使用 Marshaller 将 Java 对象转换为 Json [英] Converting Java Object to Json using Marshaller

问题描述

使用 Marshaller 将 java 对象转换为 XML 非常容易.但是我需要单独使用 marshaller 将 java 对象转换为 JSON.我知道使用 gson 或 Xstream 之类的东西很好.但我需要使用 Marshaller.如何实现?

Its quite easy to convert a java object to XML by using Marshaller. But I need to convert a java object to JSON by using marshaller alone. I know its good to use gson or Xstream like things., but I need to do using Marshaller.How to achieve it?

提前致谢.

推荐答案

注意:我是EclipseLink JAXB (MOXy) 领导和成员 JAXB (JSR-222) 专家组，

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group,

如果您使用 MOXy 作为您的 JAXB 提供程序，以下是如何做到这一点.

Below is how this can be done if you are using MOXy as your JAXB provider.

• http://blog.bdoughan.com/2011/08/json-binding-with-eclipselink-moxy.html

Java 模型

客户

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

@XmlRootElement(namespace="http://www.example.com")
@XmlType(namespace="http://www.example.com")
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer {

    @XmlAttribute
    private int id;

    @XmlElement(namespace="http://www.example.com")
    private String firstName;

    @XmlElement(namespace="http://www.example.com", nillable=true)
    private String lastName;

    @XmlElement(namespace="http://www.example.com")
    private List<PhoneNumber> phoneNumbers = new ArrayList<PhoneNumber>();

}

电话号码

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
public class PhoneNumber {

    @XmlAttribute
    private String type;

    @XmlValue
    private String number;

}

jaxb.properties

要将 MOXy 指定为您的 JAXB 提供程序，您需要在与域模型相同的包中包含一个名为 jaxb.properties 的文件，其中包含以下条目(请参阅:http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html)

To specify MOXy as your JAXB provider you need to include a file called jaxb.properties in the same package as your domain model with the following entry (see: http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html)

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

演示代码

input.xml

<?xml version="1.0" encoding="UTF-8"?>
<ns0:customer xmlns:ns0="http://www.example.com" id="123">
   <ns0:firstName>Jane</ns0:firstName>
   <ns0:lastName xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
   <ns0:phoneNumbers type="work">555-1111</ns0:phoneNumbers>
</ns0:customer>

演示

在下面的演示代码中，我们将使用相同的 JAXB 元数据将 XML 文档转换为 Java 对象，然后将这些对象转换回 JSON.使用 MOXy，您可以通过在 Marshaller 上设置属性来指定 JSON 输出.

In the demo code below we will use the same JAXB metadata to convert an XML document to Java objects, and then convert those objects back to JSON. With MOXy you can specify JSON output by setting a property on the Marshaller.

import java.io.File;
import javax.xml.bind.*;
import org.eclipse.persistence.jaxb.MarshallerProperties;

public class Demo {

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

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum15357366/input.xml");
        Customer customer = (Customer) unmarshaller.unmarshal(xml)
                ;
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty(MarshallerProperties.MEDIA_TYPE, "application/json");
        marshaller.setProperty(MarshallerProperties.JSON_INCLUDE_ROOT, false);
        marshaller.marshal(customer, System.out);
    }

}

JSON 输出

以下是 JSON 输出.请注意没有与命名空间或 XML 属性相对应的指示符.另请注意，大小为 1 的集合正确表示为 JSON 数组(其他一些方法存在问题).

Below is the JSON output. Note how there are no indicators corresponding to namespaces or XML attributes. Also note the collection of size one was correctly represented as a JSON array (a problem with some other approaches).

{
   "id" : 123,
   "firstName" : "Jane",
   "lastName" : null,
   "phoneNumbers" : [ {
      "type" : "work",
      "value" : "555-1111"
   } ]
}

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