/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package sun.jvm.hotspot.utilities.soql;

import java.util.*;
import sun.jvm.hotspot.oops.*;
import sun.jvm.hotspot.memory.*;
import sun.jvm.hotspot.runtime.*;
import sun.jvm.hotspot.utilities.*;

This is SOQL (Simple Object Query Language) engine. This uses JavaScript engine for the "select" and "where" expression parts.
/** * This is SOQL (Simple Object Query Language) engine. This * uses JavaScript engine for the "select" and "where" expression * parts. */
public class SOQLEngine extends JSJavaScriptEngine { public static synchronized SOQLEngine getEngine() { if (soleInstance == null) { soleInstance = new SOQLEngine(); } return soleInstance; }
Query is of the form select <java script code to select> [ from [instanceof] <class name> [<identifier>] [ where <java script boolean expression> ] ]
/** Query is of the form select &lt;java script code to select&gt; [ from [instanceof] &lt;class name&gt; [&lt;identifier&gt;] [ where &lt;java script boolean expression&gt; ] ] */
public synchronized void executeQuery(String query, ObjectVisitor visitor) throws SOQLException { debugPrint("query : " + query); StringTokenizer st = new StringTokenizer(query); if (st.hasMoreTokens()) { String first = st.nextToken(); if (! first.equals("select") ) { throw new SOQLException("query syntax error: no 'select' clause"); } } else { throw new SOQLException("query syntax error: no 'select' clause"); } int selectStart = query.indexOf("select"); int fromStart = query.indexOf("from"); String selectExpr = null; String className = null; boolean isInstanceOf = false; String whereExpr = null; String identifier = null; if (fromStart != -1) { selectExpr = query.substring(selectStart + "select".length(), fromStart); st = new StringTokenizer(query.substring(fromStart + "from".length())); if (st.hasMoreTokens()) { String tmp = st.nextToken(); if (tmp.equals("instanceof")) { isInstanceOf = true; if (! st.hasMoreTokens()) { throw new SOQLException("no class name after 'instanceof'"); } className = st.nextToken(); } else { className = tmp; } } else { throw new SOQLException("query syntax error: class name must follow 'from'"); } if (st.hasMoreTokens()) { identifier = st.nextToken(); if (identifier.equals("where")) { throw new SOQLException("query syntax error: identifier should follow class name"); } if (st.hasMoreTokens()) { String tmp = st.nextToken(); if (! tmp.equals("where")) { throw new SOQLException("query syntax error: 'where' clause expected after 'from' clause"); } int whereEnd = query.lastIndexOf("where") + 5; // "where".length whereExpr = query.substring(whereEnd); } } else { throw new SOQLException("query syntax error: identifier should follow class name"); } } else { // no from clause selectExpr = query.substring(selectStart + "select".length(), query.length()); } executeQuery(new SOQLQuery(selectExpr, isInstanceOf, className, identifier, whereExpr), visitor); } private void executeQuery(SOQLQuery q, ObjectVisitor visitor) throws SOQLException { InstanceKlass kls = null; if (q.className != null) { kls = SystemDictionaryHelper.findInstanceKlass(q.className); if (kls == null) { throw new SOQLException(q.className + " is not found!"); } } StringBuffer buf = new StringBuffer(); buf.append("function result("); if (q.identifier != null) { buf.append(q.identifier); } buf.append(") { return "); buf.append(q.selectExpr.replace('\n', ' ')); buf.append("; }"); String selectCode = buf.toString(); debugPrint(selectCode); String whereCode = null; if (q.whereExpr != null) { buf = new StringBuffer(); buf.append("function filter("); buf.append(q.identifier); buf.append(") { return "); buf.append(q.whereExpr.replace('\n', ' ')); buf.append("; }"); whereCode = buf.toString(); debugPrint(whereCode); } else { whereCode = "filter = null;"; } beginQuery(); // compile select expression and where condition evalString(selectCode, "", 1); evalString(whereCode, "", 1); // iterate thru heap, if needed if (q.className != null) { try { iterateOops(kls, visitor, q.isInstanceOf); } finally { endQuery(); } } else { // simple "select <expr>" query try { Object select = call("result", new Object[] {}); visitor.visit(select); } catch (Exception e) { e.printStackTrace(); } } } private void dispatchObject(Oop oop, ObjectVisitor visitor, boolean filterExists) { JSJavaObject jsObj = factory.newJSJavaObject(oop); Object[] args = new Object[] { jsObj }; boolean b = true; try { if (filterExists) { Object res = call("filter", args); if (res instanceof Boolean) { b = ((Boolean)res).booleanValue(); } else if (res instanceof Number) { b = ((Number)res).intValue() != 0; } else { b = (res != null); } } if (b) { Object select = call("result", args); visitor.visit(select); } } catch (Exception e) { throw new RuntimeException(e); } } private void iterateOops(final InstanceKlass ik, final ObjectVisitor visitor, boolean includeSubtypes) { ObjectHeap oh = VM.getVM().getObjectHeap(); oh.iterateObjectsOfKlass(new HeapVisitor() { boolean filterExists; public void prologue(long usedSize) { filterExists = getScriptEngine().get("filter") != null; } public boolean doObj(Oop obj) { dispatchObject(obj, visitor, filterExists); return false; } public void epilogue() {} }, ik, includeSubtypes); } // we create fresh ObjectReader and factory to avoid // excessive cache across queries. private void beginQuery() { objReader = new ObjectReader(); factory = new JSJavaFactoryImpl(); } // at the end of query we clear object reader cache // and factory cache private void endQuery() { objReader = null; factory = null; } protected ObjectReader getObjectReader() { return objReader; } protected JSJavaFactory getJSJavaFactory() { return factory; } protected boolean isQuitting() { return false; } protected void quit() { // do nothing } private static void debugPrint(String msg) { if (debug) System.out.println(msg); } private static final boolean debug; static { debug = System.getProperty("sun.jvm.hotspot.utilities.soql.SOQLEngine.debug") != null; } protected SOQLEngine() { super(debug); start(); } private ObjectReader objReader; private JSJavaFactory factory; private static SOQLEngine soleInstance; }