bdbmultipleworkqueues.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="421" href="#421">421</a> <em>     * @throws DatabaseException</em>
<a name="422" href="#422">422</a> <em>     */</em>
<a name="423" href="#423">423</a>     <strong>public</strong> <strong>void</strong> delete(<a href="../../../../org/archive/crawler/datamodel/CrawlURI.html">CrawlURI</a> item) throws DatabaseException {
<a name="424" href="#424">424</a>         OperationStatus status;
<a name="425" href="#425">425</a>         status = pendingUrisDB.delete(<strong>null</strong>, (DatabaseEntry) item.getHolderKey());
<a name="426" href="#426">426</a>         <strong>if</strong> (status != OperationStatus.SUCCESS) {
<a name="427" href="#427">427</a>             LOGGER.severe(<span class="string">"expected item not present: "</span>
<a name="428" href="#428">428</a>                     + item
<a name="429" href="#429">429</a>                     + <span class="string">"("</span>
<a name="430" href="#430">430</a>                     + (<strong>new</strong> BigInteger(((DatabaseEntry) item.getHolderKey())
<a name="431" href="#431">431</a>                             .getData())).toString(16) + <span class="string">")"</span>);
<a name="432" href="#432">432</a>         }
<a name="433" href="#433">433</a> 
<a name="434" href="#434">434</a>     }
<a name="435" href="#435">435</a>     
<a name="436" href="#436">436</a>     <em>/**<em>*</em></em>
<a name="437" href="#437">437</a> <em>     * Method used by BdbFrontier during checkpointing.</em>
<a name="438" href="#438">438</a> <em>     * &lt;p>The backing bdbje database has been marked deferred write so we save</em>
<a name="439" href="#439">439</a> <em>     * on writes to disk.  Means no guarantees disk will have whats in memory</em>
<a name="440" href="#440">440</a> <em>     * unless a sync is called (Calling sync on the bdbje Environment is not</em>
<a name="441" href="#441">441</a> <em>     * sufficent).</em>
<a name="442" href="#442">442</a> <em>     * &lt;p>Package access only because only Frontiers of this package would ever</em>
<a name="443" href="#443">443</a> <em>     * need access.</em>
<a name="444" href="#444">444</a> <em>     * @see &lt;a href="<a href="http://www.sleepycat.com/jedocs/GettingStartedGuide/DB.html" target="alexandria_uri">http://www.sleepycat.com/jedocs/GettingStartedGuide/DB.html</a>">Deferred Write Databases&lt;/a></em>
<a name="445" href="#445">445</a> <em>     */</em>
<a name="446" href="#446">446</a>     <strong>void</strong> sync() {
<a name="447" href="#447">447</a>     	<strong>if</strong> (<strong>this</strong>.pendingUrisDB == <strong>null</strong>) {
<a name="448" href="#448">448</a>     		<strong>return</strong>;
<a name="449" href="#449">449</a>     	}
<a name="450" href="#450">450</a>         <strong>try</strong> {
<a name="451" href="#451">451</a>             <strong>this</strong>.pendingUrisDB.sync();
<a name="452" href="#452">452</a>         } <strong>catch</strong> (DatabaseException e) {
<a name="453" href="#453">453</a>             e.printStackTrace();
<a name="454" href="#454">454</a>         }
<a name="455" href="#455">455</a>     }
<a name="456" href="#456">456</a>     
<a name="457" href="#457">457</a>     <em>/**<em>*</em></em>
<a name="458" href="#458">458</a> <em>     * clean up </em>
<a name="459" href="#459">459</a> <em>     *</em>
<a name="460" href="#460">460</a> <em>     */</em>
<a name="461" href="#461">461</a>     <strong>public</strong> <strong>void</strong> close() {
<a name="462" href="#462">462</a>         <strong>try</strong> {
<a name="463" href="#463">463</a>             <strong>this</strong>.pendingUrisDB.close();
<a name="464" href="#464">464</a>         } <strong>catch</strong> (DatabaseException e) {
<a name="465" href="#465">465</a>             e.printStackTrace();
<a name="466" href="#466">466</a>         }
<a name="467" href="#467">467</a>     }
<a name="468" href="#468">468</a>     
<a name="469" href="#469">469</a>     <em>/**<em>*</em></em>
<a name="470" href="#470">470</a> <em>     * Marker for remembering a position within the BdbMultipleWorkQueues.</em>
<a name="471" href="#471">471</a> <em>     * </em>
<a name="472" href="#472">472</a> <em>     * @author gojomo</em>
<a name="473" href="#473">473</a> <em>     */</em>
<a name="474" href="#474">474</a>     <strong>public</strong> <strong>class</strong> BdbFrontierMarker implements <a href="../../../../org/archive/crawler/framework/FrontierMarker.html">FrontierMarker</a> {
<a name="475" href="#475">475</a>         DatabaseEntry startKey;
<a name="476" href="#476">476</a>         Pattern pattern; 
<a name="477" href="#477">477</a>         <strong>int</strong> nextItemNumber;
<a name="478" href="#478">478</a>         
<a name="479" href="#479">479</a>         <em>/**<em>*</em></em>
<a name="480" href="#480">480</a> <em>         * Create a marker pointed at the given start location.</em>
<a name="481" href="#481">481</a> <em>         * </em>
<a name="482" href="#482">482</a> <em>         * @param startKey</em>
<a name="483" href="#483">483</a> <em>         * @param regexpr</em>
<a name="484" href="#484">484</a> <em>         */</em>
<a name="485" href="#485">485</a>         <strong>public</strong> BdbFrontierMarker(DatabaseEntry startKey, String regexpr) {
<a name="486" href="#486">486</a>             <strong>this</strong>.startKey = startKey;
<a name="487" href="#487">487</a>             pattern = Pattern.compile(regexpr);
<a name="488" href="#488">488</a>             nextItemNumber = 1;
<a name="489" href="#489">489</a>         }
<a name="490" href="#490">490</a>         
<a name="491" href="#491">491</a>         <em>/**<em>*</em></em>
<a name="492" href="#492">492</a> <em>         * @param curi</em>
<a name="493" href="#493">493</a> <em>         * @return whether the marker accepts the given CrawlURI</em>
<a name="494" href="#494">494</a> <em>         */</em>
<a name="495" href="#495">495</a>         <strong>public</strong> <strong>boolean</strong> accepts(<a href="../../../../org/archive/crawler/datamodel/CrawlURI.html">CrawlURI</a> curi) {
<a name="496" href="#496">496</a>             <strong>boolean</strong> retVal = pattern.matcher(curi.toString()).matches();
<a name="497" href="#497">497</a>             <strong>if</strong>(retVal==<strong>true</strong>) {
<a name="498" href="#498">498</a>                 nextItemNumber++;
<a name="499" href="#499">499</a>             }
<a name="500" href="#500">500</a>             <strong>return</strong> retVal;
<a name="501" href="#501">501</a>         }
<a name="502" href="#502">502</a>         
<a name="503" href="#503">503</a>         <em>/**<em>*</em></em>
<a name="504" href="#504">504</a> <em>         * @param key position for marker</em>
<a name="505" href="#505">505</a> <em>         */</em>
<a name="506" href="#506">506</a>         <strong>public</strong> <strong>void</strong> setStartKey(DatabaseEntry key) {
<a name="507" href="#507">507</a>             startKey = key;
<a name="508" href="#508">508</a>         }
<a name="509" href="#509">509</a>         
<a name="510" href="#510">510</a>         <em>/**<em>*</em></em>
<a name="511" href="#511">511</a> <em>         * @return startKey</em>
<a name="512" href="#512">512</a> <em>         */</em>
<a name="513" href="#513">513</a>         <strong>public</strong> DatabaseEntry getStartKey() {
<a name="514" href="#514">514</a>             <strong>return</strong> startKey;
<a name="515" href="#515">515</a>         }
<a name="516" href="#516">516</a>         
<a name="517" href="#517">517</a>         <em class="comment">/*<em class="comment"> (non-Javadoc)</em></em>
<a name="518" href="#518">518</a> <em class="comment">         * @see org.archive.crawler.framework.FrontierMarker#getMatchExpression()</em>
<a name="519" href="#519">519</a> <em class="comment">         */</em>
<a name="520" href="#520">520</a>         <strong>public</strong> String getMatchExpression() {
<a name="521" href="#521">521</a>             <strong>return</strong> pattern.pattern();
<a name="522" href="#522">522</a>         }
<a name="523" href="#523">523</a>         
<a name="524" href="#524">524</a>         <em class="comment">/*<em class="comment"> (non-Javadoc)</em></em>
<a name="525" href="#525">525</a> <em class="comment">         * @see org.archive.crawler.framework.FrontierMarker#getNextItemNumber()</em>
<a name="526" href="#526">526</a> <em class="comment">         */</em>
<a name="527" href="#527">527</a>         <strong>public</strong> <strong>long</strong> getNextItemNumber() {
<a name="528" href="#528">528</a>             <strong>return</strong> nextItemNumber;
<a name="529" href="#529">529</a>         }
<a name="530" href="#530">530</a>         
<a name="531" href="#531">531</a>         <em class="comment">/*<em class="comment"> (non-Javadoc)</em></em>
<a name="532" href="#532">532</a> <em class="comment">         * @see org.archive.crawler.framework.FrontierMarker#hasNext()</em>
<a name="533" href="#533">533</a> <em class="comment">         */</em>
<a name="534" href="#534">534</a>         <strong>public</strong> <strong>boolean</strong> hasNext() {
<a name="535" href="#535">535</a>             <em class="comment">// as long as any startKey is stated, consider as having next</em>
<a name="536" href="#536">536</a>             <strong>return</strong> startKey != <strong>null</strong>;
<a name="537" href="#537">537</a>         }
<a name="538" href="#538">538</a>     }
<a name="539" href="#539">539</a> 
<a name="540" href="#540">540</a>     <em>/**<em>*</em></em>
<a name="541" href="#541">541</a> <em>     * Add a dummy 'cap' entry at the given insertion key. Prevents</em>
<a name="542" href="#542">542</a> <em>     * 'seeks' to queue heads from holding lock on last item of </em>
<a name="543" href="#543">543</a> <em>     * 'preceding' queue. See:</em>
<a name="544" href="#544">544</a> <em>     * <a href="http://sourceforge.net/tracker/index.php?func=detail&amp;aid=1262665&amp;group_id=73833&amp;atid=539102" target="alexandria_uri">http://sourceforge.net/tracker/index.php?func=detail&amp;aid=1262665&amp;group_id=73833&amp;atid=539102</a></em>
<a name="545" href="#545">545</a> <em>     * </em>
<a name="546" href="#546">546</a> <em>     * @param origin key at which to insert the cap</em>
<a name="547" href="#547">547</a> <em>     */</em>
<a name="548" href="#548">548</a>     <strong>public</strong> <strong>void</strong> addCap(byte[] origin) {
<a name="549" href="#549">549</a>         <strong>try</strong> {
<a name="550" href="#550">550</a>             pendingUrisDB.put(<strong>null</strong>, <strong>new</strong> DatabaseEntry(origin),
<a name="551" href="#551">551</a>                     <strong>new</strong> DatabaseEntry(<strong>new</strong> byte[0]));
<a name="552" href="#552">552</a>         } <strong>catch</strong> (DatabaseException e) {
<a name="553" href="#553">553</a>             <strong>throw</strong> <strong>new</strong> RuntimeException(e);
<a name="554" href="#554">554</a>         }
<a name="555" href="#555">555</a>     }
<a name="556" href="#556">556</a> }
</pre>
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