如何在使用 DocumentBuilder.parse 解析格式良好的 XML 时关闭验证？

Question

我正在使用Java 6。我想解析已知格式正确的XHTML文档。因此，我不想对文档中引用的DTD或其他模式进行任何验证。但是，我无法弄清如何关闭验证。我有以下代码：

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(false);
    final DocumentBuilder b = factory.newDocumentBuilder();
    final InputSource s = new InputSource(new StringReader(str));
    org.w3c.dom.Document result = b.parse(s);

但是最后一行仍然会出现异常...

java.net.SocketException: Unexpected end of file from server
    at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:777)
    at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:640)
    at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:774)
    at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:640)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1195)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:677)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startEntity(XMLEntityManager.java:1315)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startDTDEntity(XMLEntityManager.java:1282)
    at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.setInputSource(XMLDTDScannerImpl.java:283)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.dispatch(XMLDocumentScannerImpl.java:1194)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.next(XMLDocumentScannerImpl.java:1090)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:1003)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:235)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:284)
    at com.myco.myproj.util.XmlUtilities.getStringAsDocument(XmlUtilities.java:130)
    at com.myco.myproj.util.NetUtilities.getUrlAsDocument(NetUtilities.java:30)
    at com.myco.myproj.parsers.impl.AbstractChicagoReaderParser.parsePage(AbstractChicagoReaderParser.java:144)
    at com.myco.myproj.parsers.impl.AbstractChicagoReaderParser.getEvents(AbstractChicagoReaderParser.java:112)
    at com.myco.myproj.parsers.impl.ChicagoReaderParserTest.testParser(ChicagoReaderParserTest.java:29)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

我不希望我的解析器连接到互联网。如何禁用它？谢谢。- Dave 编辑：根据Traroth的建议，我尝试了下面的代码，但是仍然遇到同样的异常。

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setValidating(false);
    final DocumentBuilder builder = factory.newDocumentBuilder();
    builder.setEntityResolver(new EntityResolver() {
        @Override
            public InputSource resolveEntity(String publicId, String systemId) {
                    return null;
            }
        });
    final InputSource s = new InputSource(new StringReader(str));
    org.w3c.dom.Document result = builder.parse(s);

- Dave

---

如果您显示或记录DocumentBuilderFactory的isValidating()，会发生什么？ - Alexis Dufrenoy

Answer 1

以下是创建一个DocumentBuilder的方法，它将忽略所有外部引用实体，包括DTD：

final DocumentBuilder builder = factory.newDocumentBuilder();
builder.setEntityResolver(new EntityResolver() {
    @Override
        public InputSource resolveEntity(String publicId, String systemId) {
                // it might be a good idea to insert a trace logging here that you are ignoring publicId/systemId
                return new InputSource(new StringReader("")); // Returns a valid dummy source
        }
    });

- Morten

Answer 2

可能与实体解析器问题有关。你可以在这里看一下：

如何在Java中读取格式良好的XML，但跳过模式？

- Alexis Dufrenoy

---

我猜你在谈论那个帖子中的被采纳的答案。我尝试了建议（我的代码包含在编辑中），但我仍然得到相同的异常。我有什么遗漏吗？ - Dave

@Dave - 是的。返回 null 与不应用实体解析器相同。您需要遵循另一条路径，返回一个输入源。只需将 "foo.dtd" 更改为 XML 文件的 DTD 的系统 ID 即可。 - Alohci

是的，如果您查看答案中的示例代码，您将看到 resolveEntity() 方法返回一个实际的非空 InputSource，如果 XML 引用了 DTD，则返回 null。 - Alexis Dufrenoy

我理解你用例子所说的内容。但我的问题是，我不想进行任何验证/ DTD 解析，我只想得到一堆元素。我能让解析器忽略任何DTD引用吗？ - Dave