Cache configuration in Spring Boot - Step-by-Step Execution

Concept Flow - Cache configuration

Start Application

↓

Enable Cache Support

↓

Define Cache Manager

↓

Annotate Methods with @Cacheable

↓

Method Called

↓

Check Cache for Key

↓

Return Cached

↓

Return Result

↓

End Call

This flow shows how Spring Boot enables caching: it checks cache before method runs, returns cached data if found, otherwise runs method and caches result.

Execution Sample

Spring Boot

@SpringBootApplication
@EnableCaching
public class App {
  @Cacheable("books")
  public Book findBook(String isbn) {
    // fetch book from DB
    return null; // placeholder return
  }
}

This code enables caching and caches results of findBook method by ISBN.

Execution Table

Step	Action	Cache State	Method Called	Result Returned
1	Application starts with @EnableCaching	Cache empty	No	No result
2	Call findBook("123")	Cache empty	Yes - fetch from DB	Book object fetched
3	Store Book in cache with key "123"	Cache has key "123"	No	No result
4	Call findBook("123") again	Cache has key "123"	No - return cached	Book object from cache
5	Call findBook("456")	Cache has key "123"	Yes - fetch from DB	Book object fetched
6	Store Book in cache with key "456"	Cache has keys "123", "456"	No	No result
7	Call findBook("789")	Cache has keys "123", "456"	Yes - fetch from DB	Book object fetched
8	Store Book in cache with key "789"	Cache has keys "123", "456", "789"	No	No result
9	Call findBook("123") again	Cache has keys "123", "456", "789"	No - return cached	Book object from cache

💡 Execution stops when no more method calls are made.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	After Step 6	After Step 7	After Step 8	Final
Cache Keys	[]	[]	["123"]	["123"]	["123", "456"]	["123", "456"]	["123", "456", "789"]	["123", "456", "789"]

Key Moments - 3 Insights

Why does the method not run every time it is called?

Because after the first call, the result is stored in cache (see step 3), so subsequent calls with the same key return cached data (see step 4).

What happens if a new key is used in the method call?

The method runs again to fetch fresh data (see step 5), then the result is cached for that new key (step 6).

Does the cache grow indefinitely?

By default, cache stores all keys unless configured otherwise. This example shows keys accumulating (see variable_tracker).

Visual Quiz - 3 Questions

Look at the execution table, what is the cache state after step 3?

A Cache has keys "123" and "456"

B Cache is empty

C Cache has key "123"

D Cache has keys "123", "456", "789"

💡 Hint

Check the 'Cache State' column in row for step 3.

At which step does the method run to fetch data for key "456"?

A Step 4

B Step 5

C Step 7

D Step 9

💡 Hint

Look for 'Method Called' = Yes and 'Method Called' column in execution_table.

If the cache was cleared after step 6, what would happen at step 9?

A Method would run again to fetch data

B Cached data would be returned

C An error would occur

D Nothing would happen

💡 Hint

Refer to variable_tracker and execution_table for cache keys presence.

Concept Snapshot

Spring Boot Cache Configuration:
- Add @EnableCaching to enable cache support
- Define cache manager bean or use defaults
- Use @Cacheable on methods to cache results
- On method call, cache checked first
- If cached, return cached result
- If not, run method and store result in cache
- Cache keys are method parameters by default

Full Transcript

This visual execution shows how Spring Boot cache configuration works. When the application starts with @EnableCaching, the cache is empty. Calling a method annotated with @Cacheable checks if the result for the given key is in cache. If not, the method runs and the result is stored in cache. Subsequent calls with the same key return cached data without running the method again. New keys cause the method to run and cache new results. The cache grows as new keys are added unless configured otherwise.