i < 3; i++) {
			EMPLOYEES.add(new Employee(i, "user" + i, 20 + i, "desc " + i + "."));
		}
	}

	public static Employee findEmployee(int id) {
		for (Employee e : EMPLOYEES) {
			if (e.getId() == id) {
				return e;
			}
		}
		return null;
	}

	public static List<Employee> findAllEmployees() {
		return EMPLOYEES;
	}

	public static synchronized void addEmployee(Employee employee) {
		EMPLOYEES.add(employee);
	}

	public static void updateEmployee(Employee employee) {
		for (Employee e : EMPLOYEES) {
			if (e.getId() == employee.getId()) {
				e.setName(employee.getName());
				e.setAge(employee.getAge());
				e.setDesc(employee.getDesc());
				return;
			}
		}
	}

	public static void deleteEmployee(int id) {
		Iterator<Employee> it = EMPLOYEES.iterator();
		while (it.hasNext()) {
			Employee e = it.next();
			if (e.getId() == id) {
				it.remove();
				return;
			}
		}
	}

	public static void deleteAll() {
		EMPLOYEES.clear();
	}
}

3. Code Structure

4. Run The RESTful service

C:\D\work\projects\sts\springboot-restful>java -jar target/restful-service-0.0.1-RELEASE.jar

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::       (v1.5.14.RELEASE)

2018-07-04 13:48:45.735  INFO 23120 --- [           main] com.my.study.restful.Main                : Starting Main v0.0.1-RELEASE on CNENWANGS56L1C with PID 23120 (C:\D\work\projects\sts\springboot-restful\target\restful-service-0.0.1-RELEASE.jar started by wangs56 in C:\D\work\projects\sts\springboot-restful)
2018-07-04 13:48:45.747  INFO 23120 --- [           main] com.my.study.restful.Main                : No active profile set, falling back to default profiles: default
2018-07-04 13:48:45.997  INFO 23120 --- [           main] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@69663380: startup date [Wed Jul 04 13:48:45 CST 2018]; root of context hierarchy
......
2018-07-04 13:48:53.963  INFO 23120 --- [           main] s.w.s.m.m.a.RequestMappingHandlerMapping : Mapped "{[/error],produces=[text/html]}" onto public org.springframework.web.servlet.ModelAndView org.springframework.boot.autoconfigure.web.BasicErrorController.errorHtml(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
2018-07-04 13:48:54.036  INFO 23120 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/webjars/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-04 13:48:54.037  INFO 23120 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-04 13:48:54.146  INFO 23120 --- [           main] o.s.w.s.handler.SimpleUrlHandlerMapping  : Mapped URL path [/**/favicon.ico] onto handler of type [class org.springframework.web.servlet.resource.ResourceHttpRequestHandler]
2018-07-04 13:48:54.459  INFO 23120 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2018-07-04 13:48:54.620  INFO 23120 --- [           main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8080 (http)
2018-07-04 13:48:54.649  INFO 23120 --- [           main] com.my.study.restful.Main                : Started Main in 10.318 seconds (JVM running for 12.145)

To gracefully exit the application, press ctrl-c.

5. Testing RESTful service