org.apache.crimson.parser
Class Resolver

java.lang.Object
  org.apache.crimson.parser.Resolver

All Implemented Interfaces:

org.xml.sax.EntityResolver

public class Resolver

extends Object

implements org.xml.sax.EntityResolver

This entity resolver class provides a number of utilities which can help managment of external parsed entities in XML. These are commonly used to hold markup declarations that are to be used as part of a Document Type Declaration (DTD), or to hold text marked up with XML.

Features include:

• Static factory methods are provided for constructing SAX InputSource objects from Files, URLs, or MIME objects. This eliminates a class of error-prone coding in applications.
• Character encodings for XML documents are correctly supported:
  • The encodings defined in the RFCs for MIME content types (2046 for general MIME, and 2376 for XML in particular), are supported, handling charset=... attributes and accepting content types which are known to be safe for use with XML;
  • The character encoding autodetection algorithm identified in the XML specification is used, and leverages all of the JDK 1.1 (and later) character encoding support.
  • The use of MIME typing may optionally be disabled, forcing the use of autodetection, to support web servers which don't correctly report MIME types for XML. For example, they may report text that is encoded in EUC-JP as being US-ASCII text, leading to fatal errors during parsing.
  • The InputSource objects returned by this class always have a java.io.Reader available as the "character stream" property.
• Catalog entries can map public identifiers to Java resources or to local URLs. These are used to reduce network dependencies and loads, and will often be used for external DTD components. For example, packages shipping DTD files as resources in JAR files can eliminate network traffic when accessing them, and sites may provide local caches of common DTDs. Note that no particular catalog syntax is supported by this class, only the notion of a set of entries.

Subclasses can perform tasks such as supporting new URI schemes for URIs which are not URLs, such as URNs (see RFC 2396) or for accessing MIME entities which are part of a multipart/related group (see RFC 2387). They may also be used to support particular catalog syntaxes, such as the SGML/Open Catalog (SOCAT) which supports the SGML notion of "Formal Public Identifiers (FPIs).

Author:

David Brownell, Rajiv Mordani

Field Summary

private Hashtable	id2loader
private Hashtable	id2resource
private Hashtable	id2uri
private boolean	ignoringMIME
private static String[]	types

Constructor Summary

Resolver()
Constructs a resolver.

Method Summary

static org.xml.sax.InputSource	createInputSource(File file) Creates an input source from a given file, autodetecting the character encoding.
static org.xml.sax.InputSource	createInputSource(String contentType, InputStream stream, boolean checkType, String scheme) Returns an input source, using the MIME type information and URL scheme to statically determine the correct character encoding if possible and otherwise autodetecting it.
static org.xml.sax.InputSource	createInputSource(URL uri, boolean checkType) Creates an input source from a given URI.
boolean	isIgnoringMIME() Returns true if this resolver is ignoring MIME types in the documents it returns, to work around bugs in how servers have reported the documents' MIME types.
private InputStream	mapResource(String publicId)
private String	name2uri(String publicId)
void	registerCatalogEntry(String publicId, String uri) Registers the given public ID as corresponding to a particular URI, typically a local copy.
void	registerCatalogEntry(String publicId, String resourceName, ClassLoader loader) Registers a given public ID as corresponding to a particular Java resource in a given class loader, typically distributed with a software package.
org.xml.sax.InputSource	resolveEntity(String name, String uri) SAX: Resolve the given entity into an input source.
void	setIgnoringMIME(boolean value) Tells the resolver whether to ignore MIME types in the documents it retrieves.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ignoringMIME

private boolean ignoringMIME

id2uri

private Hashtable id2uri

id2resource

private Hashtable id2resource

id2loader

private Hashtable id2loader

types

private static final String[] types

Constructor Detail

Resolver

public Resolver()

Constructs a resolver.

Method Detail

createInputSource

public static org.xml.sax.InputSource createInputSource(String contentType,
                                                        InputStream stream,
                                                        boolean checkType,
                                                        String scheme)
                                                 throws IOException

Returns an input source, using the MIME type information and URL scheme to statically determine the correct character encoding if possible and otherwise autodetecting it. MIME carefully specifies the character encoding defaults, and how attributes of the content type can change it. XML further specifies two mandatory encodings (UTF-8 and UTF-16), and includes an XML declaration which can be used to internally label most documents encoded using US-ASCII supersets (such as Shift_JIS, EUC-JP, ISO-2022-*, ISO-8859-*, and more).

This method can be used to access XML documents which do not have URIs (such as servlet input streams, or most JavaMail message entities) and to support access methods such as HTTP POST or PUT. (URLs normally return content using the GET method.)

The caller should set the system ID in order for relative URIs found in this document to be interpreted correctly. In some cases, a custom resolver will need to be used; for example, documents may be grouped in a single MIME "multipart/related" bundle, and relative URLs would refer to other documents in that bundle.

Parameters:

contentType - The MIME content type for the source for which an InputSource is desired, such as text/xml;charset=utf-8.

stream - The input byte stream for the input source.

checkType - If true, this verifies that the content type is known to support XML documents, such as application/xml.

scheme - Unless this is "file", unspecified MIME types default to US-ASCII. Files are always autodetected since most file systems discard character encoding information.

Throws:

IOException

createInputSource

public static org.xml.sax.InputSource createInputSource(URL uri,
                                                        boolean checkType)
                                                 throws IOException

Creates an input source from a given URI.

Parameters:

uri - the URI (system ID) for the entity

checkType - if true, the MIME content type for the entity is checked for document type and character set encoding.

Throws:

IOException

createInputSource

public static org.xml.sax.InputSource createInputSource(File file)
                                                 throws IOException

Creates an input source from a given file, autodetecting the character encoding.

Throws:

IOException

resolveEntity

public org.xml.sax.InputSource resolveEntity(String name,
                                             String uri)
                                      throws IOException,
                                             org.xml.sax.SAXException

SAX: Resolve the given entity into an input source. If the name can't be mapped to a preferred form of the entity, the URI is used. To resolve the entity, first a local catalog mapping names to URIs is consulted. If no mapping is found there, a catalog mapping names to java resources is consulted. Finally, if neither mapping found a copy of the entity, the specified URI is used.

When a URI is used, createInputSource is used to correctly deduce the character encoding used by this entity. No MIME type checking is done.

Specified by:

resolveEntity in interface org.xml.sax.EntityResolver

Parameters:

name - Used to find alternate copies of the entity, when this value is non-null; this is the XML "public ID".

uri - Used when no alternate copy of the entity is found; this is the XML "system ID", normally a URI.

Throws:

IOException

org.xml.sax.SAXException

isIgnoringMIME

public boolean isIgnoringMIME()

Returns true if this resolver is ignoring MIME types in the documents it returns, to work around bugs in how servers have reported the documents' MIME types.

setIgnoringMIME

public void setIgnoringMIME(boolean value)

Tells the resolver whether to ignore MIME types in the documents it retrieves. Many web servers incorrectly assign text documents a default character encoding, even when that is incorrect. For example, all HTTP text documents default to use ISO-8859-1 (used for Western European languages), and other MIME sources default text documents to use US-ASCII (a seven bit encoding). For XML documents which include text encoding declarations (as most should do), these server bugs can be worked around by ignoring the MIME type entirely.

name2uri

private String name2uri(String publicId)

registerCatalogEntry

public void registerCatalogEntry(String publicId,
                                 String uri)

Registers the given public ID as corresponding to a particular URI, typically a local copy. This URI will be used in preference to ones provided as system IDs in XML entity declarations. This mechanism would most typically be used for Document Type Definitions (DTDs), where the public IDs are formally managed and versioned.

Parameters:

publicId - The managed public ID being mapped

uri - The URI of the preferred copy of that entity

mapResource

private InputStream mapResource(String publicId)

registerCatalogEntry

public void registerCatalogEntry(String publicId,
                                 String resourceName,
                                 ClassLoader loader)

Registers a given public ID as corresponding to a particular Java resource in a given class loader, typically distributed with a software package. This resource will be preferred over system IDs included in XML documents. This mechanism should most typically be used for Document Type Definitions (DTDs), where the public IDs are formally managed and versioned.

If a mapping to a URI has been provided, that mapping takes precedence over this one.

Parameters:

publicId - The managed public ID being mapped

resourceName - The name of the Java resource

loader - The class loader holding the resource, or null if it is a system resource.