Snippet

Custom Thread-Local Scope Implementation

Custom Scopes allow developers to manage bean lifecycles beyond 'singleton' or 'prototype'. A ThreadScope is an expert pattern used in high-concurrency scenarios to ensure state is isolated per execution thread without passing parameters.

snippet.java

java

public class ThreadScope implements Scope {
    private final ThreadLocal<Map<String, Object>> threadObjects = ThreadLocal.withInitial(HashMap::new);
 
    @Override
    public Object get(String name, ObjectFactory<?> objectFactory) {
        return threadObjects.get().computeIfAbsent(name, k -> objectFactory.getObject());
    }
 
    @Override
    public Object remove(String name) {
        return threadObjects.get().remove(name);
    }
 
    @Override
    public void registerDestructionCallback(String name, Runnable callback) {}
 
    @Override
    public String getConversationId() {
        return Thread.currentThread().getName();
    }
}

spring

Breakdown

implements Scope

The core SPI for extending Spring's bean lifecycle management.

threadObjects.get().computeIfAbsent(...)

Uses a ThreadLocal map to store and retrieve bean instances, ensuring thread isolation.

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Custom Thread-Local Scope Implementation

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