\u5355\u6001\u5b9a\u4e49:
\nSingleton\u6a21\u5f0f\u4e3b\u8981\u4f5c\u7528\u662f\u4fdd\u8bc1\u5728Java\u5e94\u7528\u7a0b\u5e8f\u4e2d\uff0c\u4e00\u4e2a\u7c7bClass\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\u5b58\u5728\u3002<\/p>\n
\u5728\u5f88\u591a\u64cd\u4f5c\u4e2d\uff0c\u6bd4\u5982\u5efa\u7acb\u76ee\u5f55 \u6570\u636e\u5e93\u8fde\u63a5\u90fd\u9700\u8981\u8fd9\u6837\u7684\u5355\u7ebf\u7a0b\u64cd\u4f5c\u3002
\n<\/p>\n
\u8fd8\u6709, singleton\u80fd\u591f\u88ab\u72b6\u6001\u5316; \u8fd9\u6837\uff0c\u591a\u4e2a\u5355\u6001\u7c7b\u5728\u4e00\u8d77\u5c31\u53ef\u4ee5\u4f5c\u4e3a\u4e00\u4e2a\u72b6\u6001\u4ed3\u5e93\u4e00\u6837\u5411\u5916\u63d0\u4f9b\u670d\u52a1\uff0c\u6bd4\u5982\uff0c\u4f60\u8981\u8bba\u575b\u4e2d\u7684\u5e16\u5b50\u8ba1\u6570\u5668\uff0c\u6bcf\u6b21\u6d4f\u89c8\u4e00\u6b21\u9700\u8981\u8ba1\u6570\uff0c\u5355\u6001\u7c7b\u80fd\u5426\u4fdd\u6301\u4f4f\u8fd9\u4e2a\u8ba1\u6570\uff0c\u5e76\u4e14\u80fdsynchronize\u7684\u5b89\u5168\u81ea\u52a8\u52a01\uff0c\u5982\u679c\u4f60\u8981\u628a\u8fd9\u4e2a\u6570\u5b57\u6c38\u4e45\u4fdd\u5b58\u5230\u6570\u636e\u5e93\uff0c\u4f60\u53ef\u4ee5\u5728\u4e0d\u4fee\u6539\u5355\u6001\u63a5\u53e3\u7684\u60c5\u51b5\u4e0b\u65b9\u4fbf\u7684\u505a\u5230\u3002<\/p>\n
\u53e6\u5916\u65b9\u9762\uff0cSingleton\u4e5f\u80fd\u591f\u88ab\u65e0\u72b6\u6001\u5316\u3002\u63d0\u4f9b\u5de5\u5177\u6027\u8d28\u7684\u529f\u80fd\uff0c<\/p>\n
Singleton\u6a21\u5f0f\u5c31\u4e3a\u6211\u4eec\u63d0\u4f9b\u4e86\u8fd9\u6837\u5b9e\u73b0\u7684\u53ef\u80fd\u3002\u4f7f\u7528Singleton\u7684\u597d\u5904\u8fd8\u5728\u4e8e\u53ef\u4ee5\u8282\u7701\u5185\u5b58\uff0c\u56e0\u4e3a\u5b83\u9650\u5236\u4e86\u5b9e\u4f8b\u7684\u4e2a\u6570\uff0c\u6709\u5229\u4e8eJava\u5783\u573e\u56de\u6536\uff08garbage collection\uff09\u3002<\/p>\n
\u6211\u4eec\u5e38\u5e38\u770b\u5230\u5de5\u5382\u6a21\u5f0f\u4e2d\u7c7b\u88c5\u5165\u5668(class loader)\u4e2d\u4e5f\u7528Singleton\u6a21\u5f0f\u5b9e\u73b0\u7684,\u56e0\u4e3a\u88ab\u88c5\u5165\u7684\u7c7b\u5b9e\u9645\u4e5f\u5c5e\u4e8e\u8d44\u6e90\u3002
\n\u5982\u4f55\u4f7f\u7528?
\n\u4e00\u822cSingleton\u6a21\u5f0f\u901a\u5e38\u6709\u51e0\u79cd\u5f62\u5f0f:<\/p>\n
[java]public class Singleton {<\/p>\n
\u3000\u3000private Singleton(){}<\/p>\n
\u3000\u3000\/\/\u5728\u81ea\u5df1\u5185\u90e8\u5b9a\u4e49\u81ea\u5df1\u4e00\u4e2a\u5b9e\u4f8b\uff0c\u662f\u4e0d\u662f\u5f88\u5947\u602a\uff1f
\n\u3000\u3000\/\/\u6ce8\u610f\u8fd9\u662fprivate \u53ea\u4f9b\u5185\u90e8\u8c03\u7528<\/p>\n
\u3000\u3000private static Singleton instance = new Singleton();<\/p>\n
\u3000\u3000\/\/\u8fd9\u91cc\u63d0\u4f9b\u4e86\u4e00\u4e2a\u4f9b\u5916\u90e8\u8bbf\u95ee\u672cclass\u7684\u9759\u6001\u65b9\u6cd5\uff0c\u53ef\u4ee5\u76f4\u63a5\u8bbf\u95ee\u3000\u3000
\n\u3000\u3000public static Singleton getInstance() {
\n\u3000\u3000\u3000\u3000return instance; \u3000\u3000
\n\u3000\u3000 }
\n}[\/java]<\/p>\n
\u7b2c\u4e8c\u79cd\u5f62\u5f0f:<\/p>\n
[java]public class Singleton {
\n\u3000\u3000private static Singleton instance = null;<\/p>\n
\u3000\u3000public static synchronized Singleton getInstance() {<\/p>\n
\u3000\u3000if (instance==null)
\n\u3000\u3000\u3000\u3000instance\uff1dnew Singleton();
\n\u3000\u3000return instance; \u3000\u3000}<\/p>\n
}
\n[\/java]<\/p>\n
\u4f7f\u7528Singleton.getInstance()\u53ef\u4ee5\u8bbf\u95ee\u5355\u6001\u7c7b\u3002<\/p>\n
\u4e0a\u9762\u7b2c\u4e8c\u4e2d\u5f62\u5f0f\u662flazy initialization\uff0c\u4e5f\u5c31\u662f\u8bf4\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6\u521d\u59cbSingleton\uff0c\u4ee5\u540e\u5c31\u4e0d\u7528\u518d\u751f\u6210\u4e86\u3002<\/p>\n
\u6ce8\u610f\u5230lazy initialization\u5f62\u5f0f\u4e2d\u7684synchronized\uff0c\u8fd9\u4e2asynchronized\u5f88\u91cd\u8981\uff0c\u5982\u679c\u6ca1\u6709synchronized\uff0c\u90a3\u4e48\u4f7f\u7528getInstance()\u662f\u6709\u53ef\u80fd\u5f97\u5230\u591a\u4e2aSingleton\u5b9e\u4f8b\u3002\u5173\u4e8elazy initialization\u7684Singleton\u6709\u5f88\u591a\u6d89\u53cadouble-checked locking (DCL)\u7684\u8ba8\u8bba\uff0c\u6709\u5174\u8da3\u8005\u8fdb\u4e00\u6b65\u7814\u7a76\u3002<\/p>\n
\u4e00\u822c\u8ba4\u4e3a\u7b2c\u4e00\u79cd\u5f62\u5f0f\u8981\u66f4\u52a0\u5b89\u5168\u4e9b\u3002<\/p>\n
\u4f7f\u7528Singleton\u6ce8\u610f\u4e8b\u9879\uff1a
\n\u6709\u65f6\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\uff0c\u4f7f\u7528Singleton\u5e76\u4e0d\u80fd\u8fbe\u5230Singleton\u7684\u76ee\u7684\uff0c\u5982\u6709\u591a\u4e2aSingleton\u5bf9\u8c61\u540c\u65f6\u88ab\u4e0d\u540c\u7684\u7c7b\u88c5\u5165\u5668\u88c5\u8f7d\uff1b\u5728EJB\u8fd9\u6837\u7684\u5206\u5e03\u5f0f\u7cfb\u7edf\u4e2d\u4f7f\u7528\u4e5f\u8981\u6ce8\u610f\u8fd9\u79cd\u60c5\u51b5\uff0c\u56e0\u4e3aEJB\u662f\u8de8\u670d\u52a1\u5668\uff0c\u8de8JVM\u7684\u3002<\/p>\n
\u6211\u4eec\u4ee5SUN\u516c\u53f8\u7684\u5ba0\u7269\u5e97\u6e90\u7801(Pet Store 1.3.1)\u7684ServiceLocator\u4e3a\u4f8b\u7a0d\u5fae\u5206\u6790\u4e00\u4e0b\uff1a<\/p>\n
\u5728Pet Store\u4e2dServiceLocator\u6709\u4e24\u79cd\uff0c\u4e00\u4e2a\u662fEJB\u76ee\u5f55\u4e0b\uff1b\u4e00\u4e2a\u662fWEB\u76ee\u5f55\u4e0b\uff0c\u6211\u4eec\u68c0\u67e5\u8fd9\u4e24\u4e2aServiceLocator\u4f1a\u53d1\u73b0\u5185\u5bb9\u5dee\u4e0d\u591a\uff0c\u90fd\u662f\u63d0\u4f9bEJB\u7684\u67e5\u8be2\u5b9a\u4f4d\u670d\u52a1\uff0c\u53ef\u662f\u4e3a\u4ec0\u4e48\u8981\u5206\u5f00\u5462\uff1f\u4ed4\u7ec6\u7814\u7a76\u5bf9\u8fd9\u4e24\u79cdServiceLocator\u624d\u53d1\u73b0\u533a\u522b\uff1a\u5728WEB\u4e2d\u7684ServiceLocator\u7684\u91c7\u53d6Singleton\u6a21\u5f0f\uff0cServiceLocator\u5c5e\u4e8e\u8d44\u6e90\u5b9a\u4f4d\uff0c\u7406\u6240\u5f53\u7136\u5e94\u8be5\u4f7f\u7528Singleton\u6a21\u5f0f\u3002\u4f46\u662f\u5728EJB\u4e2d\uff0cSingleton\u6a21\u5f0f\u5df2\u7ecf\u5931\u53bb\u4f5c\u7528\uff0c\u6240\u4ee5ServiceLocator\u624d\u5206\u6210\u4e24\u79cd\uff0c\u4e00\u79cd\u9762\u5411WEB\u670d\u52a1\u7684\uff0c\u4e00\u79cd\u662f\u9762\u5411EJB\u670d\u52a1\u7684\u3002<\/p>\n
Singleton\u6a21\u5f0f\u770b\u8d77\u6765\u7b80\u5355\uff0c\u4f7f\u7528\u65b9\u6cd5\u4e5f\u5f88\u65b9\u4fbf\uff0c\u4f46\u662f\u771f\u6b63\u7528\u597d\uff0c\u662f\u975e\u5e38\u4e0d\u5bb9\u6613\uff0c\u9700\u8981\u5bf9Java\u7684\u7c7b \u7ebf\u7a0b \u5185\u5b58\u7b49\u6982\u5ff5\u6709\u76f8\u5f53\u7684\u4e86\u89e3\u3002<\/p>\n
\u603b\u4e4b\uff1a\u5982\u679c\u4f60\u7684\u5e94\u7528\u57fa\u4e8e\u5bb9\u5668\uff0c\u90a3\u4e48Singleton\u6a21\u5f0f\u5c11\u7528\u6216\u8005\u4e0d\u7528\uff0c\u53ef\u4ee5\u4f7f\u7528\u76f8\u5173\u66ff\u4ee3\u6280\u672f\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5355\u6001\u5b9a\u4e49: Singleton\u6a21\u5f0f\u4e3b\u8981\u4f5c\u7528\u662f\u4fdd\u8bc1\u5728Java\u5e94\u7528\u7a0b\u5e8f\u4e2d\uff0c\u4e00\u4e2a\u7c7bClass\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\u5b58\u5728\u3002 \u5728\u5f88 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[58],"tags":[],"_links":{"self":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/635"}],"collection":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=635"}],"version-history":[{"count":1,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/635\/revisions"}],"predecessor-version":[{"id":636,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/635\/revisions\/636"}],"wp:attachment":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=635"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=635"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=635"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}