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Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically
embedded into Java applications to provide scripting to end users.
/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.javascript;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.concurrent.CopyOnWriteArrayList;
/**
* This class reflects Java methods into the JavaScript environment and
* handles overloading of methods.
*
* @author Mike Shaver
* @see NativeJavaArray
* @see NativeJavaPackage
* @see NativeJavaClass
*/
public class NativeJavaMethod extends BaseFunction
{
private static final long serialVersionUID = -3440381785576412928L;
NativeJavaMethod(MemberBox[] methods)
{
this.functionName = methods[0].getName();
this.methods = methods;
}
NativeJavaMethod(MemberBox[] methods, String name)
{
this.functionName = name;
this.methods = methods;
}
NativeJavaMethod(MemberBox method, String name)
{
this.functionName = name;
this.methods = new MemberBox[] { method };
}
public NativeJavaMethod(Method method, String name)
{
this(new MemberBox(method), name);
}
@Override
public String getFunctionName()
{
return functionName;
}
static String scriptSignature(Object[] values)
{
StringBuilder sig = new StringBuilder();
for (int i = 0; i != values.length; ++i) {
Object value = values[i];
String s;
if (value == null) {
s = "null";
} else if (value instanceof Boolean) {
s = "boolean";
} else if (value instanceof String) {
s = "string";
} else if (value instanceof Number) {
s = "number";
} else if (value instanceof Scriptable) {
if (value instanceof Undefined) {
s = "undefined";
} else if (value instanceof Wrapper) {
Object wrapped = ((Wrapper)value).unwrap();
s = wrapped.getClass().getName();
} else if (value instanceof Function) {
s = "function";
} else {
s = "object";
}
} else {
s = JavaMembers.javaSignature(value.getClass());
}
if (i != 0) {
sig.append(',');
}
sig.append(s);
}
return sig.toString();
}
@Override
String decompile(int indent, int flags)
{
StringBuilder sb = new StringBuilder();
boolean justbody = (0 != (flags & Decompiler.ONLY_BODY_FLAG));
if (!justbody) {
sb.append("function ");
sb.append(getFunctionName());
sb.append("() {");
}
sb.append("/*\n");
sb.append(toString());
sb.append(justbody ? "*/\n" : "*/}\n");
return sb.toString();
}
@Override
public String toString()
{
StringBuilder sb = new StringBuilder();
for (int i = 0, N = methods.length; i != N; ++i) {
// Check member type, we also use this for overloaded constructors
if (methods[i].isMethod()) {
Method method = methods[i].method();
sb.append(JavaMembers.javaSignature(method.getReturnType()));
sb.append(' ');
sb.append(method.getName());
} else {
sb.append(methods[i].getName());
}
sb.append(JavaMembers.liveConnectSignature(methods[i].argTypes));
sb.append('\n');
}
return sb.toString();
}
@Override
public Object call(Context cx, Scriptable scope, Scriptable thisObj,
Object[] args)
{
// Find a method that matches the types given.
if (methods.length == 0) {
throw new RuntimeException("No methods defined for call");
}
int index = findCachedFunction(cx, args);
if (index < 0) {
Class c = methods[0].method().getDeclaringClass();
String sig = c.getName() + '.' + getFunctionName() + '(' +
scriptSignature(args) + ')';
throw Context.reportRuntimeError1("msg.java.no_such_method", sig);
}
MemberBox meth = methods[index];
Class[] argTypes = meth.argTypes;
if (meth.vararg) {
// marshall the explicit parameters
Object[] newArgs = new Object[argTypes.length];
for (int i = 0; i < argTypes.length-1; i++) {
newArgs[i] = Context.jsToJava(args[i], argTypes[i]);
}
Object varArgs;
// Handle special situation where a single variable parameter
// is given and it is a Java or ECMA array or is null.
if (args.length == argTypes.length &&
(args[args.length-1] == null ||
args[args.length-1] instanceof NativeArray ||
args[args.length-1] instanceof NativeJavaArray))
{
// convert the ECMA array into a native array
varArgs = Context.jsToJava(args[args.length-1],
argTypes[argTypes.length - 1]);
} else {
// marshall the variable parameters
Class componentType = argTypes[argTypes.length - 1].
getComponentType();
varArgs = Array.newInstance(componentType,
args.length - argTypes.length + 1);
for (int i = 0; i < Array.getLength(varArgs); i++) {
Object value = Context.jsToJava(args[argTypes.length-1 + i],
componentType);
Array.set(varArgs, i, value);
}
}
// add varargs
newArgs[argTypes.length-1] = varArgs;
// replace the original args with the new one
args = newArgs;
} else {
// First, we marshall the args.
Object[] origArgs = args;
for (int i = 0; i < args.length; i++) {
Object arg = args[i];
Object coerced = Context.jsToJava(arg, argTypes[i]);
if (coerced != arg) {
if (origArgs == args) {
args = args.clone();
}
args[i] = coerced;
}
}
}
Object javaObject;
if (meth.isStatic()) {
javaObject = null; // don't need an object
} else {
Scriptable o = thisObj;
Class c = meth.getDeclaringClass();
for (;;) {
if (o == null) {
throw Context.reportRuntimeError3(
"msg.nonjava.method", getFunctionName(),
ScriptRuntime.toString(thisObj), c.getName());
}
if (o instanceof Wrapper) {
javaObject = ((Wrapper)o).unwrap();
if (c.isInstance(javaObject)) {
break;
}
}
o = o.getPrototype();
}
}
if (debug) {
printDebug("Calling ", meth, args);
}
Object retval = meth.invoke(javaObject, args);
Class staticType = meth.method().getReturnType();
if (debug) {
Class actualType = (retval == null) ? null
: retval.getClass();
System.err.println(" ----- Returned " + retval +
" actual = " + actualType +
" expect = " + staticType);
}
Object wrapped = cx.getWrapFactory().wrap(cx, scope,
retval, staticType);
if (debug) {
Class actualType = (wrapped == null) ? null
: wrapped.getClass();
System.err.println(" ----- Wrapped as " + wrapped +
" class = " + actualType);
}
if (wrapped == null && staticType == Void.TYPE) {
wrapped = Undefined.instance;
}
return wrapped;
}
int findCachedFunction(Context cx, Object[] args) {
if (methods.length > 1) {
for (ResolvedOverload ovl : overloadCache) {
if (ovl.matches(args)) {
return ovl.index;
}
}
int index = findFunction(cx, methods, args);
// As a sanity measure, don't let the lookup cache grow longer
// than twice the number of overloaded methods
if (overloadCache.size() < methods.length * 2) {
ResolvedOverload ovl = new ResolvedOverload(args, index);
overloadCache.addIfAbsent(ovl);
}
return index;
}
return findFunction(cx, methods, args);
}
/**
* Find the index of the correct function to call given the set of methods
* or constructors and the arguments.
* If no function can be found to call, return -1.
*/
static int findFunction(Context cx,
MemberBox[] methodsOrCtors, Object[] args)
{
if (methodsOrCtors.length == 0) {
return -1;
} else if (methodsOrCtors.length == 1) {
MemberBox member = methodsOrCtors[0];
Class[] argTypes = member.argTypes;
int alength = argTypes.length;
if (member.vararg) {
alength--;
if ( alength > args.length) {
return -1;
}
} else {
if (alength != args.length) {
return -1;
}
}
for (int j = 0; j != alength; ++j) {
if (!NativeJavaObject.canConvert(args[j], argTypes[j])) {
if (debug) printDebug("Rejecting (args can't convert) ",
member, args);
return -1;
}
}
if (debug) printDebug("Found ", member, args);
return 0;
}
int firstBestFit = -1;
int[] extraBestFits = null;
int extraBestFitsCount = 0;
search:
for (int i = 0; i < methodsOrCtors.length; i++) {
MemberBox member = methodsOrCtors[i];
Class[] argTypes = member.argTypes;
int alength = argTypes.length;
if (member.vararg) {
alength--;
if ( alength > args.length) {
continue search;
}
} else {
if (alength != args.length) {
continue search;
}
}
for (int j = 0; j < alength; j++) {
if (!NativeJavaObject.canConvert(args[j], argTypes[j])) {
if (debug) printDebug("Rejecting (args can't convert) ",
member, args);
continue search;
}
}
if (firstBestFit < 0) {
if (debug) printDebug("Found first applicable ", member, args);
firstBestFit = i;
} else {
// Compare with all currently fit methods.
// The loop starts from -1 denoting firstBestFit and proceed
// until extraBestFitsCount to avoid extraBestFits allocation
// in the most common case of no ambiguity
int betterCount = 0; // number of times member was prefered over
// best fits
int worseCount = 0; // number of times best fits were prefered
// over member
for (int j = -1; j != extraBestFitsCount; ++j) {
int bestFitIndex;
if (j == -1) {
bestFitIndex = firstBestFit;
} else {
bestFitIndex = extraBestFits[j];
}
MemberBox bestFit = methodsOrCtors[bestFitIndex];
if (cx.hasFeature(Context.FEATURE_ENHANCED_JAVA_ACCESS) &&
bestFit.isPublic() != member.isPublic())
{
// When FEATURE_ENHANCED_JAVA_ACCESS gives us access
// to non-public members, continue to prefer public
// methods in overloading
if (!bestFit.isPublic())
++betterCount;
else
++worseCount;
} else {
int preference = preferSignature(args, argTypes,
member.vararg,
bestFit.argTypes,
bestFit.vararg );
if (preference == PREFERENCE_AMBIGUOUS) {
break;
} else if (preference == PREFERENCE_FIRST_ARG) {
++betterCount;
} else if (preference == PREFERENCE_SECOND_ARG) {
++worseCount;
} else {
if (preference != PREFERENCE_EQUAL) Kit.codeBug();
// This should not happen in theory
// but on some JVMs, Class.getMethods will return all
// static methods of the class hierarchy, even if
// a derived class's parameters match exactly.
// We want to call the derived class's method.
if (bestFit.isStatic() &&
bestFit.getDeclaringClass().isAssignableFrom(
member.getDeclaringClass()))
{
// On some JVMs, Class.getMethods will return all
// static methods of the class hierarchy, even if
// a derived class's parameters match exactly.
// We want to call the derived class's method.
if (debug) printDebug(
"Substituting (overridden static)",
member, args);
if (j == -1) {
firstBestFit = i;
} else {
extraBestFits[j] = i;
}
} else {
if (debug) printDebug(
"Ignoring same signature member ",
member, args);
}
continue search;
}
}
}
if (betterCount == 1 + extraBestFitsCount) {
// member was prefered over all best fits
if (debug) printDebug(
"New first applicable ", member, args);
firstBestFit = i;
extraBestFitsCount = 0;
} else if (worseCount == 1 + extraBestFitsCount) {
// all best fits were prefered over member, ignore it
if (debug) printDebug(
"Rejecting (all current bests better) ", member, args);
} else {
// some ambiguity was present, add member to best fit set
if (debug) printDebug(
"Added to best fit set ", member, args);
if (extraBestFits == null) {
// Allocate maximum possible array
extraBestFits = new int[methodsOrCtors.length - 1];
}
extraBestFits[extraBestFitsCount] = i;
++extraBestFitsCount;
}
}
}
if (firstBestFit < 0) {
// Nothing was found
return -1;
} else if (extraBestFitsCount == 0) {
// single best fit
return firstBestFit;
}
// report remaining ambiguity
StringBuilder buf = new StringBuilder();
for (int j = -1; j != extraBestFitsCount; ++j) {
int bestFitIndex;
if (j == -1) {
bestFitIndex = firstBestFit;
} else {
bestFitIndex = extraBestFits[j];
}
buf.append("\n ");
buf.append(methodsOrCtors[bestFitIndex].toJavaDeclaration());
}
MemberBox firstFitMember = methodsOrCtors[firstBestFit];
String memberName = firstFitMember.getName();
String memberClass = firstFitMember.getDeclaringClass().getName();
if (methodsOrCtors[0].isCtor()) {
throw Context.reportRuntimeError3(
"msg.constructor.ambiguous",
memberName, scriptSignature(args), buf.toString());
}
throw Context.reportRuntimeError4(
"msg.method.ambiguous", memberClass,
memberName, scriptSignature(args), buf.toString());
}
/** Types are equal */
private static final int PREFERENCE_EQUAL = 0;
private static final int PREFERENCE_FIRST_ARG = 1;
private static final int PREFERENCE_SECOND_ARG = 2;
/** No clear "easy" conversion */
private static final int PREFERENCE_AMBIGUOUS = 3;
/**
* Determine which of two signatures is the closer fit.
* Returns one of PREFERENCE_EQUAL, PREFERENCE_FIRST_ARG,
* PREFERENCE_SECOND_ARG, or PREFERENCE_AMBIGUOUS.
*/
private static int preferSignature(Object[] args,
Class[] sig1,
boolean vararg1,
Class[] sig2,
boolean vararg2 )
{
int totalPreference = 0;
for (int j = 0; j < args.length; j++) {
Class type1 = vararg1 && j >= sig1.length ? sig1[sig1.length-1] : sig1[j];
Class type2 = vararg2 && j >= sig2.length ? sig2[sig2.length-1] : sig2[j];
if (type1 == type2) {
continue;
}
Object arg = args[j];
// Determine which of type1, type2 is easier to convert from arg.
int rank1 = NativeJavaObject.getConversionWeight(arg, type1);
int rank2 = NativeJavaObject.getConversionWeight(arg, type2);
int preference;
if (rank1 < rank2) {
preference = PREFERENCE_FIRST_ARG;
} else if (rank1 > rank2) {
preference = PREFERENCE_SECOND_ARG;
} else {
// Equal ranks
if (rank1 == NativeJavaObject.CONVERSION_NONTRIVIAL) {
if (type1.isAssignableFrom(type2)) {
preference = PREFERENCE_SECOND_ARG;
} else if (type2.isAssignableFrom(type1)) {
preference = PREFERENCE_FIRST_ARG;
} else {
preference = PREFERENCE_AMBIGUOUS;
}
} else {
preference = PREFERENCE_AMBIGUOUS;
}
}
totalPreference |= preference;
if (totalPreference == PREFERENCE_AMBIGUOUS) {
break;
}
}
return totalPreference;
}
private static final boolean debug = false;
private static void printDebug(String msg, MemberBox member,
Object[] args)
{
if (debug) {
StringBuilder sb = new StringBuilder();
sb.append(" ----- ");
sb.append(msg);
sb.append(member.getDeclaringClass().getName());
sb.append('.');
if (member.isMethod()) {
sb.append(member.getName());
}
sb.append(JavaMembers.liveConnectSignature(member.argTypes));
sb.append(" for arguments (");
sb.append(scriptSignature(args));
sb.append(')');
System.out.println(sb);
}
}
MemberBox[] methods;
private String functionName;
private transient final CopyOnWriteArrayList overloadCache = new CopyOnWriteArrayList<>();
}
class ResolvedOverload {
final Class[] types;
final int index;
ResolvedOverload(Object[] args, int index) {
this.index = index;
types = new Class[args.length];
for (int i = 0, l = args.length; i < l; i++) {
Object arg = args[i];
if (arg instanceof Wrapper)
arg = ((Wrapper)arg).unwrap();
types[i] = arg == null ? null : arg.getClass();
}
}
boolean matches(Object[] args) {
if (args.length != types.length) {
return false;
}
for (int i = 0, l = args.length; i < l; i++) {
Object arg = args[i];
if (arg instanceof Wrapper)
arg = ((Wrapper)arg).unwrap();
if (arg == null) {
if (types[i] != null) return false;
} else if (arg.getClass() != types[i]) {
return false;
}
}
return true;
}
@Override
public boolean equals(Object other) {
if (!(other instanceof ResolvedOverload)) {
return false;
}
ResolvedOverload ovl = (ResolvedOverload) other;
return Arrays.equals(types, ovl.types) && index == ovl.index;
}
@Override
public int hashCode() {
return Arrays.hashCode(types);
}
}
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