我如何在 jaxb 中解组并在不使用显式模式文件的情况下享受模式验证 [英] how can i unmarshall in jaxb and enjoy the schema validation without using an explicit schema file

问题描述

我将 jaxb 用于我的应用程序配置

I am using jaxb for my application configurations

我觉得我在做一些非常不正当的事情，我正在寻找一种不需要实际文件或此交易的方法.

I feel like I am doing something really crooked and I am looking for a way to not need an actual file or this transaction.

正如你在代码 I 中看到的:

As you can see in code I:

1.从我的 JaxbContext 中创建一个模式到一个文件中(实际上来自我的类​​注释)2.设置此模式文件以便在我解组时允许真正的验证

1.create a schema into a file from my JaxbContext (from my class annotation actually) 2.set this schema file in order to allow true validation when I unmarshal

JAXBContext context = JAXBContext.newInstance(clazz);
Schema mySchema = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI).newSchema(schemaFile);
jaxbContext.generateSchema(new MySchemaOutputResolver()); // ultimately creates schemaFile   
Unmarshaller u = m_context.createUnmarshaller();
u.setSchema(mySchema);
u.unmarshal(...);

你们中有人知道如何验证 jaxb，而无需在我的计算机中创建架构文件吗?

do any of you know how I can validate jaxb without needing to create a schema file that sits in my computer?

我是否需要创建一个模式进行验证，当我通过 JaxbContect.generateSchema 获得它时它看起来是多余的?

Do I need to create a schema for validation, it looks redundant when I get it by JaxbContect.generateSchema ?

你是怎么做到的?

推荐答案

关于上面ekeren的解决方案，在单线程中使用PipedOutputStream/PipedInputStream并不是一个好主意，以免溢出缓冲区导致死锁.ByteArrayOutputStream/ByteArrayInputStream 有效，但如果您的 JAXB 类生成多个模式(在不同的命名空间中)，您需要多个 StreamSource.

Regarding ekeren's solution above, it's not a good idea to use PipedOutputStream/PipedInputStream in a single thread, lest you overflow the buffer and cause a deadlock. ByteArrayOutputStream/ByteArrayInputStream works, but if your JAXB classes generate multiple schemas (in different namespaces) you need multiple StreamSources.

我最终得到了这个:

JAXBContext jc = JAXBContext.newInstance(Something.class);
final List<ByteArrayOutputStream> outs = new ArrayList<ByteArrayOutputStream>();
jc.generateSchema(new SchemaOutputResolver(){
    @Override
    public Result createOutput(String namespaceUri, String suggestedFileName) throws IOException {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        outs.add(out);
        StreamResult streamResult = new StreamResult(out);
        streamResult.setSystemId("");
        return streamResult;
    }});
StreamSource[] sources = new StreamSource[outs.size()];
for (int i=0; i<outs.size(); i++) {
    ByteArrayOutputStream out = outs.get(i);
    // to examine schema: System.out.append(new String(out.toByteArray()));
    sources[i] = new StreamSource(new ByteArrayInputStream(out.toByteArray()),"");
}
SchemaFactory sf = SchemaFactory.newInstance( XMLConstants.W3C_XML_SCHEMA_NS_URI );
m.setSchema(sf.newSchema(sources));
m.marshal(docs, new DefaultHandler());  // performs the schema validation

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