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java.lang.Objectedu.emory.mathcs.util.classloader.ResourceLoader
This class aids in accessing remote resources referred by URLs.
The URLs are resolved into resource handles
which can
be used to access the resources directly and uniformly, regardless of the
URL type. The resource loader
is particularly useful when dealing with resources fetched from JAR files.
It maintains the cache of opened JAR files (so that so that
subsequent requests for resources coming from the same base Jar file can be
handled efficiently). It fully supports JAR class-path (references from
a JAR file to other JAR files) and JAR index (JAR containing information
about content of other JARs). The caching policy of downloaded JAR files can
be customized via the constructor parameter jarHandler
; the
default policy is to use separate cache per each
ResourceLoader instance.
This class is particularly useful when implementing custom class loaders.
It provides bottom-level resource fetching functionality. By using one of
the loader methods which accepts an array of URLs, it
is straightforward to implement class-path searching similar to that
of URLClassLoader
, with JAR dependencies (Class-Path)
properly resolved and with JAR indexes properly handled.
This class provides two set of methods: get methods that return
ResourceHandle
s (or their enumerations) and find methods that
return URLs (or their enumerations). If the resource is not found,
null (or empty enumeration) is returned. Resource handles represent a
connection to the resource and they should be closed when done
processing, just like input streams. In contrast, find methods return
URLs that can be used to open multiple connections to the resource. In
typical class loader applications, when a single retrieval is sufficient,
it is preferable to use get methods since they pose slightly smaller
communication overhead.
Constructor Summary | |
ResourceLoader()
Constructs new ResourceLoadeer with default JAR caching policy, that is, to create and use separate cache for this ResourceLoader instance. |
|
ResourceLoader(java.net.URLStreamHandler jarHandler)
Constructs new ResourceLoader with specified JAR file handler which can implement custom JAR caching policy. |
Method Summary | |
java.net.URL |
findResource(java.net.URL[] sources,
java.lang.String name)
Finds resource with given name at the given search path. |
java.net.URL |
findResource(java.net.URL source,
java.lang.String name)
Fined resource with given name at the given source URL. |
java.util.Enumeration |
findResources(java.net.URL[] sources,
java.lang.String name)
Finds all resources with given name at the given search path. |
java.util.Enumeration |
findResources(java.net.URL source,
java.lang.String name)
Finds all resources with given name at the given source URL. |
ResourceHandle |
getResource(java.net.URL[] sources,
java.lang.String name)
Gets resource with given name at the given search path. |
ResourceHandle |
getResource(java.net.URL source,
java.lang.String name)
Gets resource with given name at the given source URL. |
java.util.Enumeration |
getResources(java.net.URL[] sources,
java.lang.String name)
Gets all resources with given name at the given search path. |
java.util.Enumeration |
getResources(java.net.URL source,
java.lang.String name)
Gets all resources with given name at the given source URL. |
protected static boolean |
isDir(java.net.URL url)
Test whether given URL points to a directory. |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public ResourceLoader()
public ResourceLoader(java.net.URLStreamHandler jarHandler)
jarHandler
- JAR file handlerMethod Detail |
public ResourceHandle getResource(java.net.URL source, java.lang.String name)
source
- the source URLname
- the resource name
public ResourceHandle getResource(java.net.URL[] sources, java.lang.String name)
sources
- the source URL pathname
- the resource name
public java.util.Enumeration getResources(java.net.URL source, java.lang.String name)
The search is lazy, that is, "find next resource" operation is triggered
by calling Enumeration.hasMoreElements()
.
source
- the source URLname
- the resource name
public java.util.Enumeration getResources(java.net.URL[] sources, java.lang.String name)
The search is lazy, that is, "find next resource" operation is triggered
by calling Enumeration.hasMoreElements()
.
sources
- the source URL pathname
- the resource name
public java.net.URL findResource(java.net.URL source, java.lang.String name)
source
- the source URLname
- the resource name
public java.net.URL findResource(java.net.URL[] sources, java.lang.String name)
sources
- the source URL pathname
- the resource name
public java.util.Enumeration findResources(java.net.URL source, java.lang.String name)
The search is lazy, that is, "find next resource" operation is triggered
by calling Enumeration.hasMoreElements()
.
source
- the source URLname
- the resource name
public java.util.Enumeration findResources(java.net.URL[] sources, java.lang.String name)
The search is lazy, that is, "find next resource" operation is triggered
by calling Enumeration.hasMoreElements()
.
sources
- the source URL pathname
- the resource name
protected static boolean isDir(java.net.URL url)
url
- the URL to test
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