Java:如何缩进Transformer生成的XML

Question

我正在使用Java的内置XML转换器来获取DOM文档并打印出生成的XML.问题是尽管明确地设置了参数"indent",但它根本没有缩进文本.

示例代码

public class TestXML {

 public static void main(String args[]) throws Exception {
  ByteArrayOutputStream s;

  Document d = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
  Transformer t = TransformerFactory.newInstance().newTransformer();

  Element a,b;

  a = d.createElement("a");
  b = d.createElement("b");

  a.appendChild(b);

  d.appendChild(a);

  t.setParameter(OutputKeys.INDENT, "yes");

  s = new ByteArrayOutputStream();

  t.transform(new DOMSource(d),new StreamResult(s));

  System.out.println(new String(s.toByteArray()));

 }
}

结果

<?xml version="1.0" encoding="UTF-8" standalone="no"?><a><b/></a>

期望的结果

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<a>
 <b/>
</a>

思考？

Answer 1

您需要启用'INDENT'并设置变压器的缩进量:

t.setOutputProperty(OutputKeys.INDENT, "yes");
t.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");

更新:

参考:如何在序列化之前从DOM中删除仅空白文本节点？

(非常感谢所有成员,特别是@ marc-novakowski,@ james-murty和@saad):

Answer 2

这些建议的解决方案都不适合我.所以我一直在寻找替代解决方案,最终成为前面提到的第二步和第三步的混合.

1. 将indent-number设置为transformerfactory
2. 启用变压器中的缩进
3. 用作者(或bufferedwriter)包装otuputstream

//(1)
TransformerFactory tf = TransformerFactory.newInstance();
tf.setAttribute("indent-number", new Integer(2));

//(2)
Transformer t = tf.newTransformer();
t.setOutputProperty(OutputKeys.INDENT, "yes");

//(3)
t.transform(new DOMSource(doc),
new StreamResult(new OutputStreamWriter(out, "utf-8"));

您必须执行(3)以解决xml处理代码的"错误"行为.

来源:johnnymac75 @ http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6296446

(如果我错误地引用了我的来源,请告诉我)

Answer 3

以下代码适用于Java 7.我在变换器(而不是变压器工厂)上设置缩进(是)和缩进量(2)以使其正常工作.

TransformerFactory tf = TransformerFactory.newInstance();
Transformer t = tf.newTransformer();
t.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
t.setOutputProperty(OutputKeys.INDENT, "yes");
t.transform(source, result);

@ mabac设置属性的解决方案对我不起作用,但@ lapo的评论证明是有帮助的.

Answer 4

import com.sun.org.apache.xml.internal.serializer.OutputPropertiesFactory

transformer.setOutputProperty(OutputPropertiesFactory.S_KEY_INDENT_AMOUNT, "2");

Answer 5

对我来说添加DOCTYPE_PUBLIC有效：

transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC,"yes");
transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "10");

Answer 6

如果要缩进，则必须将其指定为TransformerFactory。

TransformerFactory tf = TransformerFactory.newInstance();
tf.setAttribute("indent-number", new Integer(2));
Transformer t = tf.newTransformer();