FreeFoundations · 25 min · Beginner
⚡

Streaming Responses

Token-by-token SSE streaming with Spring WebFlux

💡

What Is Streaming Responses?

Simple overview · Real-world examples included

You know how ChatGPT shows text appearing word-by-word as it types? That is called "streaming" — and it makes apps feel much more responsive. Without streaming, your app waits for the complete AI response (up to 30 seconds) then shows it all at once. With streaming, users see words appearing in real time — just like ChatGPT. We will add this effect to your Spring Boot app using Server-Sent Events (SSE) and Spring WebFlux.

🎯 What You'll Learn

→How token streaming works end-to-end
→Spring WebFlux Flux
→Frontend SSE consumption
→Backpressure and error handling

🌍 Real-World Use Case

A code review assistant that streams suggestions as it analyzes your code

📊 How It Works — Interactive Flowchart

Hover nodes for quick tip · Click to open detail · Press "Run Data Flow" to animate

Click any box to learn what it does
🧑‍💻
Browser
Sends question
Step 1
⚙️
Spring Boot
Streams back
Step 2
🌐
AI API
Streams tokens
Step 3
🤖
AI Model
Word by word
Step 4
✅
SSE Stream
Live to screen
Step 5

🛠️ Step-by-Step Implementation

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Implementation ProgressClick ○ to mark a step complete
0 / 6
01
Add WebFlux dependency
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💡 WHY AM I DOING THIS?

WebFlux enables reactive/streaming responses. Without it Spring uses blocking I/O.

▶ WHAT HAPPENS IN THIS STEP

Add spring-boot-starter-webflux to pom.xml.

📄 FILES TO CREATE / MODIFY
+pom.xml
📁 FOLDER STRUCTURE
No new files
💻 CODE EXAMPLE
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
⚠ COMMON MISTAKES
⚠Adding both web and webflux — pick one
▶ HOW TO TEST
Check startup logs for "Netty started" instead of "Tomcat started"
✅ EXPECTED RESULT
Application starts on Netty server (reactive server)
02
Create streaming endpoint
Returning Flux<String> tells Spring to stream data as it arrives instead of buffering everything
▾
03
Build React EventSource client
EventSource is the browser API for receiving SSE
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04
Handle stream errors
Network drops, model errors, and timeouts must be caught or users see blank screens
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05
Add loading state
Users need visual feedback while waiting for first token — blank screen feels broken
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06
Test full flow
End-to-end testing catches timing issues invisible in unit tests
▾

✍️ How to Write the Prompt for This Topic

No special prompt for streaming — focus on keeping responses concise to minimize time-to-first-token.

🎯

Job Interview Prep

8 curated questions · 0 / 8 mastered
Click answers, then rate yourself to track progress
LEVEL:

💡 Don't memorise answers word-for-word. Understand the concept, then explain it in your own words using a real example from this topic's project — that's what impresses interviewers.

⚡ Live AI Demo

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📦 Clone & Run the Sample Project

📦
github.com / ai-dev-academy / ai-dev-academy-projects

03-streaming-responses

Live Chat UI — React frontend + Spring WebFlux streaming backend

Spring Boot 3.xSpring WebFluxSSEReact
⚡QUICK START — RUN IN 5 STEPS
1
Clone the full repo
git clone https://github.com/ai-dev-academy/ai-dev-academy-projects.git
2
Enter the topic folder
cd ai-dev-academy-projects/03-streaming-responses
3
Set up your API key
cp .env.example .env
# Then open .env and add your API key
4
Run the project
mvn spring-boot:run
5
Test the endpoint
curl -X POST http://localhost:8080/ai/chat \
  -H "Content-Type: application/json" \
  -d '"Hello, what is Streaming Responses?"'
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