java - 读取具有不同名称但类型相同的元素列表

Question

我正在尝试将 JAXB 注释添加到类中，以便解码与此类似的 XML(注意我不需要将 java bean 编码到 XML...):

    <fixture_statistics id="3812596">
      <home_team_stats id="2">
        <id>2</id>
        <tackles>58</tackles>
        <possession>1868</possession>
        <territory>2603</territory>
        <minutes_in_22>1316</minutes_in_22>
        ...
      </home_team_stats>
      <guest_team_stats id="21061">
        <id>21061</id>
        <tackles>20</tackles>
        <possession>3114</possession>
        <territory>2379</territory>
        <minutes_in_22>1171</minutes_in_22>
        ...
      </guest_team_stats>
      <home_player_1 id="2306143" teamid="2">
        <id>2306143</id>
        <tackles>3</tackles>
        <metres_gained>38</metres_gained>
        ...
      </home_player_1>
      <home_player_1 id="2306143" teamid="2">
        <id>2306143</id>
        <tackles>3</tackles>
        <metres_gained>38</metres_gained>
        ...
      </home_player_1>
      <home_player_1 id="2306143" teamid="2">
        <id>2306143</id>
        <tackles>3</tackles>
        <metres_gained>38</metres_gained>
        ...
      </home_player_1>
      ...
      <guest_player_1 id="2306143" teamid="2">
        <id>2306143</id>
        <tackles>3</tackles>
        <metres_gained>38</metres_gained>
        ...
      </guest_player_1>
      <guest_player_2 id="2306143" teamid="2">
        <id>2306143</id>
        <tackles>3</tackles>
        <metres_gained>38</metres_gained>
        ...
      </guest_player_2>
      <guest_player_3 id="2306143" teamid="2">
        <id>2306143</id>
        <tackles>3</tackles>
        <metres_gained>38</metres_gained>
        ...
      </guest_player_3>
      ...
</fixture_statistics>

* 请注意，当我复制并粘贴此问题时，请忽略某些元素值...

我已成功将“fixture_statistics”、“home_team_stats”和“guest_team_stats”元素映射到各自的类，并且我能够正确解码这些元素，但我对“home_player_n”和“guest_player_n”元素。我创建了一个类，其中包含在这些元素中找到的属性，但我不知道如何处理这些元素具有不同名称的事实 - “home_player_1”到“home_player_22”，对于 guest 玩家也是如此。

这是我的赛程统计类(class)和我的赛程球员统计类(class)的示例，以便有人可以指出我哪里出错了......

@XmlRootElement(name = "fixture_statistics")
@XmlAccessorType(XmlAccessType.FIELD)
public class FixtureStatistics {

    private Collection<FixturePlayerStatistics> homeTeamPlayerStatistics = new ArrayList<>();

    private Collection<FixturePlayerStatistics> guestTeamPlayerStatistics = new ArrayList<>();
}

@XmlAccessorType(XmlAccessType.FIELD)
public class FixturePlayerStatistics {
    @XmlElement(name="id")
    private Long playerId;
    private Integer tackles;
    @XmlElement(name="metres_gained")
    private Integer metresGained;
}

在 FixturePlayerStatistics 类上，我无法添加 XMlRootElement 注释，因为该元素可能是 44 个字符串中的 1 个，而且我还暂时从 FixtureStatistics 类中的集合中删除了任何注释，因为我真的不确定那里会发生什么。我尝试过使用 @XmlElementRef 来指定所有可能的元素名称，但这对我来说还不起作用，而且 XML 也无法更改，而且我没有可使用的架构，只有 API 调用生成的 XML。

Answer 1

有一些不同的选项可以支持此用例。但总的来说，我建议避免将索引应用于元素名称的情况。

选项#1 - 单独的字段/属性

处理此用例的一种方法是为 22 名客队玩家和 22 名主队玩家各拥有一个单独的 field /属性。

package forum13219778;

import javax.xml.bind.annotation.*;

@XmlRootElement(name = "fixture_statistics")
@XmlAccessorType(XmlAccessType.FIELD)
public class FixtureStatistics {

    FixturePlayerStatistics guest_player_1;
    FixturePlayerStatistics guest_player_2;
    FixturePlayerStatistics guest_player_3;
    ...
    FixturePlayerStatistics guest_player_22;

    FixturePlayerStatistics home_player_1;
    FixturePlayerStatistics home_player_2;
    FixturePlayerStatistics home_player_3;
    ...
    FixturePlayerStatistics home_player_22;     
}

---

选项 #2 - 使用 SAX XMLFilter去掉_#后缀

如果您的用例仅处理解码，那么您可以使用 SAX XMLFilter要去掉每个元素和 JAXB 注释中的唯一后缀，只需映射到 home_player和guest_player 。对于 XMLFilter示例参见:

• How to make JAXB unmarshaller to ignore prefixes?

---

选项 #3 - 使用 @XmlElementRefs和一个ObjectFactory

FixtureStatistics

要使用@XmlElementRefs/@XmlElementRef您需要更改集合以保存 JAXBElement<FixturePlayerStatistics> 的实例。 JAXBElement将用于保存元素名称信息。

package forum13219778;

import java.util.*;

import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.*;

@XmlRootElement(name = "fixture_statistics")
@XmlAccessorType(XmlAccessType.FIELD)
public class FixtureStatistics {

    @XmlElementRefs({ 
        @XmlElementRef(name="home_player_1"),
        @XmlElementRef(name="home_player_2"),
        @XmlElementRef(name="home_player_3")
    })
    private Collection<JAXBElement<FixturePlayerStatistics>> homeTeamPlayerStatistics = new ArrayList<>();

    @XmlElementRefs({ 
        @XmlElementRef(name="guest_player_1"),
        @XmlElementRef(name="guest_player_2"),
        @XmlElementRef(name="guest_player_3")
    })
    private Collection<JAXBElement<FixturePlayerStatistics>> guestTeamPlayerStatistics = new ArrayList<>();

}

对象工厂

与 @XmlElementRef 结合使用您需要使用 @XmlElementDecl 声明根元素注解。这是通过一个带有 @XmlRegistry 注释的对象工厂类来完成的。 .

package forum13219778;

import javax.xml.bind.JAXBElement;
import javax.xml.bind.annotation.*;
import javax.xml.namespace.QName;

@XmlRegistry
public class ObjectFactory {

    @XmlElementDecl(name = "home_player_1")
    public JAXBElement<FixturePlayerStatistics> createHomePlayer1(FixturePlayerStatistics player) {
        return new JAXBElement<FixturePlayerStatistics>(new QName("home_player_1"), FixturePlayerStatistics.class, player);
    }

    @XmlElementDecl(name = "home_player_2")
    public JAXBElement<FixturePlayerStatistics> createHomePlayer2(FixturePlayerStatistics player) {
        return new JAXBElement<FixturePlayerStatistics>(new QName("home_player_2"), FixturePlayerStatistics.class, player);
    }

    @XmlElementDecl(name = "home_player_3")
    public JAXBElement<FixturePlayerStatistics> createHomePlayer3(FixturePlayerStatistics player) {
        return new JAXBElement<FixturePlayerStatistics>(new QName("home_player_3"), FixturePlayerStatistics.class, player);
    }

    @XmlElementDecl(name = "guest_player_1")
    public JAXBElement<FixturePlayerStatistics> createGuestPlayer1(FixturePlayerStatistics player) {
        return new JAXBElement<FixturePlayerStatistics>(new QName("guest_player_1"), FixturePlayerStatistics.class, player);
    }


    @XmlElementDecl(name = "guest_player_2")
    public JAXBElement<FixturePlayerStatistics> createGuestPlayer2(FixturePlayerStatistics player) {
        return new JAXBElement<FixturePlayerStatistics>(new QName("guest_player_2"), FixturePlayerStatistics.class, player);
    }

    @XmlElementDecl(name = "guest_player_3")
    public JAXBElement<FixturePlayerStatistics> createGuestPlayer3(FixturePlayerStatistics player) {
        return new JAXBElement<FixturePlayerStatistics>(new QName("guest_player_3"), FixturePlayerStatistics.class, player);
    }

}

演示

package forum13219778;

import java.io.File;
import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(FixtureStatistics.class, ObjectFactory.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum13219778/input.xml");
        FixtureStatistics fs = (FixtureStatistics) unmarshaller.unmarshal(xml);

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

}