How to create CRUD REST APIs with Spark Framework
© Shutterstock / Shahril KHMD
In this article, Yong Mook Kim, founder at Mkyong.com shows you how to create CRUD REST APIs with Spark Java Framework and Jackson library.
Spark Java runs on an embedded Jetty web server, provide simple APIs to handle HTTP request and response, combine with the Jackson library to serve the JSON output.
I believe this is the simplest, fastest and easiest micro framework to create a REST APIs server.
Tools and technologies used :
- Spark Java 2.6.0
- Jackson 2.8.8
- Java 8
- Maven 3
- cURL (test the REST APIs)
We are going to create the following RESR APIs
POST /user/add - POST request to add an user.
GET /user/:id - GET request to get user by :id.
GET /user - GET request to get all the users.
PUT /user/:id - UPDATE request to update an user by :id.
DELETE /user/:id - DELETE request to delete an user by :id.
1. Project directory
Review the existing project directory layout, nothing special, just a standard Maven directory layout.
2. Project Dependencies
In pom.xml, declare sparkjava, jackson and logback (optional, for logging)
<?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.mkyong</groupId>
<artifactId>sparkjava</artifactId>
<version>1.0-SNAPSHOT</version>
<!-- Spark Java need Java 8 -->
<properties>
<maven.compiler.target>1.8</maven.compiler.target>
<maven.compiler.source>1.8</maven.compiler.source>
</properties>
<dependencies>
<dependency>
<groupId>com.sparkjava</groupId>
<artifactId>spark-core</artifactId>
<version>2.6.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.8.8.1</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.2</version>
</dependency>
</dependencies>
</project>
3. User & UserService
3.1 A simple POJO.
package com.mkyong.user;
public class User {
int id;
String name;
String email;
public User(int id, String name, String email) {
this.id = id;
this.name = name;
this.email = email;
}
//getters, setters and toString()
}
3.2 No database involves, just store all users’ objects into a local variable.
package com.mkyong.user;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
public class UserService {
public static Map users = new HashMap<>();
private static final AtomicInteger count = new AtomicInteger(0);
public User findById(String id) {
return users.get(id);
}
public User add(String name, String email) {
int currentId = count.incrementAndGet();
User user = new User(currentId, name, email);
users.put(String.valueOf(currentId), user);
return user;
}
public User update(String id, String name, String email) {
User user = users.get(id);
if (name != null) {
user.setName(name);
}
if (email != null) {
user.setEmail(email);
}
users.put(id, user);
return user;
}
public void delete(String id) {
users.remove(id);
}
public List findAll() {
return new ArrayList<>(users.values());
}
public UserService() {
}
}
4. Spark Java + Jackson
Time to code. Review the comments for self-explanatory.
package com.mkyong;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.mkyong.user.User;
import com.mkyong.user.UserService;
import java.util.List;
import static spark.Spark.get;
import static spark.Spark.port;
import static spark.Spark.post;
import static spark.Spark.put;
import static spark.Spark.delete;
public class Main {
private static UserService userService = new UserService();
private static ObjectMapper om = new ObjectMapper();
public static void main(String[] args) {
// Start embedded server at this port
port(8080);
// Main Page, welcome
get("/", (request, response) -> "Welcome");
// POST - Add an user
post("/user/add", (request, response) -> {
String name = request.queryParams("name");
String email = request.queryParams("email");
User user = userService.add(name, email);
response.status(201); // 201 Created
return om.writeValueAsString(user);
});
// GET - Give me user with this id
get("/user/:id", (request, response) -> {
User user = userService.findById(request.params(":id"));
if (user != null) {
return om.writeValueAsString(user);
} else {
response.status(404); // 404 Not found
return om.writeValueAsString("user not found");
}
});
// Get - Give me all users
get("/user", (request, response) -> {
List result = userService.findAll();
if (result.isEmpty()) {
return om.writeValueAsString("user not found");
} else {
return om.writeValueAsString(userService.findAll());
}
});
// PUT - Update user
put("/user/:id", (request, response) -> {
String id = request.params(":id");
User user = userService.findById(id);
if (user != null) {
String name = request.queryParams("name");
String email = request.queryParams("email");
userService.update(id, name, email);
return om.writeValueAsString("user with id " + id + " is updated!");
} else {
response.status(404);
return om.writeValueAsString("user not found");
}
});
// DELETE - delete user
delete("/user/:id", (request, response) -> {
String id = request.params(":id");
User user = userService.findById(id);
if (user != null) {
userService.delete(id);
return om.writeValueAsString("user with id " + id + " is deleted!");
} else {
response.status(404);
return om.writeValueAsString("user not found");
}
});
}
}
Done, let’s test it.
5. Test with cURL
Start Main.java and the embedded Jetty server will start as well. Those REST APIs are ready to test. Open a terminal and test the REST APIs with cURL.
//Start Main.java... 2017-05-26 16:18:49 DEBUG spark.route.Routes - Adds route: get, /, spark.RouteImpl$1@612679d6 2017-05-26 16:18:49 DEBUG spark.route.Routes - Adds route: post, /user/add, spark.RouteImpl$1@6950e31 2017-05-26 16:18:49 DEBUG spark.route.Routes - Adds route: get, /user/:id, spark.RouteImpl$1@42eca56e 2017-05-26 16:18:49 DEBUG spark.route.Routes - Adds route: get, /user, spark.RouteImpl$1@7cbd213e 2017-05-26 16:18:49 DEBUG spark.route.Routes - Adds route: put, /user/:id, spark.RouteImpl$1@3ecd23d9 2017-05-26 16:18:49 DEBUG spark.route.Routes - Adds route: delete, /user/:id, spark.RouteImpl$1@43bd930a 2017-05-26 16:18:49 INFO s.e.jetty.EmbeddedJettyServer - == Spark has ignited ... 2017-05-26 16:18:49 INFO s.e.jetty.EmbeddedJettyServer - >> Listening on 0.0.0.0:8080
Let’s test the following REST APIs :
POST /user/add - POST request to add an user. GET /user/:id - GET request to get user by :id. GET /user - GET request to get all the users. PUT /user/:id - UPDATE request to update an user by :id. DELETE /user/:id - DELETE request to delete an user by :id.
5.1 POST /user/add
# Add user 'mkyong'
$ curl -X POST -d "name=mkyong&email=test1@gmail.com" http://localhost:8080/user/add
{"id":1,"name":"mkyong","email":"test1@gmail.com"}
# Add user 'jack'
$ curl -X POST -d "name=jack&email=test2@gmail.com" http://localhost:8080/user/add
{"id":2,"name":"jack","email":"test2@gmail.com"}
5.2 GET /user/:id & GET /user
# Get user where id = 1
$ curl http://localhost:8080/user/1
{
"id" : 1,
"name" : "mkyong",
"email" : "test1@gmail.com"
}
# Get user where id = 2
$ curl http://localhost:8080/user/2
{
"id" : 2,
"name" : "jack",
"email" : "test2@gmail.com"
}
# Get all users
$ curl http://localhost:8080/user
[ {
"id" : 1,
"name" : "mkyong",
"email" : "test1@gmail.com"
}, {
"id" : 2,
"name" : "jack",
"email" : "test2@gmail.com"
} ]
5.3 PUT /user/:id
# Update
$ curl -X PUT -d "name=jack2&email=test2@yahoo.com" http://localhost:8080/user/2
"user with id 2 is updated!"
# Get user where id = 2
$ curl http://localhost:8080/user/2
{
"id" : 2,
"name" : "jack2",
"email" : "test2@yahoo.com"
}
5.4 DELETE /user/:id
# Delete user where id = 2
$ curl -X DELETE http://localhost:8080/user/2
"user with id 2 is deleted!"
# User id = 2 is no longer exists
$ curl http://localhost:8080/user/2
"user not found"
# Get all users
$ curl http://localhost:8080/user
[ {
"id" : 1,
"name" : "mkyong",
"email" : "test1@gmail.com"
} ]
Download source code
References
This post was created by mkyong.com.
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