jaxb xml生成与解析

XML 2020-06-15 
JAXB能够使用Jackson对JAXB注解的支持实现(jackson-module-jaxb-annotations)，既方便生成XML，也方便生成JSON，这样一来可以更好的标志可以转换为JSON对象的java类。JAXB允许JAVA人员将java类映射为XML表示方式，常用的注解包括：@XmlRootElement,@XmlElement等等。
JAXB（Java Architecture for XML Binding) 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。从另一方面来讲，JAXB提供了快速而简便的方法将XML模式绑定到Java表示，从而使得Java开发者在Java应用程序中能方便地结合XML数据和处理函数。

常用属性：
@XmlType ：注解用于标注类或枚举类型，用它标注的类在映射后的 schema 中中会以一个 XML 复杂数据类型的形式出现。我们可以通过 @XmlType 注解的 name 属性来定制映射的 XML 数据类型的名称，用 propOrder 属性来定制映射后的复杂数据类型的内容顺序等

@XmlElement ： XML 子节点

@XmlRootElement：XML 根目录节点

@XmlAttribute ： XML 节点属性值

@XmlAccessorType ：JAXB指定java类中的那些属性允许被访问生成xml或注入，其属性可填
　　*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。
　　XmlAccesstype.FIELD：java对象中的所有成员变量；*

@XmlAccessorOrder ：
使用@XmlAccessorOrder 包括XmlAccessorOrder.UNDEFINED XmlAccessorOrder.ALPHABETICAL两个值，默认为UNDEFINED（无序），XmlAccessorOrder.ALPHABETICAL是指按属性的字母顺序排序。
当@XmlAccessorOrder定义在一个package之上时候（Package annotations must be in file package-info.Java），此包下的所有类都遵守@XmlAccessorOrder定义的规则；当它定义在类之上时，只有该类的内容遵守规则。
就近原则：如果出现在package之上使用@XmlAccessorOrder并且在该包下的某个类又使用了@XmlAccessorOrder，那在该类上定义的@XmlAccessorOrder规则才起作用，如在package上声明@XmlAccessorOrder(XmlAccessOrder.ALPHABETICAL)，而在某类上声明为UNDEFINED，则该类遵守的规则为UNDEFINED。
使用@XmlType.propOrder：
propOrder可以定义class中字段出现在xml中的顺序，class中所有public的字段必须列的propOrder的参数列表中，如果不想将某public字段列在列表中，可在字段上使用@XmlTransient or @XmlAttribute注解标识。
默认的内容顺序为@XmlType.propOrder is {} or {“”}（not active 可认为无序？），在这种情况下，@XmlAccessorOrder 注解具有优先权。当@XmlAccessorOrder 与@XmlType.propOrder同时出现时，propOrder总是具有优先权（最终起作用）。

@XmlTransient ：不将java中的字段作为xml来解析或生成

@XmlJavaTypeAdapter：用于一些复杂的类，比如timestamp就要用自己写的adapter来转化
@Temporal(TemporalType.XXXX) –>JPA中的时间处理注解,非JAXB
@XmlElementWrapper ：用来对xml做进一步包装

示例：
@XmlRootElement：
package com.cmh.beans;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Customer {

    private int id;

    private String name;

    private String pwd;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }


}

工具类:

/** * JavaBean转换成xml * @param obj * @param encoding * @return */  
  public static String convertToXml(Object obj,String encoding) {  
      String result = null;  
      try {  
          JAXBContext context = JAXBContext.newInstance(obj.getClass());  
          Marshaller marshaller = context.createMarshaller();  
          marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,true);  
          marshaller.setProperty(Marshaller.JAXB_ENCODING,encoding);  

          StringWriter writer = new StringWriter();  
          marshaller.marshal(obj,writer);  
          result = writer.toString();  
      } catch (Exception e) {  
          e.printstacktrace();  
      }  

      return result;  
  }

  @SuppressWarnings("unchecked")  
  public static <T> T converyToJavaBean(String xml,Class<T> c) {  
      T t = null;  
      try {  
          JAXBContext context = JAXBContext.newInstance(c);  
          Unmarshaller unmarshaller = context.createUnmarshaller();  
          t = (T) unmarshaller.unmarshal(new StringReader(xml));  
      } catch (Exception e) {  
          e.printstacktrace();  
      }  

      return t;  
  }

测试代码:

Customer custommer = new Customer();
        custommer.setId(0);
        System.out.println(XMLUtil.convertToXml(custommer,"utf-8"));

测试结果

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<customer>
    <id>0</id>
</customer>

@XmlRootElement:
测试用例：

package com.cmh.beans;

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

@XmlRootElement
@XmlAccessorType(XmlAccesstype.FIELD)
public class Customer {

    @XmlElement(name="customerid")
    private int id;

    private String name;

    private String pwd;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }


}

这里加@XmlAccessorType是为了让jaxb注解知道取那个值来生成xml，若不指定的话会产生如下异常：
com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions

Class has two properties of the same name "id"
    this problem is related to the following location:
        at public int com.cmh.beans.Customer.getId()
        at com.cmh.beans.Customer
    this problem is related to the following location:
        at private int com.cmh.beans.Customer.id
        at com.cmh.beans.Customer

测试结果如下:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<customer>
    <customerid>0</customerid>
</customer>

@XmlAttribute
测试用例：

package com.cmh.beans;

import javax.xml.bind.annotation.XmlAccesstype;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAnyAttribute;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
@XmlAccessorType(XmlAccesstype.FIELD)
public class Customer {

    @XmlElement(name="customerid")
    private int id;

    @XmlAttribute
    private String name;

    @XmlAttribute
    private String pwd;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }


}

测试用例：

Customer custommer = new Customer();
        custommer.setId(0);
        custommer.setName("22");
        custommer.setPwd("x");
        System.out.println(XMLUtil.convertToXml(custommer,"utf-8"));

结果:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<customer pwd="x" name="22">
    <customerid>0</customerid>
</customer>

如果我们的类里面包含了集合类会产生什么样的结果呢
测试用例：

package com.cmh.beans;

import java.util.List;

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 javax.xml.bind.annotation.XmlValue;

@XmlRootElement
@XmlAccessorType(XmlAccesstype.FIELD)
public class Person {

    private int id;

    private String address;

    private String email;

    private int age;

    @XmlElement(name="custommer")
    private List<Customer> custommer;


    public List<Customer> getCustommer() {
        return custommer;
    }

    public void setCustommer(List<Customer> custommer) {
        this.custommer = custommer;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getAddress() {
        return address;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }



}
package com.cmh.beans;

import javax.xml.bind.annotation.XmlAccesstype;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAnyAttribute;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlAccessorType(XmlAccesstype.FIELD)
public class Customer {

    @XmlElement(name="customerid")
    private int id;

    @XmlAttribute
    private String name;

    @XmlAttribute
    private String pwd;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }


}

测试代码：

Customer custommer = new Customer();
        custommer.setId(0);
        custommer.setName("22");
        custommer.setPwd("x");


        Person p = new Person();
        List<Customer> custoomers = new ArrayList<Customer>();
        custoomers.add(custommer);
        p.setAddress("232");
        p.setAge(22);
        p.setEmail("2321");
        p.setCustommer(custoomers);
        System.out.println(XMLUtil.convertToXml(p,"utf-8"));

测试结果：

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<person>
    <id>0</id>
    <address>232</address>
    <email>2321</email>
    <age>22</age>
    <custommer pwd="x" name="22">
        <customerid>0</customerid>
    </custommer>
</person>

@XmlElements的使用，可以在list上进行赋值，记住该list不确定类型比如直接声明list而不是list,这样我们就可以为后面加进来的类型进行xml解析了，示例

package com.cmh.beans;

import java.util.List;

import javax.xml.bind.annotation.XmlAccesstype;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlValue;

@XmlRootElement
@XmlAccessorType(XmlAccesstype.FIELD)
public class Person {

    private int id;

    private String address;

    private String email;

    private int age;

    @XmlElements( value = { 
            @XmlElement(name="custommer",type=Customer.class),@XmlElement(name="user",type=User.class) 
    })
    private List custommer;


    public List getCustommer() {
        return custommer;
    }

    public void setCustommer(List custommer) {
        this.custommer = custommer;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getAddress() {
        return address;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }



}
package com.cmh.beans;

import javax.xml.bind.annotation.XmlAccesstype;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAnyAttribute;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlAccessorType(XmlAccesstype.FIELD)
public class Customer {

    @XmlElement(name="customerid")
    private int id;

    @XmlAttribute
    private String name;

    @XmlAttribute
    private String pwd;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }


}
package com.cmh.beans;

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

@XmlAccessorType(XmlAccesstype.FIELD)
public class User {

    @XmlElement(name="customerid")
    private int id;

    @XmlAttribute
    private String name;

    @XmlAttribute
    private String pwd;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

}

测试代码：

Customer custommer = new Customer();
        custommer.setId(0);
        custommer.setName("22");
        custommer.setPwd("x");

        User user = new User();
        user.setId(0);
        user.setName("22");
        user.setPwd("x");

        Person p = new Person();
        List custoomers = new ArrayList<Customer>();
        custoomers.add(custommer);
        custoomers.add(user);
        p.setAddress("232");
        p.setAge(22);
        p.setEmail("2321");
        p.setCustommer(custoomers);
        System.out.println(XMLUtil.convertToXml(p,"utf-8"));

测试结果：

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<person>
    <id>0</id>
    <address>232</address>
    <email>2321</email>
    <age>22</age>
    <custommer pwd="x" name="22">
        <customerid>0</customerid>
    </custommer>
    <user pwd="x" name="22">
        <customerid>0</customerid>
    </user>
</person>

@XmlElementWrapper(name=”wrap”)：使用示例

package com.cmh.beans;

import java.util.List;

import javax.xml.bind.annotation.XmlAccesstype;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlElements;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlValue;

@XmlRootElement
@XmlAccessorType(XmlAccesstype.FIELD)
public class Person {

    private int id;

    private String address;

    private String email;

    private int age;

    @XmlElementWrapper(name="wrap")
    @XmlElements( value = { 
            @XmlElement(name="custommer",type=User.class) 
    })
    private List custommer;


    public List getCustommer() {
        return custommer;
    }

    public void setCustommer(List custommer) {
        this.custommer = custommer;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getAddress() {
        return address;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }



}

测试结果：

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<person>
    <id>0</id>
    <address>232</address>
    <email>2321</email>
    <age>22</age>
    <wrap>
        <custommer pwd="x" name="22">
            <customerid>0</customerid>
        </custommer>
        <user pwd="x" name="22">
            <customerid>0</customerid>
        </user>
    </wrap>
</person>

由于时间有点晚了，我得睡觉了，本来还想写以下xml to bean得，不过下次再写吧，如果你觉得楼主还有什么没写到位得，请在评论区写下你的其他方法，让你我他更多得人来学习

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