Class loaders may typically be used by security managers to indicate * security domains. * + *
In addition to loading classes, a class loader is also responsible for + * locating resources. A resource is some data (a "{@code .class}" file, + * configuration data, or an image for example) that is identified with an + * abstract '/'-separated path name. Resources are typically packaged with an + * application or library so that they can be located by code in the + * application or library. In some cases, the resources are included so that + * they can be located by other libraries. + * *
The {@code ClassLoader} class uses a delegation model to search for * classes and resources. Each instance of {@code ClassLoader} has an - * associated parent class loader. When requested to find a class or - * resource, a {@code ClassLoader} instance will delegate the search for the - * class or resource to its parent class loader before attempting to find the - * class or resource itself. + * associated parent class loader. When requested to find a class or + * resource, a {@code ClassLoader} instance will usually delegate the search + * for the class or resource to its parent class loader before attempting to + * find the class or resource itself. * *
Class loaders that support concurrent loading of classes are known as * {@linkplain #isRegisteredAsParallelCapable() parallel capable} class @@ -129,11 +137,13 @@ * classes and JDK-specific run-time classes that are defined by the * platform class loader or its ancestors. *
To allow for upgrading/overriding of modules defined to the platform - * class loader, and where classes in the upgraded version link to - * classes in modules defined to the application class loader, the - * platform class loader may delegate to the application class loader. - * In other words, classes in named modules defined to the application - * class loader may be visible to the platform class loader. + * class loader, and where upgraded modules read modules defined to class + * loaders other than the platform class loader and its ancestors, then + * the platform class loader may have to delegate to other class loaders, + * the application class loader for example. + * In other words, classes in named modules defined to class loaders + * other than the platform class loader and its ancestors may be visible + * to the platform class loader. *
{@linkplain #getSystemClassLoader() System class loader}. * It is also known as application class loader and is distinct * from the platform class loader. @@ -498,7 +508,7 @@ * *
Invoke the {@link #loadClass(String) loadClass} method * on the parent class loader. If the parent is {@code null} the class - * loader built-in to the virtual machine is used, instead.
Invoke the {@link #findClass(String)} method to find the * class.
The name of a resource is a '{@code /}'-separated path name that - * identifies the resource. - * - *
This method will first search the parent class loader for the - * resource; if the parent is {@code null} the path of the class loader - * built-in to the virtual machine is searched. That failing, this method - * will invoke {@link #findResource(String)} to find the resource.
+ * identifies the resource. * *Resources in named modules are subject to the encapsulation rules * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}. @@ -1344,6 +1351,11 @@ * opened} unconditionally (even if the caller of this method is in the * same module as the resource).
* + * @implSpec The default implementation will first search the parent class + * loader for the resource; if the parent is {@code null} the path of the + * class loader built into the virtual machine is searched. If not found, + * this method will invoke {@link #findResource(String)} to find the resource. + * * @apiNote Where several modules are defined to the same class loader, * and where more than one module contains a resource with the given name, * then the ordering that modules are searched is not specified and may be @@ -1387,10 +1399,7 @@ * that is independent of the location of the code. * *The name of a resource is a {@code /}-separated path name that - * identifies the resource. - * - *
The delegation order for searching is described in the documentation - * for {@link #getResource(String)}.
+ * identifies the resource. * *Resources in named modules are subject to the encapsulation rules * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}. @@ -1398,7 +1407,15 @@ * name ending with "{@code .class}", this method will only find resources in * packages of named modules when the package is {@link Module#isOpen(String) * opened} unconditionally (even if the caller of this method is in the - * same module as the resource).
+ * same module as the resource). + * + * @implSpec The default implementation will first search the parent class + * loader for the resource; if the parent is {@code null} the path of the + * class loader built into the virtual machine is searched. It then + * invokes {@link #findResources(String)} to find the resources with the + * name in this class loader. It returns an enumeration whose elements + * are the URLs found by searching the parent class loader followed by + * the elements found with {@code findResources}. * * @apiNote Where several modules are defined to the same class loader, * and where more than one module contains a resource with the given name, @@ -1424,8 +1441,6 @@ * If I/O errors occur * @throws NullPointerException If {@code name} is {@code null} * - * @see #findResources(String) - * * @since 1.2 * @revised 9 * @spec JPMS @@ -1453,9 +1468,6 @@ *The name of a resource is a {@code /}-separated path name that * identifies the resource. * - *
The search order is described in the documentation for {@link - * #getResource(String)}. - * *
The resources will be located when the returned stream is evaluated. * If the evaluation results in an {@code IOException} then the I/O * exception is wrapped in an {@link UncheckedIOException} that is then @@ -1469,6 +1481,10 @@ * opened} unconditionally (even if the caller of this method is in the * same module as the resource).
* + * @implSpec The default implementation invokes {@link #getResources(String) + * getResources} to find all the resources with the given name and returns + * a stream with the elements in the enumeration as the source. + * * @apiNote When overriding this method it is recommended that an * implementation ensures that any delegation is consistent with the {@link * #getResource(java.lang.String) getResource(String)} method. This should @@ -1486,8 +1502,6 @@ * * @throws NullPointerException If {@code name} is {@code null} * - * @see #findResources(String) - * * @since 9 */ public StreamFor resources in named modules then the method must implement the * rules for encapsulation specified in the {@code Module} {@link @@ -1515,6 +1529,8 @@ * modules unless the package is {@link Module#isOpen(String) opened} * unconditionally.
* + * @implSpec The default implementation returns {@code null}. + * * @param name * The resource name * @@ -1535,8 +1551,7 @@ /** * Returns an enumeration of {@link java.net.URL URL} objects * representing all the resources with the given name. Class loader - * implementations should override this method to specify where to load - * resources from. + * implementations should override this method. * *For resources in named modules then the method must implement the * rules for encapsulation specified in the {@code Module} {@link @@ -1545,6 +1560,9 @@ * modules unless the package is {@link Module#isOpen(String) opened} * unconditionally.
* + * @implSpec The default implementation returns an enumeration that + * contains no elements. + * * @param name * The resource name * @@ -1899,7 +1917,8 @@ // the system class loader is the built-in app class loader during startup return getBuiltinAppClassLoader(); case 3: - throw new InternalError("getSystemClassLoader should only be called after VM booted"); + String msg = "getSystemClassLoader should only be called after VM booted"; + throw new InternalError(msg); case 4: // system fully initialized assert VM.isBooted() && scl != null;