--- a/jdk/src/share/classes/java/lang/invoke/MethodHandleInfo.java Tue Sep 03 23:47:27 2013 -0400
+++ b/jdk/src/share/classes/java/lang/invoke/MethodHandleInfo.java Tue Sep 03 21:42:56 2013 -0700
@@ -24,80 +24,246 @@
*/
package java.lang.invoke;
+
+import java.lang.reflect.*;
+import java.util.*;
import java.lang.invoke.MethodHandleNatives.Constants;
+import java.lang.invoke.MethodHandles.Lookup;
+import static java.lang.invoke.MethodHandleStatics.*;
/**
- * Cracking (reflecting) method handles back into their constituent symbolic parts.
+ * A symbolic reference obtained by cracking a method handle into its consitutent symbolic parts.
+ * To crack a direct method handle, call {@link Lookup#revealDirect Lookup.revealDirect}.
+ * <p>
+ * A <em>direct method handle</em> represents a method, constructor, or field without
+ * any intervening argument bindings or other transformations.
+ * The method, constructor, or field referred to by a direct method handle is called
+ * its <em>underlying member</em>.
+ * Direct method handles may be obtained in any of these ways:
+ * <ul>
+ * <li>By executing an {@code ldc} instruction on a {@code CONSTANT_MethodHandle} constant.
+ * (See the Java Virtual Machine Specification, sections 4.4.8 and 5.4.3.)
+ * <li>By calling one of the <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>,
+ * such as {@link Lookup#findVirtual Lookup.findVirtual},
+ * to resolve a symbolic reference into a method handle.
+ * A symbolic reference consists of a class, name string, and type.
+ * <li>By calling the factory method {@link Lookup#unreflect Lookup.unreflect}
+ * or {@link Lookup#unreflectSpecial Lookup.unreflectSpecial}
+ * to convert a {@link Method} into a method handle.
+ * <li>By calling the factory method {@link Lookup#unreflectConstructor Lookup.unreflectConstructor}
+ * to convert a {@link Constructor} into a method handle.
+ * <li>By calling the factory method {@link Lookup#unreflectGetter Lookup.unreflectGetter}
+ * or {@link Lookup#unreflectSetter Lookup.unreflectSetter}
+ * to convert a {@link Field} into a method handle.
+ * </ul>
+ * In all of these cases, it is possible to crack the resulting direct method handle
+ * to recover a symbolic reference for the underlying method, constructor, or field.
+ * Cracking must be done via a {@code Lookup} object equivalent to that which created
+ * the target method handle, or which has enough access permissions to recreate
+ * an equivalent method handle.
*
+ * <h1><a name="refkinds"></a>Reference kinds</h1>
+ * The <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>
+ * correspond to all major use cases for methods, constructors, and fields.
+ * These use cases may be distinguished using small integers as follows:
+ * <table border=1 cellpadding=5 summary="reference kinds">
+ * <tr><th>reference kind</th><th>descriptive name</th><th>scope</th><th>member</th><th>behavior</th></tr>
+ * <tr>
+ * <td>{@code 1}</td><td>{@code REF_getField}</td><td>{@code class}</td>
+ * <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 2}</td><td>{@code REF_getStatic}</td><td>{@code class} or {@code interface}</td>
+ * <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 3}</td><td>{@code REF_putField}</td><td>{@code class}</td>
+ * <td>{@code FT f;}</td><td>{@code this.f = x;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 4}</td><td>{@code REF_putStatic}</td><td>{@code class}</td>
+ * <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 5}</td><td>{@code REF_invokeVirtual}</td><td>{@code class}</td>
+ * <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 6}</td><td>{@code REF_invokeStatic}</td><td>{@code class} or {@code interface}</td>
+ * <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 7}</td><td>{@code REF_invokeSpecial}</td><td>{@code class} or {@code interface}</td>
+ * <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 8}</td><td>{@code REF_newInvokeSpecial}</td><td>{@code class}</td>
+ * <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>
+ * </tr>
+ * <tr>
+ * <td>{@code 9}</td><td>{@code REF_invokeInterface}</td><td>{@code interface}</td>
+ * <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
+ * </tr>
+ * </table>
+ * @since 1.8
*/
-final class MethodHandleInfo {
- public static final int
- REF_getField = Constants.REF_getField,
- REF_getStatic = Constants.REF_getStatic,
- REF_putField = Constants.REF_putField,
- REF_putStatic = Constants.REF_putStatic,
- REF_invokeVirtual = Constants.REF_invokeVirtual,
- REF_invokeStatic = Constants.REF_invokeStatic,
- REF_invokeSpecial = Constants.REF_invokeSpecial,
- REF_newInvokeSpecial = Constants.REF_newInvokeSpecial,
- REF_invokeInterface = Constants.REF_invokeInterface;
-
- private final Class<?> declaringClass;
- private final String name;
- private final MethodType methodType;
- private final int referenceKind;
-
- public MethodHandleInfo(MethodHandle mh) {
- MemberName mn = mh.internalMemberName();
- if (mn == null) throw new IllegalArgumentException("not a direct method handle");
- this.declaringClass = mn.getDeclaringClass();
- this.name = mn.getName();
- this.methodType = mn.getMethodOrFieldType();
- byte refKind = mn.getReferenceKind();
- if (refKind == REF_invokeSpecial && !mh.isInvokeSpecial())
- // Devirtualized method invocation is usually formally virtual.
- refKind = REF_invokeVirtual;
- this.referenceKind = refKind;
- }
+public
+interface MethodHandleInfo {
+ /**
+ * A direct method handle reference kind,
+ * as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
+ */
+ public static final int
+ REF_getField = Constants.REF_getField,
+ REF_getStatic = Constants.REF_getStatic,
+ REF_putField = Constants.REF_putField,
+ REF_putStatic = Constants.REF_putStatic,
+ REF_invokeVirtual = Constants.REF_invokeVirtual,
+ REF_invokeStatic = Constants.REF_invokeStatic,
+ REF_invokeSpecial = Constants.REF_invokeSpecial,
+ REF_newInvokeSpecial = Constants.REF_newInvokeSpecial,
+ REF_invokeInterface = Constants.REF_invokeInterface;
- public Class<?> getDeclaringClass() {
- return declaringClass;
- }
+ /**
+ * Returns the reference kind of the cracked method handle, which in turn
+ * determines whether the method handle's underlying member was a constructor, method, or field.
+ * See the <a href="MethodHandleInfo.html#refkinds">table above</a> for definitions.
+ * @return the integer code for the kind of reference used to access the underlying member
+ */
+ public int getReferenceKind();
- public String getName() {
- return name;
- }
+ /**
+ * Returns the class in which the cracked method handle's underlying member was defined.
+ * @return the declaring class of the underlying member
+ */
+ public Class<?> getDeclaringClass();
+
+ /**
+ * Returns the name of the cracked method handle's underlying member.
+ * This is {@code "<init>"} if the underlying member was a constructor,
+ * else it is a simple method name or field name.
+ * @return the simple name of the underlying member
+ */
+ public String getName();
- public MethodType getMethodType() {
- return methodType;
- }
+ /**
+ * Returns the nominal type of the cracked symbolic reference, expressed as a method type.
+ * If the reference is to a constructor, the return type will be {@code void}.
+ * If it is to a non-static method, the method type will not mention the {@code this} parameter.
+ * If it is to a field and the requested access is to read the field,
+ * the method type will have no parameters and return the field type.
+ * If it is to a field and the requested access is to write the field,
+ * the method type will have one parameter of the field type and return {@code void}.
+ * <p>
+ * Note that original direct method handle may include a leading {@code this} parameter,
+ * or (in the case of a constructor) will replace the {@code void} return type
+ * with the constructed class.
+ * The nominal type does not include any {@code this} parameter,
+ * and (in the case of a constructor) will return {@code void}.
+ * @return the type of the underlying member, expressed as a method type
+ */
+ public MethodType getMethodType();
- public int getModifiers() {
- return -1; //TODO
- }
+ // Utility methods.
+ // NOTE: class/name/type and reference kind constitute a symbolic reference
+ // member and modifiers are an add-on, derived from Core Reflection (or the equivalent)
- public int getReferenceKind() {
- return referenceKind;
- }
+ /**
+ * Reflects the underlying member as a method, constructor, or field object.
+ * If the underlying member is public, it is reflected as if by
+ * {@code getMethod}, {@code getConstructor}, or {@code getField}.
+ * Otherwise, it is reflected as if by
+ * {@code getDeclaredMethod}, {@code getDeclaredConstructor}, or {@code getDeclaredField}.
+ * The underlying member must be accessible to the given lookup object.
+ * @param <T> the desired type of the result, either {@link Member} or a subtype
+ * @param expected a class object representing the desired result type {@code T}
+ * @param lookup the lookup object that created this MethodHandleInfo, or one with equivalent access privileges
+ * @return a reference to the method, constructor, or field object
+ * @exception ClassCastException if the member is not of the expected type
+ * @exception NullPointerException if either argument is {@code null}
+ * @exception IllegalArgumentException if the underlying member is not accessible to the given lookup object
+ */
+ public <T extends Member> T reflectAs(Class<T> expected, Lookup lookup);
- static String getReferenceKindString(int referenceKind) {
- switch (referenceKind) {
- case REF_getField: return "getfield";
- case REF_getStatic: return "getstatic";
- case REF_putField: return "putfield";
- case REF_putStatic: return "putstatic";
- case REF_invokeVirtual: return "invokevirtual";
- case REF_invokeStatic: return "invokestatic";
- case REF_invokeSpecial: return "invokespecial";
- case REF_newInvokeSpecial: return "newinvokespecial";
- case REF_invokeInterface: return "invokeinterface";
- default: return "UNKNOWN_REFENCE_KIND" + "[" + referenceKind + "]";
- }
+ /**
+ * Returns the access modifiers of the underlying member.
+ * @return the Java language modifiers for underlying member,
+ * or -1 if the member cannot be accessed
+ * @see Modifier
+ * @see reflectAs
+ */
+ public int getModifiers();
+
+ /**
+ * Determines if the underlying member was a variable arity method or constructor.
+ * Such members are represented by method handles that are varargs collectors.
+ * @implSpec
+ * This produces a result equivalent to:
+ * <pre>{@code
+ * getReferenceKind() >= REF_invokeVirtual && Modifier.isTransient(getModifiers())
+ * }</pre>
+ *
+ *
+ * @return {@code true} if and only if the underlying member was declared with variable arity.
+ */
+ // spelling derived from java.lang.reflect.Executable, not MethodHandle.isVarargsCollector
+ public default boolean isVarArgs() {
+ // fields are never varargs:
+ if (MethodHandleNatives.refKindIsField((byte) getReferenceKind()))
+ return false;
+ // not in the public API: Modifier.VARARGS
+ final int ACC_VARARGS = 0x00000080; // from JVMS 4.6 (Table 4.20)
+ assert(ACC_VARARGS == Modifier.TRANSIENT);
+ return Modifier.isTransient(getModifiers());
}
- @Override
- public String toString() {
- return String.format("%s %s.%s:%s", getReferenceKindString(referenceKind),
- declaringClass.getName(), name, methodType);
+ /**
+ * Returns the descriptive name of the given reference kind,
+ * as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
+ * The conventional prefix "REF_" is omitted.
+ * @param referenceKind an integer code for a kind of reference used to access a class member
+ * @return a mixed-case string such as {@code "getField"}
+ * @exception IllegalArgumentException if the argument is not a valid
+ * <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
+ */
+ public static String referenceKindToString(int referenceKind) {
+ if (!MethodHandleNatives.refKindIsValid(referenceKind))
+ throw newIllegalArgumentException("invalid reference kind", referenceKind);
+ return MethodHandleNatives.refKindName((byte)referenceKind);
+ }
+
+ /**
+ * Returns a string representation for a {@code MethodHandleInfo},
+ * given the four parts of its symbolic reference.
+ * This is defined to be of the form {@code "RK C.N:MT"}, where {@code RK} is the
+ * {@linkplain #referenceKindToString reference kind string} for {@code kind},
+ * {@code C} is the {@linkplain java.lang.Class#getName name} of {@code defc}
+ * {@code N} is the {@code name}, and
+ * {@code MT} is the {@code type}.
+ * These four values may be obtained from the
+ * {@linkplain #getReferenceKind reference kind},
+ * {@linkplain #getDeclaringClass declaring class},
+ * {@linkplain #getName member name},
+ * and {@linkplain #getMethodType method type}
+ * of a {@code MethodHandleInfo} object.
+ *
+ * @implSpec
+ * This produces a result equivalent to:
+ * <pre>{@code
+ * String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type)
+ * }</pre>
+ *
+ * @param kind the {@linkplain #getReferenceKind reference kind} part of the symbolic reference
+ * @param defc the {@linkplain #getDeclaringClass declaring class} part of the symbolic reference
+ * @param name the {@linkplain #getName member name} part of the symbolic reference
+ * @param type the {@linkplain #getMethodType method type} part of the symbolic reference
+ * @return a string of the form {@code "RK C.N:MT"}
+ * @exception IllegalArgumentException if the first argument is not a valid
+ * <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
+ * @exception NullPointerException if any reference argument is {@code null}
+ */
+ public static String toString(int kind, Class<?> defc, String name, MethodType type) {
+ Objects.requireNonNull(name); Objects.requireNonNull(type);
+ return String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type);
}
}