@CachePut for updating cache in Spring Boot - Step-by-Step Execution

Concept Flow - @CachePut for updating cache

Method call with @CachePut

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Method executes and returns value

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Cache updated with new value

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Return updated value to caller

When a method annotated with @CachePut is called, it runs the method and updates the cache with the returned value before returning it.

Execution Sample

Spring Boot

@CachePut(value = "users", key = "#user.id")
public User updateUser(User user) {
    // update user in DB
    return user;
}

This method updates a user and refreshes the cache entry for that user.

Execution Table

Step	Action	Input	Cache Before	Cache Update	Return Value
1	Call updateUser with user{id=1, name='Alice'}	user{id=1, name='Alice'}	{}	{}	pending
2	Execute method: update DB and return user	user{id=1, name='Alice'}	{}	{}	user{id=1, name='Alice'}
3	Update cache 'users' with key=1	user{id=1, name='Alice'}	{}	{1: user{id=1, name='Alice'}}	user{id=1, name='Alice'}
4	Return updated user	user{id=1, name='Alice'}	{1: user{id=1, name='Alice'}}	{1: user{id=1, name='Alice'}}	user{id=1, name='Alice'}
5	Call updateUser with user{id=1, name='Alice Smith'}	user{id=1, name='Alice Smith'}	{1: user{id=1, name='Alice'}}	{1: user{id=1, name='Alice'}}	pending
6	Execute method: update DB and return user	user{id=1, name='Alice Smith'}	{1: user{id=1, name='Alice'}}	{1: user{id=1, name='Alice'}}	user{id=1, name='Alice Smith'}
7	Update cache 'users' with key=1	user{id=1, name='Alice Smith'}	{1: user{id=1, name='Alice'}}	{1: user{id=1, name='Alice Smith'}}	user{id=1, name='Alice Smith'}
8	Return updated user	user{id=1, name='Alice Smith'}	{1: user{id=1, name='Alice Smith'}}	{1: user{id=1, name='Alice Smith'}}	user{id=1, name='Alice Smith'}
9	Call updateUser with user{id=2, name='Bob'}	user{id=2, name='Bob'}	{1: user{id=1, name='Alice Smith'}}	{1: user{id=1, name='Alice Smith'}}	pending
10	Execute method: update DB and return user	user{id=2, name='Bob'}	{1: user{id=1, name='Alice Smith'}}	{1: user{id=1, name='Alice Smith'}}	user{id=2, name='Bob'}
11	Update cache 'users' with key=2	user{id=2, name='Bob'}	{1: user{id=1, name='Alice Smith'}}	{1: user{id=1, name='Alice Smith'}, 2: user{id=2, name='Bob'}}	user{id=2, name='Bob'}
12	Return updated user	user{id=2, name='Bob'}	{1: user{id=1, name='Alice Smith'}, 2: user{id=2, name='Bob'}}	{1: user{id=1, name='Alice Smith'}, 2: user{id=2, name='Bob'}}	user{id=2, name='Bob'}
13	No more calls	-	{1: user{id=1, name='Alice Smith'}, 2: user{id=2, name='Bob'}}	{1: user{id=1, name='Alice Smith'}, 2: user{id=2, name='Bob'}}	-

💡 No more method calls; cache holds latest updated users.

Variable Tracker

Variable	Start	After Step 3	After Step 7	After Step 11	Final
cache 'users'	{}	{1: user{id=1, name='Alice'}}	{1: user{id=1, name='Alice Smith'}}	{1: user{id=1, name='Alice Smith'}, 2: user{id=2, name='Bob'}}	{1: user{id=1, name='Alice Smith'}, 2: user{id=2, name='Bob'}}
return value	N/A	user{id=1, name='Alice'}	user{id=1, name='Alice Smith'}	user{id=2, name='Bob'}	user{id=2, name='Bob'}

Key Moments - 2 Insights

Why does the cache update even if the method is called multiple times with the same key?

Because @CachePut always runs the method and updates the cache with the returned value, as shown in steps 3 and 7 where the cache entry for key=1 is replaced.

Does @CachePut skip method execution if the cache already has the key?

No, @CachePut always executes the method and then updates the cache, unlike @Cacheable which may skip execution if cache hit occurs. This is clear in steps 5-8.

Visual Quiz - 3 Questions

Look at the execution table at step 7. What is the cache content after updating user with id=1?

A {1: user{id=1, name='Alice Smith'}}

B {1: user{id=1, name='Alice'}}

C {}

D {2: user{id=2, name='Bob'}}

💡 Hint

Check the 'Cache Update' column at step 7 in the execution table.

At which step does the cache first get a new entry for user id=2?

A Step 9

B Step 11

C Step 10

D Step 12

💡 Hint

Look for when the cache 'users' key=2 appears in the 'Cache Update' column.

If the method returned a different user object but with the same id, what would happen to the cache?

A Cache would clear all entries

B Cache would keep the old user object

C Cache would update with the new user object for that id

D Cache would throw an error

💡 Hint

Refer to how cache updates at steps 3 and 7 with new user objects for the same key.

Concept Snapshot

@CachePut runs the method every time and updates the cache with the returned value.
Use it to refresh cache entries after updates.
Unlike @Cacheable, it does not skip method execution.
Specify cache name and key to control cache entry.
Cache is updated after method returns.

Full Transcript

When you use @CachePut on a method, every time you call that method, it runs fully and then updates the cache with the result. For example, if you update a user, the method saves the user to the database and then puts the updated user into the cache under the user's id. This means the cache always has the latest data after the method runs. Unlike @Cacheable, which can skip running the method if the cache already has data, @CachePut always runs the method and refreshes the cache. This is useful when you want to keep the cache in sync after changes. The cache key is usually the id or unique identifier of the data. So, calling updateUser with a changed user will replace the old cached user with the new one. This way, your cache stays fresh and your app uses the latest data.