如何解析 XML header 中的属性 Java？

Question

我正在尝试解析 XML 文档。

我已经成功解析了带有 id 标签的属性，但我还想解析 header 属性；

<?xml version="1.0" encoding="UTF-8"?>
<XMLExample
    xmlns="http://www.example.com"
appID="YYYYY" txnID="XXXX" userID="system" ver="v2.6" lk="LLLL"
ts="Wed Apr 09 11:33:40 IST 2014" scope="XYXYXY" filter="LALALLA"
idType="id">
    <id>000000</id>
</XMLExample>

我在这里获取“id”的值。

但我正在尝试从 XML header.

中获取“appId”、“txnID”、“userID”

提前致谢

Answer 1

如果您想使用 DOM 解析器从 XML 字符串中的 XMLExample 节点（id 是一个元素）获取全部或部分属性，那么您可以这样做这样：

仅示例演示：

String xmlString = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
        + "<XMLExample\n"
        + "    xmlns=\"http://www.example.com\"\n"
        + "appID=\"YYYYY\" txnID=\"XXXX\" userID=\"system\" ver=\"v2.6\" lk=\"LLLL\"\n"
        + "ts=\"Wed Apr 09 11:33:40 IST 2014\" scope=\"XYXYXY\" filter=\"LALALLA\"\n"
        + "idType=\"id\">\n"
        + "    <id>000000</id>\n"
        + "</XMLExample>";

String xPathExpression = "//XMLExample";

org.w3c.dom.Document documento = null;
javax.xml.xpath.XPath xpath = null;
org.w3c.dom.NodeList nodos = null;

try {
    // Carga del documento xml
    javax.xml.parsers.DocumentBuilderFactory factory = 
                      javax.xml.parsers.DocumentBuilderFactory.newInstance();
    javax.xml.parsers.DocumentBuilder builder = factory.newDocumentBuilder();
    InputStream inputStream = new ByteArrayInputStream(xmlString.getBytes());
    documento = builder.parse(inputStream);
        
    // If from file instead of XML String...
    //documento = builder.parse(new File("./src/hmmmm_Testing/Some_XML_File.xml"));
}
catch (Exception e) {
    System.out.println(e.getMessage());
}

try {
    // Preparación de xpath
    xpath = javax.xml.xpath.XPathFactory.newInstance().newXPath();

    // Consultas
    nodos = (org.w3c.dom.NodeList) xpath.evaluate(xPathExpression, documento, javax.xml.xpath.XPathConstants.NODESET);
}
catch (Exception e) {
    System.out.println(e.getMessage());
}

for (int i = 0; i < nodos.getLength(); i++) {
    System.out.println("************* Using DOM **************");
    // You can of course apply the following to variables if you like.
    System.out.println("xmlnx:  ->  " + nodos.item(i).getAttributes().getNamedItem("xmlns").getNodeValue());
    System.out.println("appID:  ->  " + nodos.item(i).getAttributes().getNamedItem("appID").getNodeValue());
    System.out.println("txnID:  ->  " + nodos.item(i).getAttributes().getNamedItem("txnID").getNodeValue());
    System.out.println("userID: ->  " + nodos.item(i).getAttributes().getNamedItem("userID").getNodeValue());
    System.out.println("ver:    ->  " + nodos.item(i).getAttributes().getNamedItem("ver").getNodeValue());
    System.out.println("lk:     ->  " + nodos.item(i).getAttributes().getNamedItem("lk").getNodeValue());
    System.out.println("ts:     ->  " + nodos.item(i).getAttributes().getNamedItem("ts").getNodeValue());
    System.out.println("scope:  ->  " + nodos.item(i).getAttributes().getNamedItem("scope").getNodeValue());
    System.out.println("filter: ->  " + nodos.item(i).getAttributes().getNamedItem("filter").getNodeValue());
    System.out.println("idType: ->  " + nodos.item(i).getAttributes().getNamedItem("idType").getNodeValue());
    System.out.println("**************************************");
}

这会将以下内容打印到控制台 Window:

************* Using DOM **************
xmlnx:  ->  http://www.example.com
appID:  ->  YYYYY
txnID:  ->  XXXX
userID: ->  system
ver:    ->  v2.6
lk:     ->  LLLL
ts:     ->  Wed Apr 09 11:33:40 IST 2014
scope:  ->  XYXYXY
filter: ->  LALALLA
idType: ->  id
**************************************

或者对于像这样的小 XML 字符串，您可以使用 getBetween() 方法，例如：

String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
        + "<XMLExample\n"
        + "    xmlns=\"http://www.example.com\"\n"
        + "appID=\"YYYYY\" txnID=\"XXXX\" userID=\"system\" ver=\"v2.6\" lk=\"LLLL\"\n"
        + "ts=\"Wed Apr 09 11:33:40 IST 2014\" scope=\"XYXYXY\" filter=\"LALALLA\"\n"
        + "idType=\"id\">\n"
        + "    <id>000000</id>\n"
        + "</XMLExample>";

// Remove indenting.
xml = xml.replaceAll("\s+", " ");

// Get all values from all attributes and the id element...
System.out.println("************* Using getBetween() **************");
// You can of course apply the following to variables if you like.
System.out.println("xmlns:  ->  " + getBetween(xml, "xmlns=\"", "\"")[0]);
System.out.println("appID:  ->  " + getBetween(xml, "appID=\"", "\"")[0]);
System.out.println("txnID:  ->  " + getBetween(xml, "txnID=\"", "\"")[0]);
System.out.println("userID: ->  " + getBetween(xml, "userID=\"", "\"")[0]);
System.out.println("ver:    ->  " + getBetween(xml, "ver=\"", "\"")[0]);
System.out.println("lk:     ->  " + getBetween(xml, "lk=\"", "\"")[0]);
System.out.println("ts:     ->  " + getBetween(xml, "ts=\"", "\"")[0]);
System.out.println("scope:  ->  " + getBetween(xml, "scope=\"", "\"")[0]);
System.out.println("filter: ->  " + getBetween(xml, "filter=\"", "\"")[0]);
System.out.println("idType: ->  " + getBetween(xml, "idType=\"", "\"")[0]);
System.out.println("The ID: ->  " + getBetween(xml, "<id>", "</id>")[0]);
System.out.println("**************************************");
System.out.println();

这会将以下内容打印到控制台 Window:

************* Using getBetween() **************
xmlns:  ->  http://www.example.com
appID:  ->  YYYYY
txnID:  ->  XXXX
userID: ->  system
ver:    ->  v2.6
lk:     ->  LLLL
ts:     ->  Wed Apr 09 11:33:40 IST 2014
scope:  ->  XYXYXY
filter: ->  LALALLA
idType: ->  id
The ID: ->  000000
**************************************

getBetween()方法：

/**
 * Retrieves any string data located between the supplied string leftString
 * parameter and the supplied string rightString parameter.<br><br>
 * <p>
 * This method will return all instances of a substring located between the
 * supplied Left String and the supplied Right String which may be found
 * within the supplied Input String.<br>
 *
 * @param inputString (String) The string to look for substring(s) in.<br>
 *
 * @param leftString  (String) What may be to the Left side of the substring
 *                    we want within the main input string. Sometimes the
 *                    substring you want may be contained at the very
 *                    beginning of a string and therefore there is no
 *                    Left-String available. In this case you would simply
 *                    pass a Null String ("") to this parameter which
 *                    basically informs the method of this fact. Null can
 *                    not be supplied and will ultimately generate a
 *                    NullPointerException.<br>
 *
 * @param rightString (String) What may be to the Right side of the
 *                    substring we want within the main input string.
 *                    Sometimes the substring you want may be contained at
 *                    the very end of a string and therefore there is no
 *                    Right-String available. In this case you would simply
 *                    pass a Null String ("") to this parameter which
 *                    basically informs the method of this fact. Null can
 *                    not be supplied and will ultimately generate a
 *                    NullPointerException.<br>
 *
 * @param options     (Optional - Boolean - 2 Parameters):<pre>
 *
 *      ignoreLetterCase    - Default is false. This option works against the
 *                            string supplied within the leftString parameter
 *                            and the string supplied within the rightString
 *                            parameter. If set to true then letter case is
 *                            ignored when searching for strings supplied in
 *                            these two parameters. If left at default false
 *                            then letter case is not ignored.
 *
 *      trimFound           - Default is true. By default this method will trim
 *                            off leading and trailing white-spaces from found
 *                            sub-string items. General sentences which obviously
 *                            contain spaces will almost always give you a white-
 *                            space within an extracted sub-string. By setting
 *                            this parameter to false, leading and trailing white-
 *                            spaces are not trimmed off before they are placed
 *                            into the returned Array.</pre>
 *
 * @return (1D String Array) Returns a Single Dimensional String Array
 *         containing all the sub-strings found within the supplied Input
 *         String which are between the supplied Left String and supplied
 *         Right String. You can shorten this method up a little by
 *         returning a List&lt;String&gt; ArrayList and removing the 'List
 *         to 1D Array' conversion code at the end of this method. This
 *         method initially stores its findings within a List Interface
 *         anyways.
 */
public static String[] getBetween(String inputString, String leftString, String rightString, boolean... options) {
    // Return null if nothing was supplied.
    if (inputString.isEmpty() || (leftString.isEmpty() && rightString.isEmpty())) {
        return null;
    }

    // Prepare optional parameters if any supplied.
    // If none supplied then use Defaults...
    boolean ignoreCase = false;      // Default.
    boolean trimFound = true;        // Default.
    if (options.length > 0) {
        if (options.length >= 1) {
            ignoreCase = options[0];
            if (options.length >= 2) {
                trimFound = options[1];
            }
        }
    }

    // Remove any control characters from the
    // supplied string (if they exist).
    String modString = inputString.replaceAll("\p{Cntrl}", "");

    // Establish a List String Array Object to hold
    // our found substrings between the supplied Left
    // String and supplied Right String.
    List<String> list = new ArrayList<>();

    // Use Pattern Matching to locate our possible
    // substrings within the supplied Input String.
    String regEx = Pattern.quote(leftString) + "{1,}"
            + (!rightString.isEmpty() ? "(.*?)" : "(.*)?")
            + Pattern.quote(rightString);
    if (ignoreCase) {
        regEx = "(?i)" + regEx;
    }

    Pattern pattern = Pattern.compile(regEx);
    Matcher matcher = pattern.matcher(modString);
    while (matcher.find()) {
        // Add the found substrings into the List.
        String found = matcher.group(1);
        if (trimFound) {
            found = found.trim();
        }
        list.add(found);
    }
    return list.toArray(new String[list.size()]);
}

当然 getBetween() 方法也可用于从 XML 以外的其他字符串中解析出项目。

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