我正在使用java.nio.file包并尝试使用以下代码创建文件。
private static void printReport(String filename, String str)throws Exception{
ErrorCheck ec = new ErrorCheck();
String fileName = "/var/Emails_log/"+filename;
Path filePath = Paths.get(fileName);
File file = new File(fileName);
final BufferedWriter out = Files.newBufferedWriter(filePath, StandardCharsets.UTF_8, StandardOpenOption.APPEND);
try{
final Path tmp = filePath.getParent();
if (tmp != null){ // null will be returned if the path has no parent
Files.createDirectories(tmp);
}
else{
out.write(str);
out.write('\n');
}
}catch (Exception e){
ec.errorMsg("ERROR: GSW.SendEmail.Exception =>",e);
}
finally {
if (out != null) {
out.flush();
out.close();
}
}
}
这会抛出以下异常：
java.nio.file.NoSuchFileException: /var/Emails_log/GSWvalidSentAddresses.txt
at sun.nio.fs.UnixException.translateToIOException(UnixException.java:86)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102)
at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107)
at sun.nio.fs.UnixFileSystemProvider.newByteChannel(UnixFileSystemProvider.java:214)
at java.nio.file.spi.FileSystemProvider.newOutputStream(FileSystemProvider.java:430)
at java.nio.file.Files.newOutputStream(Files.java:170)
at java.nio.file.Files.newBufferedWriter(Files.java:2720)
at SendEmail.printReport(SendEmail.java:114) SendEmail.send(SendEmail.java:87)
我的问题是为什么不创建文件？
请告知
感谢您的期待
答案 0 :(得分：7)
更新了答案：
现在您已经显示了完整的代码，有两个主要问题：
您正在尝试打开该文件，然后确保存在导致该目录的目录，
您正在使用StandardOpenOption.APPEND，但不会创建文件;它将附加到现有的文件。
......以及与实际代码行数相关的最佳实践的大量问题。
见评论：
private static void printReport(String filename, String str) throws Exception /* No, it doesn't. The only calls you had outside your catch-all `try` don't throw exceptions. */ {
ErrorCheck ec = new ErrorCheck(); // Recommend not creating this until/unless you need it
String fileName = "/var/Emails_log/"+filename; // VERY poor practice having two locals that only differ by the capitalization of one character in the middle (`filename` and `fileName`)
Path filePath = Paths.get(fileName);
// File file = new File(fileName); <== Removed, since you never use it for anything
try {
// Make sure the directories exist
Files.createDirectories(filePath.getParent()); // No need for your null check, so I removed it; based on `fileName`, it will always have a parent
// Open the file, creating it if it doesn't exist
try (
final BufferedWriter out = Files.newBufferedWriter(
filePath,
StandardCharsets.UTF_8,
StandardOpenOption.CREATE,
StandardOpenOption.APPEND)
) {
// Write to out here
}
} catch (Exception e) {
// Log-and-continue isn't generally best practice; and if you're going to do it
ec.errorMsg("ERROR: GSW.SendEmail.Exception =>",e); // <== Um...send mail failed? This isn't sending mail, it's putting something in a file.
}
// Using the try-with-resources, we don't have to worry about the flush and close calls
}
但这是我建议你写的方式：
private static void printReport(String filename, String str) throws IOException {
Path filePath = Paths.get("/var/Emails_log/" + filename);
// Make sure the directories exist
Files.createDirectories(filePath.getParent());
// Open the file, creating it if it doesn't exist
try (
final BufferedWriter out = Files.newBufferedWriter(
filePath,
StandardCharsets.UTF_8,
StandardOpenOption.CREATE,
StandardOpenOption.APPEND)
) {
// Write to out here, perhaps outputting `str`?
}
}
...并处理调用层中的异常。请注意，同样，因为我们使用的是try-with-resources，close是自动的（无论何时出现异常，何时出现异常）。
或者，如果您真的想要记录并继续：
private static void printReport(String filename, String str) {
try {
Path filePath = Paths.get("/var/Emails_log/" + filename);
// Make sure the directories exist
Files.createDirectories(filePath.getParent());
// Open the file, creating it if it doesn't exist
try (
final BufferedWriter out = Files.newBufferedWriter(
filePath,
StandardCharsets.UTF_8,
StandardOpenOption.CREATE,
StandardOpenOption.APPEND)
) {
// Write to out here, perhaps outputting `str`?
}
}
catch (Exception e) {
new ErrorCheck().errorMsg("ERROR: GSW.SendEmail.Exception =>", e); // <== But surely this message is suspect? I don't see anything sending email here.
}
}
原始答案：
您尚未显示实际失败的代码，即调用newBufferedWriter（this一个或this一个）。 newBufferedWriter需要OpenOption个，其标准集可从StandardOpenOption获得。确保您已指定StandardOpenOption.CREATE或StandardOpenOption.CREATE_NEW，
如果您使用其中一个标记，并且 newBufferedWriter调用之前问题中的代码是，除非出现其他问题（权限），否则它应该有效：
String fileName = "/var/Emails_log/"+filename;
Path filePath = Paths.get(fileName);
final Path tmp = filePath.getParent();
if (tmp != null) { // <== Note: There's no point to this check, given
// your filename above, the path WILL have a parent.
// You could remove the `if` and just use
// `Files.createDirectories(tmp)` unless the `fileName`
// is actually coming from somewhere else and so could
// be a root (roots don't have parents)
Files.createDirectories(tmp);
}
else {
out.write(str); // I assume this is for logging or display?
out.write('\n'); // Specifically, that it's *not* trying to write
// to the file you're trying to create.
}
try (BufferedWriter writer = Files.newBufferedWriter(filePath, StandardOpenOption.CREATE)) {
// ------------------------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^
// Write to the file here
}