JAXB2 Mtom附件被BOM打破

Question

我正在使用JAXB2在Spring中执行OXM。我指定的XSD需要一个大的XML文件来附加到soap消息，所以我使用MTOM来传输该文件，并在我的JAXB2Marshaller上启用了MTOM。

当JAXB2封送具有预期mime类型的文本/xml的MTOM附件时，它将该元素作为javax.xml.transform.Source对象传递。经过一些搜索之后，我能够找到如何将Source对象发送到文件中。

final Source source = request.getSource();
StreamSource streamSource = (StreamSource) source;
TransformerFactory factory = TransformerFactory.newInstance();
Transformer transformer = factory.newTransformer();
File file = new File ("/tempxmlfile.xml");
try{
    transformer.transform(streamSource, new StreamResult(file));
    LOG.info("File saved in "+file.getAbsolutePath());
    }
catch(Exception ex){
        ex.getMessage();
    }

我遇到的问题是，当我发送一个UTF-8编码文件作为附件时，我会得到以下错误：

[Fatal Error] :1:1: Content is not allowed in prolog.
ERROR:  'Content is not allowed in prolog.'

这是由文件中编码文本前面的Byte Order Mark造成的，虽然UTF-8编码文件不需要此BOM，但Unicode标准允许使用此BOM，但Java不支持UTF-8编码流中的BOM。

我可以通过发送一个没有BOM的文件来解决这个问题，但是这实际上是不可行的，因为它会在大多数Microsoft产品中引起问题，因为大多数Microsoft产品都会插入BOM。

Sun/Oracle拒绝用流解决此问题有很多解决办法，但它们都要求您能够访问流，JAXB2提供的源对象没有InputStream --它只有一个InputStream对象。我是否有办法解决这个问题，要么用一个知道如何忽略UTF-8编码中的BOM的读取器来包装source对象，要么改变JAXB2将附件读取到源中的方式，以便它可以忽略UTF-8编码中的BOM。

谢谢你，克雷格

Answer 1

诀窍是“标记”读者。如果您的读取器不支持标记，则可以将其包装在BufferedReader中，这样可以：

• http://download.oracle.com/javase/6/docs/api/java/io/BufferedReader.html#markSupported%28%29

选项1-检查BOM并删除它

我相信我的原始代码写错了BOM。下面的源代码更有意义：

import java.io.*;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

public class Demo {

    private static char[] UTF32BE = {0x00, 0x00, 0xFE, 0xFF}; 
    private static char[] UTF32LE = {0xFF, 0xFE, 0x00, 0x00};
    private static char[] UTF16BE = {0xFE, 0xFF}; 
    private static char[] UTF16LE = {0xFF, 0xFE};
    private static char[] UTF8 = {0xEF, 0xBB, 0xBF};

    public static void main(String[] args) throws Exception {
        // Create an XML document with a BOM
        FileOutputStream fos = new FileOutputStream("bom.xml");
        writeBOM(fos, UTF16LE);

        OutputStreamWriter oswUTF8 = new OutputStreamWriter(fos, "UTF-8");
        oswUTF8.write("<root/>");
        oswUTF8.close();

        // Create a Source based on a Reader to simulate source.getRequest()
        StreamSource attachment = new StreamSource(new FileReader(new File("bom.xml")));

        // Wrap reader in BufferedReader so it will support marking
        Reader reader = new BufferedReader(attachment.getReader());

        // Remove the BOM
        removeBOM(reader);

        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer t = tf.newTransformer();
        t.transform(new StreamSource(reader), new StreamResult(System.out));
    }

    private static void writeBOM(OutputStream os, char[] bom) throws Exception {
        for(int x=0; x<bom.length; x++) {
            os.write((byte) bom[x]);
        }
    }

    private static void removeBOM(Reader reader) throws Exception {
        if(removeBOM(reader, UTF32BE)) {
            return;
        }
        if(removeBOM(reader, UTF32LE)) {
            return;
        }
        if(removeBOM(reader, UTF16BE)) {
            return;
        }
        if(removeBOM(reader, UTF16LE)) {
            return;
        }
        if(removeBOM(reader, UTF8)) {
            return;
        }
    }

    private static boolean removeBOM(Reader reader, char[] bom) throws Exception {
        int bomLength = bom.length;
        reader.mark(bomLength);
        char[] possibleBOM = new char[bomLength];
        reader.read(possibleBOM);
        for(int x=0; x<bomLength; x++) {
            if(bom[x] != possibleBOM[x]) {
                reader.reset();
                return false;
            }
        }
        return true;
    }

}

选项#2 -查找“<”并将读取器提前到那个点

阅读直到您达到“<”杠杆标记/重置：

import java.io.*;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

public class Demo2 {

    private static char[] UTF32BE = {0x00, 0x00, 0xFE, 0xFF}; 
    private static char[] UTF32LE = {0xFF, 0xFE, 0x00, 0x00};
    private static char[] UTF16BE = {0xFE, 0xFF}; 
    private static char[] UTF16LE = {0xFF, 0xFE};
    private static char[] UTF8 = {0xEF, 0xBB, 0xBF};

    public static void main(String[] args) throws Exception {
        // Create an XML document with a BOM
        FileOutputStream fos = new FileOutputStream("bom.xml");
        writeBOM(fos, UTF16BE);

        OutputStreamWriter oswUTF8 = new OutputStreamWriter(fos, "UTF-8");
        oswUTF8.write("<root/>");
        oswUTF8.close();

        // Create a Source based on a Reader to simulate source.getRequest()
        StreamSource attachment = new StreamSource(new FileReader(new File("bom.xml")));

        // Wrap reader in BufferedReader so it will support marking
        Reader reader = new BufferedReader(attachment.getReader());

        // Remove the BOM
        removeBOM(reader);

        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer t = tf.newTransformer();
        t.transform(new StreamSource(reader), new StreamResult(System.out));
    }

    private static void writeBOM(OutputStream os, char[] bom) throws Exception {
        for(int x=0; x<bom.length; x++) {
            os.write((byte) bom[x]);
        }
    }

    private static Reader removeBOM(Reader reader) throws Exception {
        reader.mark(1);
        char[] potentialStart = new char[1];
        reader.read(potentialStart);
        if('<' == potentialStart[0]) {
            reader.reset();
            return reader;
        } else {
            return removeBOM(reader);
        }
    }

}