java - Apache commons IO 如何将我的 XML header 从 UTF-8 转换为 UTF-16？

Question

我使用的是 Java 6。我有一个 XML 模板，其开头如下

<?xml version="1.0" encoding="UTF-8"?>

但是，我注意到当我使用以下代码解析并输出它时(使用 Apache Commons-io 2.4)...

    Document doc = null;
    InputStream in = this.getClass().getClassLoader().getResourceAsStream(“my-template.xml”);

    try
    {
        byte[] data = org.apache.commons.io.IOUtils.toByteArray( in );
        InputSource src = new InputSource(new StringReader(new String(data)));

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        doc = builder.parse(src);
    }
    finally
    {
        in.close();
    }

第一行输出为

<?xml version="1.0" encoding="UTF-16”?>

解析/输出文件时我需要做什么才能使 header 编码保持为“UTF-8”？

编辑:根据给出的建议，我将代码更改为

    Document doc = null;
    InputStream in = this.getClass().getClassLoader().getResourceAsStream(name);

    try
    {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        doc = builder.parse(in);
    }
    finally
    {
        in.close();
    }

但尽管如此，我的输入元素模板文件的第一行是

<?xml version="1.0" encoding="UTF-8"?>

当我将文档输出为字符串时，它会生成

<?xml version="1.0" encoding="UTF-16"?>

作为第一行。这是我用来将“doc”对象输出为字符串的内容...

private String getDocumentString(Document doc)
{
    DOMImplementationLS domImplementation = (DOMImplementationLS)doc.getImplementation();
    LSSerializer lsSerializer = domImplementation.createLSSerializer();
    return lsSerializer.writeToString(doc);  
}

Answer 1

new StringReader(new String(data))

这是错误的。您应该让解析器使用(例如)DocumentBuilder.parse(InputStream) 来检测文档编码。 :

doc = builder.parse(in);

DOM 序列化为什么编码取决于您如何编写它。内存中的 DOM 没有编码的概念。

将文档写入带有 UTF-8 声明的字符串:

import java.io.StringWriter;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.ls.*;

public class DomIO {
    public static void main(String[] args) throws Exception {
        Document doc = DocumentBuilderFactory.newInstance()
                                             .newDocumentBuilder()
                                             .newDocument();
        doc.appendChild(doc.createElement("foo"));
        System.out.println(getDocumentString(doc));
    }

    public static String getDocumentString(Document doc) {
        DOMImplementationLS domImplementation = (DOMImplementationLS) 
                                                 doc.getImplementation();
        LSSerializer lsSerializer = domImplementation.createLSSerializer();
        LSOutput lsOut = domImplementation.createLSOutput();
        lsOut.setEncoding("UTF-8");
        lsOut.setCharacterStream(new StringWriter());
        lsSerializer.write(doc, lsOut);
        return lsOut.getCharacterStream().toString();
    }
}

LSOutput还有binary stream support如果您希望序列化器在输出时正确编码文档。