XStream的基本使用

先准备两个bean

 public class Book {
  private int bookId;
  private String bookName;
  private String bookCode;

 ...(get和set方法省略)
 }

public class BookShelf {
    private int number;
    private List<Book> books;
    private String remark;
    private Date date;
    public BookShelf(){
        books=new ArrayList<Book>();
    }
    ...(get和set方法省略)
}

使用

 Book book1=new Book();
 book1.setBookCode("001");
 book1.setBookId(1);
 book1.setBookName("java编程");
 Book book2=new Book();
 book2.setBookCode("002");
 book2.setBookId(2);
 book2.setBookName("jsp编程");
 BookShelf bookShelf=new BookShelf();
 bookShelf.setNumber(1);
 bookShelf.setRemark("第一个书架");
 bookShelf.getBooks().add(book1);
 bookShelf.getBooks().add(book2);
 bookShelf.setDate(new Date());

 XStream xStream=new XStream(new DomDriver());
 String str= xStream.toXML(bookShelf);
 System.out.println(str);

输出结果：

<xml.BookShelf>
  <number>1</number>
  <books>
    <xml.Book>
      <bookId>1</bookId>
      <bookName>java编程</bookName>
      <bookCode>001</bookCode>
    </xml.Book>
    <xml.Book>
      <bookId>2</bookId>
      <bookName>jsp编程</bookName>
      <bookCode>002</bookCode>
    </xml.Book>
  </books>
  <remark>第一个书架</remark>
  <date>2014-07-04 07:03:34.485 UTC</date>
</xml.BookShelf>

输出的结果里，类名转换为节点名，但前面多了个xml（不爽），时间格式字符串也不爽，那下面就来改造一下吧！

1、先处理一下时间格式问题，这个需要我们自己定义date类型的字段要怎么转换，当然xstream为我们提供了接口，实现它吧

public class MuConverter implements Converter {
    //判断字段是否属于要转换的类型
   @Override
    public boolean canConvert(Class paramClass) {
        return Date.class.isAssignableFrom(paramClass);
    }

    //对象转化为xml
    @Override
    public void marshal(Object object, HierarchicalStreamWriter writer,
                                    MarshallingContext context) {
        SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");
        writer.setValue(format.format(object));
    }

    //xml转化为对象
   @Override
    public Object unmarshal(HierarchicalStreamReader reader,
                UnmarshallingContext context) {
        try {
                  Date date= DateFormat.getInstance().parse(reader.getValue());
                  return date;
        } catch (ParseException e) {
                  return null;
        }
    }
}

2、为各字段换个名字

xStream.alias("BookShelf", BookShelf.class);
xStream.alias("Book", Book.class);
 //修改节点名称
xStream.aliasField("other", BookShelf.class,"remark");

//字段不做为节点，而是属性
xStream.aliasAttribute(Book.class, "bookId", "id");
xStream.useAttributeFor(Book.class, "bookId");

//去掉集体节点的父节点
//xStream.addImplicitCollection(BookShelf.class, "books");

//自定义转换器
xStream.registerConverter(new MuConverter());*/

输出结果

<BookShelf>
  <number>1</number>
  <books>
    <Book id="1">
      <bookName>java编程</bookName>
      <bookCode>001</bookCode>
    </Book>
    <Book id="2">
      <bookName>jsp编程</bookName>
      <bookCode>002</bookCode>
    </Book>
  </books>
  <other>第一个书架</other>
  <date>2014-07-04</date>
</BookShelf>

3、如果觉得上面的指定代码太复杂了，也可以使用注解来实现
首先来看两个bean

@XStreamAlias("Book")
public class Book {

    @XStreamAlias("id")
    @XStreamAsAttribute
    private int bookId;
    private String bookName;
    private String bookCode;

   ...
}

@XStreamAlias("BookShelf")
public class BookShelf {
    private int number;
    //去掉集体节点的父节点
    //@XStreamImplicit
    private List<Book> books;
    private String remark;
    @XStreamConverter(MuConverter.class)
    private Date date;
    public BookShelf(){
        books=new ArrayList<Book>();
    }

    ...
}

没有注解的字段按字段名默认来转换
直接调用方法即可

 xStream.autodetectAnnotations(true);
//也可以分别调用
//xStream.processAnnotations(BookShelf.class);
//xStream.processAnnotations(Book.class);

---

上面的是对象转换为xml，现在来实现xml转换为对象，很简单（注意：xml转换成对象，需要通过上面的别名或注解的方式来指明转换，不能直接调用下面的代码）

XStream xStream=new XStream(new DomDriver());
xStream.autodetectAnnotations(true);
BookShelf bookShelf2=(BookShelf)xStream.fromXML(str);

---

序列化和反序列化支持

不多说，直接上代码

1、反序列化

ObjectInputStream input=xStream.createObjectInputStream(inputStream);
BookShelf bookShelf=(BookShelf)input.readObject();

2、序列化

ObjectOutputStream out=xstream.createObjectOutputStream(outputStream);
out.writeObject(bookShelf);
out.close();

3、PrettyPrintWriter、CompactWriter
这两个是XStream自带的用于输出xml文件，区别在于后者输出的xml是连接的，前者输出的是有格式的xml