java socket报文通信（三）java对象和xml格式文件的相互转换

前两节讲了socket服务端，客户端的建立以及报文的封装。今天就来讲一下java对象和xml格式文件的相互转换。

上一节中我们列举了一个报文格式，其实我们可以理解为其实就是一个字符串。但是我们不可能每次都去写字符串啊，这样的话肯定要疯。既然是面向对象的编程，肯定会有好的办法来解决这个问题。我们使用JAXBContext这个工具。以上两个方法可以将java对象可xml文件相互转换。

接下来我们看看怎么使用。

package cn.com.egj.entity.shortcutTransfer.test;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.net.URLEncoder;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamWriter;

/**
* Jaxb2工具类
*/
@XmlRootElement
public class JaxbUtil {

/**
* JavaBean转换成xml
*
* @param obj
* @param encoding
* @return
*/
public static String convertToXml(Object obj) {

try {
JAXBContext context = JAXBContext.newInstance(obj.getClass());
Marshaller marshaller = context.createMarshaller();

marshaller.setProperty(Marshaller.JAXB_ENCODING, "GBK");
marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);

ByteArrayOutputStream baos = new ByteArrayOutputStream();
//注意jdk版本
XMLOutputFactory xmlOutputFactory = XMLOutputFactory.newInstance();
XMLStreamWriter xmlStreamWriter = xmlOutputFactory
.createXMLStreamWriter(baos, (String) marshaller
.getProperty(Marshaller.JAXB_ENCODING));
xmlStreamWriter.writeStartDocument(
(String) marshaller.getProperty(Marshaller.JAXB_ENCODING),
"1.0");
marshaller.marshal(obj, xmlStreamWriter);
xmlStreamWriter.writeEndDocument();
xmlStreamWriter.close();
return new String(baos.toString("GBK"));

} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;

}

/**
* xml转换成JavaBean
*
* @param xml
* @param c
* @return
*/
@SuppressWarnings("unchecked")
public static <T> T converyToJavaBean(String xml, Class<T> c) {
T t = null;
try {
JAXBContext context = JAXBContext.newInstance(c);
Unmarshaller unmarshaller = context.createUnmarshaller();
t = (T) unmarshaller.unmarshal(new StringReader(xml));
} catch (Exception e) {
e.printStackTrace();
}

return t;
}

}

1）首先我们要建立需要转换的类：

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)//表示使用这个类中的 private 非静态字段作为 XML 的序列化的属性或者元素,对应属性要使用get、set方法。
@XmlRootElement(name="ROOT")
@XmlType(propOrder={"code","name","age"})//xml格式数据的显示的顺序名字要和定义变量的一样，而不是@XmlElement中的name
public class MySocket {
    @XmlElement(name="Code",required=true)//定义xml中显示的数据
    private  String code;
    @XmlElement(name="Name",required=true)
    private String name;
    @XmlElement(name="Age",required=true)
    private String age;
    public String getCode() {
        return code;
    }
    public String getName() {
        return name;
    }
    public String getAge() {
        return age;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(String age) {
        this.age = age;
    }
    
    public String toString(){
        return this.name+","+this.age+","+this.code;
    }
}

2）建立测试类：

public class Test {
    public static void main(String[] args) {
        objectToXml();
    }    
    public static  void objectToXml(){
        MySocket mySocket = new MySocket();
        mySocket.setName("张三");
        mySocket.setCode("00012");
        mySocket.setAge("25");
        String xml = JaxbUtil.convertToXml(mySocket);
        System.out.println(xml);
    }    
}

运行测试类，我们将看到控制台输出：<?xml version="1.0" encoding="GBK"?><ROOT><Code>00012</Code><Age>25</Age></ROOT>

对于Object转xml,我们建立测试方法：

public static void xmlToObjetct(){
        String xml = "<?xml version=\"1.0\" encoding=\"GBK\"?><ROOT><Code>00011</Code><Name>李四</Name><Age>26</Age></ROOT>";
        MySocket mySocket= JaxbUtil.converyToJavaBean(xml, MySocket.class);
        System.out.println(mySocket.toString());
    }

运行测试类，我们将看到控制台输出：李四,26,00011

3）有时候我们的java对象中会存在集合，这时我们像如下这么做：

3.1）首先我们建立袋集合的对象：

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name="ROOT")
@XmlType(propOrder={"name","age","books"})
public class ListSocket {

    @XmlElement(name="Name",required=true)
    private String name;
    @XmlElement(name="Age",required=true)
    private String age;
    @XmlElementWrapper(name="ROWS")//@XmlElementWrapper注解表示生成一个包装 XML 表示形式的包装器元素。 此元素主要用于生成一个包装集合的包装器 XML 元素
    @XmlElement(name="LIST",required=true)
    private List<Book> books;
    public String getName() {
        return name;
    }
    public String getAge() {
        return age;
    }
    public List<Book> getBooks() {
        return books;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAge(String age) {
        this.age = age;
    }
    public void setBooks(List<Book> books) {
        this.books = books;
    }
    
    public String toString(){
        String result = "";
        result=this.age+","+this.name+",集合的数据：";
        for (Book book:books) {
            result+=book.getAuthor()+book.getTime()+book.getBookName();
        }
        return result;
    }
}

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder={"bookName","time","author"})
public class Book {
    @XmlElement(name="BookName")
    private String bookName;
    @XmlElement(name="Time")
    private String time;
    @XmlElement(name="Author")
    private String author;
    public String getBookName() {
        return bookName;
    }
    public String getTime() {
        return time;
    }
    public String getAuthor() {
        return author;
    }
    public void setBookName(String bookName) {
        this.bookName = bookName;
    }
    public void setTime(String time) {
        this.time = time;
    }
    public void setAuthor(String author) {
        this.author = author;
    }
}

3.2）建立测试类：

public class ListSocketTest {
    public static void main(String[] args) {
        objectToXml();
        xmlToObject();
    }
    
    public static void objectToXml(){
        ListSocket listSocket = new ListSocket();
        listSocket.setName("张三");
        listSocket.setAge("26");
        List<Book> books = new ArrayList<Book>();
        Book book1 = new Book();
        book1.setAuthor("作者1");
        book1.setTime("2014-12-28");
        book1.setBookName("How to use JAXB");
        Book book2= new Book();
        book2.setAuthor("作者2");
        book2.setTime("2014-06-06");
        book2.setBookName("How to use SOCKET");
        books.add(book1);
        books.add(book2);
        listSocket.setBooks(books);
        String xml = JaxbUtil.convertToXml(listSocket);
        System.out.println(xml);
    }
    
    public static void xmlToObject(){
        String xml = "<?xml version=\"1.0\" encoding=\"GBK\"?><ROOT><Name>张三</Name><Age>26</Age><ROWS><LIST>"
                       +"<BookName>How to use JAXB</BookName><Time>2014-12-28</Time><Author>作者1</Author>"
                       +"</LIST><LIST><BookName>How to use SOCKET</BookName><Time>2014-06-06</Time><Author>作者2</Author></LIST></ROWS></ROOT>";
        ListSocket listSocket = JaxbUtil.converyToJavaBean(xml, ListSocket.class);
        System.out.println(listSocket);
    }

运行主函数，我们可以看见转换后的xml对象和类对象。使用就是这么的简单^_^!!!