Package com.google.inject.internal

Class BytecodeGen

  • public final class BytecodeGen
extends java.lang.Object
    Utility methods for runtime code generation and class loading. We use this stuff for faster reflection, method interceptors and to proxy circular dependencies.

    When loading classes, we need to be careful of:

    • Memory leaks. Generated classes need to be garbage collected in long-lived applications. Once an injector and any instances it created can be garbage collected, the corresponding generated classes should be collectable.
    • Visibility. Containers like OSGi use class loader boundaries to enforce modularity at runtime.

    For each generated class, there's multiple class loaders involved:

    • The related class's class loader. Every generated class services exactly one user-supplied class. This class loader must be used to access members with protected and package visibility.
    • Guice's class loader.
    • Our bridge class loader. This is a child of the user's class loader. It selectively delegates to either the user's class loader (for user classes) or the Guice class loader (for internal classes that are used by the generated classes). This class loader that owns the classes generated by Guice.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      (package private) static java.lang.String CGLIB_PACKAGE
      either "net.sf.cglib", or "com.google.inject.internal.cglib"
      private static com.google.common.cache.LoadingCache<java.lang.ClassLoader,​java.lang.ClassLoader> CLASS_LOADER_CACHE
      Weak cache of bridge class loaders that make the Guice implementation classes visible to various code-generated proxies of client classes.
      (package private) static net.sf.cglib.core.NamingPolicy ENHANCER_NAMING_POLICY  
      (package private) static net.sf.cglib.core.NamingPolicy FASTCLASS_NAMING_POLICY  
      (package private) static java.lang.ClassLoader GUICE_CLASS_LOADER  
      (package private) static java.lang.String GUICE_INTERNAL_PACKAGE
      ie.
      (package private) static java.util.logging.Logger logger  

    • Constructor Summary

      Constructors 
      Constructor Description
      BytecodeGen()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      private static java.lang.ClassLoader canonicalize​(java.lang.ClassLoader classLoader)
      Attempts to canonicalize null references to the system class loader.
      static java.lang.ClassLoader getClassLoader​(java.lang.Class<?> type)
      Returns the class loader to host generated classes for type.
      private static java.lang.ClassLoader getClassLoader​(java.lang.Class<?> type, java.lang.ClassLoader delegate)  
      private static boolean hasSameVersionOfCglib​(java.lang.ClassLoader classLoader)
      Returns true if the types classloader has the same version of cglib that BytecodeGen has.
      private static boolean isPubliclyCallable​(java.lang.reflect.Member member)
      Returns true if the member can be called by a fast class generated in a different classloader.
      static net.sf.cglib.proxy.Enhancer newEnhancer​(java.lang.Class<?> type, BytecodeGen.Visibility visibility)  
      static net.sf.cglib.reflect.FastClass newFastClassForMember​(java.lang.Class<?> type, java.lang.reflect.Member member)
      Returns a FastClass proxy for invoking the given member or null if access rules disallow it.
      static net.sf.cglib.reflect.FastClass newFastClassForMember​(java.lang.reflect.Member member)
      Returns a FastClass proxy for invoking the given member or null if access rules disallow it.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • logger

        static final java.util.logging.Logger logger

      • GUICE_CLASS_LOADER

        static final java.lang.ClassLoader GUICE_CLASS_LOADER

      • GUICE_INTERNAL_PACKAGE

        static final java.lang.String GUICE_INTERNAL_PACKAGE
        ie. "com.google.inject.internal"

      • CGLIB_PACKAGE

        static final java.lang.String CGLIB_PACKAGE
        either "net.sf.cglib", or "com.google.inject.internal.cglib"

      • FASTCLASS_NAMING_POLICY

        static final net.sf.cglib.core.NamingPolicy FASTCLASS_NAMING_POLICY

      • ENHANCER_NAMING_POLICY

        static final net.sf.cglib.core.NamingPolicy ENHANCER_NAMING_POLICY

      • CLASS_LOADER_CACHE

        private static final com.google.common.cache.LoadingCache<java.lang.ClassLoader,​java.lang.ClassLoader> CLASS_LOADER_CACHE
        Weak cache of bridge class loaders that make the Guice implementation classes visible to various code-generated proxies of client classes.

    • Constructor Detail

      • BytecodeGen

        public BytecodeGen()

    • Method Detail

      • canonicalize

        private static java.lang.ClassLoader canonicalize​(java.lang.ClassLoader classLoader)
        Attempts to canonicalize null references to the system class loader. May return null if for some reason the system loader is unavailable.

      • getClassLoader

        public static java.lang.ClassLoader getClassLoader​(java.lang.Class<?> type)
        Returns the class loader to host generated classes for type.

      • getClassLoader

        private static java.lang.ClassLoader getClassLoader​(java.lang.Class<?> type,
                                                    java.lang.ClassLoader delegate)

      • newFastClassForMember

        public static net.sf.cglib.reflect.FastClass newFastClassForMember​(java.lang.reflect.Member member)
        Returns a FastClass proxy for invoking the given member or null if access rules disallow it.
        See Also:
        for a full description

      • newFastClassForMember

        public static net.sf.cglib.reflect.FastClass newFastClassForMember​(java.lang.Class<?> type,
                                                                   java.lang.reflect.Member member)
        Returns a FastClass proxy for invoking the given member or null if access rules disallow it.

        FastClass works by generating a type in the same package as the target type. This may or may not work depending on the access level of the class/member. It breaks down into the following cases depending on accessibility:

        • Public: This always works since we can generate the type into the BytecodeGen.BridgeClassLoader which ensures there are no versioning issues.
        • Package private and Protected: This works as long as:
          • We can generate into the same classloader as the type. This is not possible for JDK types which use the 'bootstrap' loader.
          • The classloader of the type has the same version of FastClass as we do. This may be violated when running in OSGI bundles.
        • Private: This never works.
        If we are unable to generate the type, then we return null and callers should work around by using normal java reflection.

      • hasSameVersionOfCglib

        private static boolean hasSameVersionOfCglib​(java.lang.ClassLoader classLoader)
        Returns true if the types classloader has the same version of cglib that BytecodeGen has. This only returns false in strange OSGI situations, but it prevents us from using FastClass for non public members.

      • isPubliclyCallable

        private static boolean isPubliclyCallable​(java.lang.reflect.Member member)
        Returns true if the member can be called by a fast class generated in a different classloader.

      • newEnhancer

        public static net.sf.cglib.proxy.Enhancer newEnhancer​(java.lang.Class<?> type,
                                                      BytecodeGen.Visibility visibility)