{"id":1078,"date":"2019-10-21T10:40:26","date_gmt":"2019-10-21T02:40:26","guid":{"rendered":"http:\/\/www.rain1024.com\/?p=1078"},"modified":"2023-08-07T20:57:24","modified_gmt":"2023-08-07T12:57:24","slug":"%e3%80%8aheadfirst%e8%ae%be%e8%ae%a1%e6%a8%a1%e5%bc%8f%e3%80%8b%e7%ac%ac%e4%ba%94%e7%ab%a0%e5%8d%95%e4%bb%b6%e6%a8%a1%e5%bc%8f-%e8%af%bb%e4%b9%a6%e7%ac%94%e8%ae%b0","status":"publish","type":"post","link":"http:\/\/rain1024.com\/index.php\/2019\/10\/21\/%e3%80%8aheadfirst%e8%ae%be%e8%ae%a1%e6%a8%a1%e5%bc%8f%e3%80%8b%e7%ac%ac%e4%ba%94%e7%ab%a0%e5%8d%95%e4%bb%b6%e6%a8%a1%e5%bc%8f-%e8%af%bb%e4%b9%a6%e7%ac%94%e8%ae%b0\/","title":{"rendered":"\u300aHeadFirst\u8bbe\u8ba1\u6a21\u5f0f\u300b\u7b2c\u4e94\u7ae0\u5355\u4ef6\u6a21\u5f0f-\u8bfb\u4e66\u7b14\u8bb0"},"content":{"rendered":"<h1>\u300aHeadFirst\u8bbe\u8ba1\u6a21\u5f0f\u300b\u7b2c\u4e94\u7ae0\u5355\u4ef6\u6a21\u5f0f-\u8bfb\u4e66\u7b14\u8bb0<\/h1>\n<h3>\u6848\u4f8b\u4ee3\u7801\u94fe\u63a5\uff1ahttps:\/\/github.com\/rainweb521\/My-tutorial\/tree\/master\/Design_patterns<\/h3>\n<h2>1. \u4ec0\u4e48\u662f\u5355\u4ef6<\/h2>\n<p>\u5728\u6211\u4eec\u7684\u7cfb\u7edf\u4e2d\uff0c\u6709\u4e00\u4e9b\u5bf9\u8c61\u5176\u5b9e\u6211\u4eec\u53ea\u9700\u8981\u4e00\u4e2a\uff0c\u6bd4\u5982\u8bf4\uff1a\u7ebf\u7a0b\u6c60\u3001\u7f13\u5b58\u3001\u5bf9\u8bdd\u6846\u3001\u6ce8\u518c\u8868\u3001\u65e5\u5fd7\u5bf9\u8c61\u3001\u5145\u5f53\u6253\u5370\u673a\u3001\u663e\u5361\u7b49\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u7684\u5bf9\u8c61\u3002\u4e8b\u5b9e\u4e0a\uff0c\u8fd9\u4e00\u7c7b\u5bf9\u8c61\u53ea\u80fd\u6709\u4e00\u4e2a\u5b9e\u4f8b\uff0c\u5982\u679c\u5236\u9020\u51fa\u591a\u4e2a\u5b9e\u4f8b\u5c31\u53ef\u80fd\u4f1a\u5bfc\u81f4\u4e00\u4e9b\u95ee\u9898\u7684\u4ea7\u751f\uff0c\u6bd4\u5982\uff1a\u7a0b\u5e8f\u7684\u884c\u4e3a\u5f02\u5e38\u3001\u8d44\u6e90\u4f7f\u7528\u8fc7\u91cf\u3001\u6216\u8005\u4e0d\u4e00\u81f4\u6027\u7684\u7ed3\u679c\u3002<\/p>\n<p><strong>\u4f7f\u7528\u5355\u4f8b\u6a21\u5f0f\u7684\u597d\u5904:<\/strong><\/p>\n<ul>\n<li>\u5bf9\u4e8e\u9891\u7e41\u4f7f\u7528\u7684\u5bf9\u8c61\uff0c\u53ef\u4ee5\u7701\u7565\u521b\u5efa\u5bf9\u8c61\u6240\u82b1\u8d39\u7684\u65f6\u95f4\uff0c\u8fd9\u5bf9\u4e8e\u90a3\u4e9b\u91cd\u91cf\u7ea7\u5bf9\u8c61\u800c\u8a00\uff0c\u662f\u975e\u5e38\u53ef\u89c2\u7684\u4e00\u7b14\u7cfb\u7edf\u5f00\u9500\uff1b<\/li>\n<li>\u7531\u4e8e new \u64cd\u4f5c\u7684\u6b21\u6570\u51cf\u5c11\uff0c\u56e0\u800c\u5bf9\u7cfb\u7edf\u5185\u5b58\u7684\u4f7f\u7528\u9891\u7387\u4e5f\u4f1a\u964d\u4f4e\uff0c\u8fd9\u5c06\u51cf\u8f7b GC \u538b\u529b\uff0c\u7f29\u77ed GC \u505c\u987f\u65f6\u95f4\u3002<\/li>\n<\/ul>\n<h2>2.spring\u4e2d\u7684\u5355\u4ef6\u6a21\u5f0f<\/h2>\n<p><strong>Spring \u4e2d bean \u7684\u9ed8\u8ba4\u4f5c\u7528\u57df\u5c31\u662f singleton(\u5355\u4f8b)\u7684\u3002<\/strong> \u9664\u4e86 singleton \u4f5c\u7528\u57df\uff0cSpring \u4e2d bean \u8fd8\u6709\u4e0b\u9762\u51e0\u79cd\u4f5c\u7528\u57df\uff1a<\/p>\n<ul>\n<li>prototype : \u6bcf\u6b21\u8bf7\u6c42\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684 bean \u5b9e\u4f8b\u3002<\/li>\n<li>request : \u6bcf\u4e00\u6b21HTTP\u8bf7\u6c42\u90fd\u4f1a\u4ea7\u751f\u4e00\u4e2a\u65b0\u7684bean\uff0c\u8be5bean\u4ec5\u5728\u5f53\u524dHTTP request\u5185\u6709\u6548\u3002<\/li>\n<li>session : \u6bcf\u4e00\u6b21HTTP\u8bf7\u6c42\u90fd\u4f1a\u4ea7\u751f\u4e00\u4e2a\u65b0\u7684 bean\uff0c\u8be5bean\u4ec5\u5728\u5f53\u524d HTTP session \u5185\u6709\u6548\u3002<\/li>\n<li>global-session\uff1a \u5168\u5c40session\u4f5c\u7528\u57df\uff0c\u4ec5\u4ec5\u5728\u57fa\u4e8eportlet\u7684web\u5e94\u7528\u4e2d\u624d\u6709\u610f\u4e49\uff0cSpring5\u5df2\u7ecf\u6ca1\u6709\u4e86\u3002Portlet\u662f\u80fd\u591f\u751f\u6210\u8bed\u4e49\u4ee3\u7801(\u4f8b\u5982\uff1aHTML)\u7247\u6bb5\u7684\u5c0f\u578bJava Web\u63d2\u4ef6\u3002\u5b83\u4eec\u57fa\u4e8eportlet\u5bb9\u5668\uff0c\u53ef\u4ee5\u50cfservlet\u4e00\u6837\u5904\u7406HTTP\u8bf7\u6c42\u3002\u4f46\u662f\uff0c\u4e0e servlet \u4e0d\u540c\uff0c\u6bcf\u4e2a portlet \u90fd\u6709\u4e0d\u540c\u7684\u4f1a\u8bdd<\/li>\n<\/ul>\n<h2>3.\u7ecf\u5178\u7684\u5355\u4ef6\u6a21\u5f0f<\/h2>\n<p><img decoding=\"async\" src=\"http:\/\/cos.rain1024.com\/markdown\/image-20191019084155597.png\" alt=\"\" \/><\/p>\n<h2>4.\u8bbe\u8ba1\u6a21\u5f0f<\/h2>\n<blockquote><p>\n  <strong>\u5355\u4ef6\u6a21\u5f0f<\/strong>\uff1a\u786e\u4fdd\u4e00\u4e2a\u7c7b\u53ea\u6709\u4e00\u4e2a\u5b9e\u4f8b\uff0c\u5e76\u63d0\u4f9b\u4e00\u4e2a\u5168\u5c40\u8bbf\u95ee\u70b9\n<\/p><\/blockquote>\n<h2>5.\u6539\u5584\u591a\u7ebf\u7a0b<\/h2>\n<h3>5.1\u4f7f\u7528synchronized<\/h3>\n<pre><code>\/\/    \u7528getInstance\u65b9\u6cd5\u5b9e\u4f8b\u5316\u5bf9\u8c61\uff0c\u5e76\u8fd4\u56de\u8fd9\u4e2a\u5b9e\u4f8b\n\/\/    \u901a\u8fc7\u589e\u52a0synchronized\u5173\u952e\u5b57\u5230getInstance\u65b9\u6cd5\u4e2d\uff0c\u6211\u4eec\u8feb\u4f7f\u6bcf\u4e2a\n\/\/    \u7ebf\u7a0b\u5728\u8fdb\u5165\u8fd9\u4e2a\u65b9\u6cd5\u4e4b\u524d\uff0c\u8981\u5148\u7b49\u5019\u522b\u7684\u7ebf\u7a0b\u79bb\u5f00\u8be5\u65b9\u6cd5\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\n\/\/    \u4e0d\u4f1a\u6709\u4e24\u4e2a\u7ebf\u7a0b\u53ef\u4ee5\u540c\u65f6\u8fdb\u5165\u8fd9\u4e2a\u65b9\u6cd5\u3002\n    public static synchronized Singleton2 getInstance() {\n        if (uniqueInstance==null){\n            uniqueInstance = new Singleton2();\n        }\n        return uniqueInstance;\n    }\n<\/code><\/pre>\n<blockquote><p>\n  \u540c\u6b65\u4f1a\u964d\u4f4e\u6027\u80fd\uff0c\u53ea\u6709\u7b2c\u4e00\u6b21\u6267\u884c\u6b64\u65b9\u6cd5\u65f6\uff0c\u624d\u771f\u6b63\u9700\u8981\u540c\u6b65\u3002\u6362\u53e5\u8bdd\u8bf4,\u4e00\u65e6\u8bbe\u7f6e\u597d uniquelnstance\u53d8\u91cf,\u5c31\u4e0d\u518d\u9700\u8981\u540c\u6b65\u8fd9\u4e2a\u65b9\u6cd5\u4e86\u3002\u4e4b\u540e\u6bcf\u6b21\u8c03\u7528\u8fd9\u4e2a\u65b9\u6cd5,\u540c\u6b65\u90fd\u662f\u4e00\u79cd\u7d2f\u8d58\u3002<\/p>\n<p>  \u5982\u679c\u4f60\u7684\u5e94\u7528\u7a0b\u5e8f\u53ef\u4ee5\u63a5\u53d7 getlnstance\u9020\u6210\u7684\u989d\u5916\u8d1f\u62c5,\u5c31\u5fd8\u4e86\u8fd9\u4ef6\u4e8b\u5427\u3002\u540c\u6b65 getinstance\u7684\u65b9\u6cd5\u65e2\u7b80\u5355\u53c8\u6709\u6548\u3002\u4f46\u662f\u4f60\u5fc5\u987b\u77e5\u9053,\u540c\u6b65\u4e00\u4e2a\u65b9\u6cd5\u53ef\u80fd\u9020\u6210\u7a0b\u5e8f\u6267\u884c\u6548\u7387\u4e0b\u964d100\u500d\u3002\u56e0\u6b64,\u5982\u679c\u5c06 getinstance\u7684\u7a0b\u5e8f\u4f7f\u7528\u5728\u9891\u7e41\u8fd0\u884c\u7684\u5730\u65b9,\u4f60\u53ef\u80fd\u5c31\u5f97\u91cd\u65b0\u8003\u8651\u4e86\u3002\n<\/p><\/blockquote>\n<h3>5.2\u4f7f\u7528\"\u6025\u5207\"\u521b\u5efa\u5b9e\u4f8b\uff0c\u800c\u4e0d\u7528\u5ef6\u8fdf\u5b9e\u4f8b\u5316\u7684\u505a\u6cd5<\/h3>\n<blockquote><p>\n  \u5982\u679c\u5e94\u7528\u7a0b\u5e8f\u603b\u662f\u521b\u5efa\u5e76\u4f7f\u7528\u5355\u4ef6\u5b9e\u4f8b,\u6216\u8005\u5728\u521b\u5efa\u548c\u8fd0\u884c\u65f6\u65b9\u9762\u7684\u8d1f\u62c5\u4e0d\u592a\u7e41\u91cd,\u4f60\u53ef\u80fd\u60f3\u8981\u6025\u5207( eagerly)\u521b\u5efa\u6b64\u5355\u4ef6,\u5982\u4e0b\u6240\u793a\u3002\n<\/p><\/blockquote>\n<pre><code>public class Singleton3 {\n\n\/\/    \u5229\u7528\u4e00\u4e2a\u9759\u6001\u53d8\u91cf\u6765\u8bb0\u5f55Singleton\u7c7b\u5bf9\u552f\u4e00\u5b9e\u4f8b\n\/\/    \u5728\u9759\u6001\u521d\u59cb\u5316\u5668\u4e2d\u521b\u5efa\u5355\u4ef6\uff0c\u8fd9\u6bb5\u4ee3\u7801\u4fdd\u8bc1\u4e86\u7ebf\u7a0b\u5b89\u5168\n    private static Singleton3 uniqueInstance = new Singleton3();\n\n\/\/    \u628a\u6784\u9020\u5668\u58f0\u660e\u4e3a\u79c1\u6709\u7684\uff0c\u53ea\u6709\u81eaSingleton\u7c7b\u5185\u624d\u53ef\u4ee5\u8c03\u7528\u6784\u9020\u5668\n    private Singleton3() {}\n\n\/\/    \u7528getInstance\u65b9\u6cd5\u5b9e\u4f8b\u5316\u5bf9\u8c61\uff0c\u5e76\u8fd4\u56de\u8fd9\u4e2a\u5b9e\u4f8b\n    public static Singleton3 getInstance() {\n\n        return uniqueInstance;\n    }\n}\n<\/code><\/pre>\n<blockquote><p>\n  \u5229\u7528\u8fd9\u4e2a\u505a\u6cd5,\u6211\u4eec\u4f9d\u8d56JVM\u5728\u52a0\u8f7d\u8fd9\u4e2a\u7c7b\u65f6\u9a6c\u4e0a\u521b\u5efa\u6b64\u552f\u4e00\u7684\u5355\u4ef6\u5b9e\u4f8b\u3002JWM\u4fdd\u8bc1\u5728\u4efb\u4f55\u7ebf\u7a0b\u8bbf\u95ee uniquelnstancei\u9759\u6001\u53d8\u91cf\u4e4b\u524d,\u4e00\u5b9a\u5148\u521b\u5efa\u6b64\u5b9e\u4f8b\u3002\n<\/p><\/blockquote>\n<h3>5.3\u201c\u53cc\u91cd\u68c0\u67e5\u52a0\u9501\u201d,\u5728 getinstance()\u4e2d\u5c11\u4f7f\u7528\u540c\u6b65<\/h3>\n<blockquote><p>\n  \u5229\u7528\u53cc\u91cd\u68c0\u67e5\u52a0\u9501( double- checked locking),\u9996\u5148\u68c0\u67fb\u662f\u5426\u5b9e\u4f8b\u5df2\u7ecf\u521b\u5efa\u4e86,\u5982\u679c\u5c1a\u672a\u521b\u5efa,\u201c\u30aa\u201d\u8fdb\u884c\u540c\u6b65\u3002\u8fd9\u6837\u4e00\u6765,\u53ea\u6709\u7b2c\u4e00\u6b21\u4f1a\u540c\u6b65,\u8fd9\u6b63\u662f\u6211\u4eec\u60f3\u8981\u7684\u3002\n<\/p><\/blockquote>\n<pre><code>public class Singleton4 {\n\n\/\/    \u5229\u7528\u4e00\u4e2a\u9759\u6001\u53d8\u91cf\u6765\u8bb0\u5f55Singleton\u7c7b\u5bf9\u552f\u4e00\u5b9e\u4f8b\n\/\/    volatile\u5e76\u5065\u8bcd\u786e\u4fdd:\u5f53uniqueInstance\u53d8\u91cf\u88ab\u521d\u59cb\u5316\u6210Singleton\u5b9e\u4f8b\u65f6,\n\/\/    \u591a\u4e2a\u7ebf\u7a0b\u6b63\u786e\u7684\u5904\u7406uniqueInstance\u53d8\u91cf\n    private volatile static Singleton4 uniqueInstance;\n\n\/\/    \u628a\u6784\u9020\u5668\u58f0\u660e\u4e3a\u79c1\u6709\u7684\uff0c\u53ea\u6709\u81eaSingleton\u7c7b\u5185\u624d\u53ef\u4ee5\u8c03\u7528\u6784\u9020\u5668\n    private Singleton4() {}\n\n\/\/    \u7528getInstance\u65b9\u6cd5\u5b9e\u4f8b\u5316\u5bf9\u8c61\uff0c\u5e76\u8fd4\u56de\u8fd9\u4e2a\u5b9e\u4f8b\n\/\/    \u68c0\u67e5\u5b9e\u4f8b\uff0c\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u5c31\u8fdb\u5165\u540c\u6b65\u533a\n    public static Singleton4 getInstance() {\n\/\/        \u53ea\u6709\u7b2c\u4e00\u6b21\u624d\u5f7b\u5e95\u6267\u884c\u8fd9\u91cc\u7684\u4ee3\u7801\u3002\n        if (uniqueInstance==null){\n            synchronized (Singleton4.class){\n\/\/                \u8fdb\u5165\u533a\u5757\u540e\uff0c\u518d\u68c0\u67e5\u4e00\u6b21\uff0c\u5982\u679c\u4ecd\u662fnull\uff0c\u624d\u521b\u5efa\u5b9e\u4f8b\n                if (uniqueInstance == null){\n                    uniqueInstance = new Singleton4();\n                }\n            }\n        }\n        return uniqueInstance;\n    }\n}\n<\/code><\/pre>\n<blockquote><p>\n  \u5982\u679c\u6027\u80fd\u662f\u4f60\u5173\u5fc3\u7684\u91cd\u70b9,\u90a3\u4e48\u8fd9\u4e2a\u505a\u6cd5\u53ef\u4ee5\u5e2e\u4f60\u5927\u5927\u5730\u51cf\u5c11 getlnstanceo\u7684\u65f6\u95f4\u8017\u8d39\u3002\n<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>\u5728\u6211\u4eec\u7684\u7cfb\u7edf\u4e2d\uff0c\u6709\u4e00\u4e9b\u5bf9\u8c61\u5176\u5b9e\u6211\u4eec\u53ea\u9700\u8981\u4e00\u4e2a\uff0c\u6bd4\u5982\u8bf4\uff1a\u7ebf\u7a0b\u6c60\u3001\u7f13\u5b58\u3001\u5bf9\u8bdd\u6846\u3001\u6ce8\u518c\u8868\u3001\u65e5\u5fd7\u5bf9\u8c61\u3001\u5145\u5f53\u6253\u5370\u673a\u3001\u663e\u5361\u7b49\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u7684\u5bf9\u8c61\u3002\u4e8b\u5b9e\u4e0a\uff0c\u8fd9\u4e00\u7c7b\u5bf9\u8c61\u53ea\u80fd\u6709\u4e00\u4e2a\u5b9e\u4f8b\uff0c\u5982\u679c\u5236\u9020\u51fa\u591a\u4e2a\u5b9e\u4f8b\u5c31\u53ef\u80fd\u4f1a\u5bfc\u81f4\u4e00\u4e9b\u95ee\u9898\u7684\u4ea7\u751f\uff0c\u6bd4\u5982\uff1a\u7a0b\u5e8f\u7684\u884c\u4e3a\u5f02\u5e38\u3001\u8d44\u6e90\u4f7f\u7528\u8fc7\u91cf\u3001\u6216\u8005\u4e0d\u4e00\u81f4\u6027\u7684\u7ed3\u679c\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[91],"class_list":["post-1078","post","type-post","status-publish","format-standard","hentry","category-23","tag-91"],"_links":{"self":[{"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/posts\/1078","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/comments?post=1078"}],"version-history":[{"count":1,"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/posts\/1078\/revisions"}],"predecessor-version":[{"id":1373,"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/posts\/1078\/revisions\/1373"}],"wp:attachment":[{"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/media?parent=1078"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/categories?post=1078"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/rain1024.com\/index.php\/wp-json\/wp\/v2\/tags?post=1078"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}