java--- xml和对象之间的互相转换

2023-08-31 18:17

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例子是把xml映射成bean成对象

第一种方法是使用 JAXB（Java Architecture for XML Binding) 实现XML与Bean的相互转换

简介

JAXB是一个业界的标准，是一项可以根据XML Schema产生Java类的技术。该过程中，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。我们不需要下载第三方jar包即可做到轻松转换。Jaxb2使用了JDK的新特性，如：Annotation、GenericType等，需要在即将转换的JavaBean中添加annotation注解。

重要的使用有:

JAXBContext类，是应用的入口，用于管理XML/Java绑定信息。
Marshaller接口，将Java对象序列化为XML数据。
Unmarshaller接口，将XML数据反序列化为Java对象。
@XmlType，将Java类或枚举类型映射到XML模式类型
@XmlAccessorType(XmlAccessType.FIELD) ，控制字段或属性的序列化。FIELD表示JAXB将自动绑定Java类中的每个非静态的（static）、非瞬态的（由@XmlTransient标注）字段到XML。其他值还有XmlAccessType.PROPERTY和XmlAccessType.NONE。
@XmlAccessorOrder，控制JAXB 绑定类中属性和字段的排序。
@XmlJavaTypeAdapter，使用定制的适配器（即扩展抽象类XmlAdapter并覆盖marshal()和unmarshal()方法），以序列化Java类为XML。
@XmlElementWrapper ，对于数组或集合（即包含多个元素的成员变量），生成一个包装该数组或集合的XML元素（称为包装器）。
@XmlRootElement，将Java类或枚举类型映射到XML元素。
@XmlElement，将Java类的一个属性映射到与属性同名的一个XML元素。
@XmlAttribute，将Java类的一个属性映射到与属性同名的一个XML属性。

city的bean

import lombok.Data;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlAttribute;import javax.xml.bind.annotation.XmlRootElement;@Data//根元素@XmlRootElement(name = "d")//访问类型，通过字段@XmlAccessorType(XmlAccessType.FIELD)public class City {    @XmlAttribute(name = "d1")    private String cityId;    @XmlAttribute(name = "d2")    private String cityName;    @XmlAttribute(name = "d3")    private String cityCode;    @XmlAttribute(name = "d4")    private String area;}

CityList的bean

import lombok.Data;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 java.util.List;@Data@XmlRootElement(name = "c")@XmlAccessorType(XmlAccessType.FIELD)public class CityList {    @XmlElement(name = "d")    private List cityList;}

需要指定bean中的属性和xml的属性一一对应

需要有个工具类XmlBuilder，主要是将XML转为指定的对象里面只需要一个方法

import com.thoughtworks.xstream.XStream;import javax.xml.bind.JAXBContext;import javax.xml.bind.Unmarshaller;import java.io.Reader;import java.io.StringReader;public class XmlBuilder {        public static Object JAXB_XmlToBean(Class clazz, String xml) {        try {            Object xmlObject;            Reader reader;            JAXBContext context = JAXBContext.newInstance(clazz);            // XML 转为对象的接口            Unmarshaller unmarshaller = context.createUnmarshaller();            reader = new StringReader(xml);            //以文件流的方式传入这个string            xmlObject = unmarshaller.unmarshal(reader);            reader.close();            return xmlObject;        } catch (Exception e) {            e.printStackTrace();        }        return null;    }        public static Object XStream_ToBean(Class clazz, String xml) {        Object xmlObject;        XStream xstream = new XStream();        xstream.processAnnotations(clazz);        xstream.autodetectAnnotations(true);        xmlObject = xstream.fromXML(xml);        return xmlObject;    }}

controller

import com.zoo.weixin.test.api.xstream.CityList;import com.zoo.weixin.test.api.xstream.XmlBuilder;import lombok.Cleanup;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import javax.servlet.ServletInputStream;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.nio.charset.StandardCharsets;@RestControllerpublic class XStreamController {    @RequestMapping("JAXB")    public CityList XStream(HttpServletRequest request, HttpServletResponse response) {        StringBuilder xml = new StringBuilder();        try {            @Cleanup ServletInputStream in = request.getInputStream();            // 将流转换为字符串            byte[] b = new byte[4096];            for (int n; (n = in.read(b)) != -1; ) {                xml.append(new String(b, 0, n, StandardCharsets.UTF_8));            }            // XML转为Java对象            CityList cityList = (CityList) XmlBuilder.JAXB_XmlToBean(CityList.class, xml.toString());            return cityList;        } catch (Exception e) {            e.printStackTrace();        }        return null;    }}

第二种方法是使用XStream

利用XStream在Java对象和XML之间相互转换
简介
Xstream是一种OXMapping 技术，是用来处理XML文件序列化的框架,在将JavaBean序列化，或将XML文件反序列化的时候，不需要其它辅助类和映射文件，使得XML序列化不再繁索。Xstream也可以将JavaBean序列化成Json或反序列化，使用非常方便。
主要使用
@XStreamAlias(“alis”)java对象在xml中以标签的形式显示时，如果名字与类名或者属性名不一致，可以使用该标签并在括号内注明别名。
@XStreamOmitField在输出XML的时候忽略该属性
@XStreamImplicit如果该属性是一个列表或者数组，在XML中不显示list或者Array字样
@XStreamAsAttribute该属性不单独显示成XML节点，而是作为属性显示出来
@XStreamContainedType
@XStreamConverter设置转换器
@XStreamConverters converter主要用于将某些字段进行复杂的转换，转换过程写在一个类中。
然后将其注册到XStream。

首先导入jar包

                            com.thoughtworks.xstream            xstream            1.4.11.1

最外层bean

package com.guoyao.emergency.vo;import com.thoughtworks.xstream.annotations.XStreamAlias;import lombok.Data;import java.io.Serializable;@Data@XStreamAlias("InterFaceFile")public class xmlVo implements Serializable {    private static final long serialVersionUID = 1L;    @XStreamAlias("employee")    Employee employee;    @XStreamAlias("user")    User user;}

两个内层bean

package com.guoyao.emergency.vo;import com.guoyao.emergency.common.MessageType;import com.thoughtworks.xstream.annotations.XStreamAlias;import lombok.Data;import org.springframework.beans.factory.annotation.Autowired;import java.io.Serializable;@Data@XStreamAlias("employee")public class Employee implements Serializable {    private static final long serialVersionUID = 1L;    @XStreamAlias("employeeId")    private int employeeId;    @XStreamAlias("employeeName")    private String employeeName;    @XStreamAlias("department")    private String department;    public Employee() {    }    public String getDepartment() {        return department;    }    public void setDepartment(String department) {        this.department = department;    }    public int getEmployeeId() {        return employeeId;    }    public void setEmployeeId(int employeeId) {        this.employeeId = employeeId;    }    public String getEmployeeName() {        return employeeName;    }    public void setEmployeeName(String employeeName) {        this.employeeName = employeeName;    }    public Employee(int employeeId, String employeeName, String department) {        this.employeeId = employeeId;        this.employeeName = employeeName;        this.department = department;    }}

package com.guoyao.emergency.vo;import com.thoughtworks.xstream.annotations.XStreamAlias;import lombok.Data;@Data@XStreamAlias("user")public class User {    @XStreamAlias("username")    private String username;    @XStreamAlias("password")    private String password;    @XStreamAlias("number")    private int number;    public User(String username, String password, int number) {        this.username = username;        this.password = password;        this.number = number;    }    public User() {        this.username = username;        this.password = password;    }}

工具类及使用方法

package com.guoyao.emergency.util;import com.guoyao.emergency.common.IBasicXml;import com.guoyao.emergency.vo.Employee;import com.guoyao.emergency.vo.User;import com.guoyao.emergency.vo.xmlVo;import com.thoughtworks.xstream.XStream;import com.thoughtworks.xstream.io.xml.DomDriver;import org.springframework.beans.factory.annotation.Value;import org.w3c.dom.Document;import org.xml.sax.InputSource;import org.xml.sax.SAXException;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.ParserConfigurationException;import javax.xml.transform.Transformer;import javax.xml.transform.TransformerException;import javax.xml.transform.TransformerFactory;import javax.xml.transform.dom.DOMSource;import javax.xml.transform.stream.StreamResult;import java.io.File;import java.io.IOException;import java.io.StringReader;public class xmlUtil extends XStream {        public static String serialize(xmlVo vo) {        // 将employee对象序列化为XML        XStream xStream = new XStream(new DomDriver());        // 设置employee类的别名        xStream.alias("InterFaceFile", xmlVo.class);        String personXml = xStream.toXML(vo);        return personXml;    }        public xmlVo deserialize(String personXml) {        // 将employee对象序列化为XML        XStream xstream = new XStream(new DomDriver());        XStream.setupDefaultSecurity(this); // to be removed after 1.5        xstream.allowTypesByWildcard(new String[]{                "com.xttblog.package.**"        });        xmlVo employee = (xmlVo) xstream.fromXML(personXml);        return employee;    }        public static  T xmlToBean(String xmlStr, Class cls) {        XStream xstream = new XStream();        //不使用默认的类加载器，需要手动设置类加载器        xstream.setClassLoader(cls.getClassLoader());        xstream.processAnnotations(cls);        xstream.allowTypesByRegExp(new String[]{".*"});        Object obj = xstream.fromXML(xmlStr);        return (T) obj;    }        public static void stringToDom(String xmlSource)            throws SAXException, ParserConfigurationException, IOException, TransformerException {        // Parse the given input        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();        DocumentBuilder builder = factory.newDocumentBuilder();        Document doc = builder.parse(new InputSource(new StringReader(xmlSource)));        // Write the parsed document to an xml file        TransformerFactory transformerFactory = TransformerFactory.newInstance();        Transformer transformer = transformerFactory.newTransformer();        DOMSource source = new DOMSource(doc);        System.out.println(source);        StreamResult result = new StreamResult(new File("my-file.xml"));        transformer.transform(source, result);    }    public static void main(String[] args) throws IOException, ParserConfigurationException, TransformerException, SAXException {        xmlVo vo = new xmlVo();        Employee employee = new Employee();        employee.setEmployeeId(1);        employee.setEmployeeName("赵新国1111");        employee.setDepartment("软件工程师");        User user = new User();        user.setUsername("zhangsan");        user.setPassword("10");        vo.setEmployee(employee);        vo.setUser(user);        // 序列化        String serialize = serialize(vo);        System.out.println(serialize);//        stringToDom(serialize);        // 反序列化        xmlVo xmlVo = xmlToBean(serialize, xmlVo.class);        System.out.println(xmlVo.toString());        User user1 = xmlVo.getUser();        System.out.println(user1.getUsername());//        xmlUtil util = new xmlUtil();//        xmlVo deserialize = util.deserialize(serialize);//        System.out.println(deserialize.toString());//        User user1 = deserialize.getUser();//        System.out.println(user1.getUsername());    }}

重命名注解：@XStreamAlias()

这些命名都需要和解析的xml的属性名一一对应，一旦不对应就会报com.thoughtworks.xstream.mapper.CannotResolveClassException异常，找不到对应的类属性
集合属性的需要使用：@XStreamImplicit,不然会报com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter$DuplicateFieldException转换器映射异常

省略集合根节点：@XStreamImplicit
把字段节点设置成属性：@XStreamAsAttribute

拓展了解

XStream提供了很多方法供我们使用
autodetectAnnotations()自动检测注解
processAnnotations()应用传过来的类的注解
fromXML()XML反序列化(JSON也是一样)
toXML()XML序列化(JSON也是一样)
自定义解析器
Xstream序列化XML，解析器用StaxDriver
指定解析器：XStream xstream = new XStream(new StaxDriver());
Xstream序列化Json，解析器用JettisonMappedXmlDriver
指定解析器：XStream xstream = new XStream(new JettisonMappedXmlDriver());
也可以不具体指定解析器，也是没问题的

深入了解

XStreamxstream = new XStream();
默认情况下，XStream会采用Xpp3库，XPP3是一种运行效率非常高的XML全解析实现。如果你不想依靠Xpp3库的话，也可以使用一个标准的JAXP DOM解析器，可以采用以下语句进行初始化：
//不使用XPP3库
XStreamxstream = new XStream(new DomDriver());
此xstream实例，为线程安全的，可以供多个线程进行调用，共享使用。系统提供了多种标识解析器供我们选择，包括，DomDriver、 JDomDriver、StaxDriver等等。

Xstream提供了对Json的支持，是因为Xstream内置了两个Driver：
1.JsonHierarchicalStreamDriver：不依赖其他类库，只实现 obj->JSON
2.JettisonMappedXmlDriver：依赖jettison类库，实现 JSON->obj or obj->JSON
两种Driver在处理相同设置的Object时会得到不同的JSON串，JsonHierarchicalStreamDriver得到的串更简洁，确如官网所说。
JsonHierarchicalStreamDriver有个小问题——默认输出带格式的JSON串，结构中带空举