fairgenericobjectpool.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="208" href="#208">208</a>                         } <strong>catch</strong>(NoSuchElementException e) {
<a name="209" href="#209">209</a>                             ; <em class="comment">/*<em class="comment"> ignored */</em></em>
<a name="210" href="#210">210</a>                         }
<a name="211" href="#211">211</a>                     }
<a name="212" href="#212">212</a>     
<a name="213" href="#213">213</a>                     <em class="comment">// otherwise</em>
<a name="214" href="#214">214</a>                     <strong>if</strong>(<strong>null</strong> == pair) {
<a name="215" href="#215">215</a>                         <em class="comment">// check if we can create one</em>
<a name="216" href="#216">216</a>                         <em class="comment">// (note we know that the num sleeping is 0, else we wouldn't be here)</em>
<a name="217" href="#217">217</a>                         <strong>if</strong>(eligible &amp;&amp; (_maxActive &lt; 0 || _numActive &lt; _maxActive)) {
<a name="218" href="#218">218</a>                             <em class="comment">// allow new object to be created</em>
<a name="219" href="#219">219</a>                         } <strong>else</strong> {
<a name="220" href="#220">220</a>                             <em class="comment">// the pool is exhausted</em>
<a name="221" href="#221">221</a>                             <em class="comment">// or current thread is ineligible due to fairness</em>
<a name="222" href="#222">222</a>                             <strong>switch</strong>(_whenExhaustedAction) {
<a name="223" href="#223">223</a>                                 <strong>case</strong> WHEN_EXHAUSTED_GROW:
<a name="224" href="#224">224</a>                                     <em class="comment">// allow new object to be created</em>
<a name="225" href="#225">225</a>                                     <strong>break</strong>;
<a name="226" href="#226">226</a>                                 <strong>case</strong> WHEN_EXHAUSTED_FAIL:
<a name="227" href="#227">227</a>                                     <strong>throw</strong> <strong>new</strong> NoSuchElementException(<span class="string">"Pool exhausted"</span>);
<a name="228" href="#228">228</a>                                 <strong>case</strong> WHEN_EXHAUSTED_BLOCK:
<a name="229" href="#229">229</a>                                     <strong>try</strong> {
<a name="230" href="#230">230</a>                                         <strong>if</strong>(_maxWait &lt;= 0) {
<a name="231" href="#231">231</a>                                             wait();
<a name="232" href="#232">232</a>                                         } <strong>else</strong> {
<a name="233" href="#233">233</a>                                             <em class="comment">// this code may be executed again after a notify then continue cycle</em>
<a name="234" href="#234">234</a>                                             <em class="comment">// so, need to calculate the amount of time to wait</em>
<a name="235" href="#235">235</a>                                             <strong>final</strong> <strong>long</strong> elapsed = (System.currentTimeMillis() - starttime);
<a name="236" href="#236">236</a>                                             <strong>final</strong> <strong>long</strong> waitTime = _maxWait - elapsed;
<a name="237" href="#237">237</a>                                             <strong>if</strong> (waitTime > 0)
<a name="238" href="#238">238</a>                                             {
<a name="239" href="#239">239</a>                                                 wait(waitTime);
<a name="240" href="#240">240</a>                                             }
<a name="241" href="#241">241</a>                                         }
<a name="242" href="#242">242</a>                                     } <strong>catch</strong>(InterruptedException e) {
<a name="243" href="#243">243</a>                                         <em class="comment">// ignored</em>
<a name="244" href="#244">244</a>                                     }
<a name="245" href="#245">245</a>                                     <strong>if</strong>(_maxWait > 0 &amp;&amp; ((System.currentTimeMillis() - starttime) >= _maxWait)) {
<a name="246" href="#246">246</a>                                         <strong>throw</strong> <strong>new</strong> NoSuchElementException(<span class="string">"Timeout waiting for idle object"</span>);
<a name="247" href="#247">247</a>                                     } <strong>else</strong> {
<a name="248" href="#248">248</a>                                         <strong>continue</strong>; <em class="comment">// keep looping</em>
<a name="249" href="#249">249</a>                                     }
<a name="250" href="#250">250</a>                                 <strong>default</strong>:
<a name="251" href="#251">251</a>                                     <strong>throw</strong> <strong>new</strong> IllegalArgumentException(<span class="string">"WhenExhaustedAction property "</span> + _whenExhaustedAction + <span class="string">" not recognized."</span>);
<a name="252" href="#252">252</a>                             }
<a name="253" href="#253">253</a>                         }
<a name="254" href="#254">254</a>                     }
<a name="255" href="#255">255</a>                     _numActive++;
<a name="256" href="#256">256</a>     
<a name="257" href="#257">257</a>                     <em class="comment">// create new object when needed</em>
<a name="258" href="#258">258</a>                     <strong>boolean</strong> newlyCreated = false;
<a name="259" href="#259">259</a>                     <strong>if</strong>(<strong>null</strong> == pair) {
<a name="260" href="#260">260</a>                         <strong>try</strong> {
<a name="261" href="#261">261</a>                             Object obj = _factory.makeObject();
<a name="262" href="#262">262</a>                             pair = <strong>new</strong> ObjectTimestampPair(obj);
<a name="263" href="#263">263</a>                             newlyCreated = <strong>true</strong>;
<a name="264" href="#264">264</a>                             <strong>return</strong> pair.value;
<a name="265" href="#265">265</a>                         } <strong>finally</strong> {
<a name="266" href="#266">266</a>                             <strong>if</strong> (!newlyCreated) {
<a name="267" href="#267">267</a>                                 <em class="comment">// object cannot be created</em>
<a name="268" href="#268">268</a>                                 _numActive--;
<a name="269" href="#269">269</a>                                 notifyAll();
<a name="270" href="#270">270</a>                             }
<a name="271" href="#271">271</a>                         }
<a name="272" href="#272">272</a>                     }
<a name="273" href="#273">273</a>     
<a name="274" href="#274">274</a>                     <em class="comment">// activate &amp; validate the object</em>
<a name="275" href="#275">275</a>                     <strong>try</strong> {
<a name="276" href="#276">276</a>                         _factory.activateObject(pair.value);
<a name="277" href="#277">277</a>                         <strong>if</strong>(_testOnBorrow &amp;&amp; !_factory.validateObject(pair.value)) {
<a name="278" href="#278">278</a>                             <strong>throw</strong> <strong>new</strong> Exception(<span class="string">"ValidateObject failed"</span>);
<a name="279" href="#279">279</a>                         }
<a name="280" href="#280">280</a>                         <strong>return</strong> pair.value;
<a name="281" href="#281">281</a>                     }
<a name="282" href="#282">282</a>                     <strong>catch</strong> (Throwable e) {
<a name="283" href="#283">283</a>                         <em class="comment">// object cannot be activated or is invalid</em>
<a name="284" href="#284">284</a>                         _numActive--;
<a name="285" href="#285">285</a>                         notifyAll();
<a name="286" href="#286">286</a>                         <strong>try</strong> {
<a name="287" href="#287">287</a>                             _factory.destroyObject(pair.value);
<a name="288" href="#288">288</a>                         }
<a name="289" href="#289">289</a>                         <strong>catch</strong> (Throwable e2) {
<a name="290" href="#290">290</a>                             <em class="comment">// cannot destroy broken object</em>
<a name="291" href="#291">291</a>                         }
<a name="292" href="#292">292</a>                         <strong>if</strong>(newlyCreated) {
<a name="293" href="#293">293</a>                             <strong>throw</strong> <strong>new</strong> NoSuchElementException(<span class="string">"Could not create a validated object, cause: "</span> + e.getMessage());
<a name="294" href="#294">294</a>                         }
<a name="295" href="#295">295</a>                         <strong>else</strong> {
<a name="296" href="#296">296</a>                             <strong>continue</strong>; <em class="comment">// keep looping</em>
<a name="297" href="#297">297</a>                         }
<a name="298" href="#298">298</a>                     }
<a name="299" href="#299">299</a>                 }
<a name="300" href="#300">300</a>             } 
<a name="301" href="#301">301</a>         } <strong>finally</strong> {
<a name="302" href="#302">302</a>             <em class="comment">// remove thread from queue on any method exit</em>
<a name="303" href="#303">303</a>             _borrowerQueue.remove(Thread.currentThread());
<a name="304" href="#304">304</a>         }
<a name="305" href="#305">305</a>     }
<a name="306" href="#306">306</a> 
<a name="307" href="#307">307</a>     <em>/**<em>* Waiting borrowers (threads in #borrowObject ) */</em></em>
<a name="308" href="#308">308</a>     <strong>protected</strong> List _borrowerQueue;
<a name="309" href="#309">309</a> }
</pre>
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