您可以为此利用 AttachementMarshaller 和 AttachmentUnmarshaller。这是 JAXB/JAX-WS 用来将二进制内容作为附件传递的桥梁。您可以利用相同的机制来做您想做的事。
概念证明
下面是它的实现方式。这应该适用于任何 JAXB impl（它适用于我的 EclipseLink JAXB (MOXy) 和参考实现）。
消息格式
[xml_length][xml][attach1_length][attach1]...[attachN_length][attachN]
根
这是一个具有多个 byte[] 属性的对象。
import javax.xml.bind.annotation.XmlRootElement;
@XmlRootElement
public class Root {
private byte[] foo;
private byte[] bar;
public byte[] getFoo() {
return foo;
}
public void setFoo(byte[] foo) {
this.foo = foo;
}
public byte[] getBar() {
return bar;
}
public void setBar(byte[] bar) {
this.bar = bar;
}
}
演示
这个类用来演示MessageWriter和MessageReader是如何使用的：
import java.io.FileInputStream;
import java.io.FileOutputStream;
import javax.xml.bind.JAXBContext;
public class Demo {
public static void main(String[] args) throws Exception {
JAXBContext jc = JAXBContext.newInstance(Root.class);
Root root = new Root();
root.setFoo("HELLO WORLD".getBytes());
root.setBar("BAR".getBytes());
MessageWriter writer = new MessageWriter(jc);
FileOutputStream outStream = new FileOutputStream("file.xml");
writer.write(root, outStream);
outStream.close();
MessageReader reader = new MessageReader(jc);
FileInputStream inStream = new FileInputStream("file.xml");
Root root2 = (Root) reader.read(inStream);
inStream.close();
System.out.println(new String(root2.getFoo()));
System.out.println(new String(root2.getBar()));
}
}
MessageWriter
负责将消息写入所需的格式：
import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;
import javax.activation.DataHandler;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.attachment.AttachmentMarshaller;
public class MessageWriter {
private JAXBContext jaxbContext;
public MessageWriter(JAXBContext jaxbContext) {
this.jaxbContext = jaxbContext;
}
/**
* Write the message in the following format:
* [xml_length][xml][attach1_length][attach1]...[attachN_length][attachN]
*/
public void write(Object object, OutputStream stream) {
try {
Marshaller marshaller = jaxbContext.createMarshaller();
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);
BinaryAttachmentMarshaller attachmentMarshaller = new BinaryAttachmentMarshaller();
marshaller.setAttachmentMarshaller(attachmentMarshaller);
ByteArrayOutputStream xmlStream = new ByteArrayOutputStream();
marshaller.marshal(object, xmlStream);
byte[] xml = xmlStream.toByteArray();
xmlStream.close();
ObjectOutputStream messageStream = new ObjectOutputStream(stream);
messageStream.write(xml.length); //[xml_length]
messageStream.write(xml); // [xml]
for(Attachment attachment : attachmentMarshaller.getAttachments()) {
messageStream.write(attachment.getLength()); // [attachX_length]
messageStream.write(attachment.getData(), attachment.getOffset(), attachment.getLength()); // [attachX]
}
messageStream.flush();
} catch(Exception e) {
throw new RuntimeException(e);
}
}
private static class BinaryAttachmentMarshaller extends AttachmentMarshaller {
private static final int THRESHOLD = 10;
private List<Attachment> attachments = new ArrayList<Attachment>();
public List<Attachment> getAttachments() {
return attachments;
}
@Override
public String addMtomAttachment(DataHandler data, String elementNamespace, String elementLocalName) {
return null;
}
@Override
public String addMtomAttachment(byte[] data, int offset, int length, String mimeType, String elementNamespace, String elementLocalName) {
if(data.length < THRESHOLD) {
return null;
}
int id = attachments.size() + 1;
attachments.add(new Attachment(data, offset, length));
return "cid:" + String.valueOf(id);
}
@Override
public String addSwaRefAttachment(DataHandler data) {
return null;
}
@Override
public boolean isXOPPackage() {
return true;
}
}
public static class Attachment {
private byte[] data;
private int offset;
private int length;
public Attachment(byte[] data, int offset, int length) {
this.data = data;
this.offset = offset;
this.length = length;
}
public byte[] getData() {
return data;
}
public int getOffset() {
return offset;
}
public int getLength() {
return length;
}
}
}
消息阅读器
负责阅读消息：
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.attachment.AttachmentUnmarshaller;
public class MessageReader {
private JAXBContext jaxbContext;
public MessageReader(JAXBContext jaxbContext) {
this.jaxbContext = jaxbContext;
}
/**
* Read the message from the following format:
* [xml_length][xml][attach1_length][attach1]...[attachN_length][attachN]
*/
public Object read(InputStream stream) {
try {
ObjectInputStream inputStream = new ObjectInputStream(stream);
int xmlLength = inputStream.read(); // [xml_length]
byte[] xmlIn = new byte[xmlLength];
inputStream.read(xmlIn); // [xml]
BinaryAttachmentUnmarshaller attachmentUnmarshaller = new BinaryAttachmentUnmarshaller();
int id = 1;
while(inputStream.available() > 0) {
int length = inputStream.read(); // [attachX_length]
byte[] data = new byte[length]; // [attachX]
inputStream.read(data);
attachmentUnmarshaller.getAttachments().put("cid:" + String.valueOf(id++), data);
}
Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
unmarshaller.setAttachmentUnmarshaller(attachmentUnmarshaller);
ByteArrayInputStream byteInputStream = new ByteArrayInputStream(xmlIn);
Object object = unmarshaller.unmarshal(byteInputStream);
byteInputStream.close();
inputStream.close();
return object;
} catch(Exception e) {
throw new RuntimeException(e);
}
}
private static class BinaryAttachmentUnmarshaller extends AttachmentUnmarshaller {
private Map<String, byte[]> attachments = new HashMap<String, byte[]>();
public Map<String, byte[]> getAttachments() {
return attachments;
}
@Override
public DataHandler getAttachmentAsDataHandler(String cid) {
byte[] bytes = attachments.get(cid);
return new DataHandler(new ByteArrayDataSource(bytes));
}
@Override
public byte[] getAttachmentAsByteArray(String cid) {
return attachments.get(cid);
}
@Override
public boolean isXOPPackage() {
return true;
}
}
private static class ByteArrayDataSource implements DataSource {
private byte[] bytes;
public ByteArrayDataSource(byte[] bytes) {
this.bytes = bytes;
}
public String getContentType() {
return "application/octet-stream";
}
public InputStream getInputStream() throws IOException {
return new ByteArrayInputStream(bytes);
}
public String getName() {
return null;
}
public OutputStream getOutputStream() throws IOException {
return null;
}
}
}
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