在 Java 中针对 XSD 验证 XML/获取 schemaLocation [英] Validate an XML against an XSD in Java / Getting a hold of the schemaLocation

问题描述

如何在 Java 中使用 XSD 验证 XML 文件?我们事先并不知道模式.我希望能够获取 schemaLocation、下载 XSD、缓存它，然后执行实际验证.

How can one validate an XML file using an XSD in Java? We don't know the schema in advance. I would like to be able to get the schemaLocation, download the XSD, cache it and then perform the actual validation.

问题是，使用 javax.xml.parsers.DocumentBuilder/DocumentBuilderFactory 类我似乎无法获得 schemaLocation 提前.这有什么诀窍?我应该研究哪些课程?

The problem is, that with javax.xml.parsers.DocumentBuilder/DocumentBuilderFactory classes I can't seem to be able to get a hold of the schemaLocation in advance. What's the trick for this? Which classes should I look into?

也许我可以使用更合适的 API?整个问题是我们需要动态验证，而不是(必须)在本地拥有 XSD.

Perhaps there's a more suitable API I can use? The whole problem is that we need to validate dynamically, without (necessarily) having the XSDs locally.

如何获取 XSD 文件中定义的 schemaLocation 的 URL?

How could one get a hold of the URL of schemaLocation defined in the XSD file?

我知道您可以设置功能/属性，但那是另一回事.我需要先从 XSD 中获取 schemaLocation.

I know you can set features/attributes, but that's a different thing. I need to get the schemaLocation from the XSD first.

请指教！

推荐答案

鉴于您使用的是 Xerces(或 JDK 默认)，您是否尝试过在出厂时将此功能设置为 true:http://apache.org/xml/features/validation/schema.您还可以使用有关架构的其他功能:http://xerces.apache.org/xerces2-j/features.html

Given that you are using Xerces (or JDK default), have you tried setting this feature to true on the factory: http://apache.org/xml/features/validation/schema. There are other features that you can play with regarding schemas: http://xerces.apache.org/xerces2-j/features.html

更新 2(用于缓存):

UPDATE 2 (for caching):

实现一个 org.w3c.dom.ls.LSResourceResolver 并使用 setResourceResolver 方法在 SchemaFactory 上设置它.这个解析器要么从缓存中获取架构，要么从位置所指的任何地方获取它.

Implement a org.w3c.dom.ls.LSResourceResolver and set this on the SchemaFactory using the setResourceResolver method. This resolver would either get the schema from cache or fetch it from wherever the location refers to.

更新 3:

LSResourceresolver 示例(我认为这对您来说是一个很好的起点):

LSResourceresolver example (which I think will be a good starting point for you):

/**
 * Resolves resources from a base URL
 */
public class URLBasedResourceResolver implements LSResourceResolver {

private static final Logger log = LoggerFactory
        .getLogger(URLBasedResourceResolver.class);

private final URI base;

private final Map<URI, String> nsmap;

public URLBasedResourceResolver(URL base, Map<URI, String> nsmap)
        throws URISyntaxException {
    super();
    this.base = base.toURI();
    this.nsmap = nsmap;
}

@Override
public LSInput resolveResource(String type, String namespaceURI,
        String publicId, String systemId, String baseURI) {
    if (log.isDebugEnabled()) {
        String msg = String
                .format("Resolve: type=%s, ns=%s, publicId=%s, systemId=%s, baseUri=%s.",
                        type, namespaceURI, publicId, systemId, baseURI);
        log.debug(msg);
    }
    if (type.equals(XMLConstants.W3C_XML_SCHEMA_NS_URI)) {
        if (namespaceURI != null) {
            try {
                URI ns = new URI(namespaceURI);
                if (nsmap.containsKey(ns))
                    return new MyLSInput(base.resolve(nsmap.get(ns)));
            } catch (URISyntaxException e) {
                // ok
            }
        }
    }
    return null;
}

}

MyLSInput 的实现真的很无聊:

The implementation of MyLSInput is really boring:

class MyLSInput implements LSInput {

private final URI url;

public MyLSInput(URI url) {
    super();
    this.url = url;
}

@Override
public Reader getCharacterStream() {
    return null;
}

@Override
public void setCharacterStream(Reader characterStream) {

}

@Override
public InputStream getByteStream() {
    return null;
}

@Override
public void setByteStream(InputStream byteStream) {

}

@Override
public String getStringData() {
    return null;
}

@Override
public void setStringData(String stringData) {

}

@Override
public String getSystemId() {
    return url.toASCIIString();
}

@Override
public void setSystemId(String systemId) {
}

@Override
public String getPublicId() {
    return null;
}

@Override
public void setPublicId(String publicId) {
}

@Override
public String getBaseURI() {
    return null;
}

@Override
public void setBaseURI(String baseURI) {

}

@Override
public String getEncoding() {
    return null;
}

@Override
public void setEncoding(String encoding) {

}

@Override
public boolean getCertifiedText() {
    return false;
}

@Override
public void setCertifiedText(boolean certifiedText) {

}

}

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