Web服务响应是否应包含空值？ [英] Should a web service response include empty values?

问题描述

在调用Web服务时，我得到XML格式的动态响应。

When invoking a web service I get a dynamic response in XML format.

因此响应可能是：

<response>
<test1>test1</test1>
<test2>test1</test2>
<test3>test1</test3>
<test4>test1</test4>
</response>

或：

<response>
<test1>test1</test1>
<test2>test1</test2>
</response>

但我认为响应应该是静态的，以便从XML中正确地解组Java类。

But I think the response should be static in order for the Java class to be unmarshalled correctly from the XML.

所以而不是

<response>
<test1>test1</test1>
<test2>test1</test2>
</response>

这应该是：

<response>
<test1>test1</test1>
<test2>test1</test2>
<test3></test3>
<test4></test4>
</response>

这意味着我现在可以处理响应并检查缺失的数据。

This means I can now handle the response and check for missing data.

我的想法是否正确？

推荐答案

默认空表示

默认情况下，JAXB（JSR-222）实现会将属性视为可选元素。因此，空值表示为文档中不存在的元素。

Default Null Representation

By default a JAXB (JSR-222) implementation will treat a property as an optional element. As such null values are represented as the element being absent from the document.

或者你可以通过包含 xsi表示null： nil =true属性。这可以通过使用 @XmlElement（nillable = true）注释您的财产来实现。

Alternatively you have null represented by including the xsi:nil="true" attribute on it. This is achieved by annotating your property with @XmlElement(nillable=true).

<date xsi:nil="true" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>

无效的空表示

空元素不是null的有效表示。它将被视为一个空字符串，对所有非String类型都是无效的。

Invalid Null Representation

An empty element is not a valid representation for null. It will be treated as an empty String which will be invalid for all non-String types.

<date/>

更多信息

• http：//blog.bdoughan .com / 2012/04 / binding-to-json-xml-handling-null.html



For More Information

• http://blog.bdoughan.com/2012/04/binding-to-json-xml-handling-null.html




SO test1 test1是
a有效响应但是字段test3& test4将被设置为null？

SO test1 test1 is a valid response but the fields test3 & test4 will be set to null ?

对于与缺席节点相对应的字段/属性，没有做任何事情。它们将保留默认值，默认情况下初始化为 null 。

What happens is that nothing is done for the fields/properties that correspond to absent nodes. They will keep there default values, which are by default initialized to null.

Java模型（Root） ）

在下面的模型类中，我初始化了字段，使其值不是 null 。

In the model class below I have initialed the fields to have values that are not null.

import javax.xml.bind.annotation.*;

@XmlRootElement
public class Root {

    @XmlElement
    String foo = "Hello";

    String bar = "World";

    public String getBar() {
        return bar;
    }

    public void setBar(String bar) {
        this.bar = bar;
    }

}

演示

正在编组的文件< root /> 没有与映射字段对应的任何元素/模型类中的属性。

The document being marshalled <root/> does not have any elements corresponding to the mapped fields/properties in the model class.

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

public class Demo {

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

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        StringReader xml = new StringReader("<root/>");
        Root root = (Root) unmarshaller.unmarshal(xml);

        System.out.println(root.foo);
        System.out.println(root.bar);
    }

}

输出

我们看到输出的默认值。这表明没有为缺席节点执行设置操作。

We see that the default values were output. This shows that a set operation was not performed for the absent nodes.

Hello
World

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