java 24 lines · 6 steps

Posting an order with Java's HttpClient

Serialize an order, POST it over HTTP, branch on the status code, and deserialize the reply.

Explained by highlit
Intermediate http-client json-serialization error-handling rest-api
1public OrderConfirmation submitOrder(Order order) throws IOException, InterruptedException {
2 String payload = objectMapper.writeValueAsString(order);
3 
4 HttpRequest request = HttpRequest.newBuilder()
5 .uri(URI.create(baseUrl + "/api/v1/orders"))
6 .timeout(Duration.ofSeconds(10))
7 .header("Content-Type", "application/json")
8 .header("Accept", "application/json")
9 .header("Authorization", "Bearer " + apiToken)
10 .POST(HttpRequest.BodyPublishers.ofString(payload, StandardCharsets.UTF_8))
11 .build();
12 
13 HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
14 
15 int status = response.statusCode();
16 if (status == 429) {
17 throw new RateLimitedException(response.headers().firstValue("Retry-After").orElse("5"));
18 }
19 if (status >= 400) {
20 throw new OrderApiException("Order submission failed with status " + status + ": " + response.body());
21 }
22 
23 return objectMapper.readValue(response.body(), OrderConfirmation.class);
24}
01 / 01
STEP 01

Walkthrough

Space play ←→ step click any line
Three takeaways
  1. 1Jackson's ObjectMapper bookends the request: one call to serialize outbound, one to deserialize the response.
  2. 2Inspecting the status code before parsing lets you fail fast with meaningful exceptions instead of a broken body.
  3. 3The builder pattern on HttpRequest makes headers, timeout, and body read as a single declarative description of the call.

Related explainers

ruby 
class Order
  class InvalidTransition < StandardError; end
 
  TRANSITIONS = {

A state machine for order transitions in Ruby

state-machine data-driven error-handling
Intermediate 8 steps
java 
public class SlidingLogRateLimiter {
 
    private final int maxRequests;
    private final long windowMillis;

How a sliding-log rate limiter works

rate-limiting concurrency sliding-window
Advanced 8 steps
java 
public final class Slugifier {
 
    private static final Pattern NON_LATIN = Pattern.compile("[^\\w-]");
    private static final Pattern WHITESPACE = Pattern.compile("[\\s]+");

Building a URL slugifier in Java

regex unicode-normalization string-processing
Intermediate 8 steps
rust 
use std::cmp::Ordering;
use std::str::FromStr;
 
#[derive(Debug, Clone, PartialEq, Eq)]

Parsing and ordering semantic versions in Rust

parsing trait-implementation ordering
Intermediate 8 steps
javascript 
'use client';
 
import { useEffect } from 'react';
import * as Sentry from '@sentry/nextjs';

How a Next.js error boundary recovers

error-boundary error-handling observability
Intermediate 8 steps
ruby 
class Registration < ApplicationRecord
  belongs_to :event
 
  validates :email, presence: true, format: { with: URI::MailTo::EMAIL_REGEXP }

Validating registrations in Rails

validations i18n error-handling
Intermediate 8 steps

Share this explainer

Here's the card — post it anywhere.

Posting an order with Java's HttpClient — share card
Made with highlit — turn any snippet into a walkthrough like this in about a minute.
Explain your code