杰克逊(Jackson)的XML中的平面阵列列出了Pojo列表

Question

您可以帮助我解析以下XML文件吗？

<?xml version="1.0" encoding="UTF-8"?>
<dataset xmlns="http:/foo.com">
   <date>2017-10-25T09:13:54+02:00</date>
   <element>
      <id>1</id>
      <name>Stuart</name>
      <age>34</age>
      <regdate><date>2017-10-25T09:13:54+02:00</date></regdate>
   </element>
   <element>
      <id>2</id>
      <name>Lora</name>
      <age>12</age>
      <regdate><date>2017-10-25T09:13:54+02:00</date></regdate>
   </element>
   <element>
      <id>3</id>
      <name>Ben</name>
      <age>50</age>
      <regdate><date>2017-10-25T09:13:54+02:00</date></regdate>
   </element>
</dataset >

我试图创建这样的pojo：

@Getter
@Setter
@JacksonXmlRootElement(localName = "element")
public class ElementXML {
    @JacksonXmlProperty(localName = "id")
    private Long id;    
    @JacksonXmlProperty(localName = "name")
    private String name;
    @JacksonXmlProperty(localName = "age")
    private Long age;
    @JacksonXmlProperty(localName = "regdate")
    private LocalDateTime regdate;
}

和我使用的解析机制在这里：

    XMLInputFactory f = XMLInputFactory.newFactory();
    File inputFile = new File("some path");
    XMLStreamReader sr = f.createXMLStreamReader(new FileInputStream(inputFile));

    ObjectMapper xmlMapper = new XmlMapper();
    

我之所以被卡住，是因为我不知道如何将元素标签放入我创建的pojo element xml的列表中。您知道如何解决吗？

编辑通过答案进行编辑后的跟踪：

com.fasterxml.jackson.databind.JsonMappingException: Expected END_ELEMENT, got event of type 1 (through reference chain: com.xml.Dataset["element"]->java.lang.Object[][1])
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:394)
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:365)
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:206)
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:21)
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:288)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
    at com.fasterxml.jackson.dataformat.xml.deser.WrapperHandlingDeserializer.deserialize(WrapperHandlingDeserializer.java:113)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4013)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2902)
    at com.xml.data.ParseXmlTest.test(ParseXmlTest.java:62)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:74)
    at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:84)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.CommandLineWrapper.main(CommandLineWrapper.java:67)
Caused by: java.io.IOException: Expected END_ELEMENT, got event of type 1
    at com.fasterxml.jackson.dataformat.xml.deser.XmlTokenStream.skipEndElement(XmlTokenStream.java:190)
    at com.fasterxml.jackson.dataformat.xml.deser.FromXmlParser.nextToken(FromXmlParser.java:584)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:283)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:195)
    ... 43 more

Answer 1

您的问题有些棘手，因为您需要解决一些问题。让我们开始一个一个一个。

1。该型号不适合XML有效载荷。

首先，您需要创建一个适合您payload的模型。它不取决于格式，因为对于JSON和XML，它几乎相同。为此，我建议总是从序列化过程开始。在Java中构建模型并尝试序列化要容易得多。如果看起来与预期更新模型所需的预期相同。您迭代这些步骤：update和serialise，直到找到有效的模型为止。之后，您可以在没有任何问题的情况下对给定的payload进行挑选。

2。杰克逊注释。

即使如此，Jackson的注释也很棒，也不是没有原因的。如果POJO属性与XML中的节点名称相同，则无需添加JacksonXmlProperty注释。当POJO和payload中的名称不同时，您必须添加它。在其他情况下，这使POJO结构过于复杂。我们应该使它尽可能简单。您需要使用一个棘手的注释：JacksonXmlElementWrapper。当我们有节点收集时，它被使用了。

在这两个简单的段落之后，让我们对您的案件进行认可。我们需要扩展您的POJO结构，它应该看起来像以下内容：

class Dataset {
    private LocalDateTime date;
    @JacksonXmlProperty(localName = "element")
    @JacksonXmlElementWrapper(useWrapping = false)
    private List<Element> elements;
    public LocalDateTime getDate() {
        return date;
    }
    public void setDate(LocalDateTime date) {
        this.date = date;
    }
    public List<Element> getElements() {
        return elements;
    }
    public void setElements(List<Element> element) {
        this.elements = element;
    }
    @Override
    public String toString() {
        return "Dataset{" +
                "date=" + date +
                ", element=" + elements +
                '}';
    }
}
class Element {
    private Long id;
    private String name;
    private Long age;
    private RegDate regdate;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Long getAge() {
        return age;
    }
    public void setAge(Long age) {
        this.age = age;
    }
    public RegDate getRegdate() {
        return regdate;
    }
    public void setRegdate(RegDate regdate) {
        this.regdate = regdate;
    }
    @Override
    public String toString() {
        return "ElementXML{" +
                "id=" + id +
                ", name='" + name + ''' +
                ", age=" + age +
                ", regdate=" + regdate.getDate() +
                '}';
    }
}
class RegDate {
    private LocalDateTime date;
    public RegDate() {
        this(null);
    }
    public RegDate(LocalDateTime date) {
        this.date = date;
    }
    public LocalDateTime getDate() {
        return date;
    }
    public void setDate(LocalDateTime date) {
        this.date = date;
    }
    @Override
    public String toString() {
        return "RegDate{" +
                "date=" + date +
                '}';
    }
}

一个示例用法：

import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;
import java.io.File;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.List;
public class XmlMapperApp {
    public static void main(String[] args) throws Exception {
        File jsonFile = new File("./resource/test.xml").getAbsoluteFile();
        JavaTimeModule module = new JavaTimeModule();
        module.addDeserializer(LocalDateTime.class, new LocalDateTimeDeserializer(DateTimeFormatter.ISO_DATE_TIME));
        XmlMapper xmlMapper = new XmlMapper();
        xmlMapper.registerModule(module);
        xmlMapper.enable(SerializationFeature.INDENT_OUTPUT);
        Dataset dataset = xmlMapper.readValue(jsonFile, Dataset.class);
        dataset.getElements().forEach(System.out::println);
    }
}

上面的代码打印：

ElementXML{id=1, name='Stuart', age=34, regdate=2017-10-25T09:13:54}
ElementXML{id=2, name='Lora', age=12, regdate=2017-10-25T09:13:54}
ElementXML{id=3, name='Ben', age=50, regdate=2017-10-25T09:13:54}

上述代码的两个额外评论。当您使用java.time.*类并且Jackson工作时，可以从注册来自Jackson-Datatype-JSR310模块的JavaTimeModule开始。由于我们正在使用它，因此我们可以指示使用ISO_DATE_TIME格式用于LocalDateTime类。在其他答案中，您可以找到使用JsonFormat注释的示例。这也是很好的解决方案，但是当所有日期具有相同格式的定义更容易时。

有关更多信息，请阅读：

• 如何更新RESTTEMPLATE以正确映射Java日期？
• 与杰克逊JSR310模块的localdatetime
• 找不到伪影杰克逊模型 - 贾瓦8：jar

Answer 2

不可能仅通过一个POJO类对给定的XML内容进行建模。您将需要几个POJO类来正确建模XML内容。

用于建模<dataset> root元素您需要类，我们称其为Dataset。

@Getter
@Setter
@JacksonXmlRootElement(localName = "dataset")
public class Dataset {
    @JacksonXmlProperty(localName = "date")
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ssXXX")
    private LocalDateTime date;
    @JacksonXmlProperty(localName = "element")
    @JacksonXmlElementWrapper(useWrapping = false)
    private List<ElementXML> elements;
}

在上面的代码中注意

• date属性用@JsonFormat注释以指定使用日期时间格式
• elements用@JacksonXmlElementWrapper(useWrapping = false)注释告诉解析器不要期望<element>的顺序额外包装

接下来，您需要一个用于建模<element>...</element>之间的XML内容的类非常喜欢您的ElementXML类。

@Getter
@Setter
public class ElementXML {
    @JacksonXmlProperty(localName = "id")
    private Long id;
    @JacksonXmlProperty(localName = "name")
    private String name;
    @JacksonXmlProperty(localName = "age")
    private Long age;
    @JacksonXmlProperty(localName = "regdate")
    private RegDate regdate;
}

在上面的代码中注意，您需要对regdate属性进行建模更精致。因为XML内容看起来不像<regdate>2017-10-25T09:13:54+02:00</regdate>您不能简单地将其声明为LocalDate regdate。相反，XML看起来像<regdate><date>2017-10-25T09:13:54+02:00</date></regdate>。因此，您需要用另一个类对其进行建模（我们称其为RegDate）

最后，这是用于建模XML内容的RegDate类在<regdate>...</regdate>之间。

@Getter
@Setter
public class RegDate {
    @JacksonXmlProperty(localName = "date")
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ssXXX")
    private LocalDateTime date;
}

再次注意使用@JsonFormat指定日期时间格式。

使用上面的类，您可以像这样解析xml

    File inputFile = new File("some path");
    ObjectMapper xmlMapper = new XmlMapper();
    xmlMapper.registerModule(new JavaTimeModule());
    Dataset dataset = xmlMapper.readValue(inputFile, Dataset.class);