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详解Java解析XML的四种方法

2019年07月22日  | 移动技术网IT编程  | 我要评论

xml现在已经成为一种通用的数据交换格式,它的平台无关性,语言无关性,系统无关性,给数据集成与交互带来了极大的方便。对于xml本身的语法知识与技术细节,需要阅读相关的技术文献,这里面包括的内容有dom(document object model),dtd(document type definition),sax(simple api for xml),xsd(xml schema definition),xslt(extensible stylesheet language transformations),具体可参阅w3c官方网站文档获取更多信息。

xml在不同的语言里解析方式都是一样的,只不过实现的语法不同而已。基本的解析方式有两种,一种叫sax，另一种叫dom。sax是基于事件流的解析,dom是基于xml文档树结构的解析。假设我们xml的内容和结构如下:

<?xml version="1.0" encoding="utf-8"?>  
<employees>  
<employee>  
<name>ddviplinux</name>  
<sex>m</sex>  
<age>30</age>  
</employee>  
</employees>

本文使用java语言来实现dom与sax的xml文档生成与解析。

首先定义一个操作xml文档的接口xmldocument 它定义了xml文档的建立与解析的接口。

/** 
* 
* @author hongliang.dinghl 
* 定义xml文档建立与解析的接口 
*/  
public interface xmldocument {  
/** 
* 建立xml文档 
* @param filename 文件全路径名称 
*/  
public void createxml(string filename);  
/** 
* 解析xml文档 
* @param filename 文件全路径名称 
*/  
public void parserxml(string filename);  
}

1.dom生成和解析xml文档

为 xml 文档的已解析版本定义了一组接口。解析器读入整个文档，然后构建一个驻留内存的树结构，然后代码就可以使用 dom 接口来操作这个树结构。优点：整个文档树在内存中，便于操作；支持删除、修改、重新排列等多种功能；缺点：将整个文档调入内存（包括无用的节点），浪费时间和空间；使用场合：一旦解析了文档还需多次访问这些数据；硬件资源充足（内存、cpu）。

import java.io.fileinputstream;  
import java.io.filenotfoundexception;  
import java.io.fileoutputstream;  
import java.io.ioexception;  
import java.io.inputstream;  
import java.io.printwriter;  
import javax.xml.parsers.documentbuilder;  
import javax.xml.parsers.documentbuilderfactory;  
import javax.xml.parsers.parserconfigurationexception;  
import javax.xml.transform.outputkeys;  
import javax.xml.transform.transformer;  
import javax.xml.transform.transformerconfigurationexception;  
import javax.xml.transform.transformerexception;  
import javax.xml.transform.transformerfactory;  
import javax.xml.transform.dom.domsource;  
import javax.xml.transform.stream.streamresult;  
import org.w3c.dom.document;  
import org.w3c.dom.element;  
import org.w3c.dom.node;  
import org.w3c.dom.nodelist;  
import org.xml.sax.saxexception;  
/** 
* 
* @author hongliang.dinghl 
* dom生成与解析xml文档 
*/  
public class domdemo implements xmldocument {  
private document document;  
private string filename;  
public void init() {  
try {  
documentbuilderfactory factory = documentbuilderfactory  
.newinstance();  
documentbuilder builder = factory.newdocumentbuilder();  
this.document = builder.newdocument();  
} catch (parserconfigurationexception e) {  
system.out.println(e.getmessage());  
}  
}  
public void createxml(string filename) {  
element root = this.document.createelement("employees");  
this.document.appendchild(root);  
element employee = this.document.createelement("employee");  
element name = this.document.createelement("name");  
name.appendchild(this.document.createtextnode("丁宏亮"));  
employee.appendchild(name);  
element sex = this.document.createelement("sex");  
sex.appendchild(this.document.createtextnode("m"));  
employee.appendchild(sex);  
element age = this.document.createelement("age");  
age.appendchild(this.document.createtextnode("30"));  
employee.appendchild(age);  
root.appendchild(employee);  
transformerfactory tf = transformerfactory.newinstance();  
try {  
transformer transformer = tf.newtransformer();  
domsource source = new domsource(document);  
transformer.setoutputproperty(outputkeys.encoding, "gb2312");  
transformer.setoutputproperty(outputkeys.indent, "yes");  
printwriter pw = new printwriter(new fileoutputstream(filename));  
streamresult result = new streamresult(pw);  
transformer.transform(source, result);  
system.out.println("生成xml文件成功!");  
} catch (transformerconfigurationexception e) {  
system.out.println(e.getmessage());  
} catch (illegalargumentexception e) {  
system.out.println(e.getmessage());  
} catch (filenotfoundexception e) {  
system.out.println(e.getmessage());  
} catch (transformerexception e) {  
system.out.println(e.getmessage());  
}  
}  
public void parserxml(string filename) {  
try {  
documentbuilderfactory dbf = documentbuilderfactory.newinstance();  
documentbuilder db = dbf.newdocumentbuilder();  
document document = db.parse(filename);  
nodelist employees = document.getchildnodes();  
for (int i = 0; i < employees.getlength(); i++) {  
node employee = employees.item(i);  
nodelist employeeinfo = employee.getchildnodes();  
for (int j = 0; j < employeeinfo.getlength(); j++) {  
node node = employeeinfo.item(j);  
nodelist employeemeta = node.getchildnodes();  
for (int k = 0; k < employeemeta.getlength(); k++) {  
system.out.println(employeemeta.item(k).getnodename()  
+ ":" + employeemeta.item(k).gettextcontent());  
}  
}  
}  
system.out.println("解析完毕");  
} catch (filenotfoundexception e) {  
system.out.println(e.getmessage());  
} catch (parserconfigurationexception e) {  
system.out.println(e.getmessage());  
} catch (saxexception e) {  
system.out.println(e.getmessage());  
} catch (ioexception e) {  
system.out.println(e.getmessage());  
}  
}  
}

2.sax生成和解析xml文档

为解决dom的问题，出现了sax。sax ，事件驱动。当解析器发现元素开始、元素结束、文本、文档的开始或结束等时，发送事件，程序员编写响应这些事件的代码，保存数据。优点：不用事先调入整个文档，占用资源少；sax解析器代码比dom解析器代码小，适于applet，下载。缺点：不是持久的；事件过后，若没保存数据，那么数据就丢了；无状态性；从事件中只能得到文本，但不知该文本属于哪个元素；使用场合：applet;只需xml文档的少量内容，很少回头访问；机器内存少；

import java.io.fileinputstream;   
import java.io.filenotfoundexception;   
import java.io.ioexception;   
import java.io.inputstream;   
 
import javax.xml.parsers.parserconfigurationexception;   
import javax.xml.parsers.saxparser;   
import javax.xml.parsers.saxparserfactory;   
 
import org.xml.sax.attributes;   
import org.xml.sax.saxexception;   
import org.xml.sax.helpers.defaulthandler;   
/**  
*  
* @author hongliang.dinghl  
* sax文档解析  
*/  
public class saxdemo implements xmldocument {   
 
public void createxml(string filename) {   
system.out.println("<<"+filename+">>");   
}   
 
public void parserxml(string filename) {   
saxparserfactory saxfac = saxparserfactory.newinstance();   
 
try {   
 
saxparser saxparser = saxfac.newsaxparser();   
 
inputstream is = new fileinputstream(filename);   
 
saxparser.parse(is, new mysaxhandler());   
 
} catch (parserconfigurationexception e) {   
 
e.printstacktrace();   
 
} catch (saxexception e) {   
 
e.printstacktrace();   
 
} catch (filenotfoundexception e) {   
 
e.printstacktrace();   
 
} catch (ioexception e) {   
 
e.printstacktrace();   
 
}   
 
}   
 
}   
 
class mysaxhandler extends defaulthandler {   
 
boolean hasattribute = false;   
 
attributes attributes = null;   
 
public void startdocument() throws saxexception {   
 
system.out.println("文档开始打印了");   
 
}   
 
public void enddocument() throws saxexception {   
 
system.out.println("文档打印结束了");   
 
}   
 
public void startelement(string uri, string localname, string qname,   
 
attributes attributes) throws saxexception {   
 
if (qname.equals("employees")) {   
 
return;   
 
}   
 
if (qname.equals("employee")) {   
 
system.out.println(qname);   
 
}   
 
if (attributes.getlength() > 0) {   
 
this.attributes = attributes;   
 
this.hasattribute = true;   
 
}   
 
}   
 
public void endelement(string uri, string localname, string qname)   
 
throws saxexception {   
 
if (hasattribute && (attributes != null)) {   
 
for (int i = 0; i < attributes.getlength(); i++) {   
 
system.out.println(attributes.getqname(0)   
+ attributes.getvalue(0));   
 
}   
 
}   
 
}   
 
public void characters(char[] ch, int start, int length)   
 
throws saxexception {   
 
system.out.println(new string(ch, start, length));   
 
}   
 
}  
package com.alisoft.facepay.framework.bean;  
import java.io.fileinputstream;  
import java.io.filenotfoundexception;  
import java.io.ioexception;  
import java.io.inputstream;  
import javax.xml.parsers.parserconfigurationexception;  
import javax.xml.parsers.saxparser;  
import javax.xml.parsers.saxparserfactory;  
import org.xml.sax.attributes;  
import org.xml.sax.saxexception;  
import org.xml.sax.helpers.defaulthandler;  
/** 
* 
* @author hongliang.dinghl 
* sax文档解析 
*/  
public class saxdemo implements xmldocument {  
public void createxml(string filename) {  
system.out.println("<<"+filename+">>");  
}  
public void parserxml(string filename) {  
saxparserfactory saxfac = saxparserfactory.newinstance();  
try {  
saxparser saxparser = saxfac.newsaxparser();  
inputstream is = new fileinputstream(filename);  
saxparser.parse(is, new mysaxhandler());  
} catch (parserconfigurationexception e) {  
e.printstacktrace();  
} catch (saxexception e) {  
e.printstacktrace();  
} catch (filenotfoundexception e) {  
e.printstacktrace();  
} catch (ioexception e) {  
e.printstacktrace();  
}  
}  
}  
class mysaxhandler extends defaulthandler {  
boolean hasattribute = false;  
attributes attributes = null;  
public void startdocument() throws saxexception {  
system.out.println("文档开始打印了");  
}  
public void enddocument() throws saxexception {  
system.out.println("文档打印结束了");  
}  
public void startelement(string uri, string localname, string qname,  
attributes attributes) throws saxexception {  
if (qname.equals("employees")) {  
return;  
}  
if (qname.equals("employee")) {  
system.out.println(qname);  
}  
if (attributes.getlength() > 0) {  
this.attributes = attributes;  
this.hasattribute = true;  
}  
}  
public void endelement(string uri, string localname, string qname)  
throws saxexception {  
if (hasattribute && (attributes != null)) {  
for (int i = 0; i < attributes.getlength(); i++) {  
system.out.println(attributes.getqname(0)  
+ attributes.getvalue(0));  
}  
}  
}  
public void characters(char[] ch, int start, int length)  
throws saxexception {  
system.out.println(new string(ch, start, length));  
}  
}

3.dom4j生成和解析xml文档

dom4j 是一个非常非常优秀的java xml api，具有性能优异、功能强大和极端易用使用的特点，同时它也是一个开放源代码的软件。如今你可以看到越来越多的 java 软件都在使用 dom4j 来读写 xml，特别值得一提的是连 sun 的 jaxm 也在用 dom4j。

import java.io.file;   
import java.io.filewriter;   
import java.io.ioexception;   
import java.io.writer;   
import java.util.iterator;   
 
import org.dom4j.document;   
import org.dom4j.documentexception;   
import org.dom4j.documenthelper;   
import org.dom4j.element;   
import org.dom4j.io.saxreader;   
import org.dom4j.io.xmlwriter;   
/**  
*  
* @author hongliang.dinghl  
* dom4j 生成xml文档与解析xml文档  
*/  
public class dom4jdemo implements xmldocument {   
 
public void createxml(string filename) {   
document document = documenthelper.createdocument();   
element employees=document.addelement("employees");   
element employee=employees.addelement("employee");   
element name= employee.addelement("name");   
name.settext("ddvip");   
element sex=employee.addelement("sex");   
sex.settext("m");   
element age=employee.addelement("age");   
age.settext("29");   
try {   
writer filewriter=new filewriter(filename);   
xmlwriter xmlwriter=new xmlwriter(filewriter);   
xmlwriter.write(document);   
xmlwriter.close();   
} catch (ioexception e) {   
 
system.out.println(e.getmessage());   
}   
 
 
}   
 
 
public void parserxml(string filename) {   
file inputxml=new file(filename);   
saxreader saxreader = new saxreader();   
try {   
document document = saxreader.read(inputxml);   
element employees=document.getrootelement();   
for(iterator i = employees.elementiterator(); i.hasnext();){   
element employee = (element) i.next();   
for(iterator j = employee.elementiterator(); j.hasnext();){   
element node=(element) j.next();   
system.out.println(node.getname()+":"+node.gettext());   
}   
 
}   
} catch (documentexception e) {   
system.out.println(e.getmessage());   
}   
system.out.println("dom4j parserxml");   
}   
}

4.jdom生成和解析xml 

为减少dom、sax的编码量，出现了jdom；优点：20-80原则，极大减少了代码量。使用场合：要实现的功能简单，如解析、创建等，但在底层，jdom还是使用sax（最常用）、dom、xanan文档。

import java.io.filenotfoundexception;   
import java.io.fileoutputstream;   
import java.io.ioexception;   
import java.util.list;   
 
import org.jdom.document;   
import org.jdom.element;   
import org.jdom.jdomexception;   
import org.jdom.input.saxbuilder;   
import org.jdom.output.xmloutputter;   
/**  
*  
* @author hongliang.dinghl  
* jdom 生成与解析xml文档  
*  
*/  
public class jdomdemo implements xmldocument {   
 
public void createxml(string filename) {   
document document;   
element root;   
root=new element("employees");   
document=new document(root);   
element employee=new element("employee");   
root.addcontent(employee);   
element name=new element("name");   
name.settext("ddvip");   
employee.addcontent(name);   
element sex=new element("sex");   
sex.settext("m");   
employee.addcontent(sex);   
element age=new element("age");   
age.settext("23");   
employee.addcontent(age);   
xmloutputter xmlout = new xmloutputter();   
try {   
xmlout.output(document, new fileoutputstream(filename));   
} catch (filenotfoundexception e) {   
e.printstacktrace();   
} catch (ioexception e) {   
e.printstacktrace();   
}   
 
}   
 
public void parserxml(string filename) {   
saxbuilder builder=new saxbuilder(false);   
try {   
document document=builder.build(filename);   
element employees=document.getrootelement();   
list employeelist=employees.getchildren("employee");   
for(int i=0;ielement employee=(element)employeelist.get(i);   
list employeeinfo=employee.getchildren();   
for(int j=0;jsystem.out.println(((element)employeeinfo.get(j)).getname()+":"+((element)employeeinfo.get(j)).getvalue());   
 
}   
}   
} catch (jdomexception e) {   
 
e.printstacktrace();   
} catch (ioexception e) {   
 
e.printstacktrace();   
}   
 
}   
}

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