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java - 如何从Java中结构类似于XML的文件中获取特定元素

问题描述

我有一个 .sic 文件，其结构类似于 XML，但不完全。有一个部分Channel2我想阅读一些元素。部分是这样的：

.
.
.
<SI name = "Channel2" type = "list">
           <SI name = "SecsPortConfig" type = "list">
              <SI name = "PortType" type = "string">'XXX'</SI>
              <SI name = "Protocol" type = "string">'XXX'</SI>
              <SI name = "Serial" type = "list">
                 <SI name = "Port" type = "int">'XXX'</SI>
                 <SI name = "Speed" type = "int">'XXXX'</SI>
              </SI>
              <SI name = "Socket" type = "list">
                 <SI name = "ConnectionMode" type = "string">'XXX'</SI>
                 <SI name = "LocalHost" type = "string">'XXX.XXX.XXX.XXX'</SI>
                 <SI name = "LocalPort" type = "int">'XXX'</SI>
                 <SI name = "RemoteHost" type = "string">'XXX.XXX.XXX'</SI>
                 <SI name = "RemotePort" type = "int">'XXX'</SI>
              </SI>
              <SI name = "HSMS" type = "list">
                 <SI name = "T5" type = "int">'XXX'</SI>
                 <SI name = "T6" type = "int">'XXX'</SI>
                 <SI name = "T7" type = "int">'XXX'</SI>
                 <SI name = "T8" type = "int">'XXX'</SI>
                 <SI name = "LinkTestTime" type = "int">'XXX'</SI>
              </SI>
              <SI name = "SECSI" type = "list">
                 <SI name = "T1" type = "int">'XXX'</SI>
                 <SI name = "T2" type = "int">'XXX'</SI>
                 <SI name = "T4" type = "int">'XXX'</SI>
                 <SI name = "RTY" type = "int">'XXX'</SI>
                 <SI name = "IsHost" type = "bool">'XXX'</SI>
                 <SI name = "IsMaster" type = "bool">'XXX'</SI>
                 <SI name = "InterleaveBlocks" type = "bool">'XXX'</SI>
              </SI>
              <SI name = "SECSII" type = "list">
                 <SI name = "DeviceID" type = "int">'XXX'</SI>
                 <SI name = "T3" type = "int">'XXX'</SI>
                 <SI name = "MultipleOpen" type = "bool">'XXX'</SI>
                 <SI name = "AutoDeviceID" type = "bool">'XXX'</SI>
              </SI>
              <SI name = "Log" type = "list">
                 <SI name = "LogCharError" type = "bool">'XXX'</SI>
                 <SI name = "LogCharEvent" type = "bool">'XXX'</SI>
                 <SI name = "LogCharReceive" type = "bool">'XXX'</SI>
                 <SI name = "LogCharSend" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIHsmsError" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIHsmsEvent" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIHsmsReceive" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIHsmsSend" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIIError" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIIEvent" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIIReceive" type = "bool">'XXX'</SI>
                 <SI name = "LogSecsIISend" type = "bool">'XXX'</SI>
              </SI>
           </SI>
           <SI name = "UseSeparateSECSLogFile" type = "bool">'XXX'</SI>
           <SI name = "Connected" type = "bool">'XXX'</SI>
           <SI name = "MessageFilters" type = "list">
              <SI name = "DeviceIDList" type = "list"/>
              <SI name = "StreamFunctionList" type = "list"/>
           </SI>
           <SI name = "SafeMessageFilters" type = "list">
              <SI name = "DeviceIDList" type = "list"/>
              <SI name = "StreamFunctionList" type = "list"/>
           </SI>
        </SI>
        .
        .
        .

如果它是一个 xml 文件，我可以解析它并读出元素，但是我该如何处理这种文件呢？我想提取元素RemoteHost和RemotePort. 我现在使用 BufferedReader 进行了尝试，并Channel2通过在字符串中插入此部分来从文件中获取部分，但是如何提取我想要的元素的特定值？我可能可以使用子字符串和其他一些字符串方法来做到这一点，但没有更简单的方法吗？到目前为止，这是我的代码：

    File file = new File("C:\\Users\\but\\Desktop\\ExternalswPassThroughSrv.sic");

    int counter = 0;

    BufferedReader br = new BufferedReader(new FileReader(file));

    String cl;
    String finalString = "";
    while ((cl = br.readLine()) != null) {
        if (cl.contains("Channel2")) {
            counter = 63;
        }
        if(counter != 0){
            //System.out.println(cl);
            finalString += cl + "\n";
            counter--;
        }
    }
    System.out.println(finalString);

标签： javaxmlfilesubstring

解决方案

由于我们不知道整个文件是如何形成的：
即使它不是一个完整的 XML 文档，您也可以从文件的其余部分中提取 XML-Fragment 并通过添加根将其转换为格式良好的 XML-Document元素。

之后，您可以将其解析为 Document 并使用 XPath 提取所需信息。

这是一些可以为您工作的示例 Java 代码（为了清楚起见，我没有包含 xml）

import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import java.io.IOException;
import java.io.StringReader;

public class ConvertXml {
    public static void main(String[] args) throws ParserConfigurationException, IOException, SAXException, TransformerException, XPathExpressionException {
        // Your XML-like content
        String xmlString = "xml here";

        // transform xml-Fragment into well-formed xml with root element
        String xmlStringWellformed = "<content>" + xmlString + "</content>";

        // parse well-formed xml
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document document = builder.parse(new InputSource(new StringReader(xmlStringWellformed)));

        // build xpath expression
        String xPathRemoteHost = "//SI[@name='Channel2']/SI[@name='SecsPortConfig']/SI[@name='Socket']/SI[@name='RemoteHost']/text()";
        String xPathRemotePort = "//SI[@name='Channel2']/SI[@name='SecsPortConfig']/SI[@name='Socket']/SI[@name='RemotePort']/text()";
        XPath xPath = XPathFactory.newInstance().newXPath();

        // Use XPath for extraction
        String remoteHost = (String) xPath.compile(xPathRemoteHost).evaluate(document, XPathConstants.STRING);
        String remotePort = (String) xPath.compile(xPathRemotePort).evaluate(document, XPathConstants.STRING);

        System.out.println("RemoteHost: " + remoteHost);
        System.out.println("RemotePort: " + remotePort);
    }
}

资料来源： Baeldung - 使用 Java 介绍 XPath

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