7 Proven Spring Boot Performance Optimizations for Faster Apps

1. Asynchronous Execution

Two implementation methods are provided: using the @Async annotation together with @EnableAsync on the main class, and leveraging JDK 8's CompletableFuture class.

@AllArgsConstructor
public class AskThread implements Runnable {
    private CompletableFuture<Integer> re = null;
    public void run() {
        int myRe = 0;
        try {
            myRe = re.get() * re.get();
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(myRe);
    }
    public static void main(String[] args) throws InterruptedException {
        final CompletableFuture<Integer> future = new CompletableFuture<>();
        new Thread(new AskThread(future)).start();
        Thread.sleep(1000);
        future.complete(60);
    }
}

The example starts a thread where AskThread initially blocks on myRe = re.get() * re.get() until the future is completed, after which the thread proceeds.

2. Increase Embedded Tomcat Maximum Connections

@Configuration
public class TomcatConfig {
    @Bean
    public ConfigurableServletWebServerFactory webServerFactory() {
        TomcatServletWebServerFactory tomcatFactory = new TomcatServletWebServerFactory();
        tomcatFactory.addConnectorCustomizers(new MyTomcatConnectorCustomizer());
        tomcatFactory.setPort(8005);
        tomcatFactory.setContextPath("/api-g");
        return tomcatFactory;
    }
    class MyTomcatConnectorCustomizer implements TomcatConnectorCustomizer {
        public void customize(Connector connector) {
            Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler();
            // set max connections
            protocol.setMaxConnections(20000);
            // set max threads
            protocol.setMaxThreads(2000);
            protocol.setConnectionTimeout(30000);
        }
    }
}

3. Use @ComponentScan() for Faster Package Scanning

Applying @ComponentScan() locates packages more quickly than relying on @SpringBootApplication scanning.

4. Switch Default Tomcat Container to Undertow

Undertow (JBoss) offers higher throughput (≈8000) compared to Tomcat (≈5000).

<exclusions>
    <exclusion>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
    </exclusion>
</exclusions>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-undertow</artifactId>
</dependency>

5. Use BufferedWriter for Buffering

BufferedWriter can be employed to improve I/O efficiency; implementation is left as an exercise.

6. Deferred Approach for Asynchronous Calls

@RestController
public class AsyncDeferredController {
    private final Logger logger = LoggerFactory.getLogger(this.getClass());
    private final LongTimeTask taskService;
    @Autowired
    public AsyncDeferredController(LongTimeTask taskService) {
        this.taskService = taskService;
    }
    @GetMapping("/deferred")
    public DeferredResult<String> executeSlowTask() {
        logger.info(Thread.currentThread().getName() + "进入executeSlowTask方法");
        DeferredResult<String> deferredResult = new DeferredResult<>();
        taskService.execute(deferredResult);
        logger.info(Thread.currentThread().getName() + "从executeSlowTask方法返回");
        deferredResult.onTimeout(() -> {
            logger.info(Thread.currentThread().getName() + " onTimeout");
            deferredResult.setErrorResult("time out!");
        });
        deferredResult.onCompletion(() -> {
            logger.info(Thread.currentThread().getName() + " onCompletion");
        });
        return deferredResult;
    }
}

7. Intercept Asynchronous Calls with AsyncHandlerInterceptor

@Component
public class MyAsyncHandlerInterceptor implements AsyncHandlerInterceptor {
    private static final Logger logger = LoggerFactory.getLogger(MyAsyncHandlerInterceptor.class);
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        return true;
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        logger.info(Thread.currentThread().getName() + "服务调用完成，返回结果给客户端");
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        if (ex != null) {
            System.out.println("发生异常:" + ex.getMessage());
        }
    }
    @Override
    public void afterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String resp = "my name is chhliu!";
        response.setContentLength(resp.length());
        response.getOutputStream().write(resp.getBytes());
        logger.info(Thread.currentThread().getName() + " 进入afterConcurrentHandlingStarted方法");
    }
}