原文:http://www.cnblogs.com/hoojo/archive/2011/04/22/2025197.html
xStream框架
xStream可以轻易的将Java对象和xml文档相互转换,而且可以修改某个特定的属性和节点名称,而且也支持json的转换;
前面有介绍过json-lib这个框架,在线博文:http://www.cnblogs.com/hoojo/archive/2011/04/21/2023805.html
以及Jackson这个框架,在线博文:http://www.cnblogs.com/hoojo/archive/2011/04/22/2024628.html
它们都完美支持JSON,但是对xml的支持还不是很好。一定程度上限制了对Java对象的描述,不能让xml完全体现到对Java对象的描述。这里将会介绍xStream对JSON、XML的完美支持。xStream不仅对XML的转换非常友好,而且提供annotation注解,可以在JavaBean中完成对xml节点、属性的描述。以及对JSON也支持,只需要提供相关的JSONDriver就可以完成转换。
建议:xml的转换使用xStream框架;JSON的转换使用Jackson框架。
1. 准备工作
1.1. 下载jar包、及官方资源
xStream的jar下载地址:
官方的示例很全,官方参考示例:http://xstream.codehaus.org/tutorial.html
添加xstream-1.3.1.jar文件到工程中,就可以开始下面的工作;
1.2. 需要的JavaBean
Birthday :
public class Birthday {
private String birthday;
public Birthday() {
}
public Birthday(String birthday) {
this.birthday = birthday;
}
public String getBirthday() {
return birthday;
}
public void setBirthday(String birthday) {
this.birthday = birthday;
}
}
Student :
public class Student {
private int id;
private String name;
private String email;
private String address;
private Birthday birthday;
// getter、setter
public String toString() {
return this.name + "#" + this.id + "#" + this.address + "#" + this.birthday + "#" + this.email;
}
}
ListBean:
import java.util.List;
public class ListBean {
private String name;
private List<Object> list;
// getter、setter
}
2. Java转换成XML
2.1. JavaBean转换XML
import com.thoughtworks.xstream.XStream;
/**
* Java对象和XML字符串的相互转换
*/
public class WriteBean2XML {
private static XStream xstream = new XStream();
public static void main(String[] args) {
Student bean = new Student();
bean.setAddress("china");
bean.setEmail("[email protected]");
bean.setId(1);
bean.setName("jack");
Birthday day = new Birthday();
day.setBirthday("2010-11-22");
bean.setBirthday(day);
System.out.println(xstream.toXML(bean));
System.out.println();
// 类重命名
// xstream.alias("account", Student.class);
// xstream.alias("生日", Birthday.class);
// xstream.aliasField("生日", Student.class, "birthday");
// xstream.aliasField("生日", Birthday.class, "birthday");
// fail(xstream.toXML(bean));
// 属性重命名
xstream.aliasField("邮件", Student.class, "email");
// 包重命名
xstream.aliasPackage("", "test2");
System.out.println(xstream.toXML(bean));
}
}
通过XStream对象的toXML方法就可以完成Java对象到XML的转换,toXML方法还有2个相同签名的方法,需要传递一个流。然后通过流来完成xml信息的输出。
看结果中的第一份xml内容,是没有经过然后修改或重命名的文档,按照原样输出。文档中的第二份文档的package经过重命名,email属性也经过重命名以及类名也可以进行重命名的。
运行后结果如下:
<test2.Student>
<id>1</id>
<name>jack</name>
<email>[email protected]</email>
<address>china</address>
<birthday>
<birthday>2010-11-22</birthday>
</birthday>
</test2.Student>
<Student>
<id>1</id>
<name>jack</name>
<邮件>[email protected]</邮件>
<address>china</address>
<birthday>
<birthday>2010-11-22</birthday>
</birthday>
</Student>
2.2. 将List集合转换成xml文档
import java.util.ArrayList;
import java.util.List;
import com.thoughtworks.xstream.XStream;
/**
* 将List集合转换成xml文档
*/
public class WriteList2XML {
private static XStream xstream = new XStream();
public static void main(String[] args) {
try {
ListBean listBean = new ListBean();
listBean.setName("this is a List Collection");
List<Object> list = new ArrayList<Object>();
Student bean1 = new Student();
bean1.setAddress("USA");
bean1.setEmail("[email protected]");
bean1.setId(2);
bean1.setName("tom");
Birthday day1 = new Birthday("2010-11-22");
bean1.setBirthday(day1);
list.add(bean1);
Student bean2 = new Student();
bean2.setAddress("china");
bean2.setEmail("[email protected]");
bean2.setId(2);
bean2.setName("zhansan");
Birthday day2 = new Birthday("2001-05-06");
bean2.setBirthday(day2);
list.add(bean2);
list.add(bean2);
listBean.setList(list);
// 修改元素名称
xstream.alias("beans", ListBean.class);
xstream.alias("student", Student.class);
// 将ListBean中的集合设置空元素,即不显示集合元素标签
// xstream.addImplicitCollection(ListBean.class, "list");
// 设置reference模型
//xstream.setMode(XStream.NO_REFERENCES);//不引用
xstream.setMode(XStream.ID_REFERENCES);// id引用
// xstream.setMode(XStream.XPATH_ABSOLUTE_REFERENCES);//绝对路径引用
// 将name设置为父类(Student)的元素的属性
xstream.useAttributeFor(Student.class, "name");
xstream.useAttributeFor(Birthday.class, "birthday");
// 修改属性的name
xstream.aliasAttribute("姓名", "name");
xstream.aliasField("生日", Birthday.class, "birthday");
System.out.println(xstream.toXML(listBean));
} catch (Exception e) {
e.printStackTrace();
}
}
}
运行后结果如下:
<beans id="1">
<name>this is a List Collection</name>
<list id="2">
<student id="3" 姓名="tom">
<id>2</id>
<email>[email protected]</email>
<address>USA</address>
<birthday id="4" 生日="2010-11-22"/>
</student>
<student id="5" 姓名="zhansan">
<id>2</id>
<email>[email protected]</email>
<address>china</address>
<birthday id="6" 生日="2001-05-06"/>
</student>
<student reference="5"/>
</list>
</beans>
如果不加xstream.addImplicitCollection(ListBean.class, "list");
这个设置的话,会出现一个List节点包裹着Student节点元素。添加addImplicitCollection可以忽略这个list节点元素。那么上面的list节点就不存在,只会在beans元素中出现name、student这2个xml元素标签;
setMode是设置相同的对象的引用方式,如果设置XStream.NO_REFERENCES就是不引用,会输出2分相同的 Student元素。如果是XStream.ID_REFERENCES会引用相同的那个对象的id属性,如果是 XStream.XPATH_ABSOLUTE_REFERENCES引用,那么它将显示xpath路径。上面采用的id引用,<student reference="3"/>这个引用了id=3的那个student标签元素;
useAttributeFor是设置某个节点显示到父节点的属性中,也就是将指定class中的指定属性,在这个class元素节点的属性中显示。
如:<student><name>hoojo</name></student>
设置好后就是这样的结果:<student name=”hoojo”></student>
aliasAttribute是修改属性名称。
2.3. 在JavaBean中添加Annotation注解进行重命名设置
JavaBean的代码
import java.util.Arrays;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.List;
import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.annotations.XStreamConverter;
import com.thoughtworks.xstream.annotations.XStreamImplicit;
import com.thoughtworks.xstream.annotations.XStreamOmitField;
@XStreamAlias("class")
public class Classes {
// 设置属性显示
@XStreamAsAttribute
@XStreamAlias("名称")
private String name;
// 忽略
@XStreamOmitField
private int number;
@XStreamImplicit(itemFieldName = "Students")
private List<Student> students;
@XStreamConverter(SingleValueCalendarConverter.class)
private Calendar created = new GregorianCalendar();
public Classes() {
}
public Classes(String name, Student... stu) {
this.name = name;
this.students = Arrays.asList(stu);
}
// getter、setter
}
SingleValueCalendarConverter.java这个是一个类型转换器
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
public class SingleValueCalendarConverter implements Converter {
public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
Calendar calendar = (Calendar) source;
writer.setValue(String.valueOf(calendar.getTime().getTime()));
}
public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
GregorianCalendar calendar = new GregorianCalendar();
calendar.setTime(new Date(Long.parseLong(reader.getValue())));
return calendar;
}
@SuppressWarnings("rawtypes")
public boolean canConvert(Class type) {
return type.equals(GregorianCalendar.class);
}
}
测试代码
import com.thoughtworks.xstream.XStream;
public class WriteList2XML4Annotation {
private static XStream xstream = new XStream();
public static void main(String[] args) {
try {
Student bean1 = new Student();
bean1.setAddress("USA");
bean1.setEmail("[email protected]");
bean1.setId(2);
bean1.setName("tom");
Birthday day1 = new Birthday("2010-11-22");
bean1.setBirthday(day1);
Student bean2 = new Student();
bean2.setAddress("china");
bean2.setEmail("[email protected]");
bean2.setId(2);
bean2.setName("zhansan");
Birthday day2 = new Birthday("2001-05-06");
bean2.setBirthday(day2);
Classes c = new Classes("一班", bean1, bean2);
c.setNumber(2);
// 对指定的类使用Annotation
// xstream.processAnnotations(Classes.class);
// 启用Annotation
// xstream.autodetectAnnotations(true);
xstream.alias("student", Student.class);
System.out.println(xstream.toXML(c));
} catch (Exception e) {
e.printStackTrace();
}
}
}
当启用annotation或是对某个特定的类启用annotation时,上面的classes这个类才有效果。如果不启用annotation,运行后结果如下:
<test2.Classes>
<name>一班</name>
<number>2</number>
<students class="java.util.Arrays$ArrayList">
<a class="student-array">
<student>
<id>2</id>
<name>tom</name>
<email>[email protected]</email>
<address>USA</address>
<birthday>
<birthday>2010-11-22</birthday>
</birthday>
</student>
<student>
<id>2</id>
<name>zhansan</name>
<email>[email protected]</email>
<address>china</address>
<birthday>
<birthday>2001-05-06</birthday>
</birthday>
</student>
</a>
</students>
<created>
<time>1413786635143</time>
<timezone>Asia/Shanghai</timezone>
</created>
</test2.Classes>
当启用annotation后xstream.processAnnotations(Classes.class),结果如下:
<class 名称="一班">
<Students>
<id>2</id>
<name>tom</name>
<email>[email protected]</email>
<address>USA</address>
<birthday>
<birthday>2010-11-22</birthday>
</birthday>
</Students>
<Students>
<id>2</id>
<name>zhansan</name>
<email>[email protected]</email>
<address>china</address>
<birthday>
<birthday>2001-05-06</birthday>
</birthday>
</Students>
<created>1413786890887</created>
</class>
2.4. Map集合转换xml文档
import java.util.HashMap;
import java.util.Map;
import com.thoughtworks.xstream.XStream;
/**
* Map集合转换xml文档
*/
public class writeMap2XML {
private static XStream xstream = new XStream();
public static void main(String[] args) {
try {
Student bean1 = new Student();
bean1.setAddress("china");
bean1.setEmail("[email protected]");
bean1.setId(1);
bean1.setName("tom");
Birthday day = new Birthday("2010-11-22");
bean1.setBirthday(day);
Student bean2 = new Student();
bean2.setAddress("china");
bean2.setEmail("[email protected]");
bean2.setId(2);
bean2.setName("zhansan");
Birthday day2 = new Birthday("2001-05-06");
bean2.setBirthday(day2);
Map<String, Student> map = new HashMap<String, Student>();
map.put("No.1", bean1);// put
map.put("No.2", bean2);// put
xstream.alias("student", Student.class);
xstream.alias("key", String.class);
xstream.useAttributeFor(Student.class, "id");
xstream.useAttributeFor("birthday", String.class);
System.out.println(xstream.toXML(map));
} catch (Exception e) {
e.printStackTrace();
}
}
}
运行后结果如下:
<map>
<entry>
<key>No.1</key>
<student id="1">
<name>tom</name>
<email>[email protected]</email>
<address>china</address>
<birthday birthday="2010-11-22"/>
</student>
</entry>
<entry>
<key>No.2</key>
<student id="2">
<name>zhansan</name>
<email>[email protected]</email>
<address>china</address>
<birthday birthday="2001-05-06"/>
</student>
</entry>
</map>
2.5. 用OutStream输出流写XML
import java.io.ObjectOutputStream;
import com.thoughtworks.xstream.XStream;
/**
* 用OutStream输出流写XML
*/
public class WriteXML4OutStream {
private static XStream xstream = new XStream();
private static ObjectOutputStream out = null;
public static void main(String[] args) {
try {
Student bean = new Student();
bean.setAddress("china");
bean.setEmail("[email protected]");
bean.setId(1);
bean.setName("tom");
Birthday day = new Birthday("2010-11-22");
bean.setBirthday(day);
out = xstream.createObjectOutputStream(System.out);
Student stu = new Student();
stu.setName("jack");
Classes c = new Classes("一班", bean, stu);
c.setNumber(2);
out.writeObject(stu);
out.writeObject(new Birthday("2010-05-33"));
out.write(22);// byte
out.writeBoolean(true);
out.writeFloat(22.f);
out.writeUTF("hello");
out.flush();
out.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
使用输出流后,可以通过流对象完成xml的构建,即使没有JavaBean对象,你可以用流来构建一个复杂的xml文档,运行后结果如下:
<object-stream>
<test2.Student>
<id>0</id>
<name>jack</name>
</test2.Student>
<test2.Birthday>
<birthday>2010-05-33</birthday>
</test2.Birthday>
<byte>22</byte>
<boolean>true</boolean>
<float>22.0</float>
<string>hello</string>
</object-stream>
3. XML内容转换Java对象
3.1. 用InputStream将XML文档转换成java对象
import java.io.ObjectInputStream;
import java.io.StringReader;
import com.thoughtworks.xstream.XStream;
/**
* 用InputStream将XML文档转换成java对象
*/
public class ReadXML4InputStream {
private static XStream xstream = new XStream();
public static void main(String[] args) {
try {
String s = "<object-stream><test2.Student><id>0</id><name>jack</name>"
+ "</test2.Student><test2.Birthday><birthday>2010-05-33</birthday>"
+ "</test2.Birthday><byte>22</byte><boolean>true</boolean><float>22.0</float>"
+ "<string>hello</string></object-stream>";
StringReader reader = new StringReader(s);
ObjectInputStream in = xstream.createObjectInputStream(reader);
Student stu = (Student) in.readObject();
Birthday b = (Birthday) in.readObject();
byte i = in.readByte();
boolean bo = in.readBoolean();
float f = in.readFloat();
String str = in.readUTF();
System.out.println(stu);
System.out.println(b);
System.out.println(i);
System.out.println(bo);
System.out.println(f);
System.out.println(str);
} catch (Exception e) {
e.printStackTrace();
}
}
}
读取后,转换的Java对象,结果如下:
jack#0#null#null#null
test2.Birthday@17590db
22
true
22.0
hello
XStream对JSON的也支持,但不建议使用该Jar执行转换。这里就不做介绍了。