Difference between revisions of "Catalog Resolver"

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This article is part of the [[Advanced User's Guide]].
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This article is part of the [[Advanced User's Guide]]. It clarifies how to deal with external DTD declarations when parsing and transforming XML data.
It clarifies how to deal with external DTD declarations
 
when parsing XML data.
 
  
==Overview==
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==Introduction==
  
 
XML documents often rely on Document Type Definitions (DTDs). While parsing a document with BaseX, entities can be resolved with respect to that particular DTD. By default, the DTD is only used for entity resolution.
 
XML documents often rely on Document Type Definitions (DTDs). While parsing a document with BaseX, entities can be resolved with respect to that particular DTD. By default, the DTD is only used for entity resolution.
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Fetching <code>xhtml1-strict.dtd</code> obviously involves network traffic. When dealing with single files, this may seem tolerable, but importing large collections benefits from caching these resources. Depending on the remote server, you will experience significant speed improvements when caching DTDs locally.
 
Fetching <code>xhtml1-strict.dtd</code> obviously involves network traffic. When dealing with single files, this may seem tolerable, but importing large collections benefits from caching these resources. Depending on the remote server, you will experience significant speed improvements when caching DTDs locally.
  
== XML Entity and URI Resolvers ==
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==Usage==
  
 
BaseX relies on the Apache-maintained [http://xml.apache.org/commons XML Commons Resolver]. The {{Code|xml-resolver-1.2.jar}} library is included in the full distributions of BaseX. If the resolver is not found in the classpath, and if Java 8 is used, Java’s built-in resolver will be applied (via <code>com.sun.org.apache.xml.internal.resolver.*</code>).
 
BaseX relies on the Apache-maintained [http://xml.apache.org/commons XML Commons Resolver]. The {{Code|xml-resolver-1.2.jar}} library is included in the full distributions of BaseX. If the resolver is not found in the classpath, and if Java 8 is used, Java’s built-in resolver will be applied (via <code>com.sun.org.apache.xml.internal.resolver.*</code>).
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The '''paths''' to your catalog file and the actual DTDs are either absolute or relative to the ''current working directory''. When using BaseX in Client-Server-Mode, this is relative to the ''server's'' working directory.
 
The '''paths''' to your catalog file and the actual DTDs are either absolute or relative to the ''current working directory''. When using BaseX in Client-Server-Mode, this is relative to the ''server's'' working directory.
  
===Please Note===
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===Additional Notes===
  
 
Entity resolving only works if the [[Parsers#XML Parsers|internal XML parser]] is switched off (which is the default case).
 
Entity resolving only works if the [[Parsers#XML Parsers|internal XML parser]] is switched off (which is the default case).
 
If you use the internal parser, you can manually specify whether you want to parse DTDs and entities or not.
 
If you use the internal parser, you can manually specify whether you want to parse DTDs and entities or not.
  
== More Information ==
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If no {{Code|CatalogManager.properties}} property file is found in the classpath, the following catalog resolver properties will be set (see [https://xerces.apache.org/xml-commons/components/resolver/resolver-article.html#ctrlresolver Controlling the Catalog Resolver] for more information):
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* {{Code|xml.catalog.ignoreMissing}}: {{Code|true}}
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* {{Code|xml.catalog.staticCatalog}}: {{Code|false}}
  
*[http://en.wikipedia.org/wiki/Document_Type_Definition Wikipedia on Document Type Definitions]
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==Links==
*[http://xml.apache.org/commons/components/resolver/resolver-article.html Apache XML Commons Article on Entity Resolving]
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*[http://java.sun.com/webservices/docs/1.6/jaxb/catalog.html XML Entity and URI Resolvers], Sun
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* [http://en.wikipedia.org/wiki/Document_Type_Definition Wikipedia on Document Type Definitions]
*[http://www.oasis-open.org/committees/download.php/14810/xml-catalogs.pdf XML Catalogs. OASIS Standard, Version 1.1. 07-October-2005.]
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* [http://xml.apache.org/commons/components/resolver/resolver-article.html Apache XML Commons Article on Entity Resolving]
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* [http://java.sun.com/webservices/docs/1.6/jaxb/catalog.html XML Entity and URI Resolvers], Sun
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* [http://www.oasis-open.org/committees/download.php/14810/xml-catalogs.pdf XML Catalogs. OASIS Standard, Version 1.1. 07-October-2005.]

Revision as of 12:37, 5 March 2019

This article is part of the Advanced User's Guide. It clarifies how to deal with external DTD declarations when parsing and transforming XML data.

Introduction

XML documents often rely on Document Type Definitions (DTDs). While parsing a document with BaseX, entities can be resolved with respect to that particular DTD. By default, the DTD is only used for entity resolution.

XHTML, for example, defines its doctype via the following line:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 

Fetching xhtml1-strict.dtd obviously involves network traffic. When dealing with single files, this may seem tolerable, but importing large collections benefits from caching these resources. Depending on the remote server, you will experience significant speed improvements when caching DTDs locally.

Usage

BaseX relies on the Apache-maintained XML Commons Resolver. The xml-resolver-1.2.jar library is included in the full distributions of BaseX. If the resolver is not found in the classpath, and if Java 8 is used, Java’s built-in resolver will be applied (via com.sun.org.apache.xml.internal.resolver.*).

To enable entity resolving you have to provide a valid XML Catalog file, so that the parser knows where to look for mirrored DTDs.

A simple working example for XHTML might look like this:

<catalog prefer="system" xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
  <rewriteSystem systemIdStartString="http://www.w3.org/TR/xhtml1/DTD/" rewritePrefix="file:///path/to/dtds/" />
</catalog>

This rewrites all systemIds starting with: http://www.w3.org/TR/xhtml1/DTD/ to file:///path/to/dtds/. The XHTML DTD xhtml1-strict.dtd and all its linked resources will now be loaded from the specified path.

The catalog file etc/w3-catalog.xml in the full distributions can be used out of the box. It defines rewriting for the most popular W3 DTD files.

GUI Mode

When running BaseX in GUI mode, simply provide the path to your XML Catalog file in the Parsing Tab of the Database Creation Dialog.

Console & Server Mode

To enable Entity Resolving in Console Mode, assign a catalog file path to the CATFILE option. All subsequent ADD commands will use the specified catalog file to resolve entities.

The paths to your catalog file and the actual DTDs are either absolute or relative to the current working directory. When using BaseX in Client-Server-Mode, this is relative to the server's working directory.

Additional Notes

Entity resolving only works if the internal XML parser is switched off (which is the default case). If you use the internal parser, you can manually specify whether you want to parse DTDs and entities or not.

If no CatalogManager.properties property file is found in the classpath, the following catalog resolver properties will be set (see Controlling the Catalog Resolver for more information):

  • xml.catalog.ignoreMissing: true
  • xml.catalog.staticCatalog: false

Links