[LOG4J2-1517] Add ThreadContext.setContext(Map<String, String>)

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Later
• Assignee: Gary D. Gregory
• Reporter: Gary D. Gregory
• Created: 15/Aug/16 02:13
• Updated: 05/Sep/16 18:51
• Resolved: 05/Sep/16 18:51

Description

Add Add ThreadContext.setContext(Map<String, String>).

Note that we have ThreadContext.setStack(Collection<String>) to set the whole stack but nothing to set the whole map.

My immediate goal is to be able to build a JUnit Rule to save and restore the thread context around each unit test method and/or a given class.

I have (not committed yet):

/**
 * Restores the ThreadContext to it's initial map and stack values after a JUnit test.
 */
public class ThreadContextRule extends ExternalResource {

    private final boolean restoreMap;
    private final boolean restoreStack;
    private ThreadContextHolder threadContextHolder;

    /**
     * Constructs an instance initialized to restore the stack and map.
     */
    public ThreadContextRule() {
        this(true, true);
    }

    /**
     * Constructs an instance initialized to restore the given structures.
     * 
     * @param restoreMap
     *            Whether to restore the thread context map.
     * @param restoreStack
     *            Whether to restore the thread context stack.
     */
    public ThreadContextRule(final boolean restoreMap, final boolean restoreStack) {
        super();
        this.restoreMap = restoreMap;
        this.restoreStack = restoreStack;
    }

    @Override
    protected void after() {
        if (threadContextHolder != null) {
            threadContextHolder.restore();
        }
    }

    @Override
    protected void before() throws Throwable {
        threadContextHolder = new ThreadContextHolder(restoreMap, restoreStack);
        if (restoreMap) {
            ThreadContext.clearMap();
        }
        if (restoreStack) {
            ThreadContext.clearStack();
        }
    }

}

and (in src/test):

/**
 * Holds an immutable copy of the ThreadContext stack and map.
 * 
 * TODO Use LOG4J2-1517 Add ThreadContext.setContext(Map<String, String>)
 * 
 * or
 * 
 * TODO Might be replaced by something from LOG4J2-1447.
 * 
 * or do nothing.
 * 
 * @since 2.7
 */
public class ThreadContextHolder {

    private final Map<String, String> immutableContext;
    private final ContextStack immutableStack;
    private final boolean restoreContext;
    private final boolean restoreStack;

    /**
     * Constructs a new holder initialized with an immutable copy of the ThreadContext stack and map.
     * @param restoreContext 
     * @param restoreStack 
     */
    public ThreadContextHolder(final boolean restoreContext, final boolean restoreStack) {
        this.restoreContext = restoreContext;
        this.restoreStack = restoreStack;
        this.immutableContext = restoreContext ? ThreadContext.getImmutableContext() : null;
        this.immutableStack = restoreStack ? ThreadContext.getImmutableStack() : null;
    }

    /**
     * Restores the ThreadContext stack and map based on the values saved in the constructor.
     */
    public void restore() {
        if (restoreStack) {
            ThreadContext.setStack(immutableStack);
        }
        if (restoreContext) {
            ThreadContext.setContext(immutableContext);
        }
    }
}

and in ThreadContext:

    /**
     * Sets this thread's context.
     * 
     * @param map The map to use.
     * @since 2.7
     */
    public static void setContext(final Map<String, String> map) {
        if (map.isEmpty() || !useMap) {
            return;
        }
        contextMap.clear();
        contextMap.putAll(map);
    }

For convenience:

/**
 * Restores the ThreadContext to it's initial map values after a JUnit test.
 */
public class ThreadContextMapRule extends ThreadContextRule {

    /**
     * Constructs an initialized instance.
     */
    public ThreadContextMapRule() {
        super(true, false);
    }
}

/**
 * Restores the ThreadContext to it's initial stack values after a JUnit test.
 */
public class ThreadContextStackRule extends ThreadContextRule {

    /**
     * Constructs an initialized instance.
     */
    public ThreadContextStackRule() {
        super(false, true);
    }
}

Issue Links

• is related to: LOG4J2-1349 Garbage-free ThreadContext map
• is related to: LOG4J2-1447 Garbage-free data structure for LogEvent's context map data
• relates to: LOG4J2-1516 Add ThreadContextMap.putAll(Map<String, String>)
• relates to: LOG4J2-1519 Add ThreadContext.putAll(Map<String, String>)