@xmlAttribute等註解它的用處？

 用的是jdk自帶的javax.xml.bind.JAXBContext將對象和xml字符串進行相互轉換。

       如果對要生成的 xml 格式有點些許的限制，就會對生成xml的對象就需要進行些許控制，控制對象的一個最可行的辦法就是用註解。

       （jdk 1.6 api：http://www.cs.uic.edu/~mcpc/Java_Docs/api/index.html?javax/xml/bind/JAXBContext.html）

 

       比較常用的幾個：

       @XmlRootElement：根節點

       @XmlAttribute：該屬性作爲xml的attribute

       @XmlElement：該屬性作爲xml的element，且可以增加屬性(name="NewElementName")，那麼生成的xml串的elment的標籤是NewElementName

        示例：    

       

package test;

import java.io.StringWriter;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;

import test.bean.EleClassA;
import test.bean.EleClassB;
import test.bean.RootClass;

public class Test1 {

    public static void main(String[] args) {
        RootClass rc = new RootClass();
        EleClassA a = new EleClassA();
        EleClassB b = new EleClassB();

        a.setAttrC("attrc");
        a.setEleA("eleA");
        a.setEleB("eleB");

        b.setAttrPassword("attrPassword");
        b.setAttrUserName("attrUsrName");
        b.setEleCode("eleCode");

        rc.setA(a);
        rc.setB(b);
        rc.setRoot("root");
        rc.setRootA("rootA");


        JAXBContext context;
        try {
            context = JAXBContext.newInstance(RootClass.class);
            Marshaller mar = context.createMarshaller();
            mar.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            mar.setProperty(Marshaller.JAXB_ENCODING, "UTF-8");

            StringWriter writer = new StringWriter();

            mar.marshal(rc, writer);

            System.out.println(writer.toString());
        } catch (JAXBException e) {
            e.printStackTrace();
        }

    }
}


package test.bean;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement(name="rootclass")
public class RootClass {

    private EleClassA a;
    private EleClassB b;
    private String root;
    private String rootA;

    @XmlElement(name="eleClassA")
    public EleClassA getA() {
        return a;
    }
    public void setA(EleClassA a) {
        this.a = a;
    }
    @XmlElement(name="EleclassA")
    public EleClassB getB() {
        return b;
    }
    public void setB(EleClassB b) {
        this.b = b;
    }
    public String getRoot() {
        return root;
    }
    public void setRoot(String root) {
        this.root = root;
    }
    public String getRootA() {
        return rootA;
    }
    public void setRootA(String rootA) {
        this.rootA = rootA;
    }

}


package test.bean;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;

public class EleClassA {

    private String eleA;
    private String eleB;

    private String attrC;

    @XmlElement
    public String getEleA() {
        return eleA;
    }

    public void setEleA(String eleA) {
        this.eleA = eleA;
    }

    @XmlElement(name="elebnewname")
    public String getEleB() {
        return eleB;
    }

    public void setEleB(String eleB) {
        this.eleB = eleB;
    }

    @XmlAttribute()
    public String getAttrC() {
        return attrC;
    }

    public void setAttrC(String attrC) {
        this.attrC = attrC;
    }

}


package test.bean;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;

public class EleClassB {

    private String attrUserName;
    private String attrPassword;

    private String eleCode;

    @XmlAttribute
    public String getAttrUserName() {
        return attrUserName;
    }
    public void setAttrUserName(String attrUserName) {
        this.attrUserName = attrUserName;
    }
    @XmlAttribute(name="password")
    public String getAttrPassword() {
        return attrPassword;
    }
    public void setAttrPassword(String attrPassword) {
        this.attrPassword = attrPassword;
    }
    @XmlElement
    public String getEleCode() {
        return eleCode;
    }
    public void setEleCode(String eleCode) {
        this.eleCode = eleCode;
    }


}

運行Test1類中main方法，執行結果：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<rootclass>
    <eleClassA attrC="attrc">
        <eleA>eleA</eleA>
        <elebnewname>eleB</elebnewname>
    </eleClassA>
    <EleclassA attrUserName="attrUsrName" password="attrPassword">
        <eleCode>eleCode</eleCode>
    </EleclassA>
    <root>root</root>
    <rootA>rootA</rootA>
</rootclass>