将原始二进制数据与XML一起存储的最标准Java方法是什么？ [英] What's the most standard Java way to store raw binary data along with XML?
问题描述
我需要将大量二进制数据存储到文件中，但我还想以XML格式读取/写入该文件的标题。
I need to store a huge amount of binary data into a file, but I want also to read/write the header of that file in XML format.
是的，我可以将二进制数据存储到某个XML值中，然后使用base64编码对其进行序列化。但这不会节省空间。
我可以以一种或多或少的标准方式混合XML数据和原始二进制数据吗？
Can I "mix" XML data and raw binary data in a more-or-less standardized way?
我在想两个选择：
-
有没有使用JAXB执行此操作的方法？
Is there a way to do this using JAXB?
或者有没有办法获取一些现有的XML数据并将二进制数据附加到其中，以这种方式边界被识别了吗？
Or is there a way to take some existing XML data and append binary data to it, in such a way that the the boundary is recognized?
这不是我想要以某种方式用于/用于SOAP的概念吗？
Isn't the concept I'm looking for somehow used by / for SOAP?
或者是否在电子邮件标准中使用？ （二元附件的分离）
Or is it used in the email standard? (Separation of binary attachments)
我想要实现的方案：
[meta-info-about-boundary][XML-data][boundary][raw-binary-data]
谢谢！
推荐答案
我遵循 Blaise Doughan 建议的概念，但没有附件marshallers：
I followed the concept suggested by Blaise Doughan, but without attachment marshallers:
我让 XmlAdapter 将 byte [] 转换为 URI - 引用和返回，而引用指向存储原始数据的单独文件。然后将XML文件和所有二进制文件放入zip中。
I let an XmlAdapter convert a byte[] to a URI-reference and back, while references point to separate files, where raw data is stored. The XML file and all binary files are then put into a zip.
它类似于OpenOffice和ODF格式的方法，实际上是一个拉链很少XML和二进制文件。
It is similar to the approach of OpenOffice and the ODF format, which in fact is a zip with few XMLs and binary files.
（在示例代码中，没有写入实际的二进制文件，也没有创建zip。）
import java.net.*;
import java.util.*;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.*;
final class Bindings {
static final String SCHEME = "storage";
static final Class<?>[] ALL_CLASSES = new Class<?>[]{
Root.class, RawRef.class
};
static final class RawRepository
extends XmlAdapter<URI, byte[]> {
final SortedMap<String, byte[]> map = new TreeMap<>();
final String host;
private int lastID = 0;
RawRepository(String host) {
this.host = host;
}
@Override
public byte[] unmarshal(URI o) {
if (!SCHEME.equals(o.getScheme())) {
throw new Error("scheme is: " + o.getScheme()
+ ", while expected was: " + SCHEME);
} else if (!host.equals(o.getHost())) {
throw new Error("host is: " + o.getHost()
+ ", while expected was: " + host);
}
String key = o.getPath();
if (!map.containsKey(key)) {
throw new Error("key not found: " + key);
}
byte[] ret = map.get(key);
return Arrays.copyOf(ret, ret.length);
}
@Override
public URI marshal(byte[] o) {
++lastID;
String key = String.valueOf(lastID);
map.put(key, Arrays.copyOf(o, o.length));
try {
return new URI(SCHEME, host, "/" + key, null);
} catch (URISyntaxException ex) {
throw new Error(ex);
}
}
}
@XmlRootElement
@XmlType
static final class Root {
@XmlElement
final List<RawRef> element = new LinkedList<>();
}
@XmlType
static final class RawRef {
@XmlJavaTypeAdapter(RawRepository.class)
@XmlElement
byte[] raw = null;
}
}
Main.java
Main.java
import java.io.*;
import javax.xml.bind.*;
public class _Run {
public static void main(String[] args)
throws Exception {
JAXBContext context = JAXBContext.newInstance(Bindings.ALL_CLASSES);
Marshaller marshaller = context.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
Unmarshaller unmarshaller = context.createUnmarshaller();
Bindings.RawRepository adapter = new Bindings.RawRepository("myZipVFS");
marshaller.setAdapter(adapter);
Bindings.RawRef ta1 = new Bindings.RawRef();
ta1.raw = "THIS IS A STRING".getBytes();
Bindings.RawRef ta2 = new Bindings.RawRef();
ta2.raw = "THIS IS AN OTHER STRING".getBytes();
Bindings.Root root = new Bindings.Root();
root.element.add(ta1);
root.element.add(ta2);
StringWriter out = new StringWriter();
marshaller.marshal(root, out);
System.out.println(out.toString());
}
}
输出
Output
<root>
<element>
<raw>storage://myZipVFS/1</raw>
</element>
<element>
<raw>storage://myZipVFS/2</raw>
</element>
</root>
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