Java中如何將OutputStream轉換為InputStream？

如何將OutputStream 轉換為InputStream

在軟體開發中，常常會遇到需要將資料從一個串流轉換為一個串流的情況。流類型到另一個。其中一個場景是將 OutputStream 轉換為 InputStream。

管道流簡介

這個問題的解決方案在於使用 Java 的 PipedInputStream 和 PipedOutputStream 類別。這些類別透過創建雙向管道來實現流之間的通訊。

PipedInputStream 到OutputStream（反之亦然）

Lambda 表達式：

PipedInputStream in = new PipedInputStream();
final PipedOutputStream out = new PipedOutputStream(in);
// in a background thread, write the given output stream to the PipedOutputStream for consumption
new Thread(() -> {
    originalOutputStream.writeTo(out);
}).start();

必須處理OutputStream 可能過早關閉的情況，從而導致ClosedPipeException。為了避免這種情況，您可以反轉建構子：

PipedInputStream in = new PipedInputStream(out);
new Thread(() -> {
    originalOutputStream.writeTo(out);
}).start();

Try-With-Resources:

// take the copy of the stream and re-write it to an InputStream
PipedInputStream in = new PipedInputStream();
new Thread(new Runnable() {
    public void run() {
        // try-with-resources here
        // putting the try block outside the Thread will cause the PipedOutputStream resource to close before the Runnable finishes
        try (final PipedOutputStream out = new PipedOutputStream(in)) {
            // write the original OutputStream to the PipedOutputStream
            // note that in order for the below method to work, you need to ensure that the data has finished writing to the ByteArrayOutputStream
            originalByteArrayOutputStream.writeTo(out);
        } catch (IOException e) {
            // logging and exception handling should go here
        }
    }
}).start();

PipedputStream 到InputStream 到🎜>

如果您沒有ByteArrayOutputStream，可以使用以下程式碼：

PipedInputStream in = new PipedInputStream();
final PipedOutputStream out = new PipedOutputStream(in);
new Thread(new Runnable() {
    public void run() {
        try {
            // write the original OutputStream to the PipedOutputStream
            // note that in order for the below method to work, you need to ensure that the data has finished writing to the OutputStream
            originalOutputStream.writeTo(out);
        } catch (IOException e) {
            // logging and exception handling should go here
        } finally {
            // close the PipedOutputStream here because we're done writing data
            // once this thread has completed its run
            if (out != null) {
                // close the PipedOutputStream cleanly
                out.close();
            }
        }
    }
}).start();

使用管道流有幾個好處，包括：

資料傳輸發生在單獨的執行緒中，從而實現並行處理。 記憶體效率：
• 管道流避免建立額外的緩衝區副本，從而減少記憶體消耗。

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