[LOG4J2-1629] Support for primitive values in StringMap

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.7
• Component/s: API
• Assignee: Remko Popma
• Reporter: Remko Popma
• Created: 02/Oct/16 05:04
• Updated: 17/Jan/22 23:05

Description

For some applications like financial trading systems, highly interactive games or numerical computation-heavy scientific applications, a large portion of data is stored in primitives. Applications like this sometimes need to set such values in the logging context (e.g., order ID, algo strategy instance ID, etc) and would prefer to avoid the overhead of boxing/unboxing these primitives.

Building on top of the work done for LOG4J2-1447 and LOG4J2-1349, this ticket proposes to add interfaces extending ThreadContextMap2, StringMap and ReadOnlyStringMap to add support for primitive values:

public interface HybridThreadContextMap extends ThreadContextMap2 {
    long getLong(String key);
    void putLong(String key, long value);
    boolean containsLong(String key);
    HybridStringMap getHybridStringMap();

    /** The value that {@link #getLong()} should return if the map
     * doesn't have a long value for the specified key.
     */
    long getDefaultLong();
    void setDefaultLong(long defaultValue);
}

public interface ReadOnlyHybridStringMap extends ReadOnlyStringMap {
    long getLong(String key);
    boolean containsLong(String key);

    long getDefaultLong();
    void setDefaultLong(long defaultValue);

    void forEachLong(StringLongConsumer action);
    void forEachLong(StringLongObjConsumer action);
}

public interface HybridStringMap extends StringMap, ReadOnlyHybridStringMap {
    void putLong(String key, long value);
}

The semantics remain the same as a normal map: there is at most one value for a key. Putting a value with the same key replaces the old value with that key, regardless of whether the old value was an Object or a primitive.

An API supporting only primitive long values is sufficient because all primitives can be represented as a 64 bit long. For example, a double can be converted to a long and back with the Double.doubleToLongBits(double) method and its reverse. Applications can decorate the Log4j interfaces with custom facades that provide separate methods for different primitive types if required.

For iteration, new interfaces StringLongConsumer and StringLongObjConsumer are introduced. These interfaces are similar to the previous Consumer interfaces except that their accept method takes a long parameter for the value:

public interface StringLongConsumer {
    /**
     * Performs the operation given the specified arguments.
     * @param key the first input argument
     * @param longValue the second input argument as a primitive long, or
     *              a default value if the underlying value is not a primitive value
     */
    void accept(String key, long longValue);
}

public interface StringLongObjConsumer<T> {
    void accept(String key, long value, T state);
}

Issue Links

• relates to: LOG4J2-1660 ThreadContext to expose ReadOnlyThreadContextMap internal data structure
• supercedes: LOG4J2-1401 Support changing the log level for all messages related to some domain object