Package java.net

Class URLClassLoader

java.lang.Object
java.lang.ClassLoader
java.security.SecureClassLoader
java.net.URLClassLoader
public class URLClassLoader
extends SecureClassLoader
This class loader is responsible for loading classes and resources from a list of URLs which can refer to either directories or JAR files. Classes loaded by this URLClassLoader are granted permission to access the URLs contained in the URL search list.

  • Constructor Details

    • URLClassLoader

      public URLClassLoader​(URL[] urls)
      Constructs a new URLClassLoader instance. The newly created instance will have the system ClassLoader as its parent. URLs that end with "/" are assumed to be directories, otherwise they are assumed to be JAR files.
      Parameters:
      urls - the list of URLs where a specific class or file could be found.

    • URLClassLoader

      public URLClassLoader​(URL[] urls, ClassLoader parent)
      Constructs a new URLClassLoader instance. The newly created instance will have the system ClassLoader as its parent. URLs that end with "/" are assumed to be directories, otherwise they are assumed to be JAR files.
      Parameters:
      urls - the list of URLs where a specific class or file could be found.
      parent - the class loader to assign as this loader's parent.

    • URLClassLoader

      public URLClassLoader​(URL[] searchUrls, ClassLoader parent, URLStreamHandlerFactory factory)
      Constructs a new URLClassLoader instance. The newly created instance will have the specified ClassLoader as its parent and use the specified factory to create stream handlers. URLs that end with "/" are assumed to be directories, otherwise they are assumed to be JAR files.
      Parameters:
      searchUrls - the list of URLs where a specific class or file could be found.
      parent - the ClassLoader to assign as this loader's parent.
      factory - the factory that will be used to create protocol-specific stream handlers.

  • Method Details

    • addURL

      protected void addURL​(URL url)
      Adds the specified URL to the search list.
      Parameters:
      url - the URL which is to add.

    • findResources

      public Enumeration<URL> findResources​(String name) throws IOException
      Returns all known URLs which point to the specified resource.
      Overrides:
      findResources in class ClassLoader
      Parameters:
      name - the name of the requested resource.
      Returns:
      the enumeration of URLs which point to the specified resource.
      Throws:
      IOException - if an I/O error occurs while attempting to connect.

    • getPermissions

      protected PermissionCollection getPermissions​(CodeSource codesource)
      Gets all permissions for the specified codesource. First, this method retrieves the permissions from the system policy. If the protocol is "file:/" then a new permission, FilePermission, granting the read permission to the file is added to the permission collection. Otherwise, connecting to and accepting connections from the URL is granted.
      Overrides:
      getPermissions in class SecureClassLoader
      Parameters:
      codesource - the code source object whose permissions have to be known.
      Returns:
      the list of permissions according to the code source object.

    • getURLs

      public URL[] getURLs()
      Returns the search list of this URLClassLoader.
      Returns:
      the list of all known URLs of this instance.

    • newInstance

      public static URLClassLoader newInstance​(URL[] urls)
      Returns a new URLClassLoader instance for the given URLs and the system ClassLoader as its parent.
      Parameters:
      urls - the list of URLs that is passed to the new URLClassLoader.
      Returns:
      the created URLClassLoader instance.

    • newInstance

      public static URLClassLoader newInstance​(URL[] urls, ClassLoader parentCl)
      Returns a new URLClassLoader instance for the given URLs and the specified ClassLoader as its parent.
      Parameters:
      urls - the list of URLs that is passed to the new URLClassLoader.
      parentCl - the parent class loader that is passed to the new URLClassLoader.
      Returns:
      the created URLClassLoader instance.

    • findClass

      protected Class<?> findClass​(String className) throws ClassNotFoundException
      Tries to locate and load the specified class using the known URLs. If the class could be found, a class object representing the loaded class will be returned.
      Overrides:
      findClass in class ClassLoader
      Parameters:
      className - the name of the class to look for.
      Returns:
      the Class object that is found.
      Throws:
      ClassNotFoundException - if the specified class cannot be loaded.

    • findResource

      public URL findResource​(String name)
      Returns an URL referencing the specified resource or null if the resource could not be found.
      Overrides:
      findResource in class ClassLoader
      Parameters:
      name - the name of the requested resource.
      Returns:
      the URL which points to the given resource.

    • definePackage

      protected Package definePackage​(String packageName, Manifest manifest, URL url) throws IllegalArgumentException
      Defines a new package using the information extracted from the specified manifest.
      Parameters:
      packageName - the name of the new package.
      manifest - the manifest containing additional information for the new package.
      url - the URL to the code source for the new package.
      Returns:
      the created package.
      Throws:
      IllegalArgumentException - if a package with the given name already exists.