Closeable
, AutoCloseable
MLet
public class URLClassLoader extends SecureClassLoader implements Closeable
jar:
scheme URL (see JarURLConnection
) is assumed to refer to a JAR file. Any file:
scheme URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be opened as needed. This class loader supports the loading of classes and resources from the contents of a multi-release JAR file that is referred to by a given URL.
The AccessControlContext of the thread that created the instance of URLClassLoader will be used when subsequently loading classes and resources.
The classes that are loaded are by default granted permission only to access the URLs specified when the URLClassLoader was created.
Constructor | Description |
---|---|
URLClassLoader |
Constructs a new named URLClassLoader for the specified URLs. |
URLClassLoader |
Constructs a new named URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory. |
URLClassLoader |
Constructs a new URLClassLoader for the specified URLs using the default delegation parent ClassLoader . |
URLClassLoader |
Constructs a new URLClassLoader for the given URLs. |
URLClassLoader |
Constructs a new URLClassLoader for the specified URLs, parent class loader, and URLStreamHandlerFactory. |
Modifier and Type | Method | Description |
---|---|---|
protected void |
addURL |
Appends the specified URL to the list of URLs to search for classes and resources. |
void |
close() |
Closes this URLClassLoader, so that it can no longer be used to load new classes or resources that are defined by this loader. |
protected Package |
definePackage |
Defines a new package by name in this URLClassLoader . |
protected Class |
findClass |
Finds and loads the class with the specified name from the URL search path. |
URL |
findResource |
Finds the resource with the specified name on the URL search path. |
Enumeration |
findResources |
Returns an Enumeration of URLs representing all of the resources on the URL search path having the specified name. |
protected PermissionCollection |
getPermissions |
Returns the permissions for the given codesource object. |
InputStream |
getResourceAsStream |
Returns an input stream for reading the specified resource. |
URL[] |
getURLs() |
Returns the search path of URLs for loading classes and resources. |
static URLClassLoader |
newInstance |
Creates a new instance of URLClassLoader for the specified URLs and default parent class loader. |
static URLClassLoader |
newInstance |
Creates a new instance of URLClassLoader for the specified URLs and parent class loader. |
defineClass, defineClass
clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findSystemClass, getClassLoadingLock, getDefinedPackage, getDefinedPackages, getName, getPackage, getPackages, getParent, getPlatformClassLoader, getResource, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, getUnnamedModule, isRegisteredAsParallelCapable, loadClass, loadClass, registerAsParallelCapable, resolveClass, resources, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners
public URLClassLoader(URL[] urls, ClassLoader parent)
jar:
scheme URL is assumed to refer to a JAR file. Any file:
scheme URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be downloaded and opened as needed. If there is a security manager, this method first calls the security manager's checkCreateClassLoader
method to ensure creation of a class loader is allowed.
urls
- the URLs from which to load classes and resourcesparent
- the parent class loader for delegationSecurityException
- if a security manager exists and its checkCreateClassLoader
method doesn't allow creation of a class loader.NullPointerException
- if urls
or any of its elements is null
.public URLClassLoader(URL[] urls)
ClassLoader
. The URLs will be searched in the order specified for classes and resources after first searching in the parent class loader. Any URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be downloaded and opened as needed. If there is a security manager, this method first calls the security manager's checkCreateClassLoader
method to ensure creation of a class loader is allowed.
urls
- the URLs from which to load classes and resourcesSecurityException
- if a security manager exists and its checkCreateClassLoader
method doesn't allow creation of a class loader.NullPointerException
- if urls
or any of its elements is null
.public URLClassLoader(URL[] urls, ClassLoader parent, URLStreamHandlerFactory factory)
If there is a security manager, this method first calls the security manager's checkCreateClassLoader
method to ensure creation of a class loader is allowed.
urls
- the URLs from which to load classes and resourcesparent
- the parent class loader for delegationfactory
- the URLStreamHandlerFactory to use when creating URLsSecurityException
- if a security manager exists and its checkCreateClassLoader
method doesn't allow creation of a class loader.NullPointerException
- if urls
or any of its elements is null
.public URLClassLoader(String name, URL[] urls, ClassLoader parent)
URLClassLoader
for the specified URLs. The URLs will be searched in the order specified for classes and resources after first searching in the specified parent class loader. Any URL that ends with a '/' is assumed to refer to a directory. Otherwise, the URL is assumed to refer to a JAR file which will be downloaded and opened as needed.name
- class loader name; or null
if not namedurls
- the URLs from which to load classes and resourcesparent
- the parent class loader for delegationIllegalArgumentException
- if the given name is empty.NullPointerException
- if urls
or any of its elements is null
.SecurityException
- if a security manager exists and its SecurityManager.checkCreateClassLoader()
method doesn't allow creation of a class loader.public URLClassLoader(String name, URL[] urls, ClassLoader parent, URLStreamHandlerFactory factory)
URLClassLoader
for the specified URLs, parent class loader, and URLStreamHandlerFactory. The parent argument will be used as the parent class loader for delegation. The factory argument will be used as the stream handler factory to obtain protocol handlers when creating new jar URLs.name
- class loader name; or null
if not namedurls
- the URLs from which to load classes and resourcesparent
- the parent class loader for delegationfactory
- the URLStreamHandlerFactory to use when creating URLsIllegalArgumentException
- if the given name is empty.NullPointerException
- if urls
or any of its elements is null
.SecurityException
- if a security manager exists and its checkCreateClassLoader
method doesn't allow creation of a class loader.public InputStream getResourceAsStream(String name)
The search order is described in the documentation for ClassLoader.getResource(String)
.
getResourceAsStream
in class ClassLoader
name
- The resource namenull
if the resource could not be foundNullPointerException
- If name
is null
public void close() throws IOException
In the case of jar: and file: URLs, it also closes any files that were opened by it. If another thread is loading a class when the close
method is invoked, then the result of that load is undefined.
The method makes a best effort attempt to close all opened files, by catching IOException
s internally. Unchecked exceptions and errors are not caught. Calling close on an already closed loader has no effect.
close
in interface AutoCloseable
close
in interface Closeable
IOException
- if closing any file opened by this class loader resulted in an IOException. Any such exceptions are caught internally. If only one is caught, then it is re-thrown. If more than one exception is caught, then the second and following exceptions are added as suppressed exceptions of the first one caught, which is then re-thrown.SecurityException
- if a security manager is set, and it denies RuntimePermission
("closeClassLoader")
protected void addURL(URL url)
If the URL specified is null
or is already in the list of URLs, or if this loader is closed, then invoking this method has no effect.
url
- the URL to be added to the search path of URLspublic URL[] getURLs()
protected Class<?> findClass(String name) throws ClassNotFoundException
findClass
in class ClassLoader
name
- the name of the classClassNotFoundException
- if the class could not be found, or if the loader is closed.NullPointerException
- if name
is null
.protected Package definePackage(String name, Manifest man, URL url)
URLClassLoader
. The attributes contained in the specified Manifest
will be used to obtain package version and sealing information. For sealed packages, the additional URL specifies the code source URL from which the package was loaded.name
- the package nameman
- the Manifest
containing package version and sealing informationurl
- the code source url for the package, or null if nonePackage
objectIllegalArgumentException
- if the package name is already defined by this class loaderpublic URL findResource(String name)
findResource
in class ClassLoader
name
- the name of the resourceURL
for the resource, or null
if the resource could not be found, or if the loader is closed.public Enumeration<URL> findResources(String name) throws IOException
findResources
in class ClassLoader
name
- the resource nameEnumeration
of URL
s. If the loader is closed, the Enumeration contains no elements.IOException
- if an I/O exception occursprotected PermissionCollection getPermissions(CodeSource codesource)
If the protocol of this URL is "jar", then the permission granted is based on the permission that is required by the URL of the Jar file.
If the protocol is "file" and there is an authority component, then permission to connect to and accept connections from that authority may be granted. If the protocol is "file" and the path specifies a file, then permission to read that file is granted. If protocol is "file" and the path is a directory, permission is granted to read all files and (recursively) all files and subdirectories contained in that directory.
If the protocol is not "file", then permission to connect to and accept connections from the URL's host is granted.
getPermissions
in class SecureClassLoader
codesource
- the codesourceNullPointerException
- if codesource
is null
.public static URLClassLoader newInstance(URL[] urls, ClassLoader parent)
loadClass
method of the URLClassLoader returned by this method will invoke the SecurityManager.checkPackageAccess
method before loading the class.urls
- the URLs to search for classes and resourcesparent
- the parent class loader for delegationNullPointerException
- if urls
or any of its elements is null
.public static URLClassLoader newInstance(URL[] urls)
loadClass
method of the URLClassLoader returned by this method will invoke the SecurityManager.checkPackageAccess
before loading the class.urls
- the URLs to search for classes and resourcesNullPointerException
- if urls
or any of its elements is null
.
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/net/URLClassLoader.html