聊一聊ThreadLocal-编程开发技术

1、aao»aathreadlocal - ±a3iaao»aathreadlocal0ia3d；£o oidj0eaz" 、 八 z 八八、 八 八 x c * _ _ 八oouthreadlocal ddeenezoo»5dieiaiae%pa£0threadlocalou°iooqeidia»a- 0euau ©d i amdoudaieiap ae%2»p a2»e¥aeathreadlocal±% eip aepi odo%°6»

2、d©iiuieia(iei£6lae¥daqeeuthreadlocal|4a1；au£-ie|jioiu£ 八/、八、八"keioa3i%°oo%oo»d©eioa%“o6i£o /k5aeothreadlocapqoaaaooioifaieieiamafdd'iaaemcoioga oi±uaa2ieyx«pypa-±apa(|6l6aie-!4e!4i£d»oae6ia£-f1ythreadlocal.set x 八 a、

3、八八"八八、八八x()|!%ib3lod|ja(|oi6egaib3ixo%oeioa|ja(|oi6£-i7eae(hb3iec2»d©oaaie|ja£o2 aiempaifibddaiepaeqj-madloifthreadloca庖。入3件0三。场妙训址yiod甸goy心好门血2»b»oap入侥閤£threa dlocaliaa56ib3ipadd20-0 aiepaey%yia1©d»i6i±±%£-if1y-aie ±±%axoedd

4、o pinf-danupaaea naeauf-m ooeuaeibbeua paibwaf -oeeuaeibodepa/ooifaiiepthreadlocale1paib3iau1>>±£3ox6(|aamad>>>d(|dl6£-22>>ef1yth readical.set()aze|liidpa£0eqf,yai5dib3idd|janew(|di6|ja2uxazzz!6，|ja(idi 6£-ai56ib3i!6-d»ad£-2»ee2a16i6|iaivi

5、±s>d5±±%i£f1ythreadlocal.set()«oa 5oda ' y2i aoiop adyoa±£ "aep v2 ib3ip axo%°p ao»idmap(threadaaddp athr eadlocal.threadlocalmappa±aa,)od£-'a>dib3i(|%6ddanud»idmap£-»o'ddthr eadlocal.get()e±£-.4-r

6、ib3r6xoopamapodej3d a0e¥pa(|oi6£-.ddzeei36a pae 54-xox6°ib3iodpa(|6i6£->threadlocalepayeqxiamappakeyaze,6apai£ j%'uael j/,/* threadlocal values pertwining to this thread. this map is maintained* by the threadlocal class. */threadlocalthreadlocalmap threadlocals = null

7、;/* inheritab丄ethreadloca丄 values pertaining to this thread. this map is* maintwined by the inheritablethreadlocal class.* /threadlocal.threadlocalmap inheritablethreadlocals = null; ou(aee>>a6ddanu|ja!l>a£d%6oa>dthreadlocal(|oi6,a0aed»idaae2e6ue« %0p amap£-«e

8、87;o6a 56ib3ix4-iamapp akeya' 'aejoolp aib3i±%p 0p avaluej£aep4、/、入乂八eqthreadlocalaaododo»46threadlocalmap%2i-iau2iaa£eoo%dp¥paaiai ad»i6map£->da>dmapiaa>dib3i/dd»>6±aa/,pajo1/2±zj±zi£'02eaddi£iaa3eeqt hreadloca

9、lmapp a2/, 00 zae£°i%zuae2jstatic class threadlocalmap static class entry extends weakreference<threadlocal> object value;entry (threadlocal k, object v) super(k);value = v;private static final int initial_capacity = 16;private entry table;private int size = 0;private int threshold;

10、/ default to 0/2e-oejaothreadlocal 入 aodb»i20d4%”£o t gct() protected t initialvalue() void remove() void set(t value)%fddget()-tayj%zuae3j/,public t get ()thread t = thread.currentthread();threadlocalmap map = getmap(t);if (map != null)threadlocalmap.entry e = map.getentry(this); if (e !=

11、 null)return (t)e.value;return setinitialvalue();threadlocalmap getmap(thread t)return t.threadlocals;get()!/2*,|jao'aeegeieue%£-'edox|li!/2mapddoaeoy|liakeyeqib3ithreadlocale(dayieir threadlocalmap.entry e = map.getentry(this);od|jathis£©j£edd/,xd»iagetentry(threadl

12、ocal key)paozae. j%'uae4j/,private entry getentry(threadlocal key) int i = key.threadlocalhashcode & (t日ble丄ength 1);entry e = tablei;if (e != null && e.get () = key)return e;elsereturn getentryaftermiss(key, i, e);aqa mapodp avalueeqe2a 負0£血&%宙0入7 zae£° j%'uae

13、5j,private t setinitialvalue()t value = initialvalue();thread t = thread.currentthread(); threadlocalmap map = getmap(t);if (map != null)map.set(this, value);elsecreatemap (t, value);return value;protected t initialvalue()return null;uae5odo»au1»1u2ip iytprotected tinitialvalue()-eeoaaed&#

14、187;i63de%om£-p±e»d2ieddf1yset-a3op£-%id0zoxae£°j%zuae6jpublic void set (t value) thread t = thread.currentthread();threadlocalmap map = getmap(t); if (map != null)map.set(this, value);elsecreatemap(tz value);threadlocaleeoaopodaoo-00!. overrideainitialvalue-£»

15、;2 iyseteeoaifouoodinitialvalue edo2ii%iaa«das6ayxo%d±a|jaepid£o i%zuae7jprivate static final threadlocal<long> time_threadlocal = newthreadlocal<long>()overrideprotected long initialvalue()return system.currenttimemillis();auf1yzuael°izuae2paye-i(|iieddx36£-duth

16、readaaod±£6dthreadlocal.threadlo calmappady6a£-i%xdud»5bjavaib3io»dd6jdae(|nauzadd|jad»5dthreadloc al .threadlocalmapp aoiof-i 'eoioodif zae aeeo 5e 4dentry£-i a, dentryjj akey (t hreadlocalep ay)eqeodyo a£-ivalueeqq,dy6 a£*oa|i aaaeieotjweakhashmapf

17、©i£6ap,/e6dyoapao»eqkey£-«a>dkey<|%e6dy6aojdthreadlocal£-'p±0nthreadl ocale|jaydaianulld006£-ia»6dei0iqidy6aojdthreadlocalepay£-ieud6thread locall6«»a±»gc»0eo£-ip«evaluee'2»au±»»0ed

18、£-iddiaa»raedu6ljthreadlo cal.threadlocalmapp 入90丫6(1 入 entryo®oe>i£o»od(j±c°thread% 銘 0o®°6£-£tio d。即 ±q°ib3i6d10|iiaxeoz2a»a±»gc»0edi£eudo£-ieq1uouib3i30ode16athre adlocal£-6e6uib3i»a/6a

19、3;-(|06oa»6dide%pap6aremovema»o|naeeq»a6 dieaueuaudaieiailaepouthreadlocal.threadlocalmappaget»ddbset-!-od»ai,2aaodpakeye n±»»0ed£*p-5-6aexpungestaleentry-,£©£-ie»°6!«/tavalueeedaianull£-'dasd 1|au%>°doiweakh

20、ashmapodpaexpungestaleentries()-!4-d»nuj£doxevalueoukey ±»gc°6/.eau»1»ax<je»id»(|ie±,4a£->p«xiodd2»a±»»0eo£->p«ee62»6up4-6aget» ddbset-e±£-aqazda56value%lduib3i»iu,4aip-±&

21、#187;ei-ai£j%xuae8j,private int expungestaleentry(int staleslot)entry tab = table;int len = tab<length;/ expunge entry at staleslot tabstaleslot .value = null;/ rehash until we encounter nullentry e;int i;for (i = nextindex(staleslot, len);(e = tabi)!= null;i = nextindex(i, len)threadlocal k

22、 = e.get ();if (k = null) e.value = null;tabi = null;size; else int h = k.threadlocalhashcode & (len - 1); if (h != i) tabi = null;/ unlike knuth 64 algorithm r, we must scan until/ null because multiple entries could have beenstalewhile (tabh!= null)h = nextindex(h, len);tabh = e;return i;圧述pth

23、readlocal土左总电氏惟捡p入£就呦0宜p入屮oaremove-16-74ej£threadlocalmaoloa-xiempaeqiblaepayf-aiibdoldeijayf© paoiopa-aieqodaoiowo-oaijififoowmxeoifpaieiaf-iwuoeoaaejoeiaoaiipae-i ±ee9(|，dad»>dstatic±aa£-'i-»2-aie£-'(|0threadlocal2e6aaeiodd/,d%a»»e&

24、#177;1/4aj ±pae!4j£q°obdia1©d»-y±aa£ea2»i-.|jaib3iaac|6-aie£-(|0o6obiaad»i6i b3h%iai©aed»-y±aa£-iddzeieddl-ie±-aie(|0»¥2»6oiii£ouampaodf-% aieiiaeodoryeedai-ip入 总入' aiei£danuaziau±£ond&#

25、187;6dd»46ib3iaieeu£2»»a6d3ai»i£p«eqdanuxd|4a 人八 -/ a-_-八"_a-0c 5_x_ sa1u»ae1padoauoi(|o>b2-0mao§3o2»1»i£oua3d©qeidia£-e91uioaq2»o»t-qoa (ffdd»>d±aai12ii2»ie£-(0eq>0aiidib3id»i6danu

26、|jaxe6±±%£-»eaeuaied6( aaxoauxopaf-idanuedo o-iepaiajsddidoauaead »16dpaqei6eq6dmaey%y±%ei2»eqib3io2e«|ja£-»dobe|jeud»au±»b»>6ib3ie16a£2»au±»2eaeuib3ibe±e16aj£eg1uned»>6ib3ie16aieaeou50aid&

27、#187;5dib3ie16a%i5u±%2»ldepi£danupaqe6ia£-iidaqd2ieddi%a(；6athreadlocali£threadlocal*4-oe£° 1.、"、入/s、/threadlocalaa±aaodia±%ei(|ri»iaoa±»(ifa>dib3iaz-aie£-ieur-3£±»<|- daiastatic±aa,j£2.aub>r1yop&

28、lt;pypa2iey£-.2>>dariythreadlocalz0£-iooaaoi3ethr eadlocalg a a ao a j£3.duib3i30p aqeidia£-outhreadlocald|j indu2eu|aiie3ee±£-xfaioe%p ap -oawmo ve() 力i oib3i%o2i±aai j ±odp aop i £4. dudy3£qei6iae1oathreadlocal2»»adi3eoom,eodyoapadt

29、fthreadlocal+fdiidaedyoaf-ethre adlocaloae»±»aeu(|6l66|6a£-iib3i%d2i±aa!4«ip-»0edi£inheritablethreadlocalinheritablethreadlocalethreadlocalgaxbaaf-. uaeaoueu£->ieddzd»ia£°i%zuae9j6public class inheritablethreadlocal<t> extends thre

30、adlocal<t> protected t childvalue(t parentvalue) return parentvalue;threadlocalmap getmap(thread t) return tinheritablethreadlocals;void createmap(thread t, t firstvalue) tinheritablethreadlocals = new threadlocalmap(this,firstvalue);oaaiooapa>>1eo>>a6childvalueoa5d-j£ ou'uaevode-aethreadlocalpa-!-*£-i(0e16aaainheritablethreadlocaledo ouxoib3idde i p a 4 jb3i%pdi a a p aog j£iedo2eoao0d zchildvalue£-object p