前言：
项目开始没有做好日志统计工作，每次有问题后端都得找前端对接，严重影响工作效率。最近特地在项目中加上日志保存策略，在此分享，供需要的人学习。
一.更详细的日志信息
既然决定自定义一个log，那我们就可以让它显示更多的信息，如线程信息：threadId，threadName等：
private String getFunctionName() {
StackTraceElement[] sts = Thread.currentThread().getStackTrace();
if (sts == null) {
return null;
}
for (StackTraceElement st : sts) {
if (st.isNativeMethod()) {
continue;
}
if (st.getClassName().equals(Thread.class.getName())) {
continue;
}
if (st.getClassName().equals(this.getClass().getName())) {
continue;
}
Thread t = Thread.currentThread();
return "[T(id:" + t.getId() +
", name:" + t.getName() +
", priority:" + t.getPriority() +
", groupName:" + t.getThreadGroup().getName() +
"): " + st.getFileName() + ":"
+ st.getLineNumber() + " " + st.getMethodName() + " ]";
}
return "";
}
StackTrace(堆栈轨迹)存放的就是方法调用栈的信息，我们从中获取方法执行的线程相关的信息，以及执行的方法名称等。这些信息能帮助我们更好的查找问题之所在。
private void logPrint(int logLevel, Object msg) {
if (isDebug) {
String name = getFunctionName();
customTag = TextUtils.isEmpty(customTag) ? defaultTag : customTag;
Log.println(logLevel, customTag, name + " - " + msg);
}
}
使用Log.println方法打印相关信息即可。
二.日志保存策略
后端的人在测试的时候会遇到BUG，有时候不知道到底是前端出了问题还是后端的问题，为了更好更快速的定位，后端应该知道前端的日志保存在哪里。这就需要我们制定一个日志保存策略。（即使要上传日志，也应该先保存成文件再上传文件，不然每一条日志调用一次接口，接口的压力会很大，很不合理）
由于保存日志的过程是个耗时过程，我们需要开启线程去保存。但是日志产生的频率可能很高，又不能采用一般的线程去处理，太多的线程也会损耗性能。所以我们应该考虑队列的形式保存日志，然后一条一条的去保存。
public void initSaveStrategy(Context context) {
if (saveLogStrategy != null || !isDebug) {
return;
}
final int MAX_BYTES = 1024 * 1024;
String diskPath = Environment.getExternalStorageDirectory().getAbsolutePath();
File cacheFile = context.getCacheDir();
if (cacheFile != null) {
diskPath = cacheFile.getAbsolutePath();
}
String folder = diskPath + File.separatorChar + "log";
HandlerThread ht = new HandlerThread("SohuLiveLogger." + folder);
ht.start();
Handler handler = new SaveLogStrategy.WriteHandler(ht.getLooper(), folder, MAX_BYTES);
saveLogStrategy = new SaveLogStrategy(handler);
}
public static class WriteHandler extends Handler {
private final String folder;
private final int maxFileSize;
WriteHandler(@NonNull Looper looper, @NonNull String folder, int maxFileSize) {
super(checkNotNull(looper));
this.folder = checkNotNull(folder);
this.maxFileSize = maxFileSize;
}
@Override
public void handleMessage(@NonNull Message msg) {
String content = (String) msg.obj;
FileWriter fileWriter = null;
File logFile = getLogFile(folder, "logs");
try {
fileWriter = new FileWriter(logFile, true);
writeLog(fileWriter, content);
fileWriter.flush();
fileWriter.close();
} catch (IOException e) {
if (fileWriter != null) {
try {
fileWriter.flush();
fileWriter.close();
} catch (IOException e1) {
}
}
}
}
我们使用HandlerThread来处理这个任务。HandlerThread是一个可以使用handler的Thread。当我们把消息保存到消息队列中去之后会在线程中去处理，又能保证不会产生很多线程。其实这里也可以使用instentservice实现，这个服务适合量大而不太耗时的任务。
最后在一个方法中统一打印和保存即可：
private void logPrint(int logLevel, Object msg) {
if (isDebug) {
String name = getFunctionName();
if (saveLogStrategy != null) {
saveLogStrategy.log(Log.ERROR, customTag, name + " - " + msg);
}
Log.println(logLevel, customTag, name + " - " + msg);
}
}
自定义的log策略还是比较简单，主要就是这个思想：打印日志信息详细，保存要采用队列的形式。一下是全部代码：
public class Logger {
public final static String tag = "";
private static SaveLogStrategy saveLogStrategy;
private final static boolean logFlag = true;
private static Logger logger;
private int logLevel = Log.VERBOSE;
private static boolean isDebug = BuildConfig.DEBUG;
private String customTag = null;
private Logger(String customTag) {
this.customTag = customTag;
}
public void initSaveStrategy(Context context) {
if (saveLogStrategy != null || !isDebug) {
return;
}
final int MAX_BYTES = 1024 * 1024;
String diskPath = Environment.getExternalStorageDirectory().getAbsolutePath();
File cacheFile = context.getCacheDir();
if (cacheFile != null) {
diskPath = cacheFile.getAbsolutePath();
}
String folder = diskPath + File.separatorChar + "log";
HandlerThread ht = new HandlerThread("Logger." + folder);
ht.start();
Handler handler = new SaveLogStrategy.WriteHandler(ht.getLooper(), folder, MAX_BYTES);
saveLogStrategy = new SaveLogStrategy(handler);
}
public static Logger getLogger(String tag) {
if (logger == null) {
logger = new Logger(tag);
}
return logger;
}
public static Logger getLogger() {
if (logger == null) {
logger = new Logger(tag);
}
return logger;
}
/**
* Verbose(2) 级别日志
*
* @param str String
*/
public void v(Object str) {
logLevel = Log.VERBOSE;
logPrint(logLevel, str);
}
/**
* Debug(3) 级别日志
*
* @param str String
*/
public void d(Object str) {
logLevel = Log.DEBUG;
logPrint(logLevel, str);
}
/**
* Info(4) 级别日志
*
* @param str String
*/
public void i(Object str) {
logLevel = Log.INFO;
logPrint(logLevel, str);
}
/**
* Warn(5) 级别日志
*
* @param str String
*/
public void w(Object str) {
logLevel = Log.WARN;
logPrint(logLevel, str);
}
/**
* Error(6) 级别日志
*
* @param str String
*/
public void e(Object str) {
logLevel = Log.ERROR;
logPrint(logLevel, str);
}
private void logPrint(int logLevel, Object msg) {
if (isDebug) {
String name = getFunctionName();
if (saveLogStrategy != null) {
saveLogStrategy.log(Log.ERROR, customTag, name + " - " + msg);
}
Log.println(logLevel, customTag, name + " - " + msg);
}
}
/**
* 获取当前方法名
*
* @return 方法名
*/
private String getFunctionName() {
StackTraceElement[] sts = Thread.currentThread().getStackTrace();
if (sts == null) {
return null;
}
for (StackTraceElement st : sts) {
if (st.isNativeMethod()) {
continue;
}
if (st.getClassName().equals(Thread.class.getName())) {
continue;
}
if (st.getClassName().equals(this.getClass().getName())) {
continue;
}
Thread t = Thread.currentThread();
return "[Thread(id:" + t.getId() +
", name:" + t.getName() +
", priority:" + t.getPriority() +
", groupName:" + t.getThreadGroup().getName() +
"): " + st.getFileName() + ":"
+ st.getLineNumber() + " " + st.getMethodName() + " ]";
}
return "";
}
}
public class SaveLogStrategy {
@NonNull
private final Handler handler;
public SaveLogStrategy(@NonNull Handler handler) {
this.handler = checkNotNull(handler);
}
public void log(int level, @Nullable String tag, @NonNull String message) {
checkNotNull(message);
handler.sendMessage(handler.obtainMessage(level, message));
}
static class WriteHandler extends Handler {
private final String folder;
private final int maxFileSize;
WriteHandler(@NonNull Looper looper, @NonNull String folder, int maxFileSize) {
super(checkNotNull(looper));
this.folder = checkNotNull(folder);
this.maxFileSize = maxFileSize;
}
@SuppressWarnings("checkstyle:emptyblock")
@Override
public void handleMessage(@NonNull Message msg) {
String content = (String) msg.obj;
FileWriter fileWriter = null;
File logFile = getLogFile(folder, "logs");
try {
fileWriter = new FileWriter(logFile, true);
writeLog(fileWriter, content);
fileWriter.flush();
fileWriter.close();
} catch (IOException e) {
if (fileWriter != null) {
try {
fileWriter.flush();
fileWriter.close();
} catch (IOException e1) {
}
}
}
}
private void writeLog(@NonNull FileWriter fileWriter, @NonNull String content) throws IOException {
checkNotNull(fileWriter);
checkNotNull(content);
fileWriter.append("\n").append(content);
}
private File getLogFile(@NonNull String folderName, @NonNull String fileName) {
checkNotNull(folderName);
checkNotNull(fileName);
File folder = new File(folderName);
if (!folder.exists()) {
if (!folder.mkdirs()) {
Log.println(Log.ERROR, "saveLog", "文件未创建成功，可能是读写权限没给");
}
}
int newFileCount = 0;
File newFile;
File existingFile = null;
newFile = new File(folder, String.format("%s_%s.txt", fileName, newFileCount));
while (newFile.exists()) {
existingFile = newFile;
newFileCount++;
newFile = new File(folder, String.format("%s_%s.txt", fileName, newFileCount));
}
if (existingFile != null) {
if (existingFile.length() >= maxFileSize) {
return newFile;
}
return existingFile;
}
return newFile;
}
}
}
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