Question

我想使用Jackson将以下XML文件解析为Java Object。但是它表明MismatchedInputException消息变为null。我在Employee类中指定了我需要的字段。使用这些字段，我需要创建Employee对象。

d.xml->输入xml文件

<Messages>
    <Message>
        <Uumid>45</Uumid>
        <UumidSuffix>ER.79</UumidSuffix>
        <CreationDate>20-05-2020</CreationDate>
        <Data>FRHF#%^G</Data>
    </Message>
    <Message>
        <Uumid>89</Uumid>
        <UumidSuffix>RT.12</UumidSuffix>
        <CreationDate>26-05-2020</CreationDate>
        <Data>FGRH#%^</Data>
    </Message>
</Messages>

Messages.java

package org.example;

import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlRootElement;

import java.lang.annotation.Documented;
import java.util.Arrays;


@JacksonXmlRootElement(localName ="Messages")
public final class Messages {
    @JacksonXmlElementWrapper(localName = "Message",useWrapping = true)
    private Message[] message;
    public Messages(){}
    public Messages(Message[] message){
        this.message=message;
    }

    public Message[] getMessage() {
        return message;
    }
    public void setMessage(Message[] message) {
        this.message = message;
    }


    @Override
    public String toString() {
        return "Messages{" +
                "message=" + Arrays.toString(message) +
                '}';
    }
}

Message.java

package org.example;

import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlProperty;

import javax.xml.bind.annotation.XmlAccessorOrder;


public class Message {
    @JacksonXmlProperty(localName = "Uumid")
    private String uumid;
    @JacksonXmlProperty(localName = "UumidSuffix")
    private String uumidSuffix;
    @JacksonXmlProperty(localName = "CreationDate")
    private String creationDate;

    public Message() {}
    public Message(String uumid,String uumidSuffix,String creationDate){
        this.uumid=uumid;
        this.uumidSuffix=uumidSuffix;
        this.creationDate=creationDate;
    }

    public String getUumid() {
        return uumid;
    }

    public void setUumid(String uumid) {
        this.uumid = uumid;
    }

    public String getUumidSuffix() {
        return uumidSuffix;
    }

    public void setUumidSuffix(String uumidSuffix) {
        this.uumidSuffix = uumidSuffix;
    }

    public String getCreationDate() {
        return creationDate;
    }

    public void setCreationDate(String creationDate) {
        this.creationDate = creationDate;
    }

    @Override
    public String toString() {
        return "Message{" +
                "uumid='" + uumid + '\'' +
                ", uumidSuffix='" + uumidSuffix + '\'' +
                ", CreationDate='" + creationDate + '\'' +
                '}';
    }
}

Parser.java

package org.example;


import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.xml.XmlMapper;
import org.apache.commons.lang3.StringUtils;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;

public class Parser {
    public static void main(String[] args) throws IOException {
        ObjectMapper objectMapper=new XmlMapper();

        Messages messages=objectMapper.readValue(StringUtils.toEncodedString(Files.readAllBytes(Paths.get("disk/d.xml")), StandardCharsets.UTF_8),Messages.class);
        System.out.println(messages);
    }
}

执行此错误时显示

Exception in thread "main" com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `org.example.Message` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('asdf')
 at [Source: (StringReader); line: 3, column: 20] (through reference chain: org.example.Messages["Message"]->java.lang.Object[][0])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1455)
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1081)
    at com.fasterxml.jackson.databind.deser.ValueInstantiator._createFromStringFallbacks(ValueInstantiator.java:371)
    at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromString(StdValueInstantiator.java:323)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1408)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:176)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166)
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:195)
    at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:21)
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:156)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4524)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3466)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3434)
    at org.example.Parser.main(Parser.java:17)

Process finished with exit code 1

maven依赖

<dependencies>
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.11</version>
          <scope>test</scope>
        </dependency>
        <dependency>
          <groupId>com.fasterxml.jackson.dataformat</groupId>
          <artifactId>jackson-dataformat-xml</artifactId>
          <version>2.11.2</version>
        </dependency>
        <dependency>
          <groupId>com.fasterxml.jackson.core</groupId>
          <artifactId>jackson-core</artifactId>
          <version>2.11.2</version>
        </dependency>
        <dependency>
          <groupId>org.apache.commons</groupId>
          <artifactId>commons-lang3</artifactId>
          <version>3.5</version>
        </dependency>
        <dependency>
          <groupId>com.fasterxml.jackson.core</groupId>
          <artifactId>jackson-databind</artifactId>
          <version>2.11.2</version>
        </dependency>
        <dependency>
          <groupId>com.fasterxml.jackson.core</groupId>
          <artifactId>jackson-annotations</artifactId>
          <version>2.11.2</version>
        </dependency>
      </dependencies>

Answer 1

您当前的代码告诉Jackson，您的消息应该包装在包装标签中，因此期望XML看起来像这样：

<Messages>
    <Message> <!-- this is the wrapper -->
        <Message>
            <Uumid>...</Uumid>
            ...
         </Message>
         <Message>
             ...
         </Message>
    </Message>
</Messages>

要解决此问题，您必须告诉Jaskcon不要使用包装器，并且将这些子级称为“消息”。在您的Messages类中，您必须将message字段上的注释更新为以下内容：

@JacksonXmlElementWrapper(useWrapping = false)
@JacksonXmlProperty(localName = "Message")
private Message[] message;

（顺便说一句，为什么不叫此字段messages？）

杰克逊XML解析MismatchedInputException

1 个答案: