jaxb的優點和用法

一、jaxb是什麼

    JAXB是Java Architecture for XML Binding的縮寫。可以將一個Java對象轉變成為XML格式，反之亦然。
    我們把對象與關聯式資料庫之間的映射稱為ORM，其實也可以把對象與XML之間的映射稱為OXM(Object XML Mapping)。原來JAXB是Java EE的一部分，在JDK1.6中，SUN將其放到了Java SE中，這也是SUN的一貫做法。JDK1.6中內建的這個JAXB版本是2.0，比起1.0(JSR 31)來，JAXB2(JSR 222)用JDK5的新特性Annotation來標識要作綁定的類和屬性等，這就極大簡化了開發的工作量。

    二、jaxb應用模式
    在JAVA EE 5\6中，jaxb可以很方便的與jax-rs、jax-ws整合，極大的簡化了web service介面的開發工作量。
    三、jaxb代碼舉例
第一步：需要引入javax.xml.bind.jar

第二步：編寫java bean;

package com.mkyong.core; import javax.xml.bind.annotation.XmlAttribute;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlRootElement; @XmlRootElementpublic class Customer { String name;int age;int id; public String getName() {return name;} @XmlElementpublic void setName(String name) {this.name = name;} public int getAge() {return age;} @XmlElementpublic void setAge(int age) {this.age = age;} public int getId() {return id;} @XmlAttributepublic void setId(int id) {this.id = id;} }

第三步：main方法把java bean轉化為xml字串

package com.mkyong.core; import java.io.File;import javax.xml.bind.JAXBContext;import javax.xml.bind.JAXBException;import javax.xml.bind.Marshaller; public class JAXBExample {public static void main(String[] args) {   Customer customer = new Customer();  customer.setId(100);  customer.setName("mkyong");  customer.setAge(29);   try { File file = new File("C:\\file.xml");JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);Marshaller jaxbMarshaller = jaxbContext.createMarshaller(); // output pretty printedjaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); jaxbMarshaller.marshal(customer, file);jaxbMarshaller.marshal(customer, System.out);       } catch (JAXBException e) {e.printStackTrace();      } }}

下面是輸出：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><customer id="100">    <age>29</age>    <name>mkyong</name></customer>

四、jaxb開發常用
    jdk提供了xjc工具可以使xsd自動產生相應的java bean，這大大提高了開發的效率。同時，我們也可以使用trang.jar把xml輕鬆轉化為xsd。下面是使用的舉例。

    第一步：把資料庫表映射為xml

<?xml version="1.0" encoding="UTF-8"?><User u_id="1" u_name="moto" u_email="aaa@XXX.com" u_mood="今天放假了" u_state="online" u_mobile="12345678901" u_hometown="山西" u_job="IT軟體工程師" u_avatar="w34353453543r53" />

第二步：使用trang.jar轉化為xsd檔案。在命令列執行： 

java -jar D:\lib\trang.jar user.xml user.xsd

下面，是產生的User.java。

//// This file was generated by the JavaTM Architecture for XML Binding(JAXB) Reference Implementation, vJAXB 2.1.10 in JDK 6 // See <a href="http://java.sun.com/xml/jaxb">http://java.sun.com/xml/jaxb</a> // Any modifications to this file will be lost upon recompilation of the source schema. // Generated on: 2011.11.13 at 01:26:07 ���� CST //package com.moto.server.bean;import java.math.BigInteger;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlAttribute;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"> *       <attribute name="u_avatar" use="required" type="{http://www.w3.org/2001/XMLSchema}NCName" /> *       <attribute name="u_email" use="required" type="{http://www.w3.org/2001/XMLSchema}anySimpleType" /> *       <attribute name="u_hometown" use="required" type="{http://www.w3.org/2001/XMLSchema}NCName" /> *       <attribute name="u_id" use="required" type="{http://www.w3.org/2001/XMLSchema}integer" /> *       <attribute name="u_job" use="required" type="{http://www.w3.org/2001/XMLSchema}NCName" /> *       <attribute name="u_mobile" use="required" type="{http://www.w3.org/2001/XMLSchema}integer" /> *       <attribute name="u_mood" use="required" type="{http://www.w3.org/2001/XMLSchema}NCName" /> *       <attribute name="u_name" use="required" type="{http://www.w3.org/2001/XMLSchema}NCName" /> *       <attribute name="u_state" use="required" type="{http://www.w3.org/2001/XMLSchema}NCName" /> *     </restriction> *   </complexContent> * </complexType> * </pre> *  *  */@XmlAccessorType(XmlAccessType.FIELD)@XmlType(name = "")@XmlRootElement(name = "User")public class User {    @XmlAttribute(name = "u_avatar", required = true)    @XmlJavaTypeAdapter(CollapsedStringAdapter.class)    @XmlSchemaType(name = "NCName")    protected String uAvatar;    @XmlAttribute(name = "u_email", required = true)    @XmlSchemaType(name = "anySimpleType")    protected String uEmail;    @XmlAttribute(name = "u_hometown", required = true)    @XmlJavaTypeAdapter(CollapsedStringAdapter.class)    @XmlSchemaType(name = "NCName")    protected String uHometown;    @XmlAttribute(name = "u_id", required = true)    protected BigInteger uId;    @XmlAttribute(name = "u_job", required = true)    @XmlJavaTypeAdapter(CollapsedStringAdapter.class)    @XmlSchemaType(name = "NCName")    protected String uJob;    @XmlAttribute(name = "u_mobile", required = true)    protected BigInteger uMobile;    @XmlAttribute(name = "u_mood", required = true)    @XmlJavaTypeAdapter(CollapsedStringAdapter.class)    @XmlSchemaType(name = "NCName")    protected String uMood;    @XmlAttribute(name = "u_name", required = true)    @XmlJavaTypeAdapter(CollapsedStringAdapter.class)    @XmlSchemaType(name = "NCName")    protected String uName;    @XmlAttribute(name = "u_state", required = true)    @XmlJavaTypeAdapter(CollapsedStringAdapter.class)    @XmlSchemaType(name = "NCName")    protected String uState;    /**     * Gets the value of the uAvatar property.     *      * @return     *     possible object is     *     {@link String }     *          */    public String getUAvatar() {        return uAvatar;    }    /**     * Sets the value of the uAvatar property.     *      * @param value     *     allowed object is     *     {@link String }     *          */    public void setUAvatar(String value) {        this.uAvatar = value;    }    /**     * Gets the value of the uEmail property.     *      * @return     *     possible object is     *     {@link String }     *          */    public String getUEmail() {        return uEmail;    }    /**     * Sets the value of the uEmail property.     *      * @param value     *     allowed object is     *     {@link String }     *          */    public void setUEmail(String value) {        this.uEmail = value;    }    /**     * Gets the value of the uHometown property.     *      * @return     *     possible object is     *     {@link String }     *          */    public String getUHometown() {        return uHometown;    }    /**     * Sets the value of the uHometown property.     *      * @param value     *     allowed object is     *     {@link String }     *          */    public void setUHometown(String value) {        this.uHometown = value;    }    /**     * Gets the value of the uId property.     *      * @return     *     possible object is     *     {@link BigInteger }     *          */    public BigInteger getUId() {        return uId;    }    /**     * Sets the value of the uId property.     *      * @param value     *     allowed object is     *     {@link BigInteger }     *          */    public void setUId(BigInteger value) {        this.uId = value;    }    /**     * Gets the value of the uJob property.     *      * @return     *     possible object is     *     {@link String }     *          */    public String getUJob() {        return uJob;    }    /**     * Sets the value of the uJob property.     *      * @param value     *     allowed object is     *     {@link String }     *          */    public void setUJob(String value) {        this.uJob = value;    }    /**     * Gets the value of the uMobile property.     *      * @return     *     possible object is     *     {@link BigInteger }     *          */    public BigInteger getUMobile() {        return uMobile;    }    /**     * Sets the value of the uMobile property.     *      * @param value     *     allowed object is     *     {@link BigInteger }     *          */    public void setUMobile(BigInteger value) {        this.uMobile = value;    }    /**     * Gets the value of the uMood property.     *      * @return     *     possible object is     *     {@link String }     *          */    public String getUMood() {        return uMood;    }    /**     * Sets the value of the uMood property.     *      * @param value     *     allowed object is     *     {@link String }     *          */    public void setUMood(String value) {        this.uMood = value;    }    /**     * Gets the value of the uName property.     *      * @return     *     possible object is     *     {@link String }     *          */    public String getUName() {        return uName;    }    /**     * Sets the value of the uName property.     *      * @param value     *     allowed object is     *     {@link String }     *          */    public void setUName(String value) {        this.uName = value;    }    /**     * Gets the value of the uState property.     *      * @return     *     possible object is     *     {@link String }     *          */    public String getUState() {        return uState;    }    /**     * Sets the value of the uState property.     *      * @param value     *     allowed object is     *     {@link String }     *          */    public void setUState(String value) {        this.uState = value;    }}