src/java.base/share/classes/jdk/internal/reflect/MethodHandleFieldAccessorImpl.java

/*
 * Copyright (c) 2021, 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
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package jdk.internal.reflect;

import java.lang.invoke.MethodHandle;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;

abstract class MethodHandleFieldAccessorImpl extends FieldAccessorImpl {
    private static final int IS_READ_ONLY_BIT = 0x0001;
    private static final int IS_STATIC_BIT = 0x0002;
    private static final int NONZERO_BIT = 0x8000;

    private final int fieldFlags;
    protected final MethodHandle getter;
    protected final MethodHandle setter;

    protected MethodHandleFieldAccessorImpl(Field field, MethodHandle getter, MethodHandle setter, boolean isReadOnly, boolean isStatic) {
        super(field);
        this.fieldFlags = (isReadOnly ? IS_READ_ONLY_BIT : 0) |
                          (isStatic ? IS_STATIC_BIT : 0) |
                          NONZERO_BIT;
        this.getter = getter;
        this.setter = setter;
    }

    protected final boolean isReadOnly() {
        return (fieldFlags & IS_READ_ONLY_BIT) == IS_READ_ONLY_BIT;
    }

    protected final boolean isStatic() {
        return (fieldFlags & IS_STATIC_BIT) == IS_STATIC_BIT;
    }

    protected final void ensureObj(Object o) {
        if (!isStatic()) {
            // for compatibility, check the receiver object first
            // throw NullPointerException if o is null
            if (!field.getDeclaringClass().isAssignableFrom(o.getClass())) {
                throwSetIllegalArgumentException(o);
            }
        }
    }

    private String getMessage(boolean getter, Class<?> type) {
        String err = "Can not " + (getter ? "get" : "set");
        if (Modifier.isStatic(field.getModifiers()))
            err += " static";
        if (Modifier.isFinal(field.getModifiers()))
            err += " final";
        err += " " + field.getType().getName() + " field " + getQualifiedFieldName();
        if (type != null) {
            err += " on " + type.getName();
        }
        return err;
    }

    /**
     * IllegalArgumentException because Field::get on the specified object, which
     * is not an instance of the class or interface declaring the underlying method
     */
    protected IllegalArgumentException newGetIllegalArgumentException(Object o) {
        return new IllegalArgumentException(getMessage(true, o != null ? o.getClass() : null));
    }

    /**
     * IllegalArgumentException because Field::set on the specified object, which
     * is not an instance of the class or interface declaring the underlying method
     */
    protected IllegalArgumentException newSetIllegalArgumentException(Object o) {
        return new IllegalArgumentException(getMessage(false, o != null ? o.getClass() : null));
    }
}