java-tutorials/spark-java/src/main/java/com/baeldung/sparkjava/SparkRestExample.java

package com.baeldung.sparkjava;

import static spark.Spark.delete;
import static spark.Spark.get;
import static spark.Spark.options;
import static spark.Spark.post;
import static spark.Spark.put;

import com.google.gson.Gson;

public class SparkRestExample {
    public static void main(String[] args) {
        final UserService userService = new UserServiceMapImpl();
        
        post("/users", (request, response) -> {
            response.type("application/json");
            
            User user = new Gson().fromJson(request.body(), User.class);
            userService.addUser(user);

            return new Gson().toJson(new StandardResponse(StatusResponse.SUCCESS));
        });

        get("/users", (request, response) -> {
            response.type("application/json");
            
            return new Gson().toJson(
                new StandardResponse(StatusResponse.SUCCESS,new Gson()
                    .toJsonTree(userService.getUsers())));
        });

        get("/users/:id", (request, response) -> {
            response.type("application/json");
            
            return new Gson().toJson(
                new StandardResponse(StatusResponse.SUCCESS,new Gson()
                  .toJsonTree(userService.getUser(request.params(":id")))));
        });

        put("/users/:id", (request, response) -> {
            response.type("application/json");
            
            User toEdit = new Gson().fromJson(request.body(), User.class);
            User editedUser = userService.editUser(toEdit);
                
            if (editedUser != null) {
                return new Gson().toJson(
                    new StandardResponse(StatusResponse.SUCCESS,new Gson()
                        .toJsonTree(editedUser)));
            }else  {
                return new Gson().toJson(
                    new StandardResponse(StatusResponse.ERROR,new Gson()
                        .toJson("User not found or error in edit")));
            }
        });

        delete("/users/:id", (request, response) -> {
            response.type("application/json");
            
            userService.deleteUser(request.params(":id"));
            return new Gson().toJson(
                new StandardResponse(StatusResponse.SUCCESS, "user deleted"));
        });

        options("/users/:id", (request, response) -> {
            response.type("application/json");
            
            return new Gson().toJson(
                new StandardResponse(StatusResponse.SUCCESS, 
                    (userService.userExist(
                        request.params(":id"))) ? "User exists" : "User does not exists" ));
        });

    }

}