写了一个Java读取XML文件的工具类

2022-07-15 80酷酷网 80kuku.com

　　xml如果我们有下面的一个XML文件，可以把它想象成一个Relation Database中的Table，这个XML文件就是一个名字为managers的关系表，而一个<manager>所包含的就是一条记录(Record)，而manager中的service和implementation就是一个个的栏位(Field) ！

managers table
+	service	implementation
	net.csdn.blog.xport.IDBConnectionManager	net.csdn.blog.xport.impl.DBConnectionManagerCommonImpl
	net.csdn.blog.xport.IDomainIdentify	net.csdn.blog.xport.impl.DomainIdentifyImpl

所以，在程序中，可以用类似Table Query的方式来读取XML节点(Node)上面的属性值！

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE managers SYSTEM "manager-config.dtd">
<managers>
  <manager name="DBConnectionManager" >
    <service>net.csdn.blog.xport.IDBConnectionManager</service>
    <implementation>net.csdn.blog.xport.impl.DBConnectionManagerCommonImpl</implementation>
  </manager>
  <manager name="NTAccountIdendify" >
        <service>net.csdn.blog.xport.IDomainIdentify</service>
        <implementation>net.csdn.blog.xport.impl.DomainIdentifyImpl</implementation>
  </manager>
</managers>

按照下面的代码读取：

// 查找以manager作为tag标记，属性中存在name且属性值为"DBConnectionManager"的
// XML节点, 并返回此节点的DOM Element对象！
// 类似name字段为PK值，且name="DBConnectionManager"
managerElement
        = XMLFileUtil.findElement(xmlDomContent.getRootElement(),
                                  "manager",
                                  "name",
                                  "DBConnectionManager");
if (managerElement != null) {
  //取得Element中的implementation属性对象...
  serviceImplElement = managerElement.element("implementation");
  if (serviceImplElement != null) {
    //取这个属性的值...
    serviceImplClassString = serviceImplElement.getText();
  }
}

Source of XML Utility Class：

/*

 * (#)XMLFileUtil.java    1.0 2004/12/20
 *
 * Copyright 2004 Shark Wang, All rights reserved.
 
 */
 
package net.csdn.blog.xport;

import java.net.URL;
import java.util.Iterator;

import org.apache.log4j.LogManager;
import org.apache.log4j.Logger;
import org.dom4j.Attribute;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

/**
 * The <code>XmlUtil</code> class supported your code to read/write xml
 * data from the file. all methods in this class depend on <code>dom4j</code>.
 *
 * author  Shark Wang
 * version 1.0, 2004/12/20
 * since   Tutorial 1.0
 */
public class XMLFileUtil {

  private static Logger logger = LogManager.getLogger(XMLFileUtil.class);

  /**
   * read xml content from some file, and load xml data into the
   * Document object.
   *
   * param filePath String
   * return Document
   */
  public static Document LoadXmlFile(String filePath) {

    /* marked by Shark Wang
     *****************************************************************
       //get resolver to ignore the DTD validation
       EntityResolver resolver = new EntityResolver() {
           public InputSource resolveEntity(String publicId,
                                            String systemId) {
               return new InputSource(new StringBufferInputStream(""));
           }
       };
       //create reader
       SAXReader reader = new SAXReader();
       //set reader attribute to ignore DTD validation
       reader.setEntityResolver(resolver);
       reader.setValidation(false);
       reader.setIncludeExternalDTDDeclarations(false);
       reader.setIncludeInternalDTDDeclarations(false);
     *******************************************************************
     */
    SAXReader reader = new SAXReader();
    //try to load xml data into Document object
    Document doc = null;
    try {
      String urlString = null;
      if (filePath.startsWith("/")) {
        urlString = "file://" + filePath;
      }
      else {
        urlString = "file:///" + filePath;
      }
      logger.debug("XML File's URL :" + urlString);
      doc = reader.read(new URL(urlString));
    }
    catch (Exception ex) {
      logger.info("Can not load " + filePath);
      logger.debug(ex.getMessage(), ex);
    }
    //return Document object
    return doc;
  }

  /**
   * Get attribute value by name for some xml element.
   *
   * param element Element
   * param attributeName String
   * return String
   */
  public static String getAttributeValue(Element element,
                                         String attributeName) {
    String attributeValue = null;
    for (Iterator i = element.attributeIterator(); i.hasNext(); ) {
      Attribute attribute = (Attribute) i.next();
      if (attribute.getName().equals(attributeName)) {
        attributeValue = (String) attribute.getData();
        break;
      }
    }
    return attributeValue;
  }

  public static Element findElement(Element searchedElement,
                                    String targetNodePrefix,
                                    String targetNodeAttributeName,
                                    String targetNodeAttributeValue) {
    Element elementTarget = null;
    for (Iterator i = searchedElement.elementIterator(targetNodePrefix);
         i.hasNext(); ) {
      Element element = (Element) i.next();
      String strManagerName =
          XMLFileUtil.getAttributeValue(element,
                                        targetNodeAttributeName);
      if (strManagerName.equals(targetNodeAttributeValue)) {
        elementTarget = element;
        break;
      }
    }
    return elementTarget;
  }

  private XMLFileUtil() {
  }
}