JAXB开发的技巧
大家经常都会遇到xml格式文档的开发，对于解析XML和封装XML格式，我们自然而然的会想到JAXB，JAXB允许以XML格式存储和读取数据，而不需要程序的类结构实现特定的读取XML和保存XML的代码。
首先我们需要使用XML Schema来描述XML格式，怎样自动生成xsd，我们可以通过trang.jar这个包来
现在可以使用jdk自带的xjc命令来生成代码了，xjc的具体使用方面就不多说，大家可以自己看看它的帮助文档
下面我们就可以开始来写代码了
以下是需要输出的XML文本格式
<Books>
<Book>
<name>书名A</name>
<author>作者A</author>
<price>作者A</price>
</Book>
<Book>
<name>书名B</name>
<author>作者B</author>
<price>作者B</price>
</Book>
</Books>
首先我们需要使用XML Schema来描述XML格式，怎样自动生成xsd，我们可以通过trang.jar这个包来
生成的XSD文件格式如下
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
<xs:element name="Books">
<xs:complexType>
<xs:sequence>
<xs:element maxOccurs="unbounded" ref="Book"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="Book">
<xs:complexType>
<xs:sequence>
<xs:element ref="name"/>
<xs:element ref="author"/>
<xs:element ref="price"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="name" type="xs:NCName"/>
<xs:element name="author" type="xs:NCName"/>
<xs:element name="price" type="xs:NCName"/>
</xs:schema>
现在可以使用jdk自带的xjc命令来生成代码了，xjc的具体使用方面就不多说，大家可以自己看看它的帮助文档
xjc a.xsd parsing a schema... compiling a schema... generated\Book.java generated\Books.java generated\ObjectFactory.java
package generated;
import java.util.ArrayList;
import java.util.List;
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;
/**
* <p>Java class for anonymous complex type.
*
* <p>The following schema fragment specifies the expected content contained within this class.
*
* <pre>
* <complexType>
* <complexContent>
* <restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
* <sequence>
* <element ref="{}Book" maxOccurs="unbounded"/>
* </sequence>
* </restriction>
* </complexContent>
* </complexType>
* </pre>
*
*
*/
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
"book"
})
@XmlRootElement(name = "Books")
public class Books {
@XmlElement(name = "Book", required = true)
protected List<Book> book;
/**
* Gets the value of the book property.
*
* <p>
* This accessor method returns a reference to the live list,
* not a snapshot. Therefore any modification you make to the
* returned list will be present inside the JAXB object.
* This is why there is not a <CODE>set</CODE> method for the book property.
*
* <p>
* For example, to add a new item, do as follows:
* <pre>
* getBook().add(newItem);
* </pre>
*
*
* <p>
* Objects of the following type(s) are allowed in the list
* {@link Book }
*
*
*/
public List<Book> getBook() {
if (book == null) {
book = new ArrayList<Book>();
}
return this.book;
}
}
package generated;
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.XmlSchemaType;
import javax.xml.bind.annotation.XmlType;
import javax.xml.bind.annotation.adapters.CollapsedStringAdapter;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
/**
* <p>Java class for anonymous complex type.
*
* <p>The following schema fragment specifies the expected content contained within this class.
*
* <pre>
* <complexType>
* <complexContent>
* <restriction base="{http://www.w3.org/2001/XMLSchema}anyType">
* <sequence>
* <element ref="{}name"/>
* <element ref="{}author"/>
* <element ref="{}price"/>
* </sequence>
* </restriction>
* </complexContent>
* </complexType>
* </pre>
*
*
*/
@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
"name",
"author",
"price"
})
@XmlRootElement(name = "Book")
public class Book {
@XmlElement(required = true)
@XmlJavaTypeAdapter(CollapsedStringAdapter.class)
@XmlSchemaType(name = "NCName")
protected String name;
@XmlElement(required = true)
@XmlJavaTypeAdapter(CollapsedStringAdapter.class)
@XmlSchemaType(name = "NCName")
protected String author;
@XmlElement(required = true)
@XmlJavaTypeAdapter(CollapsedStringAdapter.class)
@XmlSchemaType(name = "NCName")
protected String price;
/**
* Gets the value of the name property.
*
* @return
* possible object is
* {@link String }
*
*/
public String getName() {
return name;
}
/**
* Sets the value of the name property.
*
* @param value
* allowed object is
* {@link String }
*
*/
public void setName(String value) {
this.name = value;
}
/**
* Gets the value of the author property.
*
* @return
* possible object is
* {@link String }
*
*/
public String getAuthor() {
return author;
}
/**
* Sets the value of the author property.
*
* @param value
* allowed object is
* {@link String }
*
*/
public void setAuthor(String value) {
this.author = value;
}
/**
* Gets the value of the price property.
*
* @return
* possible object is
* {@link String }
*
*/
public String getPrice() {
return price;
}
/**
* Sets the value of the price property.
*
* @param value
* allowed object is
* {@link String }
*
*/
public void setPrice(String value) {
this.price = value;
}
}
package generated;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.XmlElementDecl;
import javax.xml.bind.annotation.XmlRegistry;
import javax.xml.bind.annotation.adapters.CollapsedStringAdapter;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import javax.xml.namespace.QName;
/**
* This object contains factory methods for each
* Java content interface and Java element interface
* generated in the generated package.
* <p>An ObjectFactory allows you to programatically
* construct new instances of the Java representation
* for XML content. The Java representation of XML
* content can consist of schema derived interfaces
* and classes representing the binding of schema
* type definitions, element declarations and model
* groups. Factory methods for each of these are
* provided in this class.
*
*/
@XmlRegistry
public class ObjectFactory {
private final static QName _Author_QNAME = new QName("", "author");
private final static QName _Price_QNAME = new QName("", "price");
private final static QName _Name_QNAME = new QName("", "name");
/**
* Create a new ObjectFactory that can be used to create new instances of schema derived classes for package: generated
*
*/
public ObjectFactory() {
}
/**
* Create an instance of {@link Book }
*
*/
public Book createBook() {
return new Book();
}
/**
* Create an instance of {@link Books }
*
*/
public Books createBooks() {
return new Books();
}
/**
* Create an instance of {@link JAXBElement }{@code <}{@link String }{@code >}}
*
*/
@XmlElementDecl(namespace = "", name = "author")
@XmlJavaTypeAdapter(CollapsedStringAdapter.class)
public JAXBElement<String> createAuthor(String value) {
return new JAXBElement<String>(_Author_QNAME, String.class, null, value);
}
/**
* Create an instance of {@link JAXBElement }{@code <}{@link String }{@code >}}
*
*/
@XmlElementDecl(namespace = "", name = "price")
@XmlJavaTypeAdapter(CollapsedStringAdapter.class)
public JAXBElement<String> createPrice(String value) {
return new JAXBElement<String>(_Price_QNAME, String.class, null, value);
}
/**
* Create an instance of {@link JAXBElement }{@code <}{@link String }{@code >}}
*
*/
@XmlElementDecl(namespace = "", name = "name")
@XmlJavaTypeAdapter(CollapsedStringAdapter.class)
public JAXBElement<String> createName(String value) {
return new JAXBElement<String>(_Name_QNAME, String.class, null, value);
}
}
下面我们就可以开始来写代码了
package generated;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;
import javax.xml.bind.JAXB;
public class Test {
public static void main(String[] args) throws FileNotFoundException {
marshal(new FileOutputStream("out.xml"));
unmarshal(new FileReader("out.xml"));
}
private static void unmarshal(FileReader reader) {
try {
Books books = JAXB.unmarshal(reader, Books.class);
System.out.println(books.getBook().size());
System.out.println(books.getBook().get(0).getName());
System.out.println(books.getBook().get(0).getAuthor());
System.out.println(books.getBook().get(0).getPrice());
} finally {
try {
reader.close();
} catch (IOException e) {
}
}
}
private static void marshal(OutputStream output) {
ObjectFactory factory = new ObjectFactory();
Books books = factory.createBooks();
List<Book> bookList = books.getBook();
Book book = factory.createBook();
book.setName("书名A");
book.setAuthor("作者A");
book.setPrice("价格A");
bookList.add(book);
book = factory.createBook();
book.setName("书名B");
book.setAuthor("作者B");
book.setPrice("价格B");
bookList.add(book);
book = factory.createBook();
book.setName("书名C");
book.setAuthor("作者C");
book.setPrice("价格C");
bookList.add(book);
try {
JAXB.marshal(books, output);
} finally {
try {
output.close();
} catch (IOException e) {
}
}
}
}