如何让 Java.xml.Transformer 输出一个没有任何无用空格或换行符的 xml？

Question

My Code Now:

import org.w3c.dom.Node;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import java.io.StringWriter;

private String getStringByJAXP(Node input) {
        StreamResult xmlOutput;
        try {
            xmlOutput = new StreamResult(new StringWriter());
            transformerFactory = TransformerFactory.newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
            transformer.transform(new DOMSource(input), xmlOutput);
        } catch (TransformerException e) {
            throw new IllegalArgumentException();
        }
        return xmlOutput.getWriter().toString();
    }

Output:

<aaa>
    <a>text a</a>
    <b>
        <c>text c</c>
    </b>
    <f>
        <g><h a="xxx"/></g>
    </f>
</aaa>

But I want to output as follows:

<aaa><a>text a</a><b><c>text c</c></b><f><g><h a="xxx" /></g></f></aaa>

Notice that I can't do that task by some simple string replaces, because the space in <a>text a</a> shouldn't be replaced( <a>texta</a> is total different from <a>text a</a> ).

EDIT:

OutputKeys.INDENT, "no" not works. Updated code:

private String getStringByJAXP(Node input) {
    StreamResult xmlOutput;
    try {
        xmlOutput = new StreamResult(new StringWriter());
        transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
        transformer.setOutputProperty(OutputKeys.INDENT, "no");
        transformer.transform(new DOMSource(input), xmlOutput);
    } catch (TransformerException e) {
        throw new IllegalArgumentException();
    }
    return xmlOutput.getWriter().toString();
}

Answer 1

I had a similar case once. I tried transformer.setOutputProperty(OutputKeys.INDENT,"no"); first, but this did not work. The problem was that my original node had additional "new line" text nodes.

The answer to Strip whitespace and newlines from XML in Java fixed it for me. Basically, you just remove the unnecessary text nodes before you transform the parent node.

I ended up using this:

public static void trimWhitespace(Node node)
{
    NodeList children = node.getChildNodes();
    for(int i = 0; i < children.getLength(); ++i) {
        Node child = children.item(i);
        if(child.getNodeType() == Node.TEXT_NODE) {
            child.setTextContent(child.getTextContent().trim());
        }
        trimWhitespace(child);
    }
}

Answer 2

You can pass an XSLT stylesheet to your Transformer which has the advantage that you will not have to parse your document twice.

InputStream xsltStream = getClass().getResourceAsStream("trim-whitespace.xslt");
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer(new StreamSource(xsltStream));

trim-whitespace.xslt

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <!-- copy all elements as they are -->
    <xsl:template match="*">
        <xsl:copy>
            <xsl:copy-of select="@*" />
            <xsl:apply-templates />
        </xsl:copy>
    </xsl:template>

    <xsl:template match="*/text()[not(normalize-space())]" />
</xsl:stylesheet>