Java解析XML的四种方法详解

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http://www.w3.org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。

package com.alisoft.facepay.framework.bean;
/**
*
* @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）。

package com.alisoft.facepay.framework.bean;
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；
java代码

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));
}
}
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。

java代码

package com.alisoft.facepay.framework.bean;
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。

package com.alisoft.facepay.framework.bean;
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();
}
}
}