2、JAXB 实现java对象与xml之间互相转换

逃离我推掉我的手 2022-03-08 15:54 681阅读 0赞

## 1 JAXB实现对象与xml互转时常用的一些注解： ##

1.  @XmlRootElement，用于类级别的注解，对应xml的跟元素。通过name属性定义这个根节点的名称。
2.  @XmlAccessorType，定义映射这个类中的何种类型都需要映射到xml。(如果不存在@XmlAccessorType,默认使用XmlAccessType.PUBLIC\_MEMBER注解)
    
    参数：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。
3.  @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。
4.  @XmlElement，指定一个字段或get/set方法映射到xml的节点。通过name属性定义这个根节点的名称。
5.  @XmlElementWrapper，为数组或集合定义一个父节点。通过name属性定义这个父节点的名称。

## 2 maven引入 jaxb-api.x.x 的依赖 ##

<dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.0</version>
    </dependency>

## 3 例子如下 ##

### 3.1 user和company实体类 ###

import java.io.Serializable;
    
    import javax.xml.bind.annotation.XmlAttribute;
    import javax.xml.bind.annotation.XmlElement;
    import javax.xml.bind.annotation.XmlRootElement;
    
    @XmlRootElement(name="user")
    public class User implements Serializable{ 
    
    	private static final long serialVersionUID = 1L;
    	private int id;
    	private String username;
    	private String password;
    	
    	@XmlAttribute(name="id")
    	public int getId() { 
    		return id;
    	}
    	public void setId(int id) { 
    		this.id = id;
    	}
    	@XmlElement(name="username")
    	public String getUsername() { 
    		return username;
    	}
    	public void setUsername(String username) { 
    		this.username = username;
    	}
    	@XmlElement(name="password")
    	public String getPassword() { 
    		return password;
    	}
    	public void setPassword(String password) { 
    		this.password = password;
    	}
    	@Override
    	public String toString() { 
    		return "User [id=" + id + ", username=" + username + ", password=" + password + "]";
    	}
    
    }
    // ----------------------分割线------------------------------
    import java.io.Serializable;
    import java.util.ArrayList;
    import java.util.List;
    
    import javax.xml.bind.annotation.XmlAttribute;
    import javax.xml.bind.annotation.XmlElement;
    import javax.xml.bind.annotation.XmlElementWrapper;
    import javax.xml.bind.annotation.XmlRootElement;
    
    @XmlRootElement(name="company")
    public class Company implements Serializable{ 
    	private static final long serialVersionUID = 1L;
    	private List<User> uList = new ArrayList<>();
    	private int cid;
    	private String companyName;
    	
    	@XmlAttribute(name="cid")
    	public int getCid() { 
    		return cid;
    	}
    	public void setCid(int cid) { 
    		this.cid = cid;
    	}
    	@XmlElement(name="companyName")
    	public String getCompanyName() { 
    		return companyName;
    	}
    	public void setCompanyName(String companyName) { 
    		this.companyName = companyName;
    	}
    	@XmlElementWrapper(name="uList")
    	@XmlElement(name="user")
    	public List<User> getuList() { 
    		return uList;
    	}
    	public void setuList(List<User> uList) { 
    		this.uList = uList;
    	}
    	@Override
    	public String toString() { 
    		return "Company [uList=" + uList + ", cid=" + cid + ", companyName=" + companyName + "]";
    	}
    }

### 3.2 jaxbutil 工具类 ###

import java.io.File;
    import java.io.IOException;
    import java.io.StringReader;
    import java.io.StringWriter;
    import java.util.Collection;
    
    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.sun.xml.internal.ws.util.StringUtils;
    
    public class JaxbUtil {   
        // 多线程安全的Context. 
        private JAXBContext jaxbContext;  
        
        
        /** * @param types 所有需要序列化的Root对象的类型. */  
        public JaxbUtil(Class<?>... types) {   
            try {   
                jaxbContext = JAXBContext.newInstance(types);  
            } catch (JAXBException e) {   
                throw new RuntimeException(e);  
            }  
        }  
        
        /** * xml文件配置转换为对象 * @param xmlPath xml文件路径 * @param load java对象.Class * @return java对象 * @throws JAXBException * @throws IOException */
        public Object xmlToBean(String xmlPath,Class<?> clazz) throws JAXBException, IOException{ 
            Unmarshaller unmarshaller = jaxbContext.createUnmarshaller(); 
            Object object = unmarshaller.unmarshal(new File(xmlPath));
            return object;
        }
      
        
      
        /** * Java Object->Xml. */  
        public String toXml(Object root, String encoding) {   
            try {   
                StringWriter writer = new StringWriter();  
                createMarshaller(encoding).marshal(root, writer);  
                return writer.toString();  
            } catch (JAXBException e) {   
                throw new RuntimeException(e);  
            }  
        }  
      
        /** * Java Object->Xml, 特别支持对Root Element是Collection的情形. */  
        public String toXml(Collection root, String rootName, 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(encoding).marshal(wrapperElement, writer);  
      
                return writer.toString();  
            } catch (JAXBException e) {   
                throw new RuntimeException(e);  
            }  
        }  
      
        /** * Xml->Java Object. */  
        @SuppressWarnings("unchecked")  
        public <T> T fromXml(String xml) {   
            try {   
                StringReader reader = new StringReader(xml);  
                return (T) createUnmarshaller().unmarshal(reader);  
            } catch (JAXBException e) {   
                throw new RuntimeException(e);  
            }  
        }  
      
        /** * Xml->Java Object, 支持大小写敏感或不敏感. */  
        @SuppressWarnings("unchecked")  
        public <T> T fromXml(String xml, boolean caseSensitive) {   
            try {   
                String fromXml = xml;  
                if (!caseSensitive)  
                    fromXml = xml.toLowerCase();  
                StringReader reader = new StringReader(fromXml);  
                return (T) createUnmarshaller().unmarshal(reader);  
            } catch (JAXBException e) {   
                throw new RuntimeException(e);  
            }  
        }  
      
        /** * 创建Marshaller, 设定encoding(可为Null). */  
        public Marshaller createMarshaller(String encoding) {   
            try {   
                Marshaller marshaller = jaxbContext.createMarshaller();  
      
                marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);  
      
                if(null != encoding && !"".equals(encoding)){ 
    // if (StringUtils.(encoding)) { 
                    marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);  
                }  
                return marshaller;  
            } catch (JAXBException e) {   
                throw new RuntimeException(e);  
            }  
        }  
      
        /** * 创建UnMarshaller. */  
        public Unmarshaller createUnmarshaller() {   
            try {   
                return jaxbContext.createUnmarshaller();  
            } catch (JAXBException e) {   
                throw new RuntimeException(e);  
            }  
        }  
      
        /** * 封装Root Element 是 Collection的情况. */  
        public static class CollectionWrapper {   
            @XmlAnyElement  
            protected Collection collection;  
        }  
    }

### 测试 ###

public class UserTest { 
    
    	
    	public static void main(String[] args) throws JAXBException, IOException { 
    		
    	    
    	    List<User> userList = new ArrayList<>();
    	    for (int i=0;i<5;i++) { 
    	        User user = new User();
    	        user.setId(1);
    	        user.setUsername("卡子锅锅"+1);
    	        user.setPassword("123"+1);
    	        userList.add(user);
    	    }
    		
    		Company cm = new Company();
    		cm.setCid(1);
    		cm.setCompanyName("还是威");
    		cm.setuList(userList);
    		
    		//将java对象转换为XML字符串 
            JaxbUtil requestBinder = new JaxbUtil(Company.class,  
                    CollectionWrapper.class);
    		
    		
            String retXml = requestBinder.toXml(cm, "utf-8");  
            System.out.println("xml:"+retXml);  
            
            //写入到xml文件中
            String xmlPath = "C:\\Users\\liping\\Desktop\\na\\userlist2.xml";
            BufferedWriter bfw = new BufferedWriter(new FileWriter(new File(xmlPath)));
            bfw.write(retXml);
            bfw.close();
            
            
            
            
            System.out.println("+++++++++++++++++++++++++++++");  
            //将xml字符串转换为java对象 
            JaxbUtil resultBinder = new JaxbUtil(Company.class,  
                    CollectionWrapper.class);  
            Company hotelObj = resultBinder.fromXml(retXml);
            System.out.println("hotelObj:"+hotelObj);  
            
            Object object = resultBinder.xmlToBean("C:\\Users\\liping\\Desktop\\na\\userlist.xml",Company.class);
            Company company = (Company)object;
            List<User> studentList = company.getuList();
    
            System.out.println("-------company>:"+company);
            System.out.println("-------studentList>:"+studentList);
            
    	}
    }