| Questions |

- Querying Xerces Version
- JIRA
- Jar file changes
- Using JAXP 1.4 on JDK 1.4 and above
- ClassCastException using Xerces
- Xerces XML, HTML and XHTML Serializers
- Obtaining smaller jars
- Validation against DTD
- International Encodings
- Accessing Documents on the Internet
- JDK Compatibility

| Answers |

| How do I find out which Xerces version I am using? |

| To find out the release version of Xerces, execute the following: `java org.apache.xerces.impl.Version`.

| How do I use JIRA to report bugs? |

| Please refer to the Reporting bugs in JIRA.

| What happened to xerces.jar? |

In order to take advantage of the fact that this parser is very often used in conjunction with other XML technologies, such as XSLT processors, which also rely on standard API's like DOM and SAX, xerces.jar was split into two jarfiles:

- `xml-apis.jar` contains the DOM level 3, SAX 2.0.2 and the JAXP 1.4 APIs;
- `xercesImpl.jar` contains the implementation of these API's as well as the XNI API.

For backwards compatibility, we have retained the ability to generate xerces.jar. For instructions, see the installation documentation.

| How can I use JAXP 1.4 on JDK 1.4 and above? |

Use the Endorsed Standards Override Mechanism to specify xml-apis.jar and xercesImpl.jar. This will override the version of JAXP in the JDK. A more complete description is available here.

The following methods do not work:

- Using the CLASSPATH environment variable or using -classpath to place the new classes in the classpath.
- Using the -jar option to explicitly execute the classes inside the new jar files.

| Why do I get a ClassCastException when I use Xerces and WebSphere Application Server? |

Xerces uses the `ObjectFactory` class to load some classes dynamically, e.g. the parser configuration. The `ObjectFactory` finds the specified implementation class by querying the system property, reading `META-INF/services/factoryId` file or using a fallback classname. After the implementation is found, the `ObjectFactory` tries to load the file using the context classloader and if it is null, the `ObjectFactory` uses the system classloader.

If you run Xerces in an environment, such as WebSphere® Application Server, that has multiple classloaders you may get ClassCastExceptions thrown from Xerces because different classloaders might get involved in loading Xerces classes. For example, ClassCastExceptions may occur when utility EAR classes that use Xerces load Xerces classes from WAR modules.

We suggest you read the "Avoiding ClassCastExceptions..." article which explains a workaround for this problem. Also you might want to read the "J2EE Class Loading Demystified" article that explains how multiple classloaders work in WebSphere Application Server.

| What should I be using instead of Xerces' XML, HTML or XHTML serializers? |

As of the 2.9.0 release Xerces-J began sharing a common serialization codebase with Xalan and now includes `serializer.jar` with its distribution for DOM Level 3 serialization support. The entire `org.apache.xml.serialize` package was deprecated in Xerces 2.9.0. The HTML and XHTML serializers were previously deprecated in the Xerces 2.6.2 release. You can find more details about the rationale for this decision here in the archives.

If you want to achieve interoperability and avoid using deprecated APIs, you should not be using Xerces serialization code directly. Instead, the JAXP Transformer API should be used to serialize HTML, XHTML, and SAX. The DOM Level 3 Load and Save API (or JAXP Transformer API) should be used to serialize DOM.

Using DOM Level 3 you can serialize XML as follows:

    import org.w3c.dom.bootstrap.DOMImplementationRegistry;
    import org.w3c.dom.Document;
    import org.w3c.dom.ls.DOMImplementationLS;
    import org.w3c.dom.ls.LSSerializer;
    import org.w3c.dom.ls.LSOutput;

    ...

    DOMImplementationRegistry registry = DOMImplementationRegistry.newInstance();

    DOMImplementationLS impl =
        (DOMImplementationLS)registry.getDOMImplementation("LS");

    ...

    LSSerializer writer = impl.createLSSerializer();
    LSOutput output = impl.createLSOutput();
    output.setByteStream(System.out);
    writer.write(document, output);

Using JAXP you can serialize HTML and XHTML as follows:

    // Create an "identity" transformer - copies input to output
    Transformer t = TransformerFactory.newInstance().newTransformer();

    // for "XHTML" serialization, use the output method "xml"
    // and set publicId as shown
    t.setOutputProperty(OutputKeys.METHOD, "xml");

    t.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC,
                        "-//W3C//DTD XHTML 1.0 Transitional//EN");

    t.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM,
                   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd");

    // For "HTML" serialization, use
    t.setOutputProperty(OutputKeys.METHOD, "html");

    // Serialize DOM tree
    t.transform(new DOMSource(doc), new StreamResult(System.out));

| I don't need all the features Xerces provides, but I'm running in an environment where space is at a premium. Is there anything I can do? |

| Partially to address this issue, we've recently begun to distribute compressed jar files instead of our traditionally uncompressed files. But if you still need a smaller jar, and don't need things like support for XML Schema or the WML/HTML DOM implementations that Xerces provides, then look at the `dtdjars` target in our buildfile.

| How do I turn on DTD validation? |

You can turn validation on and off via methods available on the SAX2 `XMLReader` interface. While only the `SAXParser` implements the `XMLReader` interface, the methods required for turning on validation are available to both parser classes, DOM and SAX.
The code snippet below shows how to turn validation on -- assume that parser is an instance of either `org.apache.xerces.parsers.SAXParser` or `org.apache.xerces.parsers.DOMParser`.
`parser.setFeature("http://xml.org/sax/features/validation", true);`

| What international encodings are supported by Xerces-J? |

- UTF-8
- UTF-16 Big Endian and Little Endian
- UCS-2 (ISO-10646-UCS-2) Big Endian and Little Endian
- UCS-4 (ISO-10646-UCS-4) Big Endian and Little Endian
- IBM-1208
- ISO Latin-1 (ISO-8859-1)
- ISO Latin-2 (ISO-8859-2) [Bosnian, Croatian, Czech, Hungarian, Polish, Romanian, Serbian (in Latin transcription), Serbocroatian, Slovak, Slovenian, Upper and Lower Sorbian]
- ISO Latin-3 (ISO-8859-3) [Maltese, Esperanto]
- ISO Latin-4 (ISO-8859-4)
- ISO Latin Cyrillic (ISO-8859-5)
- ISO Latin Arabic (ISO-8859-6)
- ISO Latin Greek (ISO-8859-7)
- ISO Latin Hebrew (ISO-8859-8)
- ISO Latin-5 (ISO-8859-9) [Turkish]
- ISO Latin-7 (ISO-8859-13)
- ISO Latin-9 (ISO-8859-15)
- Extended Unix Code, packed for Japanese (euc-jp, eucjis)
- Japanese Shift JIS (shift-jis)
- Chinese (big5)
- Chinese for PRC (mixed 1/2 byte) (gb2312)
- Japanese ISO-2022-JP (iso-2022-jp)
- Cyrillic (koi8-r)
- Extended Unix Code, packed for Korean (euc-kr)
- Russian Unix, Cyrillic (koi8-r)
- Windows Thai (cp874)
- Latin 1 Windows (cp1252) (and all other cp125? encodings recognized by IANA)
- cp858
- EBCDIC encodings:

- EBCDIC US (ebcdic-cp-us)
- EBCDIC Canada (ebcdic-cp-ca)
- EBCDIC Netherland (ebcdic-cp-nl)
- EBCDIC Denmark (ebcdic-cp-dk)
- EBCDIC Norway (ebcdic-cp-no)
- EBCDIC Finland (ebcdic-cp-fi)
- EBCDIC Sweden (ebcdic-cp-se)
- EBCDIC Italy (ebcdic-cp-it)
- EBCDIC Spain, Latin America (ebcdic-cp-es)
- EBCDIC Great Britain (ebcdic-cp-gb)
- EBCDIC France (ebcdic-cp-fr)
- EBCDIC Hebrew (ebcdic-cp-he)
- EBCDIC Switzerland (ebcdic-cp-ch)
- EBCDIC Roece (ebcdic-cp-roece)
- EBCDIC Yugoslavia (ebcdic-cp-yu)
- EBCDIC Iceland (ebcdic-cp-is)
- EBCDIC Urdu (ebcdic-cp-ar2)
- Latin 0 EBCDIC
- EBCDIC Arabic (ebcdic-cp-ar1)

| Why is the parser unable to access schema documents or external entities available on the Internet? |

The parser may not be able to access various external entities or schema documents (imported, included etc...) available on the Internet, such as the Schema for Schemas "http://www.w3.org/2001/XMLSchema.xsd" or the schema defining xml:base, xml:lang attributes etc... "http://www.w3.org/2001/xml.xsd" or any other external entity available on the Internet. There are various reasons one could experience such a problem.
One of the reasons could be that your proxy settings do not allow the parser to make URL connections through a proxy server. To solve this problem, before parsing a document, the application must set the two system properties: "http.proxyHost" and "http.proxyPort". Another reason could be due to strict firewall settings that do not allow any URL connection to be made to the outside web. The problem may also be caused by a server that is offline or inaccessible on the network, preventing documents hosted by the server from being accessed.

| What JDK level is required for Xerces? |

| As of version 2.10.0, Xerces requires JDK 1.3 or later to run and also requires JDK 1.3 or later to build the source code. Starting with the Xerces 2.11.0 release, the XML Schema 1.1 experimental distribution requires JDK 1.4 or later to run and also to build the source code.

Copyright © 1999-2010 The Apache Software Foundation. All Rights Reserved.