--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/java.base/share/classes/java/lang/invoke/LambdaMetafactory.java Sun Aug 17 15:54:13 2014 +0100
@@ -0,0 +1,476 @@
+/*
+ * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.lang.invoke;
+
+import java.io.Serializable;
+import java.util.Arrays;
+
+/**
+ * <p>Methods to facilitate the creation of simple "function objects" that
+ * implement one or more interfaces by delegation to a provided {@link MethodHandle},
+ * possibly after type adaptation and partial evaluation of arguments. These
+ * methods are typically used as <em>bootstrap methods</em> for {@code invokedynamic}
+ * call sites, to support the <em>lambda expression</em> and <em>method
+ * reference expression</em> features of the Java Programming Language.
+ *
+ * <p>Indirect access to the behavior specified by the provided {@code MethodHandle}
+ * proceeds in order through three phases:
+ * <ul>
+ * <li><em>Linkage</em> occurs when the methods in this class are invoked.
+ * They take as arguments an interface to be implemented (typically a
+ * <em>functional interface</em>, one with a single abstract method), a
+ * name and signature of a method from that interface to be implemented, a
+ * method handle describing the desired implementation behavior
+ * for that method, and possibly other additional metadata, and produce a
+ * {@link CallSite} whose target can be used to create suitable function
+ * objects. Linkage may involve dynamically loading a new class that
+ * implements the target interface. The {@code CallSite} can be considered a
+ * "factory" for function objects and so these linkage methods are referred
+ * to as "metafactories".</li>
+ *
+ * <li><em>Capture</em> occurs when the {@code CallSite}'s target is
+ * invoked, typically through an {@code invokedynamic} call site,
+ * producing a function object. This may occur many times for
+ * a single factory {@code CallSite}. Capture may involve allocation of a
+ * new function object, or may return an existing function object. The
+ * behavior {@code MethodHandle} may have additional parameters beyond those
+ * of the specified interface method; these are referred to as <em>captured
+ * parameters</em>, which must be provided as arguments to the
+ * {@code CallSite} target, and which may be early-bound to the behavior
+ * {@code MethodHandle}. The number of captured parameters and their types
+ * are determined during linkage.</li>
+ *
+ * <li><em>Invocation</em> occurs when an implemented interface method
+ * is invoked on a function object. This may occur many times for a single
+ * function object. The method referenced by the behavior {@code MethodHandle}
+ * is invoked with the captured arguments and any additional arguments
+ * provided on invocation, as if by {@link MethodHandle#invoke(Object...)}.</li>
+ * </ul>
+ *
+ * <p>It is sometimes useful to restrict the set of inputs or results permitted
+ * at invocation. For example, when the generic interface {@code Predicate<T>}
+ * is parameterized as {@code Predicate<String>}, the input must be a
+ * {@code String}, even though the method to implement allows any {@code Object}.
+ * At linkage time, an additional {@link MethodType} parameter describes the
+ * "instantiated" method type; on invocation, the arguments and eventual result
+ * are checked against this {@code MethodType}.
+ *
+ * <p>This class provides two forms of linkage methods: a standard version
+ * ({@link #metafactory(MethodHandles.Lookup, String, MethodType, MethodType, MethodHandle, MethodType)})
+ * using an optimized protocol, and an alternate version
+ * {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)}).
+ * The alternate version is a generalization of the standard version, providing
+ * additional control over the behavior of the generated function objects via
+ * flags and additional arguments. The alternate version adds the ability to
+ * manage the following attributes of function objects:
+ *
+ * <ul>
+ * <li><em>Bridging.</em> It is sometimes useful to implement multiple
+ * variations of the method signature, involving argument or return type
+ * adaptation. This occurs when multiple distinct VM signatures for a method
+ * are logically considered to be the same method by the language. The
+ * flag {@code FLAG_BRIDGES} indicates that a list of additional
+ * {@code MethodType}s will be provided, each of which will be implemented
+ * by the resulting function object. These methods will share the same
+ * name and instantiated type.</li>
+ *
+ * <li><em>Multiple interfaces.</em> If needed, more than one interface
+ * can be implemented by the function object. (These additional interfaces
+ * are typically marker interfaces with no methods.) The flag {@code FLAG_MARKERS}
+ * indicates that a list of additional interfaces will be provided, each of
+ * which should be implemented by the resulting function object.</li>
+ *
+ * <li><em>Serializability.</em> The generated function objects do not
+ * generally support serialization. If desired, {@code FLAG_SERIALIZABLE}
+ * can be used to indicate that the function objects should be serializable.
+ * Serializable function objects will use, as their serialized form,
+ * instances of the class {@code SerializedLambda}, which requires additional
+ * assistance from the capturing class (the class described by the
+ * {@link MethodHandles.Lookup} parameter {@code caller}); see
+ * {@link SerializedLambda} for details.</li>
+ * </ul>
+ *
+ * <p>Assume the linkage arguments are as follows:
+ * <ul>
+ * <li>{@code invokedType} (describing the {@code CallSite} signature) has
+ * K parameters of types (D1..Dk) and return type Rd;</li>
+ * <li>{@code samMethodType} (describing the implemented method type) has N
+ * parameters, of types (U1..Un) and return type Ru;</li>
+ * <li>{@code implMethod} (the {@code MethodHandle} providing the
+ * implementation has M parameters, of types (A1..Am) and return type Ra
+ * (if the method describes an instance method, the method type of this
+ * method handle already includes an extra first argument corresponding to
+ * the receiver);</li>
+ * <li>{@code instantiatedMethodType} (allowing restrictions on invocation)
+ * has N parameters, of types (T1..Tn) and return type Rt.</li>
+ * </ul>
+ *
+ * <p>Then the following linkage invariants must hold:
+ * <ul>
+ * <li>Rd is an interface</li>
+ * <li>{@code implMethod} is a <em>direct method handle</em></li>
+ * <li>{@code samMethodType} and {@code instantiatedMethodType} have the same
+ * arity N, and for i=1..N, Ti and Ui are the same type, or Ti and Ui are
+ * both reference types and Ti is a subtype of Ui</li>
+ * <li>Either Rt and Ru are the same type, or both are reference types and
+ * Rt is a subtype of Ru</li>
+ * <li>K + N = M</li>
+ * <li>For i=1..K, Di = Ai</li>
+ * <li>For i=1..N, Ti is adaptable to Aj, where j=i+k</li>
+ * <li>The return type Rt is void, or the return type Ra is not void and is
+ * adaptable to Rt</li>
+ * </ul>
+ *
+ * <p>Further, at capture time, if {@code implMethod} corresponds to an instance
+ * method, and there are any capture arguments ({@code K > 0}), then the first
+ * capture argument (corresponding to the receiver) must be non-null.
+ *
+ * <p>A type Q is considered adaptable to S as follows:
+ * <table summary="adaptable types">
+ * <tr><th>Q</th><th>S</th><th>Link-time checks</th><th>Invocation-time checks</th></tr>
+ * <tr>
+ * <td>Primitive</td><td>Primitive</td>
+ * <td>Q can be converted to S via a primitive widening conversion</td>
+ * <td>None</td>
+ * </tr>
+ * <tr>
+ * <td>Primitive</td><td>Reference</td>
+ * <td>S is a supertype of the Wrapper(Q)</td>
+ * <td>Cast from Wrapper(Q) to S</td>
+ * </tr>
+ * <tr>
+ * <td>Reference</td><td>Primitive</td>
+ * <td>for parameter types: Q is a primitive wrapper and Primitive(Q)
+ * can be widened to S
+ * <br>for return types: If Q is a primitive wrapper, check that
+ * Primitive(Q) can be widened to S</td>
+ * <td>If Q is not a primitive wrapper, cast Q to the base Wrapper(S);
+ * for example Number for numeric types</td>
+ * </tr>
+ * <tr>
+ * <td>Reference</td><td>Reference</td>
+ * <td>for parameter types: S is a supertype of Q
+ * <br>for return types: none</td>
+ * <td>Cast from Q to S</td>
+ * </tr>
+ * </table>
+ *
+ * @apiNote These linkage methods are designed to support the evaluation
+ * of <em>lambda expressions</em> and <em>method references</em> in the Java
+ * Language. For every lambda expressions or method reference in the source code,
+ * there is a target type which is a functional interface. Evaluating a lambda
+ * expression produces an object of its target type. The recommended mechanism
+ * for evaluating lambda expressions is to desugar the lambda body to a method,
+ * invoke an invokedynamic call site whose static argument list describes the
+ * sole method of the functional interface and the desugared implementation
+ * method, and returns an object (the lambda object) that implements the target
+ * type. (For method references, the implementation method is simply the
+ * referenced method; no desugaring is needed.)
+ *
+ * <p>The argument list of the implementation method and the argument list of
+ * the interface method(s) may differ in several ways. The implementation
+ * methods may have additional arguments to accommodate arguments captured by
+ * the lambda expression; there may also be differences resulting from permitted
+ * adaptations of arguments, such as casting, boxing, unboxing, and primitive
+ * widening. (Varargs adaptations are not handled by the metafactories; these are
+ * expected to be handled by the caller.)
+ *
+ * <p>Invokedynamic call sites have two argument lists: a static argument list
+ * and a dynamic argument list. The static argument list is stored in the
+ * constant pool; the dynamic argument is pushed on the operand stack at capture
+ * time. The bootstrap method has access to the entire static argument list
+ * (which in this case, includes information describing the implementation method,
+ * the target interface, and the target interface method(s)), as well as a
+ * method signature describing the number and static types (but not the values)
+ * of the dynamic arguments and the static return type of the invokedynamic site.
+ *
+ * @implNote The implementation method is described with a method handle. In
+ * theory, any method handle could be used. Currently supported are direct method
+ * handles representing invocation of virtual, interface, constructor and static
+ * methods.
+ */
+public class LambdaMetafactory {
+
+ /** Flag for alternate metafactories indicating the lambda object
+ * must be serializable */
+ public static final int FLAG_SERIALIZABLE = 1 << 0;
+
+ /**
+ * Flag for alternate metafactories indicating the lambda object implements
+ * other marker interfaces
+ * besides Serializable
+ */
+ public static final int FLAG_MARKERS = 1 << 1;
+
+ /**
+ * Flag for alternate metafactories indicating the lambda object requires
+ * additional bridge methods
+ */
+ public static final int FLAG_BRIDGES = 1 << 2;
+
+ private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
+ private static final MethodType[] EMPTY_MT_ARRAY = new MethodType[0];
+
+ /**
+ * Facilitates the creation of simple "function objects" that implement one
+ * or more interfaces by delegation to a provided {@link MethodHandle},
+ * after appropriate type adaptation and partial evaluation of arguments.
+ * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
+ * call sites, to support the <em>lambda expression</em> and <em>method
+ * reference expression</em> features of the Java Programming Language.
+ *
+ * <p>This is the standard, streamlined metafactory; additional flexibility
+ * is provided by {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)}.
+ * A general description of the behavior of this method is provided
+ * {@link LambdaMetafactory above}.
+ *
+ * <p>When the target of the {@code CallSite} returned from this method is
+ * invoked, the resulting function objects are instances of a class which
+ * implements the interface named by the return type of {@code invokedType},
+ * declares a method with the name given by {@code invokedName} and the
+ * signature given by {@code samMethodType}. It may also override additional
+ * methods from {@code Object}.
+ *
+ * @param caller Represents a lookup context with the accessibility
+ * privileges of the caller. When used with {@code invokedynamic},
+ * this is stacked automatically by the VM.
+ * @param invokedName The name of the method to implement. When used with
+ * {@code invokedynamic}, this is provided by the
+ * {@code NameAndType} of the {@code InvokeDynamic}
+ * structure and is stacked automatically by the VM.
+ * @param invokedType The expected signature of the {@code CallSite}. The
+ * parameter types represent the types of capture variables;
+ * the return type is the interface to implement. When
+ * used with {@code invokedynamic}, this is provided by
+ * the {@code NameAndType} of the {@code InvokeDynamic}
+ * structure and is stacked automatically by the VM.
+ * In the event that the implementation method is an
+ * instance method and this signature has any parameters,
+ * the first parameter in the invocation signature must
+ * correspond to the receiver.
+ * @param samMethodType Signature and return type of method to be implemented
+ * by the function object.
+ * @param implMethod A direct method handle describing the implementation
+ * method which should be called (with suitable adaptation
+ * of argument types, return types, and with captured
+ * arguments prepended to the invocation arguments) at
+ * invocation time.
+ * @param instantiatedMethodType The signature and return type that should
+ * be enforced dynamically at invocation time.
+ * This may be the same as {@code samMethodType},
+ * or may be a specialization of it.
+ * @return a CallSite whose target can be used to perform capture, generating
+ * instances of the interface named by {@code invokedType}
+ * @throws LambdaConversionException If any of the linkage invariants
+ * described {@link LambdaMetafactory above}
+ * are violated
+ */
+ public static CallSite metafactory(MethodHandles.Lookup caller,
+ String invokedName,
+ MethodType invokedType,
+ MethodType samMethodType,
+ MethodHandle implMethod,
+ MethodType instantiatedMethodType)
+ throws LambdaConversionException {
+ AbstractValidatingLambdaMetafactory mf;
+ mf = new InnerClassLambdaMetafactory(caller, invokedType,
+ invokedName, samMethodType,
+ implMethod, instantiatedMethodType,
+ false, EMPTY_CLASS_ARRAY, EMPTY_MT_ARRAY);
+ mf.validateMetafactoryArgs();
+ return mf.buildCallSite();
+ }
+
+ /**
+ * Facilitates the creation of simple "function objects" that implement one
+ * or more interfaces by delegation to a provided {@link MethodHandle},
+ * after appropriate type adaptation and partial evaluation of arguments.
+ * Typically used as a <em>bootstrap method</em> for {@code invokedynamic}
+ * call sites, to support the <em>lambda expression</em> and <em>method
+ * reference expression</em> features of the Java Programming Language.
+ *
+ * <p>This is the general, more flexible metafactory; a streamlined version
+ * is provided by {@link #metafactory(java.lang.invoke.MethodHandles.Lookup,
+ * String, MethodType, MethodType, MethodHandle, MethodType)}.
+ * A general description of the behavior of this method is provided
+ * {@link LambdaMetafactory above}.
+ *
+ * <p>The argument list for this method includes three fixed parameters,
+ * corresponding to the parameters automatically stacked by the VM for the
+ * bootstrap method in an {@code invokedynamic} invocation, and an {@code Object[]}
+ * parameter that contains additional parameters. The declared argument
+ * list for this method is:
+ *
+ * <pre>{@code
+ * CallSite altMetafactory(MethodHandles.Lookup caller,
+ * String invokedName,
+ * MethodType invokedType,
+ * Object... args)
+ * }</pre>
+ *
+ * <p>but it behaves as if the argument list is as follows:
+ *
+ * <pre>{@code
+ * CallSite altMetafactory(MethodHandles.Lookup caller,
+ * String invokedName,
+ * MethodType invokedType,
+ * MethodType samMethodType,
+ * MethodHandle implMethod,
+ * MethodType instantiatedMethodType,
+ * int flags,
+ * int markerInterfaceCount, // IF flags has MARKERS set
+ * Class... markerInterfaces, // IF flags has MARKERS set
+ * int bridgeCount, // IF flags has BRIDGES set
+ * MethodType... bridges // IF flags has BRIDGES set
+ * )
+ * }</pre>
+ *
+ * <p>Arguments that appear in the argument list for
+ * {@link #metafactory(MethodHandles.Lookup, String, MethodType, MethodType, MethodHandle, MethodType)}
+ * have the same specification as in that method. The additional arguments
+ * are interpreted as follows:
+ * <ul>
+ * <li>{@code flags} indicates additional options; this is a bitwise
+ * OR of desired flags. Defined flags are {@link #FLAG_BRIDGES},
+ * {@link #FLAG_MARKERS}, and {@link #FLAG_SERIALIZABLE}.</li>
+ * <li>{@code markerInterfaceCount} is the number of additional interfaces
+ * the function object should implement, and is present if and only if the
+ * {@code FLAG_MARKERS} flag is set.</li>
+ * <li>{@code markerInterfaces} is a variable-length list of additional
+ * interfaces to implement, whose length equals {@code markerInterfaceCount},
+ * and is present if and only if the {@code FLAG_MARKERS} flag is set.</li>
+ * <li>{@code bridgeCount} is the number of additional method signatures
+ * the function object should implement, and is present if and only if
+ * the {@code FLAG_BRIDGES} flag is set.</li>
+ * <li>{@code bridges} is a variable-length list of additional
+ * methods signatures to implement, whose length equals {@code bridgeCount},
+ * and is present if and only if the {@code FLAG_BRIDGES} flag is set.</li>
+ * </ul>
+ *
+ * <p>Each class named by {@code markerInterfaces} is subject to the same
+ * restrictions as {@code Rd}, the return type of {@code invokedType},
+ * as described {@link LambdaMetafactory above}. Each {@code MethodType}
+ * named by {@code bridges} is subject to the same restrictions as
+ * {@code samMethodType}, as described {@link LambdaMetafactory above}.
+ *
+ * <p>When FLAG_SERIALIZABLE is set in {@code flags}, the function objects
+ * will implement {@code Serializable}, and will have a {@code writeReplace}
+ * method that returns an appropriate {@link SerializedLambda}. The
+ * {@code caller} class must have an appropriate {@code $deserializeLambda$}
+ * method, as described in {@link SerializedLambda}.
+ *
+ * <p>When the target of the {@code CallSite} returned from this method is
+ * invoked, the resulting function objects are instances of a class with
+ * the following properties:
+ * <ul>
+ * <li>The class implements the interface named by the return type
+ * of {@code invokedType} and any interfaces named by {@code markerInterfaces}</li>
+ * <li>The class declares methods with the name given by {@code invokedName},
+ * and the signature given by {@code samMethodType} and additional signatures
+ * given by {@code bridges}</li>
+ * <li>The class may override methods from {@code Object}, and may
+ * implement methods related to serialization.</li>
+ * </ul>
+ *
+ * @param caller Represents a lookup context with the accessibility
+ * privileges of the caller. When used with {@code invokedynamic},
+ * this is stacked automatically by the VM.
+ * @param invokedName The name of the method to implement. When used with
+ * {@code invokedynamic}, this is provided by the
+ * {@code NameAndType} of the {@code InvokeDynamic}
+ * structure and is stacked automatically by the VM.
+ * @param invokedType The expected signature of the {@code CallSite}. The
+ * parameter types represent the types of capture variables;
+ * the return type is the interface to implement. When
+ * used with {@code invokedynamic}, this is provided by
+ * the {@code NameAndType} of the {@code InvokeDynamic}
+ * structure and is stacked automatically by the VM.
+ * In the event that the implementation method is an
+ * instance method and this signature has any parameters,
+ * the first parameter in the invocation signature must
+ * correspond to the receiver.
+ * @param args An {@code Object[]} array containing the required
+ * arguments {@code samMethodType}, {@code implMethod},
+ * {@code instantiatedMethodType}, {@code flags}, and any
+ * optional arguments, as described
+ * {@link #altMetafactory(MethodHandles.Lookup, String, MethodType, Object...)} above}
+ * @return a CallSite whose target can be used to perform capture, generating
+ * instances of the interface named by {@code invokedType}
+ * @throws LambdaConversionException If any of the linkage invariants
+ * described {@link LambdaMetafactory above}
+ * are violated
+ */
+ public static CallSite altMetafactory(MethodHandles.Lookup caller,
+ String invokedName,
+ MethodType invokedType,
+ Object... args)
+ throws LambdaConversionException {
+ MethodType samMethodType = (MethodType)args[0];
+ MethodHandle implMethod = (MethodHandle)args[1];
+ MethodType instantiatedMethodType = (MethodType)args[2];
+ int flags = (Integer) args[3];
+ Class<?>[] markerInterfaces;
+ MethodType[] bridges;
+ int argIndex = 4;
+ if ((flags & FLAG_MARKERS) != 0) {
+ int markerCount = (Integer) args[argIndex++];
+ markerInterfaces = new Class<?>[markerCount];
+ System.arraycopy(args, argIndex, markerInterfaces, 0, markerCount);
+ argIndex += markerCount;
+ }
+ else
+ markerInterfaces = EMPTY_CLASS_ARRAY;
+ if ((flags & FLAG_BRIDGES) != 0) {
+ int bridgeCount = (Integer) args[argIndex++];
+ bridges = new MethodType[bridgeCount];
+ System.arraycopy(args, argIndex, bridges, 0, bridgeCount);
+ argIndex += bridgeCount;
+ }
+ else
+ bridges = EMPTY_MT_ARRAY;
+
+ boolean isSerializable = ((flags & FLAG_SERIALIZABLE) != 0);
+ if (isSerializable) {
+ boolean foundSerializableSupertype = Serializable.class.isAssignableFrom(invokedType.returnType());
+ for (Class<?> c : markerInterfaces)
+ foundSerializableSupertype |= Serializable.class.isAssignableFrom(c);
+ if (!foundSerializableSupertype) {
+ markerInterfaces = Arrays.copyOf(markerInterfaces, markerInterfaces.length + 1);
+ markerInterfaces[markerInterfaces.length-1] = Serializable.class;
+ }
+ }
+
+ AbstractValidatingLambdaMetafactory mf
+ = new InnerClassLambdaMetafactory(caller, invokedType,
+ invokedName, samMethodType,
+ implMethod,
+ instantiatedMethodType,
+ isSerializable,
+ markerInterfaces, bridges);
+ mf.validateMetafactoryArgs();
+ return mf.buildCallSite();
+ }
+}