test

List<E>, NavigableSet<E>, Queue<E>, Set<E>, SortedSet<E>

JAVA平台提供了两个类：String和StringBuffer，它们可以储存和操作字符串，即包含多个字符的字符数据。这个String类提供了数值不可改变的字符串。而这个StringBuffer类提供的字符串进行修改。当你知道字符数据要改变的时候你就可以使用StringBuffer。典型地，你可以使用StringBuffers来动态构造字符数据。

Servlet被服务器实例化后，容器运行其init方法，请求到达时运行其service方法，service方法自动派遣运行与请求对应的doXXX方法（doGet，doPost）等，当服务器决定将实例销毁的时候调用其destroy方法。

JAVA解析XML的四种方法

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

1. packagecom.alisoft.facepay.framework.bean;
3. importjava.io.FileInputStream;
4. importjava.io.FileNotFoundException;
5. importjava.io.IOException;
6. importjava.io.InputStream;
8. importjavax.xml.parsers.ParserConfigurationException;
9. importjavax.xml.parsers.SAXParser;
10. importjavax.xml.parsers.SAXParserFactory;
12. importorg.xml.sax.Attributes;
13. importorg.xml.sax.SAXException;
14. importorg.xml.sax.helpers.DefaultHandler;
15. /**
16. *
17. *@authorhongliang.dinghl
18. *SAX文档解析
19. */
20. publicclassSaxDemoimplementsXmlDocument{
22. publicvoidcreateXml(StringfileName){
23. System.out.println("<<"+filename+">>");
24. }
26. publicvoidparserXml(StringfileName){
27. SAXParserFactorysaxfac=SAXParserFactory.newInstance();
29. try{
31. SAXParsersaxparser=saxfac.newSAXParser();
33. InputStreamis=newFileInputStream(fileName);
35. saxparser.parse(is,newMySAXHandler());
37. }catch(ParserConfigurationExceptione){
39. e.printStackTrace();
41. }catch(SAXExceptione){
43. e.printStackTrace();
45. }catch(FileNotFoundExceptione){
47. e.printStackTrace();
49. }catch(IOExceptione){
51. e.printStackTrace();
53. }
55. }
57. }
59. classMySAXHandlerextendsDefaultHandler{
61. booleanhasAttribute=false;
63. Attributesattributes=null;
65. publicvoidstartDocument()throwsSAXException{
67. System.out.println("文档开始打印了");
69. }
71. publicvoidendDocument()throwsSAXException{
73. System.out.println("文档打印结束了");
75. }
77. publicvoidstartElement(Stringuri,StringlocalName,StringqName,
79. Attributesattributes)throwsSAXException{
81. if(qName.equals("employees")){
83. return;
85. }
87. if(qName.equals("employee")){
89. System.out.println(qName);
91. }
93. if(attributes.getLength()>0){
95. this.attributes=attributes;
97. this.hasAttribute=true;
99. }
101. }
103. publicvoidendElement(Stringuri,StringlocalName,StringqName)
105. throwsSAXException{
107. if(hasAttribute&&(attributes!=null)){
109. for(inti=0;i<attributes.getLength();i++){
111. System.out.println(attributes.getQName(0)
112. +attributes.getValue(0));
114. }
116. }
118. }
120. publicvoidcharacters(char[]ch,intstart,intlength)
122. throwsSAXException{
124. System.out.println(newString(ch,start,length));
126. }
128. }

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

1. packagecom.alisoft.facepay.framework.bean;
3. importjava.io.File;
4. importjava.io.FileWriter;
5. importjava.io.IOException;
6. importjava.io.Writer;
7. importjava.util.Iterator;
9. importorg.dom4j.Document;
10. importorg.dom4j.DocumentException;
11. importorg.dom4j.DocumentHelper;
12. importorg.dom4j.Element;
13. importorg.dom4j.io.SAXReader;
14. importorg.dom4j.io.XMLWriter;
15. /**
16. *
17. *@authorhongliang.dinghl
18. *Dom4j生成XML文档与解析XML文档
19. */
20. publicclassDom4jDemoimplementsXmlDocument{
22. publicvoidcreateXml(StringfileName){
23. Documentdocument=DocumentHelper.createDocument();
24. Elementemployees=document.addElement("employees");
25. Elementemployee=employees.addElement("employee");
26. Elementname=employee.addElement("name");
27. name.setText("ddvip");
28. Elementsex=employee.addElement("sex");
29. sex.setText("m");
30. Elementage=employee.addElement("age");
31. age.setText("29");
32. try{
33. WriterfileWriter=newFileWriter(fileName);
34. XMLWriterxmlWriter=newXMLWriter(fileWriter);
35. xmlWriter.write(document);
36. xmlWriter.close();
37. }catch(IOExceptione){
39. System.out.println(e.getMessage());
40. }
43. }
46. publicvoidparserXml(StringfileName){
47. FileinputXml=newFile(fileName);
48. SAXReadersaxReader=newSAXReader();
49. try{
50. Documentdocument=saxReader.read(inputXml);
51. Elementemployees=document.getRootElement();
52. for(Iteratori=employees.elementIterator();i.hasNext();){
53. Elementemployee=(Element)i.next();
54. for(Iteratorj=employee.elementIterator();j.hasNext();){
55. Elementnode=(Element)j.next();
56. System.out.println(node.getName()+":"+node.getText());
57. }
59. }
60. }catch(DocumentExceptione){
61. System.out.println(e.getMessage());
62. }
63. System.out.println("dom4jparserXml");
64. }
67. }
68. 4.JDOM生成和解析XML
69. 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。
70. <prename="code"class="java">packagecom.alisoft.facepay.framework.bean;
72. importjava.io.FileNotFoundException;
73. importjava.io.FileOutputStream;
74. importjava.io.IOException;
75. importjava.util.List;
77. importorg.jdom.Document;
78. importorg.jdom.Element;
79. importorg.jdom.JDOMException;
80. importorg.jdom.input.SAXBuilder;
81. importorg.jdom.output.XMLOutputter;
82. /**
83. *
84. *@authorhongliang.dinghl
85. *JDOM生成与解析XML文档
86. *
87. */
88. publicclassJDomDemoimplementsXmlDocument{
90. publicvoidcreateXml(StringfileName){
91. Documentdocument;
92. Elementroot;
93. root=newElement("employees");
94. document=newDocument(root);
95. Elementemployee=newElement("employee");
96. root.addContent(employee);
97. Elementname=newElement("name");
98. name.setText("ddvip");
99. employee.addContent(name);
100. Elementsex=newElement("sex");
101. sex.setText("m");
102. employee.addContent(sex);
103. Elementage=newElement("age");
104. age.setText("23");
105. employee.addContent(age);
106. XMLOutputterXMLOut=newXMLOutputter();
107. try{
108. XMLOut.output(document,newFileOutputStream(fileName));
109. }catch(FileNotFoundExceptione){
110. e.printStackTrace();
111. }catch(IOExceptione){
112. e.printStackTrace();
113. }
115. }
117. publicvoidparserXml(StringfileName){
118. SAXBuilderbuilder=newSAXBuilder(false);
119. try{
120. Documentdocument=builder.build(fileName);
121. Elementemployees=document.getRootElement();
122. ListemployeeList=employees.getChildren("employee");
123. for(inti=0;i<employeeList.size();i++){
124. Elementemployee=(Element)employeeList.get(i);
125. ListemployeeInfo=employee.getChildren();
126. for(intj=0;j<employeeInfo.size();j++){
127. System.out.println(((Element)employeeInfo.get(j)).getName()+":"+((Element)employeeInfo.get(j)).getValue());
129. }
130. }
131. }catch(JDOMExceptione){
133. e.printStackTrace();
134. }catch(IOExceptione){
136. e.printStackTrace();
137. }
139. }
140. }
141. </pre>

 extends Applet

功能: 生成随机的字母和数字混杂的字符串

函数的入参是生成的随机字符串的长度

Java代码

1. publicStringgetCharacterAndNumber(intlength)
2. {
3. Stringval="";
5. Randomrandom=newRandom();
6. for(inti=0;i<length;i++)
7. {
8. StringcharOrNum=random.nextInt(2)%2==0?"char":"num";//输出字母还是数字
10. if("char".equalsIgnoreCase(charOrNum))//字符串
11. {
12. intchoice=random.nextInt(2)%2==0?65:97;//取得大写字母还是小写字母
13. val+=(char)(choice+random.nextInt(26));
14. }
15. elseif("num".equalsIgnoreCase(charOrNum))//数字
16. {
17. val+=String.valueOf(random.nextInt(10));
18. }
19. }
21. returnval;
22. }

第二种随即生成

Java产生随机数代码

1.
//根据不同的难度产生随机字母和数字
for(int i=0; readomNumStart.length()<4; i++) {
if(difficult == 1) {

//产生随机的0-9的数字
a = String.valueOf((int)(Math.random() * 10)) ;
}
if(difficult == 2) {

//在0-9和a，b，c，d中随机产生。
String[] readomWord = {"0","1","2","3","4","5","6","7","8","9","a","b","c","d"};
int readomWordIndex = (int)(Math.random() * 13);
a = readomWord[readomWordIndex];
}
if(difficult == 3) {

//产生随机的字母
char readomLetter = (char)(Math.random ()*26+'a');
a = String.valueOf(readomLetter) ;
}
if(difficult == 4) {

//产生随机的数字和字母的组合
String[] readomHard = new String[20];
int readomWordIndex = (int)(Math.random() * 19);
for(int j=0; j<20; j++) {
int readomWordNum = (int)(Math.random() * 10);
char readomLetter = (char)(Math.random ()*26+'a');
if(readomWordNum % 2 == 0) {
readomHard[j] = readomWordNum + "";
}else{
readomHard[j] = String.valueOf(readomLetter);
}
}
a = readomHard[readomWordIndex];
}


2.
char[] numbersAndLetters = ("0123456789" + "abcdefghijklmnopqrstuvwxyz" + "ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
char[] randBuffer = new char[length];
for (int i = 0; i < randBuffer.length; i++) {
randBuffer[i] = numbersAndLetters[randGen.nextInt(numbersAndLetters.length)];
}
return new String(randBuffer);