Spring Security auto-configuration in Spring Boot - Performance & Optimization

Performance: Spring Security auto-configuration

MEDIUM IMPACT

This affects the initial page load speed and backend response time by adding security filters and processing overhead.

Securing a Spring Boot web application with default settings

Spring Boot

Customize security configuration to exclude static resources and disable CSRF where not needed, reducing filter chain length.

Reduces the number of filters executed per request and avoids security checks on non-sensitive endpoints.

📈 Performance GainSaves 30-70ms per request, improving LCP by reducing backend processing delay.

Securing a Spring Boot web application with default settings

Spring Boot

spring-boot-starter-security dependency added with no customization, enabling all default filters and CSRF protection on all endpoints.

Default auto-configuration applies many security filters globally, causing unnecessary processing on static resources and simple endpoints.

📉 Performance CostAdds multiple filter executions per request, increasing backend response time by 50-100ms on average.

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Default auto-configuration with all filters	N/A (server-side)	N/A	Increases backend response delay	[X] Bad
Customized security config excluding static resources	N/A (server-side)	N/A	Reduces backend response delay	[OK] Good

Rendering Pipeline

Spring Security auto-configuration adds servlet filters that run before the controller logic, increasing server processing time before HTML is sent to the browser.

→Server Request Processing

→Response Generation

⚠️ BottleneckFilter chain execution time before response is generated

Core Web Vital Affected

LCP

This affects the initial page load speed and backend response time by adding security filters and processing overhead.

Optimization Tips

1Avoid applying security filters to static resources to reduce backend processing time.

2Disable unnecessary security features like CSRF on non-sensitive endpoints to improve response speed.

3Monitor backend response times in DevTools Network tab to detect security-related delays.

Performance Quiz - 3 Questions

How does Spring Security auto-configuration typically affect page load performance?

A It reduces CSS and JavaScript bundle sizes.

B It improves browser rendering speed by optimizing DOM updates.

C It adds server-side processing time due to filter chains before response is sent.

D It eliminates the need for client-side caching.

DevTools: Network

How to check: Open DevTools, go to Network tab, reload the page, and check the Time column for backend response time.

What to look for: Look for long server response times indicating backend processing delays caused by security filters.

Practice

1. What happens when you add spring-boot-starter-security to a Spring Boot project without any additional configuration?

easy

A. The application runs without any security restrictions.

B. All web endpoints are secured with a default login page.

C. Only REST endpoints are secured, web pages remain open.

D. The application throws an error due to missing configuration.

Solution

1. Step 1: Understand default behavior of spring-boot-starter-security

   Adding this starter enables Spring Security auto-configuration which secures all web endpoints by default.

2. Step 2: Recognize the default login page

   Spring Security provides a default login page automatically when no custom security config is provided.

3. Final Answer:

   All web endpoints are secured with a default login page. -> Option B

4. Quick Check:

   Default security = secured endpoints + login page [OK]

Hint: Default security locks all endpoints with login page [OK]

Common Mistakes:

• Thinking endpoints remain open without config
• Assuming only REST endpoints are secured
• Believing an error occurs without config

2. Which of the following is the correct way to disable Spring Security auto-configuration in a Spring Boot application?

easy

A. @Configuration(exclude = SecurityAutoConfiguration.class)

B. @EnableAutoConfiguration(exclude = SecurityAutoConfiguration.class)

C. @ComponentScan(exclude = SecurityAutoConfiguration.class)

D. @SpringBootApplication(exclude = SecurityAutoConfiguration.class)

Solution

1. Step 1: Identify the correct annotation to exclude auto-configuration

   Spring Boot allows excluding auto-configurations via the exclude attribute in @SpringBootApplication.

2. Step 2: Confirm the correct class to exclude

   The class to exclude for disabling security auto-configuration is SecurityAutoConfiguration.class.

3. Final Answer:

   @SpringBootApplication(exclude = SecurityAutoConfiguration.class) -> Option D

4. Quick Check:

   Disable auto-config = exclude in @SpringBootApplication [OK]

Hint: Exclude SecurityAutoConfiguration in @SpringBootApplication [OK]

Common Mistakes:

• Using @EnableAutoConfiguration instead of @SpringBootApplication
• Trying to exclude in @ComponentScan or @Configuration
• Not specifying the correct class to exclude

3. Given this Spring Boot application with spring-boot-starter-security added and no custom security config, what will happen when a user accesses /hello endpoint?

 @RestController
 public class HelloController {
   @GetMapping("/hello")
   public String hello() {
     return "Hello World";
   }
 }

medium

A. The user sees "Hello World" without login.

B. The endpoint returns 404 Not Found.

C. The user is redirected to a login page before seeing "Hello World".

D. The application throws a runtime exception.

Solution

1. Step 1: Recall default security behavior with no custom config

   All endpoints are secured and require authentication by default.

2. Step 2: Understand access flow to /hello endpoint

   Accessing /hello triggers Spring Security to redirect to the default login page before allowing access.

3. Final Answer:

   The user is redirected to a login page before seeing "Hello World". -> Option C

4. Quick Check:

   Default security = login redirect before access [OK]

Hint: No config means login page before any endpoint access [OK]

Common Mistakes:

• Assuming endpoints are open without login
• Expecting 404 error for existing endpoint
• Thinking runtime exception occurs

4. You added spring-boot-starter-security but your application fails to start with a bean creation error related to AuthenticationManager. What is the likely cause?

medium

A. You defined a custom SecurityFilterChain but forgot to expose an AuthenticationManager bean.

B. You did not add spring-boot-starter-web dependency.

C. You excluded SecurityAutoConfiguration but still use security annotations.

D. You have multiple @SpringBootApplication classes.

Solution

1. Step 1: Understand the error context with AuthenticationManager bean

   When customizing security by defining a SecurityFilterChain, Spring Boot no longer auto-configures AuthenticationManager.

2. Step 2: Identify missing bean definition

   You must manually expose an AuthenticationManager bean to satisfy dependencies.

3. Final Answer:

   You defined a custom SecurityFilterChain but forgot to expose an AuthenticationManager bean. -> Option A

4. Quick Check:

   Custom filter chain needs AuthenticationManager bean [OK]

Hint: Custom SecurityFilterChain requires AuthenticationManager bean [OK]

Common Mistakes:

• Blaming missing web dependency
• Ignoring need for AuthenticationManager bean
• Assuming multiple @SpringBootApplication causes this error

5. You want to customize Spring Security auto-configuration to allow public access to /public/** endpoints but secure all others with form login. Which configuration snippet correctly achieves this?

hard

A. Define a SecurityFilterChain bean with http.authorizeHttpRequests().requestMatchers("/public/**").permitAll().anyRequest().authenticated().and().formLogin().

B. Exclude SecurityAutoConfiguration and manually configure WebSecurityConfigurerAdapter to permit /public/**.

C. Add @EnableWebSecurity and override configure(HttpSecurity http) to permit /public/** and disable form login.

D. Add @SpringBootApplication(exclude = SecurityAutoConfiguration.class) and use http.csrf().disable().

Solution

1. Step 1: Use SecurityFilterChain bean to customize security rules

   Spring Security 5.7+ recommends defining a SecurityFilterChain bean for custom rules.

2. Step 2: Permit /public/** and require authentication for others with form login

   The method chain authorizeHttpRequests().requestMatchers("/public/**").permitAll().anyRequest().authenticated().and().formLogin() correctly sets these rules.

3. Final Answer:

   Define a SecurityFilterChain bean with http.authorizeHttpRequests().requestMatchers("/public/**").permitAll().anyRequest().authenticated().and().formLogin() -> Option A

4. Quick Check:

   Permit public paths + secure others + form login = Define a SecurityFilterChain bean with http.authorizeHttpRequests().requestMatchers("/public/**").permitAll().anyRequest().authenticated().and().formLogin(). [OK]

Hint: Use SecurityFilterChain bean with permitAll and formLogin [OK]

Common Mistakes:

• Excluding auto-config and using deprecated WebSecurityConfigurerAdapter
• Disabling form login when it is required
• Misusing @EnableWebSecurity without proper bean