Package java.net

Class 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 Detail

      • 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 Detail

      • 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.