java 利用Xstream生成和解析xml

1.Xstream简介；

使用限制: JDK版本不能<1.5.
虽然预处理注解是安全的,但自动侦查注解可能发生竞争条件.

特点:
简化的API;
无映射文件;
高性能,低内存占用;
整洁的XML;
不需要修改对象;支持内部私有字段,不需要setter/getter方法,final字段;非公有类,内部类;类不需要默认构造器,完全对象图支持.维护对象引用计数,循环引用. i
提供序列化接口;
自定义转换类型策略;
详细的错误诊断;
快速输出格式;当前支持 JSON 和 morphing.

使用场景
Transport 转换
Persistence 持久化对象
Configuration 配置
Unit Tests 单元测

隐式集合
当我们使用集合类时不想显示集合,只显示里面的元素即可.
使用隐式集合前:
<list>
<element />
<element />
<list>

使用隐式集合:
xstream.addImplicitCollection(Person.class, "list");

使用隐式集合后:
<element />
<element />

2.Xstream注解常用知识：
@XStreamAlias("message") 别名注解
作用目标: 类,字段
@XStreamImplicit 隐式集合
@XStreamImplicit(itemFieldName="part")
作用目标: 集合字段
@XStreamConverter(SingleValueCalendarConverter.class) 注入转换器
作用目标: 对象
@XStreamAsAttribute 转换成属性
作用目标: 字段
@XStreamOmitField 忽略字段
作用目标: 字段
Auto-detect Annotations 自动侦查注解 
xstream.autodetectAnnotations(true);
自动侦查注解与XStream.processAnnotations(Class[] cls)的区别在于性能.自动侦查注解将缓存所有类的类型.
3.案例分析： （1）同一标签下多个同名元素；
                   （2）同一标签下循环多个对象；
标签： XStream
代码片段(12) [全屏查看所有代码]
1. [代码]1.实体类：PersonBean   
01 import java.util.List;
02
03 import com.thoughtworks.xstream.annotations.XStreamAlias;
04 import com.thoughtworks.xstream.annotations.XStreamImplicit;
05
06 /**
07 *@ClassName:PersonBean
08 *@author: chenyoulong  Email: [e-mail]
09 *@date :2012-9-28 下午3:10:47
10 *@Description:TODO
11 */
12 @XStreamAlias("person")
13 public class PersonBean {
14     @XStreamAlias("firstName")
15     private String firstName;
16     @XStreamAlias("lastName")
17     private String lastName;
18     
19     @XStreamAlias("telphone")
20     private PhoneNumber tel;
21     @XStreamAlias("faxphone")
22     private PhoneNumber fax;
23     
24     //测试一个标签下有多个同名标签
25     @XStreamAlias("friends")
26     private Friends friend;
27     
28     //测试一个标签下循环对象
29     @XStreamAlias("pets")
30     private Pets pet;
31     
32     
33     //省略setter和getter
34 }
2. [代码]2.实体类：PhoneNumber   
01 @XStreamAlias("phoneNumber")
02     public  class PhoneNumber{
03         @XStreamAlias("code")
04         private int code;
05         @XStreamAlias("number")
06         private String number;
07         
08             //省略setter和getter
09         
10     }
3. [代码]3.实体类：Friends（一个标签下有多个同名标签 ）   
01 /**
02      * 用Xstream注解的方式实现：一个标签下有多个同名标签
03      *@ClassName:Friends
04      *@author: chenyoulong  Email: [e-mail]
05      *@date :2012-9-28 下午4:32:24
06      *@Description:TODO 5个name 中国，美国，俄罗斯，英国，法国
07      *http://blog.csdn.net/menhuanxiyou/article/details/5426765
08      */
09     public static class Friends{
10         @XStreamImplicit(itemFieldName="name")   //itemFieldName定义重复字段的名称，
11         /*<friends>                               <friends>
12             <name>A1</name>                         <String>A1</String>
13             <name>A2</name>    如果没有，则会变成    =====>       <String>A1</String>
14             <name>A3</name>                         <String>A1</String>
15         </friends>                                </friends>
16       */
17         private List<String> name;
18
19         public List<String> getName() {
20             return name;
21         }
22
23         public void setName(List<String> name) {
24             this.name = name;
25         }
26     }
4. [代码]4.1实体类：Animal（同一标签下循环对象实体1）   
01 //测试同一标签下循环某一对象
02     public  class Animal{
03         @XStreamAlias("name")
04         private String name;
05         @XStreamAlias("age")
06         private int age;
07         public Animal(String name,int age){
08             this.name=name;
09             this.age=age;
10         }
11         
12               //省略setter和getter
13     }
14    
5. [代码]4.2实体类：Pets（同一标签下循环对象实体2）   
01 /**
02      * 测试同一标签下循环某一对象
03      *@ClassName:Pets
04      *@author: chenyoulong  Email: [e-mail]
05      *@date :2012-9-28 下午6:26:01
06      *@Description:TODO
07      */
08     public class Pets{
09         @XStreamImplicit(itemFieldName="pet")
10         private List<Animal> animalList;
11         
12         public List<Animal> getAnimalList() {
13             return animalList;
14         }
15
16         public void setAnimalList(List<Animal> animalList) {
17             this.animalList = animalList;
18         }
19         
20     }
6. [代码]5.main函数示例1：toxml   
01 import com.thoughtworks.xstream.XStream;
02 import com.thoughtworks.xstream.io.json.JsonWriter.Format;
03 import com.thoughtworks.xstream.io.xml.DomDriver;
04
05 /**
06 *@ClassName:PersonTest
07 *@author: chenyoulong
08 *@date :2012-9-28 下午3:25:09
09 *@Description:TODO
10 */
11 public class PersonTest {
12
13     /**
14      * @Title: main
15      * @Description: TODO
16      * @param args
17      * @return void
18      */
19     public static void main(String[] args) {
20         // TODO Auto-generated method stub
21         
22         PersonBean per=new PersonBean();
23         per.setFirstName("chen");
24         per.setLastName("youlong");
25         
26         PhoneNumber tel=new PhoneNumber();
27         tel.setCode(137280);
28         tel.setNumber("137280968");
29         
30         PhoneNumber fax=new PhoneNumber();
31         fax.setCode(20);
32         fax.setNumber("020221327");
33         per.setTel(tel);
34         per.setFax(fax);
35         
36         
37         //测试一个标签下有多个同名标签
38         List<String> friendList=new ArrayList<String>();
39         friendList.add("A1");
40         friendList.add("A2");
41         friendList.add("A3");
42         Friends friend1=new Friends();
43         friend1.setName(friendList);
44         per.setFriend(friend1);
45         
46         //测试一个标签下循环对象
47         Animal dog=new Animal("Dolly",2);
48         Animal cat=new Animal("Ketty",2);
49         List<Animal> petList=new ArrayList<Animal>();
50         petList.add(dog);
51         petList.add(cat);
52         Pets pet=new Pets();
53         pet.setAnimalList(petList);
54         per.setPet(pet);
55         
56                     //java对象转换成xml
57         String xml=XmlUtil.toXml(per);
58         System.out.println("xml==="+xml);
59         
60     }
61 }
7. [代码]xml效果图   
01 xml===<person>
02   <firstName>chen</firstName>
03   <lastName>youlong</lastName>
04   <telphone>
05     <code>137280</code>
06     <number>137280968</number>
07   </telphone>
08   <faxphone>
09     <code>20</code>
10     <number>020221327</number>
11   </faxphone>
12   <friends>
13     <name>A1</name>
14     <name>A2</name>
15     <name>A3</name>
16   </friends>
17   <pets>
18     <pet>
19       <name>doly</name>
20       <age>2</age>
21     </pet>
22     <pet>
23       <name>Ketty</name>
24       <age>2</age>
25     </pet>
26   </pets>
27 </person>
8. [代码]5.2 main函数示例2：toBean   
01 public static void main(String[] args) {
02         // TODO Auto-generated method stub
03         
04         //toXml
05 //      String xmlStr=new PersonTest().toXml();
06         
07         //toBean
08 //      PersonBean per=new PersonTest().toBean();
09         String xmlStr="<person>"+
10                   "<firstName>chen</firstName>"+
11                   "<lastName>youlong</lastName>"+
12                   "<telphone>"+
13                     "<code>137280</code>"+
14                     "<number>137280968</number>"+
15                   "</telphone>"+
16                   "<faxphone>"+
17                     "<code>20</code>"+
18                     "<number>020221327</number>"+
19                   "</faxphone>"+
20                   "<friends>"+
21                     "<name>A1</name>"+
22                     "<name>A2</name>"+
23                     "<name>A3</name>"+
24                   "</friends>"+
25                   "<pets>"+
26                     "<pet>"+
27                       "<name>doly</name>"+
28                       "<age>2</age>"+
29                     "</pet>"+
30                     "<pet>"+
31                       "<name>Ketty</name>"+
32                       "<age>2</age>"+
33                     "</pet>"+
34                   "</pets>"+
35                 "</person>";
36 //用泛型的知识
37         PersonBean person=XmlUtil.toBean(xmlStr, PersonBean.class);
38         System.out.println("person=firstname=="+person.getFirstName());
39         System.out.println("person==Friends==name1=="+person.getFriend().getName().get(0));
40         System.out.println("person==Pets==name2=="+person.getPet().getAnimalList().get(1).getName());
41
42 /*
43 //效果与以下方法类同,(以下代码较为直观)
44 XStream xstream=new XStream(new DomDriver()); //注意：不是new Xstream(); 否则报错：
45
46         xstream.processAnnotations(PersonBean.class);
47         PersonBean person=(PersonBean)xstream.fromXML(xmlStr);
48         System.out.println("person=firstname=="+person.getFirstName());
49         System.out.println("person==Friends==name1=="+person.getFriend().getName().get(0));
50         System.out.println("person==Pets==name=="+person.getPet().getAnimalList().get(1).getName());
51 */
52
53         
54     }
9. [代码]6.XmlUtil工具类（toxml（）和toBean（））   
001 /**
002      * 输出xml和解析xml的工具类
003      *@ClassName:XmlUtil
004      *@author: chenyoulong  Email: [e-mail]
005      *@date :2012-9-29 上午9:51:28
006      *@Description:TODO
007      */
008     public class XmlUtil{
009         /**
010          * java 转换成xml
011          * @Title: toXml
012          * @Description: TODO
013          * @param obj 对象实例
014          * @return String xml字符串
015          */
016         public static String toXml(Object obj){
017             XStream xstream=new XStream();
018 //          XStream xstream=new XStream(new DomDriver()); //直接用jaxp dom来解释
019 //          XStream xstream=new XStream(new DomDriver("utf-8")); //指定编码解析器,直接用jaxp dom来解释
020             
021             ////如果没有这句，xml中的根元素会是<包.类名>；或者说：注解根本就没生效，所以的元素名就是类的属性
022             xstream.processAnnotations(obj.getClass()); //通过注解方式的，一定要有这句话
023             return xstream.toXML(obj);
024         }
025         
026         /**
027          *  将传入xml文本转换成Java对象
028          * @Title: toBean
029          * @Description: TODO
030          * @param xmlStr
031          * @param cls  xml对应的class类
032          * @return T   xml对应的class类的实例对象
033          *
034          * 调用的方法实例：PersonBean person=XmlUtil.toBean(xmlStr, PersonBean.class);
035          */
036         public static <T> T  toBean(String xmlStr,Class<T> cls){
037             //注意：不是new Xstream(); 否则报错：java.lang.NoClassDefFoundError: org/xmlpull/v1/XmlPullParserFactory
038             XStream xstream=new XStream(new DomDriver());
039             xstream.processAnnotations(cls);
040             T obj=(T)xstream.fromXML(xmlStr);
041             return obj;       
042         }
043
044        /**
045          * 写到xml文件中去
046          * @Title: writeXMLFile
047          * @Description: TODO
048          * @param obj 对象
049          * @param absPath 绝对路径
050          * @param fileName  文件名
051          * @return boolean
052          */
053       
054         public static boolean toXMLFile(Object obj, String absPath, String fileName ){
055             String strXml = toXml(obj);
056             String filePath = absPath + fileName;
057             File file = new File(filePath);
058             if(!file.exists()){
059                 try {
060                     file.createNewFile();
061                 } catch (IOException e) {
062                     log.error("创建{"+ filePath +"}文件失败!!!" + Strings.getStackTrace(e));
063                     return false ;
064                 }
065             }// end if
066             OutputStream ous = null ;
067             try {
068                 ous = new FileOutputStream(file);
069                 ous.write(strXml.getBytes());
070                 ous.flush();
071             } catch (Exception e1) {
072                 log.error("写{"+ filePath +"}文件失败!!!" + Strings.getStackTrace(e1));
073                 return false;
074             }finally{
075                 if(ous != null )
076                     try {
077                         ous.close();
078                     } catch (IOException e) {
079                         log.error("写{"+ filePath +"}文件关闭输出流异常!!!" + Strings.getStackTrace(e));
080                     }
081             }
082             return true ;
083         }
084         
085         /**
086          * 从xml文件读取报文
087          * @Title: toBeanFromFile
088          * @Description: TODO
089          * @param absPath 绝对路径
090          * @param fileName 文件名
091          * @param cls
092          * @throws Exception
093          * @return T
094          */
095         public static <T> T  toBeanFromFile(String absPath, String fileName,Class<T> cls) throws Exception{
096             String filePath = absPath +fileName;
097             InputStream ins = null ;
098             try {
099                 ins = new FileInputStream(new File(filePath ));
100             } catch (Exception e) {
101                 throw new Exception("读{"+ filePath +"}文件失败！", e);
102             }
103             
104             String encode = useEncode(cls);
105             XStream xstream=new XStream(new DomDriver(encode));
106             xstream.processAnnotations(cls);
107             T obj =null;
108             try {
109                 obj = (T)xstream.fromXML(ins);
110             } catch (Exception e) {
111                 // TODO Auto-generated catch block
112                 throw new Exception("解析{"+ filePath +"}文件失败！",e);
113             }
114             if(ins != null)
115                 ins.close();
116             return obj;       
117         }
118         
119     }