Java用DOM方法解析xml

最近我们项目在做系统界面颜色配置，用java dom解析xml文件来自动生成css。我上网查了些资料，简单的把java用DOM解析XML文档的方法和实例列在文章里，供自己参考。

1. DOM(Document Object Model)

　　DOM是用与平台和语言无关的方式表示XML文档的官方W3C标准。DOM是以层次结构组织的节点的集合。由于它是基于信息层次的，所以DOM被视为是基于树或基于对象的。你可以把它想象成一颗DOM树，通过节点以及节点之间的关系操作XML文档。不过用DOM操作XML需要加载整个XML文档来构造层次结构，因此消耗资源大。

　　下面这个XML文件是用来生成界面css的

 1 <cssStyleItems>
 2     <cssItem>
 3         <cssClass>
 4             <element>#header</element>
 5         </cssClass>
 6         <inherentCss>
 7             <element>margin-bottom:20px;</element>
 8             <element>min-height: 70px;</element>
 9             <element>padding: 28px 0px 0;</element>
10             <element>box-shadow: 0 5px 10px rgba(0, 0, 0, 0.4);</element>
11             <element>background-image: -moz-linear-gradient(top, rgba(255, 255, 255, 0.1) 0%, rgba(0, 0, 0, 0.1) 40%, rgba(0, 0, 0, 0.2) 98%, #FFFFFF 100%);</element>
12             <element>background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, rgba(255, 255, 255, 0.1)),
13                      color-stop(40%, rgba(0, 0, 0, 0.1)), color-stop(98%, rgba(0, 0, 0, 0.2)),color-stop(100%, #FFFFFF));</element>
14             <element>background-image: -webkit-linear-gradient(top, rgba(255, 255, 255, 0.1) 0%, rgba(0, 0, 0, 0.1) 40%, rgba(0, 0, 0, 0.2) 98%, #FFFFFF 100%);</element>
15             <element>background-image: -o-linear-gradient(top, rgba(255, 255, 255, 0.1) 0%, rgba(0, 0, 0, 0.1) 40%, rgba(0, 0, 0, 0.2) 98%, #FFFFFF 100%);</element>   
16             <element>filter: progid:DXImageTransform.Microsoft.Gradient(GradientType=0, StartColorStr='#22FFFFFF', EndColorStr='#33000000');</element>
17             <element>background-image: linear-gradient(to bottom, rgba(255, 255, 255, 0.1) 0%, rgba(0, 0, 0, 0.1) 40%, rgba(0, 0, 0, 0.2) 98%, #FFFFFF 100%);</element>
18         </inherentCss>
19         <configCss>
20             <element cssClass_id="headerBackgroundColor">background-color:</element>
21         </configCss>
22     </cssItem>
23 <cssStyleItems>

　　Java调用DOM解析XML

  1 package com.utils;
  2 
  3 import java.io.BufferedWriter;
  4 import java.io.File;
  5 import java.io.FileInputStream;
  6 import java.io.FileNotFoundException;
  7 import java.io.FileWriter;
  8 import java.io.IOException;
  9 import java.io.InputStream;
 10 import java.util.Map;
 11 
 12 import javax.xml.parsers.DocumentBuilder;
 13 import javax.xml.parsers.DocumentBuilderFactory;
 14 import javax.xml.parsers.ParserConfigurationException;
 15 import com.bean.CssLibBean;
 16 import org.slf4j.Logger;
 17 import org.slf4j.LoggerFactory;
 18 import org.w3c.dom.Document;
 19 import org.w3c.dom.NamedNodeMap;
 20 import org.w3c.dom.Node;
 21 import org.w3c.dom.NodeList;
 22 import org.xml.sax.SAXException;
 23 
 24 
 25 public class CssStyleBuilderAdv {
 26     private static final String IMPORTANT = "important"; //读取xml里important属性
 27     private static final String CSS_CLASS_ID = "cssClass_id"; //读取xml里cssClass_id属性
 28     private static final String CONFIG_CSS = "configCss"; //读取xml里configCss节点
 29     private static final String INHERENT_CSS = "inherentCss"; //读取xml里inherentCss节点
 30     private static final String CSS_CLASS = "cssClass"; //读取xml里cssClass节点
 31     private static final String WRAPPER = "    "; //设置空格
 32 
 33     private Map<String, String> cssElementMap;
 34 
 35     public CssStyleBuilderAdv(Map<String, String> cssElementMap) {
 36         this.cssElementMap = cssElementMap;
 37     }
 38 
 39 
 40     /**
 41      * 在现在的主题上解析xml生成css_build.css
 42      *
 43      * @return
 44      */
 45     //    
 46     public void buildCssFile(String currentTheme) throws FileNotFoundException {
 47         writeCssFile(readXMLFile(currentTheme), currentTheme);
 48     }
 49 
 50 
 51     /**
 52      * 读取CSS template.xml
 53      *
 54      * @return Css build
 55      */
 56     public String readXMLFile(String currentTheme) {
 57         String rebuiltCss = "";
 58         DocumentBuilderFactory domfac = DocumentBuilderFactory.newInstance();
 59         try {
 60             DocumentBuilder domBuilder = domfac.newDocumentBuilder();
 61             String cssTemplateUrl = SystemParameters.getConfigPath() + "/" + currentTheme + "/cssTemplate.xml"; //获取指定位置的xml
 62             File file = new File(cssTemplateUrl);
 63             InputStream is = new FileInputStream(file);
 64             Document doc = domBuilder.parse(is);
 65             NodeList cssItemList = doc.getElementsByTagName("cssItem"); //获取cssItem节点
 66             if (cssItemList != null) {
 67                 for (int i = 0; i < cssItemList.getLength(); i++) {  //遍历cssItem节点列表
 68                     StringBuffer cssClassList = new StringBuffer();  //定义cssItem的孩子节点cssClass列表
 69                     StringBuffer inherentCssList = new StringBuffer(); //定义cssItem的孩子节点inherentCss列表
 70                     StringBuffer configCssList = new StringBuffer();  //定义cssItem的孩子节点configCss列表
 71                     Node cssItem = cssItemList.item(i);  
 72                     NodeList childNodes = cssItem.getChildNodes();  //获取cssItem的孩子列表
 73                     for (int j = 0; j < childNodes.getLength(); j++) {  //遍历列表
 74                         StringBuffer cssClassItem = new StringBuffer();
 75                         StringBuffer inherentCss = new StringBuffer();
 76                         StringBuffer configCss = new StringBuffer();
 77                         Node cssNode = childNodes.item(j);
 78                         if (cssNode.getNodeType() == Node.ELEMENT_NODE) {
 79                             NodeList elementNodes = cssNode.getChildNodes(); //如果节点等于Node.ELEMENT_NODE,获取该节点的孩子列表
 80                             for (int z = 0; z < elementNodes.getLength(); z++) { //遍历列表
 81                                 Node elementNode = elementNodes.item(z);
 82                                 if (elementNode.getNodeType() == Node.ELEMENT_NODE) {
 83                                     if (cssNode.getNodeName().equals(CSS_CLASS)) {  
 84                                         cssClassItem.append(elementNode.getTextContent()); //将节点CSS_CLASS内容存到cssClassItem变量
 85                                         cssClassItem.append(",
");
 86                                     }
 87                                     if (cssNode.getNodeName().equals(INHERENT_CSS)) {
 88                                         inherentCss.append(WRAPPER);
 89                                         inherentCss.append(elementNode.getTextContent()); //将节点INHERENT_CSS内容存到inherentCss变量
 90                                         inherentCss.append("
");
 91                                     }
 92                                     if (cssNode.getNodeName().equals(CONFIG_CSS)) {
 93                                         configCss = configCss.append(switchValueByAttrId(elementNode, configCss)); //将节点CONFIG_CSS内容存到configCss变量
 94                                     }
 95                                 }
 96                             }
 97                             cssClassList.append(cssClassItem);
 98                             inherentCssList.append(inherentCss);
 99                             configCssList.append(configCss);
100                         }
101                     }
102                     rebuiltCss += cssClassList.toString().substring(0, cssClassList.length() - 2) + "{
"
103                             + inherentCssList + configCssList + "}

"; //rebuiltCss存放生成的css
104                 }
105             }
106         } catch (ParserConfigurationException e) {
107             LOGGER.warn("ParserConfigurationException : ", e);
108         } catch (FileNotFoundException e) {
109             LOGGER.warn("FileNotFoundException : ", e);
110         } catch (SAXException e) {
111             LOGGER.warn("SAXException : ", e);
112         } catch (IOException e) {
113             LOGGER.warn("IOException : ", e);
114         }
115         return rebuiltCss;  //返回生成的css样式
116     }
117 
118     /**
119      * 将xml解析出的css写入css_build.css
120      *
121      * @param generatedCss
122      */
123     public void writeCssFile(String generatedCss, String currentTheme) {
124         String packageName = currentTheme.substring(0, 1).toLowerCase() + currentTheme.substring(1);
125         String url = SystemParameters.getCssPath() + "/" + packageName + "/CSS_Build.css";
126         try {
127             File f = new File(url);
128             if (f.exists()) {
129                 BufferedWriter output = new BufferedWriter(new FileWriter(f));
130                 f.setWritable(true);
131                 output.write(generatedCss); 
132                 output.close();
133             } else {
134                 if (f.createNewFile()) {
135                     f.setWritable(true);
136                     BufferedWriter output = new BufferedWriter(new FileWriter(f));
137                     output.write(generatedCss);
138                     output.close();
139                 } else {
140                     LOGGER.info("Create Failed");
141                 }
142             }
143         } catch (Exception e) {
144             LOGGER.warn("Exception : ", e);
145         }
146     }
147 
148     /**
149      * 通过获取不同主题的配色方案生成动态css
150      *
151      * @param elementNode
152      * @param configCss
153      * @return
154      */
155     private StringBuffer switchValueByAttrId(Node elementNode, StringBuffer configCss) {
156         NamedNodeMap elementAttMap = elementNode.getAttributes();
157         String attributeValue = elementAttMap.getNamedItem(CSS_CLASS_ID).getTextContent(); //获取CSS_CLASS_ID属性的值
158         String importantValue = "";
159         String nodeTextContext = WRAPPER + elementNode.getTextContent() + " ";
160         if (elementAttMap.getNamedItem(IMPORTANT) != null) {
161             importantValue = "!important"; //获取important值
162         }
163         configCss.append(nodeTextContext + cssElementMap.get(attributeValue));  //cssElementMap函数调用attributeValue获取不同主题的颜色
164         configCss.append(importantValue);
165         configCss.append(";
");
166         return configCss; //返回获取主题颜色后的configCss
167     }
168 }