com.google.inject.internal

Class BytecodeGen

java.lang.Object

com.google.inject.internal.BytecodeGen

public final class BytecodeGen
extends 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.

Author:

mcculls@gmail.com (Stuart McCulloch), jessewilson@google.com (Jesse Wilson)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	BytecodeGen.Visibility The required visibility of a user's class from a Guice-generated class.

Constructor Summary

Constructors

Constructor and Description
BytecodeGen()

Method Summary

Methods

Modifier and Type	Method and Description
static ClassLoader	getClassLoader(Class<?> type) Returns the class loader to host generated classes for type.
static net.sf.cglib.proxy.Enhancer	newEnhancer(Class<?> type, BytecodeGen.Visibility visibility)
static net.sf.cglib.reflect.FastClass	newFastClassForMember(Class<?> type, 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(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

Constructor Detail

BytecodeGen

public BytecodeGen()

Method Detail

getClassLoader

public static ClassLoader getClassLoader(Class<?> type)

Returns the class loader to host generated classes for type.

newFastClassForMember

public static net.sf.cglib.reflect.FastClass newFastClassForMember(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(Class<?> type,
                                                   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 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.

newEnhancer

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