java--- xml和对象之间的互相转换

清疚 2024-03-25 15:14 108阅读 0赞

##    **例子是把xml映射成bean成对象** ##

<?xml version="1.0" encoding="UTF-8"?>
    <c c1="0">
        <d d1="101280101" d2="重庆" d3="nanping" d4="南坪"/>
        <d d1="101280102" d2="重庆" d3="yubei" d4="渝北"/>
        <d d1="101280103" d2="重庆" d3="dadukou" d4="大渡口"/>
    </c>

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<City> 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 {
    
        /**
         * JAXB将XML转为指定的POJO
         *
         * @param clazz
         * @param xml
         * @return
         */
        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;
        }
    
        /**
         * XStream将XML转为指定的POJO
         *
         * @param clazz
         * @param xml
         * @return
         */
        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;
    
    
    @RestController
    public 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

<dependency>
                <groupId>com.thoughtworks.xstream</groupId>
                <artifactId>xstream</artifactId>
                <version>1.4.11.1</version>
            </dependency>

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;
    
    /**
     * @Description: 将Java对象序列化成XML格式，将XML反序列化还原为Java对象
     */
    public class xmlUtil extends XStream {
    
    
        /**
         * 将Java对象序列化成XML格式
         *
         * @param vo
         * @return
         * @throws IOException
         */
        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;
        }
    
        /**
         * 将XML反序列化还原为Java对象
         *
         * @param personXml
         * @return
         */
        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;
        }
    
        /**
         * 将XML反序列化还原为Java对象
         * java对象类型可配置
         *
         * @param xmlStr
         * @return
         */
        public static <T> T xmlToBean(String xmlStr, Class<T> 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;
        }
    
        /**
         * 生成Xml文件，可以写入指定路径
         *
         * @param xmlSource
         * @throws SAXException
         * @throws ParserConfigurationException
         * @throws IOException
         * @throws TransformerException
         */
        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**