JAXB - 使用递归依赖进行编组 [英] JAXB - marshalling with recursive dependency

问题描述

是否有人试图通过重新审判来整理JAXB对象？我有以下课程：

is anybody try to marshal JAXB object with recurisive referency? I have following class:

public class A {

   private Long id;
   private String name;
   private List<A> aList;

}

我想把它编组到：

<a>
  <a>
    <a>...</a>
  ...
  </a>
...
</a>

我正在使用maven插件从XSD自动生成JAXB类。有什么建议吗？

I'm using maven plugin to auto generate JAXB class from XSD. Any suggestions?

推荐答案

以下是从XML模式开始支持这个用例的方法。

Below is how you can support this use case starting from your XML schema.

XML SCHEMA（schema.xsd）

以下XML架构基于您对a上一个回答（http://stackoverflow.com/a/14317461/383861）。

The following XML schema is based on the comment you made to a previous answer (http://stackoverflow.com/a/14317461/383861).

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="http://www.example.org" 
    xmlns:tns="http://www.example.org"
    elementFormDefault="qualified">

    <xs:element name="b">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="tns:a" maxOccurs="unbounded" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    <xs:element name="a">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="id" type="xs:long" />
                <xs:sequence>
                    <xs:element ref="tns:a" minOccurs="0" maxOccurs="10" />
                </xs:sequence>
            </xs:sequence>
        </xs:complexType>
    </xs:element>

</xs:schema>

生成型号

使用 xjc 工具生成以下代码。已删除get / set方法和注释以节省空间。

The following code was generated using the xjc tool. The get/set methods and comments have been removed to save space.

A

A

package org.example;

import java.util.List;
import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "id",
    "a"
})
@XmlRootElement(name = "a")
public class A {

    protected long id;
    protected List<A> a;

}

B

B

package org.example;

import java.util.List;
import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "", propOrder = {
    "a"
})
@XmlRootElement(name = "b")
public class B {

    @XmlElement(required = true)
    protected List<A> a;

}

package-info

package-info

@javax.xml.bind.annotation.XmlSchema(
        namespace = "http://www.example.org", 
        elementFormDefault = javax.xml.bind.annotation.XmlNsForm.QUALIFIED)
package org.example;

ObjectFactory

package org.example;

import javax.xml.bind.annotation.XmlRegistry;

@XmlRegistry
public class ObjectFactory {

    public ObjectFactory() {
    }

    public B createB() {
        return new B();
    }

    public A createA() {
        return new A();
    }

}

DEMO CODE

import java.io.File;
import javax.xml.bind.*;
import org.example.A;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance("org.example");

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum14306965/input.xml");
        A a = (A) unmarshaller.unmarshal(xml);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(a, System.out);
    }

}

INPUT（输入。 xml）/ OUTPUT

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<a xmlns="http://www.example.org">
    <id>1</id>
    <a>
        <id>2</id>
        <a>
            <id>3</id>
        </a>
    </a>
</a>

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