public class PureDiskLogAdapter implements LogAdapter {
// 在cache中第一个文件默认名
private static final String CACHE_LOG_FIRST_NAME = "logs_0000
.dat";
// 最大的log缓存量，支持设置 1 * 500 * 1024 ~ 9999 * 500 * 1024
// 超过则在init时删除
private static final long LOG_MAX_SIZE = 800 * 500 * 1024L; // 400Mb
private static volatile PureDiskLogAdapter instance;
private final FormatStrategy formatStrategy;
private final String logFileFolderPath;
private final byte[] encryptKey;
private AESEncrypter encrypter;
public static PureDiskLogAdapter getInstance(Context context, String appName, long limitCacheSize) {
if (instance ==
null) {
synchronized (PureDiskLogAdapter
.class) {
if (instance ==
null) {
instance = new PureDiskLogAdapter(context, appName, limitCacheSize);
}
}
}
return instance;
}
public static boolean isLoggable
() {
return instance !=
null;
}
/**
* 将日志解密到外置存储器中，
* 每次将日志解密到外置存储器时都会先暂停日志的更新，并在解密保存成功后删除cache中的文件
* <p>
* 注意：调用时需要检查文件读写权限
*
* @param decrypt true为解密， false为不解密
* @return 保存的路径
*/
public static String decryptLogger(Context context, boolean decrypt, String company, String appName) {
if (instance ==
null) {
return
null;
}
File loggerFile = new File(instance
.logFileFolderPath);
if (!loggerFile
.exists
()) {
return
null;
}
File distDir = context
.getExternalFilesDir(Environment
.DIRECTORY_DOCUMENTS);
if (distDir ==
null) {
return
null;
}
// 暂停所有log
TLog
.clean
();
String dstPath = distDir
.getAbsolutePath
();
String dstFolder =
dstPath + File
.separatorChar + company
.toUpperCase
() + File
.separatorChar + appName
.toUpperCase
();
// 用于导入日志的文件对象
File exportLogFile = instance
.generateExternalFile(dstFolder, appName);
if (loggerFile
.isFile
()) {
instance
.readEncryptFile(loggerFile, exportLogFile, decrypt);
} else {
List<File> fileList = FileUtils
.getSortedFileList(loggerFile
.listFiles
());
for (File logFile : fileList) {
instance
.readEncryptFile(logFile, exportLogFile, decrypt);
}
}
// 清除所有disk log
FileUtils
.delete(loggerFile);
// 重新开启log
reset(context, appName);
return dstFolder;
}
private static void reset(Context context, String appName) {
instance =
null;
TLog
.reset(context, appName);
}
private PureDiskLogAdapter(Context context, String appName, long limitCacheSize) {
logFileFolderPath = context
.getApplicationContext
().getCacheDir
().getAbsolutePath
() + File
.separatorChar +
"logger";
encryptKey = buildLogEncryptKey
();
// 初始化时选检查logger目录下的日志是否超过预定值，超过则清除所有日志
cleanLoggerCache(logFileFolderPath);
renameAllDiskLog(logFileFolderPath);
formatStrategy =
PureFormatStrategy
.newBuilder(context)
.tag(appName
.toUpperCase
())
.encryptKey(encryptKey)
.limitCache(limitCacheSize)
.build
();
}
@Override
public boolean isLoggable(int priority, @
Nullable String tag) {
return true;
}
@Override
public void log(int priority, @
Nullable String tag, @Non
Null String message) {
formatStrategy
.log(priority, tag, message);
}
private byte[] buildLogEncryptKey
() {
try {
// 加密key
return CodecUtils
.getMD5Byte(PlainEncryptKeyDelegate
.getEncryptKey
().getBytes("utf-8"));
} catch (Exception e) {
return
null;
}
}
/**
* 将cache中的log文件列表进行重命名，防止开启循环删除cache后，重新打开disk log文件没有按照最初的顺序排列
*/
private void renameAllDiskLog(String folderPath) {
File file = new File(folderPath);
if (!file
.exists
() || file
.isFile
()) {
return;
}
// 路径存在
List<File> fileList = FileUtils
.getSortedFileList(file
.listFiles
());
if (fileList
.isEmpty
()) {
return;
}
// 路径下文件列表不为空
if (CACHE_LOG_FIRST_NAME
.equals(fileList
.get(0)
.getName
())) {
return;
}
// 第一个文件名不匹配，需要把文件列表全部重名名
int newFileCount = 0;
for (File tempFile : fileList) {
File newFile = new File(folderPath, String
.format(Locale
.US, "logs_%04d
.dat", newFileCount));
tempFile
.renameTo(newFile);
newFileCount++;
}
}
/**
* 清除保存在cache中的log，条件为超过 LOG_MAX_SIZE
*/
private void cleanLoggerCache(String folderPath) {
File file = new File(folderPath);
if (file
.exists
()) {
long deleteRange = (long) (LOG_MAX_SIZE * 1
.2f);
if (FileUtils
.getAllFileLength(file) > deleteRange) {
FileUtils
.delete(file);
}
}
}
/**
* 生成文件名，按照 2017-08-16_16-38-22-678
.dat 的格式保存
*
* @param folderName 目录路径
*/
private File generateExternalFile(String folderName, String appName) {
File folder = new File(folderName);
if (!folder
.exists
()) {
folder
.mkdirs
();
}
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss-SSS", Locale
.US);
return new File(folder, String
.format("%s_%s
.txt", appName,
dateFormat
.format(new Date(System
.currentTimeMillis
()))));
}
/**
* 解码文件
*
* @param file 源文件
* @param externalFile 目标文件
*/
private void readEncryptFile(File file, File externalFile, boolean decrypt) {
try (File
Reader file
Reader = new File
Reader(file);
FileWriter fileWriter = new FileWriter(externalFile, true);
BufferedReader bufferedReader = new
BufferedReader(file
Reader)) {
StringBuilder stringBuilder = new StringBuilder
();
String readBuffer;
while ((readBuffer =
bufferedReader.readLine()) !=
null) {
// 每次读一行，并确定是否解密
if (decrypt) {
// 解密日志
stringBuilder
.append(decryptLoggerString(readBuffer));
} else {
stringBuilder
.append(readBuffer);
}
}
// 写入文件
fileWriter
.write(stringBuilder
.toString
());
fileWriter
.flush
();
} catch (Exception e) {
/* fail silently */
}
}
// AES解密,用getMD5Byte生成Key
private String decryptLoggerString(String encrypted) throws Exception {
byte[] enc = CodecUtils
.hexStringToByteArray(encrypted);
if (encrypter ==
null) {
encrypter = new AESEncrypter(encryptKey,
null, "AES");
}
byte[] result = encrypter
.decrypt(enc);
// 将原来写入时替换换行符的替换回来
return new String(result)
.replaceAll(PureFormatStrategy
.NEW_LINE_REPLACEMENT, PureFormatStrategy
.NEW_LINE);
}
}
Attempt to invoke direct method 'void vj0
.a
.j(java
.io
.File, java
.io
.File, boolean)' on a
null object reference
空指针分析
本文通过一个具体的编程案例，讲述了在使用Java进行HTTP请求处理时遇到的一个常见问题：在调试过程中监视表达式导致的数据流提前被消费，进而使得程序逻辑无法按预期执行。作者分享了解决这一问题的经验教训，并提醒开发者在调试涉及流读取的程序时要格外小心。
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