Question

我正在尝试使用blob列后面的字段中找到的值从blob中提取文件。我的解决方案有效，但速度很慢。

我在大约1小时内提取了169MB（727个不同的文件）。这大概是每分钟12个文件。大多数文件通常在5KB到50KB之间，但有时可能大到2MB。我正在使用本地Oracle数据库。

我能做些什么来提高我的代码效率吗？如果没有，还有哪些因素会影响流程的速度？这是方法的代码：

public void beginExtraction(String FileOutDir, String blobSQL,
        String fileSuffix, Connection conn) {

    if ((FileOutDir != null) && (blobSQL != null) && (conn != null)) {
        PreparedStatement selBlobs = null;
        FileOutputStream fos = null;

        if (conn != null) {
            if (blobSQL != null) {
                try {

                    selBlobs = conn.prepareStatement(blobSQL);
                    ResultSet rs = selBlobs.executeQuery();
                    int cols = rs.getMetaData().getColumnCount();

                    while (rs.next()) {

                        Blob blob = rs.getBlob(1);
                        InputStream is = blob.getBinaryStream();

                        String filepath = "";

                        filepath += FileOutDir + "/";

                        for (int c = 2; c <= cols; c++) {
                            filepath += rs.getObject(c).toString() + "_";
                        }

                        filepath = filepath.substring(0,
                                filepath.length() - 1);
                        filepath += fileSuffix;
                        fos = new FileOutputStream(filepath);

                        int b = 0;
                        while ((b = is.read()) != -1) {
                            fos.write(b);
                        }

                    }

                    selBlobs.close();
                    fos.close();

                } catch (Exception e) {
                    JOptionPane.showMessageDialog(gui, e.toString());
                }
            }
        }
    } else {
        if (conn == null) {
            JOptionPane.showMessageDialog(gui,
                    "You have not selected a database.");
        } else {
            if (FileOutDir == null) {
                JOptionPane.showMessageDialog(gui,
                        "You have not chosen a directory for your files.");
            } else {
                if (blobSQL == null) {
                    JOptionPane.showMessageDialog(gui,
                            "Please insert an SQL statement.");

                }
            }
        }
    }
}

Answer 1

更改为缓冲输出使得该过程呈指数级增长。我能够在一分钟内导出727文件。这里是新代码：

//...

                    while (rs.next()) {

                        blob = rs.getBlob(1);
                        is = blob.getBinaryStream();
                        filepath += "/";

                        for (int c = 2; c <= cols; c++) {
                            filepath += rs.getObject(c).toString() + "_";
                        }
                        filepath = filepath.substring(0,
                                filepath.length() - 1);
                        filepath += fileSuffix;

                        fos = new BufferedOutputStream(new FileOutputStream(filepath));

                        while ((b = is.read()) != -1) {
                            fos.write(b);
                        }

                        filepath = FileOutDir;
                        b = 0;
                    }

 //...

从Oracle blob字段中提取文件;

1 个答案: