java - 文件 -> byte[] -> 字符串 -> byte[] -> 文件转换

Question

这基本上就是我想要做的。

我想要一个文件

将其转化为字节数组

把它变成一个字符串

将其存储在 MySQL 表中

获取字符串

将其转回字节数组

将其转回文件

现在，我为您准备了一些代码，我已尽我所能对其进行注释。我的问题是，我在这段代码末尾得到的文件不正确。它缺少信息。这是一个文本文件，所以我应该能够判断文件是否完整。

据我所知，我似乎只得到了文件的最后一部分，而不是整个文件。我很确定我在这个转换的某个地方搞砸了。如果您对如何更有效地进行这种转换和检索有任何建议(仍然牢记数据库和所有这些)，也请告诉我!

代码如下

import java.io.*;
import java.util.StringTokenizer;
import java.util.logging.Level;
import java.util.logging.Logger;

public class main {
    public static void main(String[] args) {
        // The file we want to save.
        File f = new File("build.xml");
        try {
            // Make it into a byte array first
            FileInputStream fis = new FileInputStream(f);
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            byte[] buf = new byte[1024];
            try {
                for(int readNum; (readNum = fis.read(buf)) != -1;) {
                    bos.write(buf, 0, readNum);
                    System.out.println("read " + readNum + " bytes,");
                }
                StringBuilder s = new StringBuilder();
                // Now we simulate making it into a String, for easier storage
                // in a database.
                for(byte b : buf) {
                    // for debugging
                    s.append(b).append(",");
                    System.out.print(b +",");
                }
                // Now we want to retrieve the file from the database as a string
                File someFile = new File("build2.xml");
                FileOutputStream fos = new FileOutputStream(someFile);
                // We count how many bytes there are in this string.
                // One byte per Token.
                StringTokenizer st = new StringTokenizer(s.toString(),",");
                buf = new byte[st.countTokens()];
                int i = 0;
                StringBuilder t = new StringBuilder();
                // Now we parse out all Bytes from the string, and put them into
                // the prepared byte array.
                while(st.hasMoreTokens()) {
                    byte b = Byte.parseByte(st.nextToken());
                    System.out.print(b + ",");
                    buf[i] = b;
                    i++;
                    // for debugging
                    t.append(b).append(",");
                }
                // Here I print true if both strings are exactly the same
                // which they should be, which means that the bytes are intact
                // before and after conversion.
                System.out.println("\n" +(t.toString().equals(s.toString()) ? true : false));
                // Here we would make the physical file on the machine.
                fos.write(buf);
                fos.flush();
                fos.close();
            } catch (IOException ex) {
                Logger.getLogger(main.class.getName()).log(Level.SEVERE, null, ex);
            }
        } catch (FileNotFoundException ex) {
            Logger.getLogger(main.class.getName()).log(Level.SEVERE, null, ex);
        }

    }
}

http://pastebin.com/699yuE8f

Answer 1

您的方法完全忽略了编码，这不是一件好事。字符不等于或等同于字节。

如果你必须按照你描述的顺序来做，那么通过这样的方式创建字符串:

String intermediateString = new String(theByteArray,
                                       theSameEncodingTheFileWasCreatedWith);

同样，当您将字符串转换回字节时，像这样获取字节:

byte[] bytesToSave = intermediateString.getBytes(theSameEncodingTheFileWasCreatedWith);

但除此之外，使用字符串有什么意义呢？为什么不直接将字节存储到数据库中？