Class ClassLoaderResolverImpl

java.lang.Object
org.datanucleus.ClassLoaderResolverImpl
All Implemented Interfaces:
ClassLoaderResolver
public class ClassLoaderResolverImpl extends Object implements ClassLoaderResolver
A basic implementation of a ClassLoaderResolver. A ClassLoaderResolver provides a series of methods for resolving classes from their names. It supports up to 3 class loaders, based loosely on JDO Spec section 12.5. The class loaders will be used in this order:
  • The loader that loaded the class or instance referred to in the API that caused this class to be loaded.
    • In case of query, this is the loader of the candidate class, or the loader of the object passed to the newQuery
    • In case of navigation from a persistent instance, this is the loader of the class of the instance.
    • In the case of getExtent with subclasses, this is the loader of the candidate class.
    • In the case of getObjectById, this is the loader of the object id instance.
    • Other cases do not have an explicit loader.
  • The loader returned in the current context by Thread.getContextClassLoader().
  • The loader returned by Thread.getContextClassLoader() at the time of creating an ExecutionContext.
  • The loader registered for dynamically creating and loading classes at runtime.
TODO Provide a way of flushing a classname from the cached classes so we can reload a class

  • Field Details

    • contextLoader

      protected final ClassLoader contextLoader
      ClassLoader initialised by the context (ExecutionContext).

    • contextLoaderHashCode

      protected int contextLoaderHashCode
      Hash code cache for performance improvement

    • runtimeLoader

      protected ClassLoader runtimeLoader
      ClassLoader registered to load runtime created classes.

    • runtimeLoaderHashCode

      protected int runtimeLoaderHashCode
      Hash code cache for performance improvement

    • userRegisteredLoader

      protected ClassLoader userRegisteredLoader
      ClassLoader registered to load classes (e.g set in the persistence properties as the primary loader).

    • userRegisteredLoaderHashCode

      protected int userRegisteredLoaderHashCode
      Hash code cache for performance improvement

    • jreClasses

      protected Map<String,Class> jreClasses

    • loadedClasses

      protected Map<String,Class> loadedClasses
      Cache for loaded classes

    • unloadedClasses

      protected Map<String,Class> unloadedClasses
      Cache for loaded classes

    • resources

      protected Map<String,URL> resources
      Cache for resources

    • primary

      ThreadLocal primary
      The primary class

  • Constructor Details

    • ClassLoaderResolverImpl

      public ClassLoaderResolverImpl(ClassLoader ctxLoader)
      Constructor for ExecutionContext cases.
      Parameters:
      ctxLoader - Loader from ExecutionContext initialisation time.

    • ClassLoaderResolverImpl

      public ClassLoaderResolverImpl()
      Constructor for non-PersistenceManager cases so there is no PM context loader.

  • Method Details

    • loadJreClasses

      protected void loadJreClasses()

    • classForName

      public Class classForName(String name, ClassLoader primary)
      JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5). Try 3 loaders, starting with user-supplied loader, then try the current thread's loader, and finally try the PM context loader. This method does not initialize the class itself.
      Specified by:
      classForName in interface ClassLoaderResolver
      Parameters:
      name - Name of the Class to be loaded
      primary - primary ClassLoader to use (or null)
      Returns:
      The class given the name, using the required loader.
      Throws:
      ClassNotResolvedException - if the class can't be found in the classpath

    • classForNameWithInitialize

      private Class classForNameWithInitialize(String name, ClassLoader primary)
      JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5). Try 3 loaders, starting with user-supplied loader, then try the current thread's loader, and finally try the PM context loader.
      Parameters:
      name - Name of the Class to be loaded
      primary - primary ClassLoader to use (or null)
      Returns:
      The class given the name, using the required loader.
      Throws:
      ClassNotResolvedException - if the class can't be found in the classpath

    • newCacheKey

      private String newCacheKey(String prefix, ClassLoader primary, ClassLoader contextClassLoader)
      Compute the key hashCode based for all classLoaders
      Parameters:
      prefix - the key prefix
      primary - the primary ClassLoader, or null
      contextClassLoader - the context ClassLoader, or null
      Returns:
      the computed hashCode

    • classForName

      public Class classForName(String name, ClassLoader primary, boolean initialize)
      JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5).
      Specified by:
      classForName in interface ClassLoaderResolver
      Parameters:
      name - Name of the Class to be loaded
      primary - the primary ClassLoader to use (or null)
      initialize - whether to initialize the class or not.
      Returns:
      The Class given the name, using the specified ClassLoader
      Throws:
      ClassNotResolvedException - if the class can't be found in the classpath

    • classForName

      public Class classForName(String name)
      JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5). This method does not initialize the class itself.
      Specified by:
      classForName in interface ClassLoaderResolver
      Parameters:
      name - Name of the Class to be loaded
      Returns:
      The class given the name, using the required loader.

    • classForName

      public Class classForName(String name, boolean initialize)
      JDO's Class Loading mechanism (Spec 1.0.1 Chapter 12.5).
      Specified by:
      classForName in interface ClassLoaderResolver
      Parameters:
      name - Name of the Class to be loaded
      initialize - whether to initialize the class or not.
      Returns:
      The Class given the name, using the specified ClassLoader
      Throws:
      ClassNotResolvedException - if the class can't be found in the classpath

    • isAssignableFrom

      public boolean isAssignableFrom(String class_name_1, String class_name_2)
      Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism. This will check class_1.isAssignableFrom(class_2);
      Specified by:
      isAssignableFrom in interface ClassLoaderResolver
      Parameters:
      class_name_1 - Name of first class
      class_name_2 - Name of second class
      Returns:
      Whether Class 2 is assignable from Class 1

    • isAssignableFrom

      public boolean isAssignableFrom(String class_name_1, Class class_2)
      Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism. This will check class_1.isAssignableFrom(class_2);
      Specified by:
      isAssignableFrom in interface ClassLoaderResolver
      Parameters:
      class_name_1 - Name of first class
      class_2 - Second class
      Returns:
      Whether Class 2 is assignable from Class 1

    • isAssignableFrom

      public boolean isAssignableFrom(Class class_1, String class_name_2)
      Utility to check the assignability of 2 classes in accordance with JDO's Class Loading mechanism. This will check class_1.isAssignableFrom(class_2);
      Specified by:
      isAssignableFrom in interface ClassLoaderResolver
      Parameters:
      class_1 - First class
      class_name_2 - Name of second class
      Returns:
      Whether Class 2 is assignable from Class 1

    • classOrNull

      private Class classOrNull(String name, ClassLoader loader)
      Returns the Class. This method does not initialize the class
      Parameters:
      name - the class name
      loader - the ClassLoader
      Returns:
      Class the class loaded; null if not found

    • ClassOrNullWithInitialize

      private Class ClassOrNullWithInitialize(String name, ClassLoader loader)
      Returns the Class. Initializes it if found
      Parameters:
      name - the class name
      loader - the ClassLoader
      Returns:
      Class the class loaded; null if not found

    • setRuntimeClassLoader

      public void setRuntimeClassLoader(ClassLoader loader)
      ClassLoader registered to load classes created at runtime.
      Specified by:
      setRuntimeClassLoader in interface ClassLoaderResolver
      Parameters:
      loader - The ClassLoader in which classes are defined

    • registerUserClassLoader

      public void registerUserClassLoader(ClassLoader loader)
      ClassLoader registered by users to load classes. One ClassLoader can be registered, and if one ClassLoader is already registered, the registered ClassLoader is replaced by loader.
      Specified by:
      registerUserClassLoader in interface ClassLoaderResolver
      Parameters:
      loader - The ClassLoader in which classes are loaded

    • getResources

      public Enumeration getResources(String resourceName, ClassLoader primary) throws IOException
      Finds all the resources with the given name.
      Specified by:
      getResources in interface ClassLoaderResolver
      Parameters:
      resourceName - the resource name. If resourceName starts with "/", remove it before searching.
      primary - the primary ClassLoader to use (or null)
      Returns:
      An enumeration of URL objects for the resource. If no resources could be found, the enumeration will be empty. Resources that the class loader doesn't have access to will not be in the enumeration.
      Throws:
      IOException - If I/O errors occur
      See Also:

    • getResource

      public URL getResource(String resourceName, ClassLoader primary)
      Finds the resource with the given name.
      Specified by:
      getResource in interface ClassLoaderResolver
      Parameters:
      resourceName - the path to resource name relative to the classloader root path. If resourceName starts with "/", remove it before searching.
      primary - the primary ClassLoader to use (or null)
      Returns:
      A URL object for reading the resource, or null if the resource could not be found or the invoker doesn't have adequate privileges to get the resource.
      See Also:

    • setPrimary

      public void setPrimary(ClassLoader primary)
      Sets the primary classloader for the current thread
      Specified by:
      setPrimary in interface ClassLoaderResolver
      Parameters:
      primary - the primary classloader

    • unsetPrimary

      public void unsetPrimary()
      Unsets the primary classloader for the current thread
      Specified by:
      unsetPrimary in interface ClassLoaderResolver

    • toString

      public String toString()
      Overrides:
      toString in class Object