Java InputStream轉File

• 文件處於磁盤上或者流處於內存中

在輸入流有已知的和預處理的數據時，如在硬盤上的文件或者在流處於內存中。這種情況下，不需要做邊界校驗，並且內存容量條件允許的話，可以簡單的讀取並一次寫入。

InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"));
byte[] buffer = new byte[initialStream.available()];
initialStream.read(buffer);
 
File targetFile = new File("src/main/resources/targetFile.tmp");
OutputStream outStream = new FileOutputStream(targetFile);
outStream.write(buffer); 

 

基於Guava的實現

InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"));
byte[] buffer = new byte[initialStream.available()];
initialStream.read(buffer);
File targetFile = new File("src/main/resources/targetFile.tmp");
Files.write(buffer, targetFile);

 

基於Commons IO的實現

InputStream initialStream = FileUtils.openInputStream(new File("src/main/resources/sample.txt"));
File targetFile = new File("src/main/resources/targetFile.tmp");
FileUtils.copyInputStreamToFile(initialStream, targetFile);

 

• 輸入流映射正在進行的數據流

如果輸入流鏈接到正在進行的數據流上，如來自正在進行的鏈接的HTTP響應，此時可能無法一次讀取整個流。這種情況下，我們需要確保一直讀取到流的盡頭。

File targetFile = new File("src/main/resources/targetFile.tmp");
try(InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"));
    OutputStream outStream = new FileOutputStream(targetFile)) {
    byte[] buffer = new byte[8 * 1024];
    int bytesRead;
    while ((bytesRead = initialStream.read(buffer)) != -1) {
        outStream.write(buffer, 0, bytesRead);
    }
} catch (Exception e) {
    e.printStackTrace();
}

 

另一種實現方式：

try (InputStream initialStream = new FileInputStream(new File("src/main/resources/sample.txt"))) {
    File targetFile = new File("src/main/resources/targetFile.tmp");
 
    java.nio.file.Files.copy(
            initialStream,
            targetFile.toPath(),
            StandardCopyOption.REPLACE_EXISTING);
} catch (Exception e) {
    e.printStackTrace();
}