Java对象和XML的相互转换化

转载链接：Java对象和XML的相互转换化

重点：Jaxb是JavaEE的规范.全称Java Architecture for XML Binding. 可以根据XML Schema产生Java类的技术.JAXB也提供了将XML实例文档反向生成Java对象树的方法，并能将Java对象树的内容重新写到XML实例文档. JAXB 2.0是JDK 1.6的组成部分。JAXB 2.2.3是JDK 1.7的组成部分，在实际使用不需要引入新的jar.

1. 常用注解说明
常用的annotation有：
@XmlType
@XmlElement
@XmlRootElement
@XmlAttribute
@XmlAccessorType
@XmlAccessorOrder
@XmlTransient
@XmlJavaTypeAdapter
@Temporal(TemporalType.XXXX) -->JPA中的时间处理注解,非JAXB
@XmlElementWrapper

1.@XmlType
　　@XmlType用在class类的注解，常与@XmlRootElement，@XmlAccessorType一起使用。它有三个属性：name、propOrder、namespace，经常使用的只有前两个属性。如：
同时使用了@XmlType（propOrder={}）和@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)的时候，生成的xml只按照propOrder定义的顺序生成元素
@XmlType(name = "basicStruct", propOrder = {
"intValue",
"stringArray",
"stringValue"
)
在使用@XmlType的propOrder 属性时，必须列出JavaBean对象中的所有属性，否则会报错。

2.@XmlRootElement
　　@XmlRootElement用于类级别的注解，对应xml的跟元素，常与 @XmlType 和 @XmlAccessorType一起使用。如：
　　@XmlType
　　@XmlAccessorType(XmlAccessType.FIELD)
　　@XmlRootElement
　　public class Address {}

3.@XmlElement
　　@XmlElement将java对象的属性映射为xml的节点，在使用@XmlElement时，可通过name属性改变java对象属性在xml中显示的名称。如：
　　@XmlElement(name="Address")　　
　　private String yourAddress;

4.@XmlAttribute
　　@XmlAttribute用于把java对象的属性映射为xml的属性,并可通过name属性为生成的xml属性指定别名。如：
　　@XmlAttribute(name="Country")
　　private String state;

5.@XmlAccessorType
　　@XmlAccessorType用于指定由java对象生成xml文件时对java对象属性的访问方式。常与@XmlRootElement、@XmlType一起使用。它的属性值是XmlAccessType的4个枚举值，分别为:

XmlAccessType.FIELD:java对象中的所有成员变量
XmlAccessType.PROPERTY：java对象中所有通过getter/setter方式访问的成员变量
XmlAccessType.PUBLIC_MEMBER：java对象中所有的public访问权限的成员变量和通过getter/setter方式访问的成员变量
XmlAccessType.NONE:java对象的所有属性都不映射为xml的元素
注意：@XmlAccessorType的默认访问级别是XmlAccessType.PUBLIC_MEMBER，因此，如果java对象中的private成员变量设置了public权限的getter/setter方法，就不要在private变量上使用@XmlElement和@XmlAttribute注解，否则在由java对象生成xml时会报同一个属性在java类里存在两次的错误。同理，如果@XmlAccessorType的访问权限为XmlAccessType.NONE，如果在java的成员变量上使用了@XmlElement或@XmlAttribute注解，这些成员变量依然可以映射到xml文件。

注意：虽然@XmlAccessorType为XmlAccessType.NONE,但是在java类的私有属性上加了@XmlAttribute和@XmlElement注解后，这些私有成员会映射生成xml的元素

6.@XmlAccessorOrder
　　@XmlAccessorOrder用于对java对象生成的xml元素进行排序。它有两个属性值：
　　AccessorOrder.ALPHABETICAL：对生成的xml元素按字母书序排序
　　XmlAccessOrder.UNDEFINED:不排序

7.@XmlTransient
　　@XmlTransient用于标示在由java对象映射xml时，忽略此属性。即，在生成的xml文件中不出现此元素。

8.@XmlJavaTypeAdapter
　　@XmlJavaTypeAdapter常用在转换比较复杂的对象时，如map类型或者格式化日期等。使用此注解时，需要自己写一个adapter类继承XmlAdapter抽象类，并实现里面的方法。
　　@XmlJavaTypeAdapter(value=xxx.class),value为自己定义的adapter类
　　XmlAdapter 抽象接口如下：

public abstract class XmlAdapter<ValueType,BoundType> { // Do-nothing constructor for the derived classes.
    protected XmlAdapter() {}
    // Convert a value type to a bound type.
    public abstract BoundType unmarshal(ValueType v);
    // Convert a bound type to a value type.
    public abstract ValueType marshal(BoundType v);
}

下面举一个简单的例子:

1.School类 一些基本的属性，包含Student集合

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import java.util.ArrayList;
import java.util.List;

@XmlRootElement(name = "list")
public class School {
    private String name;
    private String address;
    private String level;
    private long popular;
    private List<Student> students = new ArrayList<Student>();

    @XmlElement(name = "name")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @XmlElement(name = "address")
    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    @XmlElement(name = "level")
    public String getLevel() {
        return level;
    }

    public void setLevel(String level) {
        this.level = level;
    }

    @XmlElement(name = "popular")
    public long getPopular() {
        return popular;
    }

    public void setPopular(long popular) {
        this.popular = popular;
    }

    @XmlElement(name = "Student")
    public List<Student> getStudents() {
        return students;
    }

    public void setStudents(List<Student> students) {
        this.students = students;
    }
}

 

2.Student类，包含爱好集合和一些基本的属性

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import java.util.List;

public class Student {
    String name; //姓名
    String sex; //性别
    int number; //学号
    String className; //班级
    List<String> hobby; //爱好

    public Student() {
    }

    public Student(String name, String sex, int number,
                   String className, List<String> hobby) {
        this.name = name;
        this.sex = sex;
        this.number = number;
        this.className = className;
        this.hobby = hobby;
    }

    @XmlAttribute(name = "name")
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @XmlAttribute(name = "sex")
    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @XmlAttribute(name = "number")
    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    @XmlElement(name = "className")
    public String getClassName() {
        return className;
    }

    public void setClassName(String className) {
        this.className = className;
    }

    @XmlElementWrapper(name = "hobbys")
    @XmlElement(name = "hobby")
    public List<String> getHobby() {
        return hobby;
    }

    public void setHobby(List<String> hobby) {
        this.hobby = hobby;
    }

}

 

3.工具类，提供xml到javaBean的相互转换 由 valvin大神提供，很好用(自己看其中的方法，说不定有你需要的)

import java.io.StringReader;
import java.io.StringWriter;
import java.util.Collection;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.namespace.QName;

import com.gs.mountain.common.utils.StringUtils;
import org.springframework.http.converter.HttpMessageConversionException;
import org.springframework.util.Assert;

import com.gs.mountain.common.utils.Exceptions;
import com.gs.mountain.common.utils.Reflections;

/**
 * 使用Jaxb2.0实现XML<->Java Object的Mapper.
 * <p>
 * 在创建时需要设定所有需要序列化的Root对象的Class.
 * 特别支持Root对象是Collection的情形.
 *
 * @author calvin
 * @version 2013-01-15
 */
@SuppressWarnings("rawtypes")
public class JaxbMapper {

    private static ConcurrentMap<Class, JAXBContext> jaxbContexts = new ConcurrentHashMap<Class, JAXBContext>();

    /**
     * Java Object->Xml without encoding.
     */
    public static String toXml(Object root) {
        Class clazz = Reflections.getUserClass(root);
        return toXml(root, clazz, null);
    }

    /**
     * Java Object->Xml with encoding.
     */
    public static String toXml(Object root, String encoding) {
        Class clazz = Reflections.getUserClass(root);
        return toXml(root, clazz, encoding);
    }

    /**
     * Java Object->Xml with encoding.
     */
    public static String toXml(Object root, Class clazz, String encoding) {
        try {
            StringWriter writer = new StringWriter();
            createMarshaller(clazz, encoding).marshal(root, writer);
            return writer.toString();
        } catch (JAXBException e) {
            throw Exceptions.unchecked(e);
        }
    }

    /**
     * Java Collection->Xml without encoding, 特别支持Root Element是Collection的情形.
     */
    public static String toXml(Collection<?> root, String rootName, Class clazz) {
        return toXml(root, rootName, clazz, null);
    }

    /**
     * Java Collection->Xml with encoding, 特别支持Root Element是Collection的情形.
     */
    public static String toXml(Collection<?> root, String rootName, Class clazz, String encoding) {
        try {
            CollectionWrapper wrapper = new CollectionWrapper();
            wrapper.collection = root;

            JAXBElement<CollectionWrapper> wrapperElement = new JAXBElement<CollectionWrapper>(new QName(rootName),
                    CollectionWrapper.class, wrapper);

            StringWriter writer = new StringWriter();
            createMarshaller(clazz, encoding).marshal(wrapperElement, writer);

            return writer.toString();
        } catch (JAXBException e) {
            throw Exceptions.unchecked(e);
        }
    }

    /**
     * Xml->Java Object.
     */
    @SuppressWarnings("unchecked")
    public static <T> T fromXml(String xml, Class<T> clazz) {
        try {
            StringReader reader = new StringReader(xml);
            return (T) createUnmarshaller(clazz).unmarshal(reader);
        } catch (JAXBException e) {
            throw Exceptions.unchecked(e);
        }
    }

    /**
     * 创建Marshaller并设定encoding(可为null).
     * 线程不安全，需要每次创建或pooling。
     */
    public static Marshaller createMarshaller(Class clazz, String encoding) {
        try {
            JAXBContext jaxbContext = getJaxbContext(clazz);

            Marshaller marshaller = jaxbContext.createMarshaller();

            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);

            if (StringUtils.isNotBlank(encoding)) {
                marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);
            }

            return marshaller;
        } catch (JAXBException e) {
            throw Exceptions.unchecked(e);
        }
    }

    /**
     * 创建UnMarshaller.
     * 线程不安全，需要每次创建或pooling。
     */
    public static Unmarshaller createUnmarshaller(Class clazz) {
        try {
            JAXBContext jaxbContext = getJaxbContext(clazz);
            return jaxbContext.createUnmarshaller();
        } catch (JAXBException e) {
            throw Exceptions.unchecked(e);
        }
    }

    protected static JAXBContext getJaxbContext(Class clazz) {
        Assert.notNull(clazz, "'clazz' must not be null");
        JAXBContext jaxbContext = jaxbContexts.get(clazz);
        if (jaxbContext == null) {
            try {
                jaxbContext = JAXBContext.newInstance(clazz, CollectionWrapper.class);
                jaxbContexts.putIfAbsent(clazz, jaxbContext);
            } catch (JAXBException ex) {
                throw new HttpMessageConversionException("Could not instantiate JAXBContext for class [" + clazz
                        + "]: " + ex.getMessage(), ex);
            }
        }
        return jaxbContext;
    }

    /**
     * 封装Root Element 是 Collection的情况.
     */
    public static class CollectionWrapper {

        @XmlAnyElement
        protected Collection<?> collection;
    }

}

 

4.下面是测试的代码，结果很棒，so easy!

import com.gs.mountain.common.mapper.JaxbMapper;

import javax.xml.bind.JAXBException;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class BeanToXml {

    public static void main(String[] args) throws JAXBException, IOException {
        List<String> hobby = new ArrayList();
        hobby.add("篮球");
        hobby.add("音乐");
        hobby.add("乒乓球");

        List<Student> studentList = new ArrayList();

        Student st = new Student("张三", "男", 10001, "尖子班", hobby);
        studentList.add(st);
        Student st1 = new Student("李四", "男", 10002, "普通班", hobby);
        studentList.add(st1);
        Student st2 = new Student("莉莉", "女", 10003, "普通班", hobby);
        studentList.add(st2);

        School school = new School();
        School school1;
        School school2;
        school.setAddress("成都市武侯区天府五街");
        school.setLevel("高级中学");
        school.setName("华阳中学");
        school.setPopular(5000L);
        school.setStudents(studentList);
        school1 = school;
        school2 = school;
        List<School> listSchool = new ArrayList<School>();
        listSchool.add(school);
        listSchool.add(school1);
        listSchool.add(school2);
        String str = JaxbMapper.toXml(listSchool, "schoolList", School.class);

        //写入到xml文件中
        String xmlPath = "D:/testConfig.xml";
        BufferedWriter bfw = new BufferedWriter(new FileWriter(new File(xmlPath)));
        bfw.write(str);
        bfw.close();
    }
}

 

下面是由 listSchool 转化成的 xml 文件，内容如下：

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<schoolList>
    <list>
        <address>成都市武侯区天府五街</address>
        <level>高级中学</level>
        <name>华阳中学</name>
        <popular>5000</popular>
        <Student name="张三" number="10001" sex="男">
            <className>尖子班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
        <Student name="李四" number="10002" sex="男">
            <className>普通班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
        <Student name="莉莉" number="10003" sex="女">
            <className>普通班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
    </list>
    <list>
        <address>成都市武侯区天府五街</address>
        <level>高级中学</level>
        <name>华阳中学</name>
        <popular>5000</popular>
        <Student name="张三" number="10001" sex="男">
            <className>尖子班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
        <Student name="李四" number="10002" sex="男">
            <className>普通班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
        <Student name="莉莉" number="10003" sex="女">
            <className>普通班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
    </list>
    <list>
        <address>成都市武侯区天府五街</address>
        <level>高级中学</level>
        <name>华阳中学</name>
        <popular>5000</popular>
        <Student name="张三" number="10001" sex="男">
            <className>尖子班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
        <Student name="李四" number="10002" sex="男">
            <className>普通班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
        <Student name="莉莉" number="10003" sex="女">
            <className>普通班</className>
            <hobbys>
                <hobby>篮球</hobby>
                <hobby>音乐</hobby>
                <hobby>乒乓球</hobby>
            </hobbys>
        </Student>
    </list>
</schoolList>

博主讲解的很详细，知识点罗列的很清晰，可以尝试着写写样例用到工作当中！