XStream JavaBeanConverter不序列化属性 [英] XStream JavaBeanConverter not serializing properties

问题描述

尝试使用XStream的JavaBeanConverter并遇到问题.我很可能错过了一些简单的东西，或者对XStream的转换器处理得不够好.

Attempting to use XStream's JavaBeanConverter and running into an issue. Most likely I'm missng something simple, or not understanding XStream's converter handling well enough.

@XStreamAlias("test")
public class TestObject
{
    private String foo;

    public String getFoo()
    {
        //return foo; -- Adjusted for EDIT#2
        return foo.toLowerCase();
    }

    public void setFoo(String foo)
    {
        this.foo = foo;
    }
}

public void test() throws Exception
{
    XStream x = new XStream(new XppDriver());
    x.autodetectAnnotations(true);
    x.processAnnotations(TestObject.class);

    x.registerConverter(new JavaBeanConverter(x.getMapper()));

    TestObject o = new TestObject();
    //o.setFoo("bar"); -- Adjusted for EDIT#2
    o.setFoo("BAR");

    String xml = x.toXML(o);

    System.out.println(xml);

    /*
      Expecting...
        <test>
          <foo>bar</foo>
        </test>

      But instead getting...
        <test>
          <foo/>
        </test>         
    */
}

我尝试在TestObject.getFoo()方法上添加跟踪，它似乎已被XStream调用，但数据并未写入输出流.

I tried adding a trace on the TestObject.getFoo() method and it appears it is being called by XStream, but the data isn't being written to the output stream.

查看JavaBeanConverter的源代码后，看来我的实现应该可以工作，这使我相信我在XStream设置过程中未正确配置某些东西.

After looking at the source for JavaBeanConverter, it looks like my implementation should work, which leads me to believe I haven't configured something correctly during the XStream setup.

我只是缺少一些简单的东西吗?

Am I just missing something simple?

谢谢！

---

编辑1

此外，如果有帮助，我正在为此使用以下Maven部门...

Also, if it helps, I'm using the following Maven deps for this...

<dependency>
    <groupId>org.apache.servicemix.bundles</groupId>
    <artifactId>org.apache.servicemix.bundles.xstream</artifactId>
    <version>1.3_3</version>
</dependency>
<dependency>
    <groupId>org.apache.servicemix.bundles</groupId>
    <artifactId>org.apache.servicemix.bundles.xpp3</artifactId>
    <version>1.1.4c_3</version>
</dependency>

---

编辑2

我更改了TestObject.getFoo()方法以更好地说明我的目标.

I altered the TestObject.getFoo() method to better explain my objective.

我正在尝试使用getters/setter方法对内部对象的数据进行清理". 具体来说，我正在尝试清理传入的反序列化数据，同时试图避免实现Serializable的readResolve()方法.

I'm trying to use the getters/setters to do "sanitation" of the internal object's data. Specifically, I'm trying to clean up incoming deserialized data, while trying to avoid having to implement Serializable's readResolve() method.

如果我实现了readResolve的方法，则必须同时在setter方法(对于其他未反序列化的传入数据集)和readResolve(对于我反序列化的XML数据)中进行清理.

If I implemented readResolve's method I would have to do the cleanup in both the setter method (for any non-deserialized incoming data set elsewhere) and also in the readResolve (for XML data I deserialized).

这就是为什么我使用JavaBeanConverter而不是XStream基于常规字段的实践的原因...迫使数据通过getter/setter方法.

That's the reason why I'm using JavaBeanConverter instead of XStream's normal field based practices... to force data through the getters/setters.

希望这可以解释得更好一些.

Hopefully this explains a little better.

谢谢.

推荐答案

逐步浏览XStream的源代码，您可以在com.thoughtworks.xstream.core.DefaultConverterLookup中找到它.

Stepping through XStream's source you can find this in com.thoughtworks.xstream.core.DefaultConverterLookup.

public Converter lookupConverterForType(Class type) {
    Converter cachedConverter = (Converter) typeToConverterMap.get(type);
    if (cachedConverter != null) return cachedConverter;
    Iterator iterator = converters.iterator();
    while (iterator.hasNext()) {
        Converter converter = (Converter) iterator.next();
        if (converter.canConvert(type)) {
            typeToConverterMap.put(type, converter);
            return converter;
        }
    }
    throw new ConversionException("No converter specified for " + type);
}

您会注意到String返回JavaBeanConverter，它这样做的原因是JavaBeanConverter将用于具有默认公共构造函数(String具有)的任何对象.

You will notice for the String it returns JavaBeanConverter and the reason it does that is that JavaBeanConverter will be used for any object with a default public constructor (which String has).

解决此问题的一种方法是赋予JavaBeanConverter较低的优先级.

One way to fix the problem is to give the JavaBeanConverter a lower priority.

x.registerConverter(new JavaBeanConverter(x.getMapper()), -10);

然后将JavaBeanConverter用于您的Bean，并将SingleValueConverterWrapper用于String值.

Then JavaBeanConverter is used for your Bean and SingleValueConverterWrapper is used for the String value.

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