Snippet

Implementing a Custom Thread-Local Bean Scope

Custom scopes allow extending Spring's bean management to specific lifecycles. A ThreadScope ensures that a single instance of a bean is shared within one thread but isolated from others, useful for complex background job processing.

snippet.java

java

public class ThreadScope implements Scope {
    private final ThreadLocal<Map<String, Object>> threadLocalScope = 
        ThreadLocal.withInitial(HashMap::new);
    @Override
    public Object get(String name, ObjectFactory<?> objectFactory) {
        return threadLocalScope.get().computeIfAbsent(name, k -> objectFactory.getObject());
    }
    @Override
    public Object remove(String name) {
        return threadLocalScope.get().remove(name);
    }
    @Override
    public void registerDestructionCallback(String name, Runnable callback) {
        // Logic for cleaning up resources when thread finishes
    }
}

spring

Breakdown

public class ThreadScope implements Scope

Defines a new strategy for how Spring manages and retrieves bean instances.

ThreadLocal.withInitial(HashMap::new);

Uses ThreadLocal storage to maintain a separate bean registry for every thread.

objectFactory.getObject()

Creates a new bean instance if it does not already exist in the current thread's registry.

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Implementing a Custom Thread-Local Bean Scope

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