一个流中的多个 XML "files"

Question

在为web服务开发适配器时，我最终遇到了这样的响应:

<?xml version="1.0" encoding="UTF-8"?>
<ResponseHeader version="1.0">
    <ResponseCode>T100</ResponseCode>
    <SubmissionIdentifier>1</SubmissionIdentifier>
</ResponseHeader>
<?xml version="1.0" encoding="UTF-8"?>
<SubmissionProgress xmlns="sss"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"        
    status="inProgress"
    submissionIdentifier="1"
    submissionType="live">
    <PFile status="rejected"
        index="1"
        pFileIdentifier="999">
        <Exception errorCode="2001" outcomeType="rejectFile">
            <Description>There.file.  </Description>
            <SourceRecord index="3">...</SourceRecord>
        </Exception>
    </PFile>
</SubmissionProgress>

ResponseHeader和SubmissionProgress(以及里面的每个元素)类已经由xjc成功生成，如果我将这个字符串分成两个不同的字符串，我可以完美地分解这两个类。但是，如果我将它保存在同一个String中，并尝试将其依次传递给两个解组器，它将在第一次解组时中断。
我用这段代码从一个字符串中解编组两个字符串:

Reader reader = new StringReader(response);
JAXBContext jcrh = JAXBContext.newInstance(ResponseHeader.class);
JAXBContext jcsp = JAXBContext.newInstance(SubmissionProgress.class);
Unmarshaller urh = jcrh.createUnmarshaller();
Unmarshaller usp = jcsp.createUnmarshaller();
ResponseHeader rh = (ResponseHeader) urh.unmarshal(reader);
SubmissionProgress sr = (SubmissionProgress) usp.unmarshal(reader);

我得到以下异常(at ResponseHeader rh = (ResponseHeader) ur .unmarshal(reader);):

uk.co.bacs.submissions.ResponseHeader@fced4
javax.xml.bind.UnmarshalException
 - with linked exception:
[org.xml.sax.SAXParseException: The processing instruction target matching "[xX][mM][lL]" is not allowed.]
    at javax.xml.bind.helpers.AbstractUnmarshallerImpl.createUnmarshalException(AbstractUnmarshallerImpl.java:315)
(...)

在这些情况下(单个流中有多个XML文件)是否有一些JAXB调整可以使用?

Answer 1

我不知道JAXB的调整;我做这类事情的方法是实现一个xmlleventreader(或XmlStreamReader)，它在需要时模拟文档结束。注意Unmarshaller.unmarshal()将接受其中一个作为参数。为了确保获得正确的事件序列，请观察"正常"文档的事件序列。您将执行两次unmarshal()操作。

Answer 2

由于JAXB本身无法读取文件，因此我找到了两个可行的解决方案。

如果流很小，第一个也是更简单的方法是将其全部读入一个字符串并将其拆分

String xml = "<?xml ... <?xml ...";
String[] xmlArray = xml.split("<\?xml");
ObjectA a = (ResponseHeader) u.unmarshal(new StringReader("<?xml"+xmlArray[1]);
ObjectB b = (SubmissionProgress) u2.unmarshal(new StringReader("<?xml"+xmlArray[2));

但是，作为练习，为了更简洁的代码和将来使用更大的流(一次处理一个对象)，我创建了MultiXMLDocReader类

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;
public class MultiXMLDocReader extends Reader {
    private BufferedReader reader;
    private String buffer;
    private int bufferPos;
    private boolean firstDocument;
    private boolean realEOF;
    private boolean enforceEOF;
    public MultiXMLDocReader(Reader reader) {
        this.reader = new BufferedReader(reader);
        firstDocument = true;
        buffer = "";
        bufferPos = 0;
        realEOF = enforceEOF = false;
    }
    @Override
    public void close() throws IOException {
        enforceEOF = false;
        if (realEOF) reader.close();
    }
    @Override
    public int read() throws IOException {
        char[] buffer = new char[1];
        int result = read(buffer, 0, 1);
        if (result < 0) return -1;
        return buffer[0];
    }
    @Override
    public int read(char[] cbuf, int off, int len) throws IOException {
        if (enforceEOF) return -1;
        int lenLeft = len;
        int read = 0;
        while (lenLeft > 0) {
            if (buffer.length()>0) {
                char[] lbuffer = buffer.toCharArray();
                int bufLen = buffer.length() - bufferPos;
                int newBufferPos = 0;
                if (lenLeft < bufLen) {
                    bufLen = lenLeft;
                    newBufferPos = bufferPos + bufLen;
                }
                else buffer = "";
                System.arraycopy(lbuffer, bufferPos, cbuf, off, bufLen);
                read += bufLen;
                lenLeft -= bufLen;
                off += bufLen;
                bufferPos = newBufferPos;
                continue;
            }
            buffer = reader.readLine();
            if (buffer == null) {
                realEOF = true;
                enforceEOF = true;
                return (read == 0 ? -1 : read);
            }
            else
                buffer += "n";
            if (buffer.startsWith("<?xml")) {
                if (firstDocument) firstDocument = false;
                else {
                    enforceEOF = true;
                    return (read == 0 ? -1 : read);
                }
            }
        }
        return read;
    }
}

可以像

一样方便地使用

MultiXMLDocReader xmlReader = new MultiXMLDocReader(new InputStreamReader(anyInputStream));
ObjectA a = (ResponseHeader) u.unmarshal(xmlReader);
ObjectB b = (SubmissionProgress) u2.unmarshal(xmlReader);