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edu.emory.mathcs.util.classloader
Class ResourceLoader
java.lang.Objectedu.emory.mathcs.util.classloader.ResourceLoader
- public class ResourceLoader
- extends java.lang.Object
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 java.net.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 ResourceHandles (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.
- Version:
- 1.0
| Nested Class Summary | |
private static class |
ResourceLoader.JarInfo
|
private static class |
ResourceLoader.JarResourceHandle
|
private class |
ResourceLoader.ResourceEnumeration
|
| Field Summary | |
private static java.lang.String |
JAR_INDEX_ENTRY_NAME
|
(package private) java.net.URLStreamHandler |
jarHandler
|
(package private) java.util.Map |
url2jarInfo
|
| 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 ResourceLoadeer 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. |
private java.net.URL |
findResource(java.net.URL source,
java.lang.String name,
java.util.Set visitedJars,
java.util.Set skip)
|
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. |
private ResourceLoader.JarInfo |
getJarInfo(java.net.URL 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. |
private ResourceHandle |
getResource(java.net.URL source,
java.lang.String name,
java.util.Set visitedJars,
java.util.Set skip)
|
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. |
private static java.net.URL[] |
parseClassPath(java.util.jar.JarFile jar,
java.net.URL source)
|
private static java.util.Map |
parseDependentJarIndex(java.net.URL cxt,
java.util.jar.JarFile jar)
|
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
JAR_INDEX_ENTRY_NAME
private static final java.lang.String JAR_INDEX_ENTRY_NAME
- See Also:
- Constant Field Values
jarHandler
final java.net.URLStreamHandler jarHandler
url2jarInfo
final java.util.Map url2jarInfo
| Constructor Detail |
ResourceLoader
public ResourceLoader()
- Constructs new ResourceLoadeer with default JAR caching policy, that is,
to create and use separate cache for this ResourceLoader instance.
ResourceLoader
public ResourceLoader(java.net.URLStreamHandler jarHandler)
- Constructs new ResourceLoadeer with specified JAR file handler which can
implement custom JAR caching policy.
| Method Detail |
getResource
public ResourceHandle getResource(java.net.URL source, java.lang.String name)
- Gets resource with given name at the given source URL. If the URL points
to a directory, the name is the file path relative to this directory.
If the URL points to a JAR file, the name identifies an entry in that
JAR file. If the URL points to a JAR file, the resource is not found
in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
getResource
public ResourceHandle getResource(java.net.URL[] sources, java.lang.String name)
- Gets resource with given name at the given search path. The path is
searched iteratively, one URL at a time. If the URL points
to a directory, the name is the file path relative to this directory.
If the URL points to the JAR file, the name identifies an entry in that
JAR file. If the URL points to the JAR file, the resource is not found
in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
getResources
public java.util.Enumeration getResources(java.net.URL source, java.lang.String name)
- Gets all resources with given name at the given source URL. If the URL
points to a directory, the name is the file path relative to this
directory. If the URL points to a JAR file, the name identifies an entry
in that JAR file. If the URL points to a JAR file, the resource is not
found in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
The search is lazy, i.e. "find next resource" operation is triggered by calling Enumeration.hasMoreElements()>
Enumeration.hasMoreElements()55 .
getResources
public java.util.Enumeration getResources(java.net.URL[] sources, java.lang.String name)
- Gets all resources with given name at the given search path. If the URL
points to a directory, the name is the file path relative to this
directory. If the URL points to a JAR file, the name identifies an entry
in that JAR file. If the URL points to a JAR file, the resource is not
found in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
The search is lazy, i.e. "find next resource" operation is triggered by calling Enumeration.hasMoreElements()>
Enumeration.hasMoreElements()55 .
getResource
private ResourceHandle getResource(java.net.URL source, java.lang.String name, java.util.Set visitedJars, java.util.Set skip)
findResource
public java.net.URL findResource(java.net.URL source, java.lang.String name)
- Fined resource with given name at the given source URL. If the URL points
to a directory, the name is the file path relative to this directory.
If the URL points to a JAR file, the name identifies an entry in that
JAR file. If the URL points to a JAR file, the resource is not found
in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
findResource
public java.net.URL findResource(java.net.URL[] sources, java.lang.String name)
- Finds resource with given name at the given search path. The path is
searched iteratively, one URL at a time. If the URL points
to a directory, the name is the file path relative to this directory.
If the URL points to the JAR file, the name identifies an entry in that
JAR file. If the URL points to the JAR file, the resource is not found
in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
findResources
public java.util.Enumeration findResources(java.net.URL source, java.lang.String name)
- Finds all resources with given name at the given source URL. If the URL
points to a directory, the name is the file path relative to this
directory. If the URL points to a JAR file, the name identifies an entry
in that JAR file. If the URL points to a JAR file, the resource is not
found in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
The search is lazy, i.e. "find next resource" operation is triggered by calling Enumeration.hasMoreElements()>
Enumeration.hasMoreElements()55 .
findResources
public java.util.Enumeration findResources(java.net.URL[] sources, java.lang.String name)
- Finds all resources with given name at the given search path. If the URL
points to a directory, the name is the file path relative to this
directory. If the URL points to a JAR file, the name identifies an entry
in that JAR file. If the URL points to a JAR file, the resource is not
found in that JAR file, and the JAR file has Class-Path attribute, the
JAR files identified in the Class-Path are also searched for the
resource.
The search is lazy, i.e. "find next resource" operation is triggered by calling Enumeration.hasMoreElements()>
Enumeration.hasMoreElements()55 .
findResource
private java.net.URL findResource(java.net.URL source, java.lang.String name, java.util.Set visitedJars, java.util.Set skip)
isDir
protected static boolean isDir(java.net.URL url)
- Test whether given URL points to a directory. URL is deemed to point
to a directory if has non-null "file" component ending with "/".
getJarInfo
private ResourceLoader.JarInfo getJarInfo(java.net.URL url) throws java.net.MalformedURLException
parseDependentJarIndex
private static java.util.Map parseDependentJarIndex(java.net.URL cxt, java.util.jar.JarFile jar) throws java.io.IOException
parseClassPath
private static java.net.URL[] parseClassPath(java.util.jar.JarFile jar, java.net.URL source) throws java.io.IOException
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SUMMARY: JAVADOC | SOURCE | DOWNLOAD | NESTED | FIELD | CONSTR | METHOD |
DETAIL: FIELD | CONSTR | METHOD | ||||||||