如何在java中unescape XML

Question

我需要unescape包含转义的XML标记的xml字符串:

<
>
&
etc...

我确实找到了一些可以执行此任务的库,但我宁愿使用一种可以执行此任务的方法.

有人可以帮忙吗？

干杯,Bas Hendriks

Answer 1

StringEscapeUtils.unescapeXml(xml)

(commons-lang,下载)

Answer 2

这是一种简单的unescape XML方法.它处理预定义的XML实体和十进制数字实体(&#nnnn;).修改它以处理十六进制实体(&#xhhhh;)应该很简单.

public static String unescapeXML( final String xml )
{
    Pattern xmlEntityRegex = Pattern.compile( "&(#?)([^;]+);" );
    //Unfortunately, Matcher requires a StringBuffer instead of a StringBuilder
    StringBuffer unescapedOutput = new StringBuffer( xml.length() );

    Matcher m = xmlEntityRegex.matcher( xml );
    Map<String,String> builtinEntities = null;
    String entity;
    String hashmark;
    String ent;
    int code;
    while ( m.find() ) {
        ent = m.group(2);
        hashmark = m.group(1);
        if ( (hashmark != null) && (hashmark.length() > 0) ) {
            code = Integer.parseInt( ent );
            entity = Character.toString( (char) code );
        } else {
            //must be a non-numerical entity
            if ( builtinEntities == null ) {
                builtinEntities = buildBuiltinXMLEntityMap();
            }
            entity = builtinEntities.get( ent );
            if ( entity == null ) {
                //not a known entity - ignore it
                entity = "&" + ent + ';';
            }
        }
        m.appendReplacement( unescapedOutput, entity );
    }
    m.appendTail( unescapedOutput );

    return unescapedOutput.toString();
}

private static Map<String,String> buildBuiltinXMLEntityMap()
{
    Map<String,String> entities = new HashMap<String,String>(10);
    entities.put( "lt", "<" );
    entities.put( "gt", ">" );
    entities.put( "amp", "&" );
    entities.put( "apos", "'" );
    entities.put( "quot", "\"" );
    return entities;
}

Answer 3

这是我在十分钟内写的一篇文章。它不使用正则表达式，仅使用简单的迭代。我不认为这可以增强得更快。

public static String unescape(final String text) {
    StringBuilder result = new StringBuilder(text.length());
    int i = 0;
    int n = text.length();
    while (i < n) {
        char charAt = text.charAt(i);
        if (charAt != '&') {
            result.append(charAt);
            i++;
        } else {
            if (text.startsWith("&amp;", i)) {
                result.append('&');
                i += 5;
            } else if (text.startsWith("&apos;", i)) {
                result.append('\'');
                i += 6;
            } else if (text.startsWith("&quot;", i)) {
                result.append('"');
                i += 6;
            } else if (text.startsWith("&lt;", i)) {
                result.append('<');
                i += 4;
            } else if (text.startsWith("&gt;", i)) {
                result.append('>');
                i += 4;
            } else i++;
        }
    }
    return result.toString();
}