聊聊logback的StatusManager

序

本文主要研究一下logback的StatusManager

StatusManager

ch/qos/logback/core/status/StatusManager.java

public interface StatusManager {/*** Add a new status message.* * @param status*/void add(Status status);/*** Obtain a copy of the status list maintained by this StatusManager.* * @return*/List<Status> getCopyOfStatusList();/*** Return the highest level of all the statii.* * @return*/// int getLevel();/*** Return the number of status entries.* * @return*/int getCount();/*** Add a status listener.* * @param listener*//*** Add a status listener. The StatusManager may decide to skip installation if* an earlier instance was already installed.* * @param listener* @return true if actually added, false if skipped*/boolean add(StatusListener listener);/*** ); Remove a status listener.* * @param listener*/void remove(StatusListener listener);/*** Clear the list of status messages.*/void clear();/*** Obtain a copy of the status listener list maintained by this StatusManager* * @return*/List<StatusListener> getCopyOfStatusListenerList();}

StatusManager接口针对status定义了add、getCopyOfStatusList、getCount、clear方法，针对StatusListener定义了add、remove、getCopyOfStatusListenerList方法

BasicStatusManager

ch/qos/logback/core/BasicStatusManager.java

public class BasicStatusManager implements StatusManager {final protected List<Status> statusList = new ArrayList<Status>();final protected CyclicBuffer<Status> tailBuffer = new CyclicBuffer<Status>(TAIL_SIZE);final protected LogbackLock statusListLock = new LogbackLock();final protected List<StatusListener> statusListenerList = new ArrayList<StatusListener>();final protected LogbackLock statusListenerListLock = new LogbackLock();//......
}

BasicStatusManager实现了StatusManager接口，它使用statusList及statusListLock来操作status，使用statusListenerList及statusListenerListLock来操作StatusListener；另外针对status还提供了tailBuffer

add status

    public void add(Status newStatus) {// LBCORE-72: fire event before the count checkfireStatusAddEvent(newStatus);count++;if (newStatus.getLevel() > level) {level = newStatus.getLevel();}synchronized (statusListLock) {if (statusList.size() < MAX_HEADER_COUNT) {statusList.add(newStatus);} else {tailBuffer.add(newStatus);}}}

add方法先加锁，再判断是否超出限制，没有则添加到statusList，超出则添加到tailBuffer

getCopyOfStatusList

    public List<Status> getCopyOfStatusList() {synchronized (statusListLock) {List<Status> tList = new ArrayList<Status>(statusList);tList.addAll(tailBuffer.asList());return tList;}}

getCopyOfStatusList则加锁，然后从statusList及tailBuffer获取status

clear

    public void clear() {synchronized (statusListLock) {count = 0;statusList.clear();tailBuffer.clear();}}

clear则加锁，重置count，清空statusList及tailBuffer

add listener

    public boolean add(StatusListener listener) {synchronized (statusListenerListLock) {if (listener instanceof OnConsoleStatusListener) {boolean alreadyPresent = checkForPresence(statusListenerList, listener.getClass());if (alreadyPresent)return false;}statusListenerList.add(listener);}return true;}private boolean checkForPresence(List<StatusListener> statusListenerList, Class<?> aClass) {for (StatusListener e : statusListenerList) {if (e.getClass() == aClass)return true;}return false;}    

add listener方法先加锁，然后判断是否已经存在，不存在则添加到statusListenerList

remove

    public void remove(StatusListener listener) {synchronized (statusListenerListLock) {statusListenerList.remove(listener);}}

remove则先加锁，然后从statusListenerList中移除

getCopyOfStatusListenerList

    public List<StatusListener> getCopyOfStatusListenerList() {synchronized (statusListenerListLock) {return new ArrayList<StatusListener>(statusListenerList);}}

getCopyOfStatusListenerList则先加锁然后拷贝statusListenerList

Status

ch/qos/logback/core/status/Status.java

public interface Status {int INFO = 0;int WARN = 1;int ERROR = 2;int getLevel();int getEffectiveLevel();Object getOrigin();String getMessage();Throwable getThrowable();/*** @eprecated. Use getTimestamp instead.* @return*/@Deprecateddefault Long getDate() {return getTimestamp();}long getTimestamp();boolean hasChildren();void add(Status child);boolean remove(Status child);Iterator<Status> iterator();}

Status接口定义了getLevel、getEffectiveLevel、getOrigin、getMessage、getThrowable、getTimestamp、hasChildren、add、remove、iterator方法

StatusBase

ch/qos/logback/core/status/StatusBase.java

abstract public class StatusBase implements Status {static private final List<Status> EMPTY_LIST = new ArrayList<Status>(0);int level;final String message;final Object origin;List<Status> childrenList;Throwable throwable;long timestamp;public synchronized void add(Status child) {if (child == null) {throw new NullPointerException("Null values are not valid Status.");}if (childrenList == null) {childrenList = new ArrayList<Status>();}childrenList.add(child);}public synchronized boolean hasChildren() {return ((childrenList != null) && (childrenList.size() > 0));}public synchronized Iterator<Status> iterator() {if (childrenList != null) {return childrenList.iterator();} else {return EMPTY_LIST.iterator();}}public synchronized boolean remove(Status statusToRemove) {if (childrenList == null) {return false;}// TODO also search in childrens' childrenreturn childrenList.remove(statusToRemove);}public synchronized int getEffectiveLevel() {int result = level;int effLevel;Iterator<Status> it = iterator();Status s;while (it.hasNext()) {s = (Status) it.next();effLevel = s.getEffectiveLevel();if (effLevel > result) {result = effLevel;}}return result;}//......}

StatusBase声明实现Status接口，它通过childrenList来存储子status

InfoStatus

ch/qos/logback/core/status/InfoStatus.java

public class InfoStatus extends StatusBase {public InfoStatus(String msg, Object origin) {super(Status.INFO, msg, origin);}public InfoStatus(String msg, Object origin, Throwable t) {super(Status.INFO, msg, origin, t);}}

InfoStatus继承了StatusBase，它的level为Status.INFO

WarnStatus

ch/qos/logback/core/status/WarnStatus.java

public class WarnStatus extends StatusBase {public WarnStatus(String msg, Object origin) {super(Status.WARN, msg, origin);}public WarnStatus(String msg, Object origin, Throwable t) {super(Status.WARN, msg, origin, t);}}

WarnStatus继承了StatusBase，它的level为Status.WARN

ErrorStatus

ch/qos/logback/core/status/ErrorStatus.java

public class ErrorStatus extends StatusBase {public ErrorStatus(String msg, Object origin) {super(Status.ERROR, msg, origin);}public ErrorStatus(String msg, Object origin, Throwable t) {super(Status.ERROR, msg, origin, t);}}

ErrorStatus继承了StatusBase，它的level为Status.ERROR

小结

logback定义了StatusManager用于管理status及其listener，其add方法会回调listener，之后加锁，再判断是否超出限制，没有则添加到statusList，超出则添加到tailBuffer；Status是个接口，它有一个抽象类为StatusBase，而InfoStatus、WarnStatus、ErrorStatus都继承了StatusBase。