在java中使用dom4j解析xml-白红宇

在java中使用dom4j解析xml

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发布时间：2019-05-07

本文共 4429 字，大约阅读时间需要 14 分钟。

虽然Java中已经有了Dom和Sax这两种标准解析方式

但其操作起来并不轻松，对于我这么一个初学者来说，其中部分代码是活生生的恶心

为此，伟大的第三方开发组开发出了Jdom和Dom4j等工具

鉴于目前的趋势，我们这里来讲讲Dom4j的基本用法，不涉及递归等复杂操作

往maven中添加的dom4j依赖如下：

</dependency>

Dom4j的用法很多，官网上的示例有那么点儿晦涩，这里就不写了

首先我们需要出创建一个xml文档，然后才能对其解析

xml文档：

                
<?
xml
version="1.0" encoding="UTF-8"?> 
<
books
>
   
<
book
id="001">
      
<
title
>Harry Potter</
title
>
      
<
author
>J K. Rowling</
author
>
   
</
book
>
   
<
book
id="002">
      
<
title
>Learning XML</
title
>
      
<
author
>Erik T. Ray</
author
>
   
</
book
>
</
books
>
        
      

示例一：用List列表的方式来解析xml

                         
import
java.io.File;
import
java.util.List;
import
org.dom4j.Attribute;
import
org.dom4j.Document;
import
org.dom4j.Element;
import
org.dom4j.io.SAXReader;
public
class
Demo { 
    
public
static
void
main(String[] args) 
throws
Exception { 
        
SAXReader reader = 
new
SAXReader();
        
File file = 
new
File(
"books.xml"
);
        
Document document = reader.read(file);
        
Element root = document.getRootElement();
        
List<Element> childElements = root.elements();
        
for
(Element child : childElements) { 
            
//未知属性名情况下
            
/*List<Attribute> attributeList = child.attributes();
            
for (Attribute attr : attributeList) { 
                
System.out.println(attr.getName() + ": " + attr.getValue());
            
}*/
            
            
//已知属性名情况下
            
System.out.println(
"id: "
+ child.attributeValue(
"id"
));
            
            
//未知子元素名情况下
            
/*List<Element> elementList = child.elements();
            
for (Element ele : elementList) { 
                
System.out.println(ele.getName() + ": " + ele.getText());
            
}
            
System.out.println();*/
            
            
//已知子元素名的情况下
            
System.out.println(
"title"
+ child.elementText(
"title"
));
            
System.out.println(
"author"
+ child.elementText(
"author"
));
            
//这行是为了格式化美观而存在
            
System.out.println();
        
}
    
}
}
        
      

示例二：使用Iterator迭代器的方式来解析xml

                         
import
java.io.File;
import
java.util.Iterator;
import
org.dom4j.Attribute;
import
org.dom4j.Document;
import
org.dom4j.Element;
import
org.dom4j.io.SAXReader;
public
class
Demo { 
    
public
static
void
main(String[] args) 
throws
Exception { 
        
SAXReader reader = 
new
SAXReader();
        
Document document = reader.read(
new
File(
"books.xml"
));
        
Element root = document.getRootElement();
        
        
Iterator it = root.elementIterator();
        
while
(it.hasNext()) { 
            
Element element = (Element) it.next();
            
            
//未知属性名称情况下
            
/*Iterator attrIt = element.attributeIterator();
            
while (attrIt.hasNext()) { 
                
Attribute a  = (Attribute) attrIt.next();
                
System.out.println(a.getValue());
            
}*/
            
            
//已知属性名称情况下
            
System.out.println(
"id: "
+ element.attributeValue(
"id"
));
            
            
//未知元素名情况下
            
/*Iterator eleIt = element.elementIterator();
            
while (eleIt.hasNext()) { 
                
Element e = (Element) eleIt.next();
                
System.out.println(e.getName() + ": " + e.getText());
            
}
            
System.out.println();*/
            
            
//已知元素名情况下
            
System.out.println(
"title: "
+ element.elementText(
"title"
));
            
System.out.println(
"author: "
+ element.elementText(
"author"
));
            
System.out.println();
        
}
    
}
}
        
      

运行结果：

示例三：创建xml文档并输出到文件

                         
import
java.io.File;
import
java.io.FileOutputStream;
import
org.dom4j.Document;
import
org.dom4j.DocumentHelper;
import
org.dom4j.Element;
import
org.dom4j.io.OutputFormat;
import
org.dom4j.io.XMLWriter;
public
class
Demo { 
    
public
static
void
main(String[] args) 
throws
Exception { 
        
Document doc = DocumentHelper.createDocument();
        
//增加根节点
        
Element books = doc.addElement(
"books"
);
        
//增加子元素
        
Element book1 = books.addElement(
"book"
);
        
Element title1 = book1.addElement(
"title"
);
        
Element author1 = book1.addElement(
"author"
);
        
        
Element book2 = books.addElement(
"book"
);
        
Element title2 = book2.addElement(
"title"
);
        
Element author2 = book2.addElement(
"author"
);
        
        
//为子节点添加属性
        
book1.addAttribute(
"id"
, 
"001"
);
        
//为元素添加内容
        
title1.setText(
"Harry Potter"
);
        
author1.setText(
"J K. Rowling"
);
        
        
book2.addAttribute(
"id"
, 
"002"
);
        
title2.setText(
"Learning XML"
);
        
author2.setText(
"Erik T. Ray"
);
        
        
//实例化输出格式对象
        
OutputFormat format = OutputFormat.createPrettyPrint();
        
//设置输出编码
        
format.setEncoding(
"UTF-8"
);
        
//创建需要写入的File对象
        
File file = 
new
File(
"D:"
+ File.separator + 
"books.xml"
);
        
//生成XMLWriter对象，构造函数中的参数为需要输出的文件流和格式
        
XMLWriter writer = 
new
XMLWriter(
new
FileOutputStream(file), format);
        
//开始写入，write方法中包含上面创建的Document对象
        
writer.write(doc);
    
}
}
        
      