cachedbdbmap.html

用JAVA编写的,在做实验的时候留下来的,本来想删的,但是传上来,大家分享吧

<a name="306" href="#306">306</a>     <strong>public</strong> <strong>synchronized</strong> <strong>void</strong> close() throws DatabaseException {
<a name="307" href="#307">307</a>         <em class="comment">// Close out my bdb db.</em>
<a name="308" href="#308">308</a>         <strong>if</strong> (<strong>this</strong>.db != <strong>null</strong>) {
<a name="309" href="#309">309</a>             <strong>try</strong> {
<a name="310" href="#310">310</a>                 <strong>this</strong>.db.close();
<a name="311" href="#311">311</a>             } <strong>catch</strong> (DatabaseException e) {
<a name="312" href="#312">312</a>                 e.printStackTrace();
<a name="313" href="#313">313</a>             } <strong>finally</strong> {
<a name="314" href="#314">314</a>                 <strong>this</strong>.db = <strong>null</strong>;
<a name="315" href="#315">315</a>             }
<a name="316" href="#316">316</a>         }
<a name="317" href="#317">317</a>         <strong>if</strong> (dbEnvironment != <strong>null</strong>) {
<a name="318" href="#318">318</a>             dbEnvironment.openDbCount--;
<a name="319" href="#319">319</a>             <strong>if</strong> (dbEnvironment.openDbCount &lt;= 0) {
<a name="320" href="#320">320</a>                 dbEnvironment.classCatalog.close();
<a name="321" href="#321">321</a>                 dbEnvironment.environment.close();
<a name="322" href="#322">322</a>                 dbEnvironmentMap.remove(dbEnvironment.dbDir.getAbsolutePath());
<a name="323" href="#323">323</a>                 dbEnvironment = <strong>null</strong>;
<a name="324" href="#324">324</a>             }
<a name="325" href="#325">325</a>         }
<a name="326" href="#326">326</a>     }
<a name="327" href="#327">327</a> 
<a name="328" href="#328">328</a>     <strong>protected</strong> <strong>void</strong> finalize() throws Throwable {
<a name="329" href="#329">329</a>         close();
<a name="330" href="#330">330</a>         <strong>super</strong>.finalize();
<a name="331" href="#331">331</a>     }
<a name="332" href="#332">332</a> 
<a name="333" href="#333">333</a>     <em>/**<em>*</em></em>
<a name="334" href="#334">334</a> <em>     * The keySet of the diskMap is all relevant keys. </em>
<a name="335" href="#335">335</a> <em>     * </em>
<a name="336" href="#336">336</a> <em>     * @see java.util.Map#keySet()</em>
<a name="337" href="#337">337</a> <em>     */</em>
<a name="338" href="#338">338</a>     <strong>public</strong> Set keySet() {
<a name="339" href="#339">339</a>         <strong>return</strong> diskMap.keySet();
<a name="340" href="#340">340</a>     }
<a name="341" href="#341">341</a>     
<a name="342" href="#342">342</a>     <strong>public</strong> Set entrySet() {
<a name="343" href="#343">343</a>         <em class="comment">// Would require complicated implementation to </em>
<a name="344" href="#344">344</a>         <em class="comment">// maintain identity guarantees, so skipping</em>
<a name="345" href="#345">345</a>         <strong>throw</strong> <strong>new</strong> UnsupportedOperationException();
<a name="346" href="#346">346</a>     }
<a name="347" href="#347">347</a> 
<a name="348" href="#348">348</a>     <strong>public</strong> <strong>synchronized</strong> Object get(<strong>final</strong> Object key) {
<a name="349" href="#349">349</a>         countOfGets++;
<a name="350" href="#350">350</a>         expungeStaleEntries();
<a name="351" href="#351">351</a>         <strong>if</strong> (countOfGets % 10000 == 0) {
<a name="352" href="#352">352</a>             logCacheSummary();
<a name="353" href="#353">353</a>         }
<a name="354" href="#354">354</a>         SoftEntry entry = (SoftEntry)memMap.get(key);
<a name="355" href="#355">355</a>         <strong>if</strong> (entry != <strong>null</strong>) {
<a name="356" href="#356">356</a>             Object val = entry.get(); <em class="comment">// get &amp; hold, so not cleared pre-return</em>
<a name="357" href="#357">357</a>             <strong>if</strong> (val != <strong>null</strong>) {
<a name="358" href="#358">358</a>                 cacheHit++;
<a name="359" href="#359">359</a>                 <strong>return</strong> val;
<a name="360" href="#360">360</a>             }
<a name="361" href="#361">361</a>             <em class="comment">// Explicitly clear this entry from referencequeue since its</em>
<a name="362" href="#362">362</a>             <em class="comment">// value is null.</em>
<a name="363" href="#363">363</a>             expungeStaleEntry(entry);
<a name="364" href="#364">364</a>         }
<a name="365" href="#365">365</a> 
<a name="366" href="#366">366</a>         <em class="comment">// check backing diskMap</em>
<a name="367" href="#367">367</a>         Object o = <strong>this</strong>.diskMap.get(key);
<a name="368" href="#368">368</a>         <strong>if</strong> (o != <strong>null</strong>) {
<a name="369" href="#369">369</a>             diskHit++;
<a name="370" href="#370">370</a>             memMap.put(key, <strong>new</strong> SoftEntry(key, o, refQueue));
<a name="371" href="#371">371</a>         }
<a name="372" href="#372">372</a>         <strong>return</strong> o;
<a name="373" href="#373">373</a>     }
<a name="374" href="#374">374</a> 
<a name="375" href="#375">375</a>     <em>/**<em>*</em></em>
<a name="376" href="#376">376</a> <em>     * Info to log, if at FINE level, on every get()</em>
<a name="377" href="#377">377</a> <em>     */</em>
<a name="378" href="#378">378</a>     <strong>private</strong> <strong>void</strong> logCacheSummary() {
<a name="379" href="#379">379</a>         <strong>if</strong> (!logger.isLoggable((Level.FINE))) {
<a name="380" href="#380">380</a>             <strong>return</strong>;
<a name="381" href="#381">381</a>         }
<a name="382" href="#382">382</a>         <strong>try</strong> {
<a name="383" href="#383">383</a>             <strong>long</strong> cacheHitPercent = (cacheHit * 100) / (cacheHit + diskHit);
<a name="384" href="#384">384</a>             logger.fine(<span class="string">"DB name: "</span> + <strong>this</strong>.db.getDatabaseName()
<a name="385" href="#385">385</a>                 + <span class="string">", Cache Hit: "</span> + cacheHitPercent
<a name="386" href="#386">386</a>                 + <span class="string">"%, Not in map: "</span> + (countOfGets - (cacheHit + diskHit))
<a name="387" href="#387">387</a>                 + <span class="string">", Total number of gets: "</span> + countOfGets);
<a name="388" href="#388">388</a>         } <strong>catch</strong> (DatabaseException e) {
<a name="389" href="#389">389</a>             <em class="comment">// This is just for logging so ignore DB Exceptions</em>
<a name="390" href="#390">390</a>         }
<a name="391" href="#391">391</a>     }
<a name="392" href="#392">392</a>     
<a name="393" href="#393">393</a>     <strong>public</strong> <strong>synchronized</strong> Object put(Object key, Object value) {
<a name="394" href="#394">394</a>         Object prevVal = get(key);
<a name="395" href="#395">395</a>         memMap.put(key, <strong>new</strong> SoftEntry(key, value, refQueue));
<a name="396" href="#396">396</a>         diskMap.put(key,value); <em class="comment">// dummy</em>
<a name="397" href="#397">397</a>         <strong>if</strong>(prevVal==<strong>null</strong>) {
<a name="398" href="#398">398</a>             diskMapSize++;
<a name="399" href="#399">399</a>         }
<a name="400" href="#400">400</a>         <strong>return</strong> prevVal;
<a name="401" href="#401">401</a>     }
<a name="402" href="#402">402</a> 
<a name="403" href="#403">403</a>     <em>/**<em>*</em></em>
<a name="404" href="#404">404</a> <em>     * Note that a call to this method CLOSEs the underlying bdbje.</em>
<a name="405" href="#405">405</a> <em>     * This instance is no longer of any use.  It must be re-initialized.</em>
<a name="406" href="#406">406</a> <em>     * We close the db here because if this BigMap is being treated as a plain</em>
<a name="407" href="#407">407</a> <em>     * Map, this is only opportunity for cleanup.</em>
<a name="408" href="#408">408</a> <em>     */</em>
<a name="409" href="#409">409</a>     <strong>public</strong> <strong>synchronized</strong> <strong>void</strong> clear() {
<a name="410" href="#410">410</a>         <strong>this</strong>.memMap.clear();
<a name="411" href="#411">411</a>         <strong>this</strong>.diskMap.clear();
<a name="412" href="#412">412</a>         <strong>this</strong>.diskMapSize = 0;
<a name="413" href="#413">413</a>         <strong>try</strong> {
<a name="414" href="#414">414</a>             close();
<a name="415" href="#415">415</a>         } <strong>catch</strong> (DatabaseException e) {
<a name="416" href="#416">416</a>             e.printStackTrace();
<a name="417" href="#417">417</a>         }
<a name="418" href="#418">418</a>     }
<a name="419" href="#419">419</a> 
<a name="420" href="#420">420</a>     <strong>public</strong> <strong>synchronized</strong> Object remove(<strong>final</strong> Object key) {
<a name="421" href="#421">421</a>         Object prevValue = get(key);
<a name="422" href="#422">422</a>         memMap.remove(key);
<a name="423" href="#423">423</a>         expungeStaleEntries();
<a name="424" href="#424">424</a>         diskMap.remove(key);
<a name="425" href="#425">425</a>         diskMapSize--;
<a name="426" href="#426">426</a>         <strong>return</strong> prevValue;
<a name="427" href="#427">427</a>     }
<a name="428" href="#428">428</a> 
<a name="429" href="#429">429</a>     <strong>public</strong> <strong>synchronized</strong> <strong>boolean</strong> containsKey(Object key) {
<a name="430" href="#430">430</a>         <strong>if</strong> (quickContainsKey(key)) {
<a name="431" href="#431">431</a>             <strong>return</strong> <strong>true</strong>;
<a name="432" href="#432">432</a>         }
<a name="433" href="#433">433</a>         <strong>return</strong> diskMap.containsKey(key);
<a name="434" href="#434">434</a>     }
<a name="435" href="#435">435</a> 
<a name="436" href="#436">436</a>     <strong>public</strong> <strong>synchronized</strong> <strong>boolean</strong> quickContainsKey(Object key) {
<a name="437" href="#437">437</a>         expungeStaleEntries();
<a name="438" href="#438">438</a>         <strong>return</strong> memMap.containsKey(key);
<a name="439" href="#439">439</a>     }
<a name="440" href="#440">440</a> 
<a name="441" href="#441">441</a>     <strong>public</strong> <strong>synchronized</strong> <strong>boolean</strong> containsValue(Object value) {
<a name="442" href="#442">442</a>         <strong>if</strong> (quickContainsValue(value)) {
<a name="443" href="#443">443</a>             <strong>return</strong> <strong>true</strong>;
<a name="444" href="#444">444</a>         }
<a name="445" href="#445">445</a>         <strong>return</strong> diskMap.containsValue(value);
<a name="446" href="#446">446</a>     }
<a name="447" href="#447">447</a> 
<a name="448" href="#448">448</a>     <strong>public</strong> <strong>synchronized</strong> <strong>boolean</strong> quickContainsValue(Object value) {
<a name="449" href="#449">449</a>         expungeStaleEntries();
<a name="450" href="#450">450</a>         <em class="comment">// FIXME this isn't really right, as memMap is of SoftEntries</em>
<a name="451" href="#451">451</a>         <strong>return</strong> memMap.containsValue(value);
<a name="452" href="#452">452</a>     }
<a name="453" href="#453">453</a> 
<a name="454" href="#454">454</a>     <strong>public</strong> <strong>int</strong> size() {
<a name="455" href="#455">455</a>         <strong>return</strong> diskMapSize;
<a name="456" href="#456">456</a>     }
<a name="457" href="#457">457</a>     
<a name="458" href="#458">458</a>     <strong>protected</strong> String getDatabaseName() {
<a name="459" href="#459">459</a>         String name = <span class="string">"DbName-Lookup-Failed"</span>;
<a name="460" href="#460">460</a>         <strong>try</strong> {
<a name="461" href="#461">461</a>             <strong>if</strong> (<strong>this</strong>.db != <strong>null</strong>) {
<a name="462" href="#462">462</a>                 name = <strong>this</strong>.db.getDatabaseName();