Go: jaxbcontext generate XML file or Java class object conversion annotations

JAXB (Java API for XML Binding) provides a quick and easy way to convert Java objects to and from XML. In Jax-WS (One of Java's WebService specifications), JDK1.6 comes with version jax-ws2.1, with the underlying support being JAXB.

JAXB can implement the conversion of Java objects to XML, in JAXB, the process of converting a Java object to XML is called Marshal, and the process of converting XML to a Java object is called Unmarshal. We can bind a Java object to a piece of XML by annotating it in a Java class, that is, annotating the Java class with annotations that define how the class is converted to XML, how it is transformed, and how an XML is parsed into the object defined by the class. You can also use JAXB's XJC tool to define the schema to bind Java objects to XML (this next study).

Here's a look at how to complete the Marshal and unmarshal process by annotating annotations. I use it.

Jaxb2_20101209.jar, you can download the latest version from [Url]http://jaxb.java.net/[/url].


First look at a small example

Define a Java class

Java code

Package COM.WHY.JAXB;

Import javax.xml.bind.annotation.XmlRootElement;



@XmlRootElement

public class People {

Public String id = "001";

Public String name = "

Grey too Wolf

";

public int age = 26;

}



Java to XML

（

Marshal

）





Java

Code



Package COM.WHY.JAXB;



Import Javax.xml.bind.JAXBContext;

Import javax.xml.bind.JAXBException;

Import Javax.xml.bind.Marshaller;



public class Java2xml {



/**

* @param args

* @throws jaxbexception

*/

public static void Main (string[] args) throws Jaxbexception {

Jaxbcontext context = jaxbcontext.newinstance (People.class);



Marshaller Marshaller = Context.createmarshaller ();

Marshaller.setproperty (marshaller.jaxb_encoding, "gb2312");//

Encoding format



Marshaller.setproperty (Marshaller.jaxb_formatted_output, true);//

Whether to format the generated XML string



Marshaller.setproperty (Marshaller.jaxb_fragment, false);//

Whether to omit the XML header information (<?xml version= "1.0" encoding= "gb2312" standalone= "yes"?>)





People people = new people ();

Marshaller.marshal (people, System.out);

}



}



XML to Java (unmarshal)

Java code

Package COM.WHY.JAXB;



Import Java.io.File;

Import Javax.xml.bind.JAXBContext;

Import javax.xml.bind.JAXBException;

Import Javax.xml.bind.Unmarshaller;

Import org.xml.sax.SAXException;



public class Xml2java {

/**

* @param args

* @throws jaxbexception

* @throws jaxbexception

* @throws saxexception

*/

public static void Main (string[] args) throws Jaxbexception {

Jaxbcontext context = jaxbcontext.newinstance (People.class);

Unmarshaller Unmarshaller = Context.createunmarshaller ();

File File = new file ("Src/people.xml");

People people = (people) Unmarshaller.unmarshal (file);

System.out.println (people.id);

System.out.println (People.name);

System.out.println (People.age);

}

}





In fact, marshal and unmarshal process is not complicated, only need to get Marshaller or Unmarshaller object from Jaxbcontext, you can let JAXB help us to convert. The main things we need to do is to define a rule that tells Jaxb how to convert a class, to what format, to XML, and here are some of the main annotations in JAXB.


@XmlRootElement
Map a Java class to the root node of an XML

Parameters:

Name to define this root node
namespace defines this root node namespace



@XmlAccessorType

Define what types of mappings in this class need to be mapped to XML. Can receive four parameters, respectively:

Xmlaccesstype.field: Mapping All fields in this class to XML

Xmlaccesstype.property: Mapping properties in this class (Get/set method) to XML

Xmlaccesstype.public_member: Maps the field or property of all public in this class to XML at the same time (default)


Xmlaccesstype.none: Not mapped




@XmlElement



Specifies a field or Get/set method that maps to the node of the XML. For example, when a class's xmlaccessortype is labeled as a property, the annotation is annotated on a field that does not have a Get/set method, and the field can be mapped
Xml.

Parameter: DefaultValue specify node default value

Name specifies the node name

Namespace specifying a node namespace
Required whether it must (default false)

nillable Whether the field contains a nillable= "true" property (False by default)

Type

Defines the type of association for the field or property

@XmlAttribute Specify a field or Get/set method to map to the attributes of the XML.


Parameter: name Specifies the property name

Namespace specifying a property namespace

Whether the required must be (false by default)



@XmlTransient Define a field or property that does not need to be mapped to XML. For example, when a class's xmlaccessortype is labeled as a property, the annotation is annotated on the field of a Get/set method, and the attribute is not mapped.



@XmlType some related rules for defining mappings


Parameter: proporder Specifies the order of nodes when mapping XML

FACTORYCLASS Specifies the factory class required to generate the Map class instance when Unmarshal is specified, which defaults to the class itself

FactoryMethod factory methods for specifying factory classes
Name defines the names of the type in the XML Schema

Namespace specifying namespaces in the schema



@XmlElementWrapper define a parent node for an array element or collection element. For example, an element in a class is a list items, and if you do not add this annotation, the element is mapped to

<items>...</items>



<items>...</items>

This form, this annotation can be wrapped in this element, such as:



@XmlElementWrapper (name= "items")

@XmlElement (name= "item")

public List items;

Such an XML style will be generated:

<items>

<item>...</item>

<item>...</item>

</items>

@XmlJavaTypeAdapter
Customize a field or attribute to map to a

The adapter for the XML. For example, if a class contains an interface, we can define an adapter (inherited from the Javax.xml.bind.annotation.adapters.XmlAdapter Class) to specify how the interface maps to XML.









@XmlSchema

To configure the namespace of the entire package, this annotation needs to be placed in the Package-info.java file.



Jaxb

Coding:



Jaxbcontext Jaxbcontext = jaxbcontext.newinstance (clazz);

Unmarshaller Unmarshaller = Jaxbcontext.createunmarshaller ();

InputStreamReader
Reader=new

InputStreamReader (InputStream, "GBK");

//

Modify the encoding here

return Unmarshaller.unmarshal (reader);

Go: jaxbcontext generate XML file or Java class object conversion annotations