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    • com.facebook.presto.jdbc.internal.jol.info.GraphWalker Maven / Gradle / Ivy

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    /*
 * 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 com.facebook.presto.jdbc.internal.jol.info;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Set;

/**
 * Basic class to walk object graphs.
 *
 * @author Aleksey Shipilev
 */
public class GraphWalker {

    private final Set visited;
    private final Object root;
    private final Collection visitors;

    public GraphWalker(Object root) {
        this.root = root;
        this.visited = Collections.newSetFromMap(new IdentityHashMap());
        this.visitors = new ArrayList();
    }

    public void addVisitor(GraphVisitor v) {
        visitors.add(v);
    }

    public void walk() {
        List curLayer = new ArrayList();
        List newLayer = new ArrayList();

        GraphPathRecord e = new GraphPathRecord("", root, 0);
        visited.add(root);
        visitObject(e);
        curLayer.add(e);

        while (!curLayer.isEmpty()) {
            newLayer.clear();
            for (GraphPathRecord next : curLayer) {
                for (GraphPathRecord ref : peelReferences(next)) {
                    if (ref != null) {
                        if (visited.add(ref.obj())) {
                            visitObject(ref);
                            newLayer.add(ref);
                        }
                    }
                }
            }
            curLayer.clear();
            curLayer.addAll(newLayer);
        }
    }

    private void visitObject(GraphPathRecord record) {
        for (GraphVisitor v : visitors) {
            v.visit(record);
        }
    }

    private List peelReferences(GraphPathRecord r) {
        List result = new ArrayList();

        Object o = r.obj();
        if (o.getClass().isArray() && !o.getClass().getComponentType().isPrimitive()) {
            int c = 0;
            for (Object e : (Object[]) o) {
                if (e != null) {
                    result.add(new GraphPathRecord(r.path() + "[" + c + "]", e, r.depth() + 1));
                }
                c++;
            }
        }

        for (Field f : getAllFields(o.getClass())) {
            f.setAccessible(true);
            if (f.getType().isPrimitive()) continue;
            if (Modifier.isStatic(f.getModifiers())) continue;

            try {
                Object e = f.get(o);
                if (e != null) {
                    result.add(new GraphPathRecord(r.path() + "." + f.getName(), e, r.depth() + 1));
                }
            } catch (IllegalAccessException e) {
                throw new IllegalStateException(e);
            }
        }

        return result;
    }

    private Collection getAllFields(Class klass) {
        List results = new ArrayList();

        for (Field f : klass.getDeclaredFields()) {
            if (!Modifier.isStatic(f.getModifiers())) {
                results.add(f);
            }
        }

        Class superKlass = klass;
        while ((superKlass = superKlass.getSuperclass()) != null) {
            for (Field f : superKlass.getDeclaredFields()) {
                if (!Modifier.isStatic(f.getModifiers())) {
                    results.add(f);
                }
            }
        }

        return results;
    }

}
    
    
    
    

    




    
    
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