{"id":5249,"date":"2021-07-21T10:01:07","date_gmt":"2021-07-21T02:01:07","guid":{"rendered":"https:\/\/www.xttblog.com\/?p=5249"},"modified":"2021-07-21T10:01:07","modified_gmt":"2021-07-21T02:01:07","slug":"%e9%9d%a2%e8%af%95%e5%ae%98%ef%bc%9ajava%e4%b8%ad%e4%bb%80%e4%b9%88%e5%9c%b0%e6%96%b9%e8%bf%9d%e5%8f%8d%e4%ba%86%e5%8f%8c%e4%ba%b2%e5%a7%94%e6%b4%be%e6%a8%a1%e5%9e%8b%ef%bc%8c%e6%89%93%e7%a0%b4","status":"publish","type":"post","link":"https:\/\/www.xttblog.com\/?p=5249","title":{"rendered":"\u9762\u8bd5\u5b98\uff1aJava\u4e2d\u4ec0\u4e48\u5730\u65b9\u8fdd\u53cd\u4e86\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\uff0c\u6253\u7834\u4e86\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\uff1f"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">\u6458\u8981<\/h2>\n\n\n\n<ul class=\"wp-block-list\"><li>SPI \u673a\u5236\u662f\u4ec0\u4e48\uff0c\u6709\u54ea\u4e9b\u5e94\u7528\u573a\u666f\uff0c\u53c8\u5e26\u6765\u4e86\u54ea\u4e9b\u95ee\u9898\uff1f\n<\/li><li><a href=\"http:\/\/mp.weixin.qq.com\/s?__biz=MzIyODE5NjUwNQ==&amp;mid=2653314597&amp;idx=1&amp;sn=3ad3f8e21d5c7e1b37125e5eb4989fe8&amp;chksm=f38757d3c4f0dec54c24d083d5dfdd1b5a967b768819936034bff1366ef3def61acf9daad5e3&amp;scene=21#wechat_redirect\">\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b<\/a>\u662f Java \u63a8\u8350\u7684\u7c7b\u52a0\u8f7d\u6a21\u578b\uff0c\u4f46\u8fdd\u80cc\u8be5\u6a21\u578b\u7684\u6848\u4f8b\u6709\u54ea\u4e9b\uff1f\u4e3a\u4ec0\u4e48\u4f1a\u8fdd\u80cc\uff0c\u53c8\u662f\u600e\u4e48\u89e3\u51b3\u8fd9\u79cd case \u7684?\n<\/li><li>JDBC \u9a71\u52a8\u52a0\u8f7d\u7684\u6848\u4f8b\u6709\u54ea\u4e9b\uff0cSPI \u673a\u5236\u4e3a\u5b83\u5e26\u6765\u4e86\u54ea\u4e9b\u65b9\u4fbf\uff1f\n<\/li><li>\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u7684\u4f5c\u7528\u4e0e\u5e94\u7528\u573a\u666f\uff1f\n<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/xmt1139057136\/xttblog\/2021\/07\/sqwp0.jpg\" alt=\"\" \/><figcaption>\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b<\/figcaption><\/figure><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001\u5f15\u5b50<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">SPI\u673a\u5236\u7b80\u4ecb<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">SPI \u7684\u5168\u540d\u4e3a<code>Service Provider Interface<\/code>\uff0c\u4e3b\u8981\u662f\u5e94\u7528\u4e8e\u5382\u5546\u81ea\u5b9a\u4e49\u7ec4\u4ef6\u6216\u63d2\u4ef6\u4e2d\uff0c\u5728<code>java.util.ServiceLoader<\/code>\u7684\u6587\u6863\u91cc\u6709\u6bd4\u8f83\u8be6\u7ec6\u7684\u4ecb\u7ecd\u3002\u7b80\u5355\u7684\u603b\u7ed3\u4e0b java SPI \u673a\u5236\u7684\u601d\u60f3\uff1a\u6211\u4eec\u7cfb\u7edf\u91cc\u62bd\u8c61\u7684\u5404\u4e2a\u6a21\u5757\uff0c\u5f80\u5f80\u6709\u5f88\u591a\u4e0d\u540c\u7684\u5b9e\u73b0\u65b9\u6848\uff0c\u6bd4\u5982\u65e5\u5fd7\u6a21\u5757\u3001xml \u89e3\u6790\u6a21\u5757\u3001jdbc \u6a21\u5757\u7b49\u65b9\u6848\u3002\u9762\u5411\u7684\u5bf9\u8c61\u7684\u8bbe\u8ba1\u91cc\uff0c\u6211\u4eec\u4e00\u822c\u63a8\u8350\u6a21\u5757\u4e4b\u95f4\u57fa\u4e8e\u63a5\u53e3\u7f16\u7a0b\uff0c\u6a21\u5757\u4e4b\u95f4\u4e0d\u5bf9\u5b9e\u73b0\u7c7b\u8fdb\u884c\u786c\u7f16\u7801\u3002\u4e00\u65e6\u4ee3\u7801\u91cc\u6d89\u53ca\u5177\u4f53\u7684\u5b9e\u73b0\u7c7b\uff0c\u5c31\u8fdd\u53cd\u4e86\u53ef\u62d4\u63d2\u7684\u539f\u5219\uff0c\u5982\u679c\u9700\u8981\u66ff\u6362\u4e00\u79cd\u5b9e\u73b0\uff0c\u5c31\u9700\u8981\u4fee\u6539\u4ee3\u7801\u3002\u4e3a\u4e86\u5b9e\u73b0\u5728\u6a21\u5757\u88c5\u914d\u7684\u65f6\u5019\u80fd\u4e0d\u5728\u7a0b\u5e8f\u91cc\u52a8\u6001\u6307\u660e\uff0c\u8fd9\u5c31\u9700\u8981\u4e00\u79cd\u670d\u52a1\u53d1\u73b0\u673a\u5236\u3002Java SPI \u5c31\u662f\u63d0\u4f9b\u8fd9\u6837\u7684\u4e00\u4e2a\u673a\u5236\uff1a\u4e3a\u67d0\u4e2a\u63a5\u53e3\u5bfb\u627e\u670d\u52a1\u5b9e\u73b0\u7684\u673a\u5236\u3002\u6709\u70b9\u7c7b\u4f3c IOC \u7684\u601d\u60f3\uff0c\u5c31\u662f\u5c06\u88c5\u914d\u7684\u63a7\u5236\u6743\u79fb\u5230\u7a0b\u5e8f\u4e4b\u5916\uff0c\u5728\u6a21\u5757\u5316\u8bbe\u8ba1\u4e2d\u8fd9\u4e2a\u673a\u5236\u5c24\u5176\u91cd\u8981\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/xmt1139057136\/xttblog\/2021\/07\/sqwp1.jpg\" alt=\"\" \/><figcaption>\u6253\u7834\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">Java SPI \u7684\u5177\u4f53\u7ea6\u5b9a\u4e3a\uff1a\u5f53\u670d\u52a1\u7684\u63d0\u4f9b\u8005\u63d0\u4f9b\u4e86\u670d\u52a1\u63a5\u53e3\u7684\u4e00\u79cd\u5b9e\u73b0\u4e4b\u540e\uff0c\u5728 jar \u5305\u7684<code>META-INF\/services\/<\/code>\u76ee\u5f55\u91cc\u540c\u65f6\u521b\u5efa\u4e00\u4e2a\u4ee5\u670d\u52a1\u63a5\u53e3\u547d\u540d\u7684\u6587\u4ef6\uff0c\u8be5\u6587\u4ef6\u91cc\u5c31\u662f\u5b9e\u73b0\u8be5\u670d\u52a1\u63a5\u53e3\u7684\u5177\u4f53\u5b9e\u73b0\u7c7b\u3002\u800c\u5f53\u5916\u90e8\u7a0b\u5e8f\u88c5\u914d\u8fd9\u4e2a\u6a21\u5757\u7684\u65f6\u5019\uff0c\u5c31\u80fd\u901a\u8fc7\u8be5 jar \u5305<code>META-INF\/services\/<\/code>\u91cc\u7684\u914d\u7f6e\u6587\u4ef6\u627e\u5230\u5177\u4f53\u7684\u5b9e\u73b0\u7c7b\u540d\uff0c\u5e76\u88c5\u8f7d\u5b9e\u4f8b\u5316\uff0c\u5b8c\u6210\u6a21\u5757\u7684\u6ce8\u5165\u3002\u57fa\u4e8e\u8fd9\u6837\u4e00\u4e2a\u7ea6\u5b9a\u5c31\u80fd\u5f88\u597d\u7684\u627e\u5230\u670d\u52a1\u63a5\u53e3\u7684\u5b9e\u73b0\u7c7b\uff0c\u800c\u4e0d\u9700\u8981\u518d\u4ee3\u7801\u91cc\u5236\u5b9a\u3002jdk \u63d0\u4f9b\u670d\u52a1\u5b9e\u73b0\u67e5\u627e\u7684\u4e00\u4e2a\u5de5\u5177\u7c7b\uff1a<code>java.util.ServiceLoader<\/code>\u3002JDBC SPI mysql \u7684\u5b9e\u73b0\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/xmt1139057136\/xttblog\/2021\/07\/sqwp2.jpg\" alt=\"JDBC SPI mysql\u7684\u5b9e\u73b0\" \/><figcaption>JDBC SPI mysql\u7684\u5b9e\u73b0<\/figcaption><\/figure><\/div>\n\n\n\n<h3 class=\"wp-block-heading\">SPI \u673a\u5236\u5e26\u6765\u7684\u95ee\u9898<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Java \u63d0\u4f9b\u4e86\u5f88\u591a\u670d\u52a1 SPI\uff0c\u5141\u8bb8\u7b2c\u4e09\u65b9\u4e3a\u8fd9\u4e9b\u63a5\u53e3\u63d0\u4f9b\u5b9e\u73b0\u3002\u8fd9\u4e9b SPI \u7684\u63a5\u53e3\u7531 Java \u6838\u5fc3\u5e93\u6765\u63d0\u4f9b\uff0c\u800c\u8fd9\u4e9b SPI \u7684\u5b9e\u73b0\u5219\u662f\u7531\u5404\u4f9b\u5e94\u5546\u6765\u5b8c\u6210\u3002\u7ec8\u7aef\u53ea\u9700\u8981\u5c06\u6240\u9700\u7684\u5b9e\u73b0\u4f5c\u4e3a Java \u5e94\u7528\u6240\u4f9d\u8d56\u7684 jar \u5305\u5305\u542b\u8fdb\u7c7b\u8def\u5f84\uff08CLASSPATH\uff09\u5c31\u53ef\u4ee5\u4e86\u3002\u95ee\u9898\u5728\u4e8e SPI \u63a5\u53e3\u4e2d\u7684\u4ee3\u7801\u7ecf\u5e38\u9700\u8981\u52a0\u8f7d\u5177\u4f53\u7684\u5b9e\u73b0\u7c7b\uff1aSPI \u7684\u63a5\u53e3\u662fJava \u6838\u5fc3\u5e93\u7684\u4e00\u90e8\u5206\uff0c\u662f\u7531\u542f\u52a8\u7c7b\u52a0\u8f7d\u5668\u6765\u52a0\u8f7d\u7684\uff1b\u800c SPI \u7684\u5b9e\u73b0\u7c7b\u662f\u7531\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668\u6765\u52a0\u8f7d\u7684\u3002\u542f\u52a8\u7c7b\u52a0\u8f7d\u5668\u662f\u65e0\u6cd5\u627e\u5230 SPI \u7684\u5b9e\u73b0\u7c7b\u7684(\u56e0\u4e3a\u5b83\u53ea\u52a0\u8f7d Java \u7684\u6838\u5fc3\u5e93)\uff0c\u6309\u7167\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\uff0c\u542f\u52a8\u7c7b\u52a0\u8f7d\u5668\u65e0\u6cd5\u59d4\u6d3e\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668\u53bb\u52a0\u8f7d\u7c7b\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u7c7b\u52a0\u8f7d\u5668\u7684\u53cc\u4eb2\u59d4\u6d3e\u6a21\u5f0f\u65e0\u6cd5\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u6b63\u597d\u89e3\u51b3\u4e86\u8fd9\u4e2a\u95ee\u9898\u3002\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u7834\u574f\u4e86\u201c\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\u201d\uff0c\u53ef\u4ee5\u5728\u6267\u884c\u7ebf\u7a0b\u4e2d\u629b\u5f03\u53cc\u4eb2\u59d4\u6d3e\u52a0\u8f7d\u94fe\u6a21\u5f0f\uff0c\u4f7f\u7a0b\u5e8f\u53ef\u4ee5\u9006\u5411\u4f7f\u7528\u7c7b\u52a0\u8f7d\u5668\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\uff08context class loader\uff09\u662f\u4ece JDK 1.2 \u5f00\u59cb\u5f15\u5165\u7684\u3002<code>Java.lang.Thread<\/code>\u4e2d\u7684\u65b9\u6cd5<code>getContextClassLoader()<\/code>\u548c <code>setContextClassLoader(ClassLoader cl)<\/code>\u7528\u6765\u83b7\u53d6\u548c\u8bbe\u7f6e\u7ebf\u7a0b\u7684\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u3002\u5982\u679c\u6ca1\u6709\u901a\u8fc7<code>setContextClassLoader(ClassLoader cl)<\/code>\u65b9\u6cd5\u8fdb\u884c\u8bbe\u7f6e\u7684\u8bdd\uff0c\u7ebf\u7a0b\u5c06\u7ee7\u627f\u5176\u7236\u7ebf\u7a0b\u7684\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u3002Java \u5e94\u7528\u8fd0\u884c\u7684\u521d\u59cb\u7ebf\u7a0b\u7684\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u662f\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668\uff0c\u5728\u7ebf\u7a0b\u4e2d\u8fd0\u884c\u7684\u4ee3\u7801\u53ef\u4ee5\u901a\u8fc7\u6b64\u7c7b\u52a0\u8f7d\u5668\u6765\u52a0\u8f7d\u7c7b\u548c\u8d44\u6e90\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u4ece\u6839\u672c\u89e3\u51b3\u4e86\u4e00\u822c\u5e94\u7528\u4e0d\u80fd\u8fdd\u80cc<a href=\"http:\/\/mp.weixin.qq.com\/s?__biz=MzIyODE5NjUwNQ==&amp;mid=2653314946&amp;idx=1&amp;sn=058e2296fc276b8f8d2d73e93ba59105&amp;chksm=f3875674c4f0df625ba73d4bdd03dd53884895b3001f2140767de51769e9590cc0e804af2cf4&amp;scene=21#wechat_redirect\">\u53cc\u4eb2\u59d4\u6d3e\u6a21\u5f0f<\/a>\u7684\u95ee\u9898\uff0c\u4f7f\u5f97 java \u7c7b\u52a0\u8f7d\u4f53\u7cfb\u663e\u5f97\u66f4\u7075\u6d3b\u3002\u4e0a\u9762\u6240\u63d0\u5230\u7684\u95ee\u9898\u6b63\u662f\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u7684\u62ff\u624b\u597d\u83dc\u3002\u5982\u679c\u4e0d\u505a\u4efb\u4f55\u7684\u8bbe\u7f6e\uff0cJava\u5e94\u7528\u7684\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u9ed8\u8ba4\u5c31\u662f\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668\u3002\u56e0\u6b64\uff0c\u5728 SPI \u63a5\u53e3\u7684\u4ee3\u7801\u4e2d\u4f7f\u7528\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\uff0c\u5c31\u53ef\u4ee5\u6210\u529f\u7684\u52a0\u8f7d\u5230 SPI \u5b9e\u73b0\u7684\u7c7b\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ Now create the class loader to use to launch the application  \ntry {  \n    loader = AppClassLoader.getAppClassLoader(extcl);  \n} catch (IOException e) {  \n    throw new InternalError(  \n\"Could not create application class loader\" );  \n}  \n  \n\/\/ Also set the context class loader for the primordial thread.  \nThread.currentThread().setContextClassLoader(loader);<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09. \u8fdd\u80cc\u53cc\u4eb2\u59d4\u6d3e\u6848\u4f8b\u4e4b JDBC<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">1\u3001JDBC \u9a71\u52a8\u6ce8\u518c\u7684\u5e38\u7528\u51e0\u79cd\u65b9\u5f0f<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Java \u6570\u636e\u5e93\u8fde\u63a5\uff08Java Database Connectivity\uff0c\u7b80\u79f0 JDBC\uff09\u662f Java \u8bed\u8a00\u7528\u6765\u89c4\u8303\u5ba2\u6237\u7aef\u7a0b\u5e8f\u5982\u4f55\u8bbf\u95ee\u6570\u636e\u5e93\u7684\u5e94\u7528\u7a0b\u5e8f\u63a5\u53e3\uff0c\u63d0\u4f9b\u4e86\u8bf8\u5982\u67e5\u8be2\u548c\u66f4\u65b0\u6570\u636e\u5e93\u4e2d\u6570\u636e\u7684\u65b9\u6cd5\u3002JDBC \u9a71\u52a8\u5305\u5c31\u662f\u4e0a\u8ff0\u63a5\u53e3\u7684\u5b9e\u73b0\uff0c\u7531\u6570\u636e\u5e93\u5382\u5546\u5f00\u53d1\uff0c\u662f java \u548c\u5177\u4f53\u6570\u636e\u5e93\u4e4b\u95f4\u7684\u8fde\u63a5\u6865\u6881\u3002\u6bcf\u4e00\u79cd\u6570\u636e\u5e93\u5bf9\u5e94\u4e00\u6b3e\u9a71\u52a8 jar\uff0c\u751a\u81f3\u6bcf\u4e00\u4e2a\u7248\u672c\u7684\u6570\u636e\u5e93\u90fd\u6709\u81ea\u5df1\u5bf9\u5e94\u7248\u672c\u7684\u9a71\u52a8\u3002\u6211\u4eec\u77e5\u9053\uff0cJDBC\u89c4\u8303\u4e2d\u660e\u786e\u8981\u6c42 Driver(\u6570\u636e\u5e93\u9a71\u52a8)\u7c7b\u5fc5\u987b\u5411 DriverManager \u6ce8\u518c\u81ea\u5df1\uff0c\u6240\u4ee5\u5728\u4e0e\u6570\u636e\u5e93\u4ea4\u4e92\u524d\u5fc5\u987b\u5b8c\u6210\u9a71\u52a8\u6ce8\u518c\uff0c\u90a3\u4e48\u5148\u6765\u770b\u770b\u5e73\u65f6\u6211\u4eec\u662f\u5982\u4f55\u6ce8\u518c JDBC \u9a71\u52a8\u7684\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u65b9\u5f0f\u4e00\uff1aClass.forName(\u201ccom.mysql.jdbc.Driver\u201d)<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>try {\n    \/\/ \u6ce8\u518c\n    Class.forName(driver);\n    conn = (Connection)DriverManager.getConnection(url, user, passwd);\n} catch (Exception e) {\n    System.out.println(e);\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4f7f\u7528\u8be5\u65b9\u5f0f\u6ce8\u518c\u7684\u5173\u952e\u5728\u4e8e<code>Class.forName(driver);<\/code>\uff0c\u8fd9\u53e5\u8bdd\u7684\u4f5c\u7528\u662f\u52a0\u8f7d\u5e76\u521d\u59cb\u5316\u6307\u5b9a\u9a71\u52a8\u3002mysql jdbc \u6b63\u662f\u5728 Driver \u521d\u59cb\u5316\u7684\u65f6\u5019\u5b8c\u6210\u6ce8\u518c\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>package com.mysql.jdbc;\n\nimport com.mysql.jdbc.NonRegisteringDriver;\nimport java.sql.DriverManager;\nimport java.sql.SQLException;\n\npublic class Driver extends NonRegisteringDriver implements java.sql.Driver {\n    public Driver() throws SQLException {\n    }\n \/\/ \u7c7b\u521d\u59cb\u5316\u65f6\u5b8c\u6210\u9a71\u52a8\u6ce8\u518c\n    static {\n        try {\n            DriverManager.registerDriver(new Driver());\n        } catch (SQLException var1) {\n            throw new RuntimeException(\"Can\\'t register driver!\");\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">\u65b9\u5f0f\u4e8c\uff1aSystem.setProperty<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><code>System.setProperty(\u201cjdbc.drivers\u201d,\u201ccom.mysql.jdbc.Driver\u201d)<\/code>\u4f7f\u7528\u65b9\u5f0f\u4e3e\u4f8b\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>try {\n    \/\/Class.forName(driver);\n    System.setProperty(\"jdbc.drivers\", driver);\n    conn = (Connection)DriverManager.getConnection(url, user, passwd);\n} catch (Exception e) {\n    System.out.println(e);\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd9\u79cd\u65b9\u5f0f\u662f\u901a\u8fc7\u7cfb\u7edf\u7684\u5c5e\u6027\u8bbe\u7f6e\u6ce8\u518c\u9a71\u52a8\uff0c\u6700\u7ec8\u8fd8\u662f\u901a\u8fc7\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668\u5b8c\u6210\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ DriverManager \u4e2d\u7684\u9759\u6001\u4ee3\u7801\u5757\nstatic {\n    loadInitialDrivers();\n    println(\"JDBC DriverManager initialized\");\n}\n\n\/\/ \u521d\u59cb\u5316 DriverManager\nprivate static void loadInitialDrivers() {\n    String drivers;\n    try {\n        drivers = AccessController.doPrivileged(new PrivilegedAction&lt;String&gt;() {\n            public String run() {\n                return System.getProperty(\"jdbc.drivers\");\n            }\n        });\n    } catch (Exception ex) {\n        drivers = null;\n    }\n    \/\/ If the driver is packaged as a Service Provider, load it.\n    \/\/ Get all the drivers through the classloader\n    \/\/ exposed as a java.sql.Driver.class service.\n    \/\/ ServiceLoader.load() replaces the sun.misc.Providers()\n\n    AccessController.doPrivileged(new PrivilegedAction&lt;Void&gt;() {\n        public Void run() {\n\n            ServiceLoader&lt;Driver&gt; loadedDrivers = ServiceLoader.load(Driver.class);\n            Iterator&lt;Driver&gt; driversIterator = loadedDrivers.iterator();\n\n            \/* Load these drivers, so that they can be instantiated.\n             * It may be the case that the driver class may not be there\n             * i.e. there may be a packaged driver with the service class\n             * as implementation of java.sql.Driver but the actual class\n             * may be missing. In that case a java.util.ServiceConfigurationError\n             * will be thrown at runtime by the VM trying to locate\n             * and load the service.\n             *\n             * Adding a try catch block to catch those runtime errors\n             * if driver not available in classpath but it's\n             * packaged as service and that service is there in classpath.\n             *\/\n            try{\n                while(driversIterator.hasNext()) {\n                    driversIterator.next();\n                }\n            } catch(Throwable t) {\n            \/\/ Do nothing\n            }\n            return null;\n        }\n    });\n\n    println(\"DriverManager.initialize: jdbc.drivers = \" + drivers);\n\n    if (drivers == null || drivers.equals(\"\")) {\n        return;\n    }\n    String[] driversList = drivers.split(\":\");\n    println(\"number of Drivers:\" + driversList.length);\n    for (String aDriver : driversList) {\n        try {\n            \/\/ \u6ce8\u518c\u9a71\u52a8\uff0c\u5e95\u5c42\u5b9e\u73b0\u8fd8\u662f\u548c\u65b9\u5f0f\u4e00\u4e00\u6837\u7684\u5957\u8def\n            println(\"DriverManager.Initialize: loading \" + aDriver);\n            Class.forName(aDriver, true,\n                    ClassLoader.getSystemClassLoader());\n        } catch (Exception ex) {\n            println(\"DriverManager.Initialize: load failed: \" + ex);\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">\u65b9\u5f0f\u4e09\uff1aSPI\u670d\u52a1\u52a0\u8f7d\u673a\u5236\u6ce8\u518c\u9a71\u52a8<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>try {\n    \/\/ Class.forName(driver);\n    conn = (Connection)DriverManager.getConnection(url, user, passwd);\n} catch (Exception e) {\n    System.out.println(e);\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5404\u4f4d\u53ef\u4ee5\u53d1\u73b0\uff0c\u8fd9\u79cd\u65b9\u5f0f\u4e0e\u7b2c\u4e00\u79cd\u65b9\u5f0f\u552f\u4e00\u7684\u533a\u522b\u5c31\u662f\u7ecf\u5e38\u5199\u7684<code>Class.forName<\/code>\u88ab\u6ce8\u91ca\u6389\u4e86\uff0c\u4f46\u7a0b\u5e8f\u4f9d\u7136\u53ef\u4ee5\u6b63\u5e38\u8fd0\u884c\uff0c\u8fd9\u662f\u4e3a\u4ec0\u4e48\u5462\uff1f\u8fd9\u662f\u56e0\u4e3a\uff0c\u4ece JDK1.6 \u5f00\u59cb\uff0cOracle \u5c31\u4fee\u6539\u4e86\u52a0\u8f7dJDBC\u9a71\u52a8\u7684\u65b9\u5f0f\uff0c\u5373  JDBC4.0\u3002\u5728 JDBC 4.0 \u4e2d\uff0c\u6211\u4eec\u4e0d\u5fc5\u518d\u663e\u5f0f\u4f7f\u7528<code>Class.forName()<\/code>\u65b9\u6cd5\u660e\u786e\u52a0\u8f7d JDBC \u9a71\u52a8\u3002\u5f53\u8c03\u7528 getConnection \u65b9\u6cd5\u65f6\uff0cDriverManager \u4f1a\u5c1d\u8bd5\u81ea\u52a8\u8bbe\u7f6e\u5408\u9002\u7684\u9a71\u52a8\u7a0b\u5e8f\u3002\u524d\u63d0\u662f\uff0c\u53ea\u8981 mysql \u7684 jar \u5305\u5728\u7c7b\u8def\u5f84\u4e2d\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u90a3\u5230\u5e95\u662f\u5728\u54ea\u4e00\u6b65\u81ea\u52a8\u6ce8\u518c\u4e86 mysql driver \u7684\u5462\uff1f\u6211\u4eec\u63a5\u4e0b\u6765\u8fdb\u4e00\u6b65\u5206\u6790\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">2\u3001SPI \u670d\u52a1\u52a0\u8f7d\u673a\u5236\u6ce8\u518c\u9a71\u52a8\u539f\u7406\u5206\u6790<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u91cd\u70b9\u5c31\u5728<code>DriverManager.getConnection()<\/code>\u4e2d\u3002\u6211\u4eec\u77e5\u9053\uff0c\u8c03\u7528\u7c7b\u7684\u9759\u6001\u65b9\u6cd5\u4f1a\u521d\u59cb\u5316\u8be5\u7c7b\uff0c\u800c\u6267\u884c\u5176\u9759\u6001\u4ee3\u7801\u5757\u662f\u521d\u59cb\u5316\u7c7b\u8fc7\u7a0b\u4e2d\u5fc5\u4e0d\u53ef\u5c11\u7684\u4e00\u73af\u3002 DriverManager \u7684\u9759\u6001\u4ee3\u7801\u5757\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>static {\n    loadInitialDrivers();\n    println(\"JDBC DriverManager initialized\");\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u521d\u59cb\u5316\u65b9\u6cd5<code>loadInitialDrivers()<\/code>\u7684\u4ee3\u7801\u6211\u4eec\u5176\u5b9e\u5df2\u7ecf\u89c1\u8fc7\u4e86\uff0c\u7b2c\u4e8c\u79cd\u548c\u7b2c\u4e09\u79cd\u7684\u9a71\u52a8\u6ce8\u518c\u903b\u8f91\u90fd\u5728\u8fd9\u91cc\u9762\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>private static void loadInitialDrivers() {\n    String drivers;\n    try {\n  \/\/ \u5148\u8bfb\u53d6\u7cfb\u7edf\u5c5e\u6027 : \u5bf9\u5e94\u4e0a\u9762\u7b2c\u4e8c\u79cd\u9a71\u52a8\u6ce8\u518c\u65b9\u5f0f\n  drivers = AccessController.doPrivileged(new PrivilegedAction&lt;String&gt;() {\n            public String run() {\n                return System.getProperty(\"jdbc.drivers\");\n            }\n        });\n    } catch (Exception ex) {\n        drivers = null;\n    }\n    \n    \/\/ \u901a\u8fc7SPI\u52a0\u8f7d\u9a71\u52a8\u7c7b\n    AccessController.doPrivileged(new PrivilegedAction&lt;Void&gt;() {\n        public Void run() {\n            ServiceLoader&lt;Driver&gt; loadedDrivers = ServiceLoader.load(Driver.class);\n            Iterator&lt;Driver&gt; driversIterator = loadedDrivers.iterator();\n            try{\n                while(driversIterator.hasNext()) {\n                    driversIterator.next();\n                }\n            } catch(Throwable t) {\n                \/\/ Do nothing\n            }\n            return null;\n        }\n    });\n    \n    \/\/ \u52a0\u8f7d\u7cfb\u7edf\u5c5e\u6027\u4e2d\u7684\u9a71\u52a8\u7c7b : \u5bf9\u5e94\u4e0a\u9762\u7b2c\u4e8c\u79cd\u9a71\u52a8\u6ce8\u518c\u65b9\u5f0f\n    if (drivers == null || drivers.equals(\"\")) {\n        return;\n    }\n    \n    String[] driversList = drivers.split(\":\");\n    println(\"number of Drivers:\" + driversList.length);\n    for (String aDriver : driversList) {\n        try {\n            println(\"DriverManager.Initialize: loading \" + aDriver);\n            \/\/ \u4f7f\u7528AppClassloader\u52a0\u8f7d\n            Class.forName(aDriver, true,\n                    ClassLoader.getSystemClassLoader());\n        } catch (Exception ex) {\n            println(\"DriverManager.Initialize: load failed: \" + ex);\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ece\u4e0a\u9762\u53ef\u4ee5\u770b\u51fa\uff0cJDBC \u4e2d\u7684 DriverManager \u52a0\u8f7d Driver \u7684\u6b65\u9aa4\u987a\u5e8f\u4f9d\u6b21\u662f\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>\u901a\u8fc7 SPI \u65b9\u5f0f\uff0c\u8bfb\u53d6<code>META-INF\/services<\/code>\u4e0b\u6587\u4ef6\u4e2d\u7684\u7c7b\u540d\uff0c\u4f7f\u7528\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u52a0\u8f7d\uff1b\n<\/li><li>\u901a\u8fc7<code>System.getProperty(\u201cjdbc.drivers\u201d)<\/code>\u83b7\u53d6\u8bbe\u7f6e\uff0c\u7136\u540e\u901a\u8fc7\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668\u52a0\u8f7d\u3002\n<\/li><\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">\u6211\u4eec\u73b0\u5728\u53ea\u8ba8\u8bba SPI \u65b9\u5f0f\u7684\u5b9e\u73b0\uff0c\u6765\u770b\u521a\u624d\u7684\u4ee3\u7801\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>ServiceLoader&lt;Driver&gt; loadedDrivers = ServiceLoader.load(Driver.class);\nIterator&lt;Driver&gt; driversIterator = loadedDrivers.iterator();\n\ntry{\n    while(driversIterator.hasNext()) {\n        driversIterator.next();\n    }\n} catch(Throwable t) {\n\/\/ Do nothing\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u6ce8\u610f<code>driversIterator.next()<\/code>\u8fd9\u6761\u8bed\u53e5\u5b8c\u6210\u4e86\u9a71\u52a8\u7684\u6ce8\u518c\u5de5\u4f5c\uff0c\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>private S nextService() {\n    if (!hasNextService())\n        throw new NoSuchElementException();\n    String cn = nextName;\n    nextName = null;\n    Class&lt;?&gt; c = null;\n    try {\n        \/\/ \u52a0\u8f7d\u5b9e\u73b0\u7c7b\uff0c\u6ce8\u610f\u8fd8\u6ca1\u6709\u521d\u59cb\u5316\uff1b\u4ee5JDBC\u4e3a\u4f8b\uff0c\u6b64\u65f6\u8fd8\u6ca1\u6709\u5b8c\u6210\u9a71\u52a8\u6ce8\u518c\n        c = Class.forName(cn, false, loader);\n    } catch (ClassNotFoundException x) {\n        fail(service,\n             \"Provider \" + cn + \" not found\");\n    }\n    \/\/ service\u5c31\u662fSPI\uff0c\u4ee5JDBC\u4e3a\u4f8b\uff0cservice\u5c31\u662fJava Driver\u63a5\u53e3\uff1b\u6b64\u5904\u5224\u65adc\u662f\u5426\u4e3aDriver\u7684\u5b9e\u73b0\n    if (!service.isAssignableFrom(c)) {\n        fail(service,\n             \"Provider \" + cn  + \" not a subtype\");\n    }\n    try {\n        \/\/ c\u662fspi\u7684\u5b9e\u73b0\uff0cc.newInstance()\u4f1a\u89e6\u53d1\u7c7b\u7684\u521d\u59cb\u5316\u52a8\u4f5c\uff0c\u4ee5JDBC\u4e3a\u4f8b\uff0c\u8fd9\u4e00\u64cd\u4f5c\u4f1a\u5b8c\u6210\u9a71\u52a8\u6ce8\u518c\n        S p = service.cast(c.newInstance());\n        providers.put(cn, p);\n        return p;\n    } catch (Throwable x) {\n        fail(service,\n             \"Provider \" + cn + \" could not be instantiated\",\n             x);\n    }\n    throw new Error();          \/\/ This cannot happen\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u597d\uff0c\u90a3\u53e5\u56e0 SPI \u800c\u7701\u7565\u7684\u4ee3\u7801\u73b0\u5728\u89e3\u91ca\u6e05\u695a\u4e86\uff0c\u90a3\u6211\u4eec\u7ee7\u7eed\u770b\u7ed9\u8fd9\u4e2a\u65b9\u6cd5\u4f20\u7684 loader \u662f\u600e\u4e48\u6765\u7684\u3002\u56e0\u4e3a<code>Class.forName(DriverName, false, loader)<\/code>\u4ee3\u7801\u6240\u5728\u7684\u7c7b\u5728<code>java.util.ServiceLoader<\/code>\u7c7b\u4e2d\uff0c\u800c<code>ServiceLoader.class<\/code>\u53c8\u52a0\u8f7d\u5728 BootrapLoader \u4e2d\uff0c\u56e0\u6b64\u4f20\u7ed9 forName \u7684 loader \u5fc5\u7136\u4e0d\u80fd\u662f BootrapLoader(\u542f\u52a8\u7c7b\u52a0\u8f7d\u5668\u53ea\u80fd\u52a0\u8f7d java \u6838\u5fc3\u7c7b\u5e93)\u3002\u8fd9\u65f6\u5019\u53ea\u80fd\u4f7f\u7528\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u4e86\uff1a\u628a\u81ea\u5df1\u52a0\u8f7d\u4e0d\u4e86\u7684\u7c7b\u52a0\u8f7d\u5230\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u4e2d\uff08\u901a\u8fc7<code>Thread.currentThread()<\/code>\u83b7\u53d6\uff09\uff0c\u800c\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u9ed8\u8ba4\u662f\u4f7f\u7528\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668 AppClassLoader\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u56de\u5934\u518d\u770b<code>ServiceLoader.load(Class)<\/code>\u7684\u4ee3\u7801\uff0c\u7684\u786e\u5982\u6b64\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public static &lt;S&gt; ServiceLoader&lt;S&gt; load(Class&lt;S&gt; service) {\n    ClassLoader cl = Thread.currentThread().getContextClassLoader();\n    return ServiceLoader.load(service, cl);\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">ContextClassLoader \u9ed8\u8ba4\u5b58\u653e\u4e86 AppClassLoader \u7684\u5f15\u7528\uff0c\u7531\u4e8e\u5b83\u662f\u5728\u8fd0\u884c\u65f6\u88ab\u653e\u5728\u4e86\u7ebf\u7a0b\u4e2d\uff0c\u6240\u4ee5\u4e0d\u7ba1\u5f53\u524d\u7a0b\u5e8f\u5904\u4e8e\u4f55\u5904\uff08BootstrapClassLoader\u6216\u662f ExtClassLoader\u7b49\uff09\uff0c\u5728\u4efb\u4f55\u9700\u8981\u7684\u65f6\u5019\u90fd\u53ef\u4ee5\u7528<code>Thread.currentThread().getContextClassLoader()<\/code>\u53d6\u51fa\u5e94\u7528\u7a0b\u5e8f\u7c7b\u52a0\u8f7d\u5668\u6765\u5b8c\u6210\u9700\u8981\u7684\u64cd\u4f5c\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5230\u8fd9\u513f\u5dee\u4e0d\u591a\u628a SPI \u673a\u5236\u89e3\u91ca\u6e05\u695a\u4e86\u3002\u76f4\u767d\u4e00\u70b9\u8bf4\u5c31\u662f\uff1a\u6211\uff08JDK\uff09\u63d0\u4f9b\u4e86\u4e00\u79cd\u5e2e\u4f60\uff08\u7b2c\u4e09\u65b9\u5b9e\u73b0\u8005\uff09\u52a0\u8f7d\u670d\u52a1\uff08\u5982\u6570\u636e\u5e93\u9a71\u52a8\u3001\u65e5\u5fd7\u5e93\uff09\u7684\u4fbf\u6377\u65b9\u5f0f\uff0c\u53ea\u8981\u4f60\u9075\u5faa\u7ea6\u5b9a\uff08\u628a\u7c7b\u540d\u5199\u5728<code>\/META-INF<\/code>\u91cc\uff09\uff0c\u90a3\u5f53\u6211\u542f\u52a8\u65f6\u6211\u4f1a\u53bb\u626b\u63cf\u6240\u6709 jar \u5305\u91cc\u7b26\u5408\u7ea6\u5b9a\u7684\u7c7b\u540d\uff0c\u518d\u8c03\u7528 forName \u52a0\u8f7d\u3002\u4f46\u6211\u7684 ClassLoader \u662f\u6ca1\u6cd5\u52a0\u8f7d\u7684\uff0c\u90a3\u5c31\u628a\u5b83\u52a0\u8f7d\u5230\u5f53\u524d\u6267\u884c\u7ebf\u7a0b\u7684\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u91cc\uff0c\u540e\u7eed\u4f60\u60f3\u600e\u4e48\u64cd\u4f5c\u5c31\u662f\u4f60\u7684\u4e8b\u4e86\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u56db. Tomcat\u4e0eSpring\u7684\u7c7b\u52a0\u8f7d\u5668\u6848\u4f8b<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\u5c06\u4ecb\u7ecd\u300a\u6df1\u5165\u7406\u89e3java\u865a\u62df\u673a\u300b\u4e00\u4e66\u4e2d\u7684\u6848\u4f8b\uff0c\u5e76\u89e3\u7b54\u5b83\u6240\u63d0\u51fa\u7684\u95ee\u9898\uff08\u90e8\u5206\u7c7b\u5bb9\u6765\u81ea\u4e8e\u4e66\u4e2d\u539f\u6587\uff09\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Tomcat\u4e2d\u7684\u7c7b\u52a0\u8f7d\u5668<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 Tomcat \u76ee\u5f55\u7ed3\u6784\u4e2d\uff0c\u6709\u4e09\u7ec4\u76ee\u5f55\uff08<code>\u201c\/common\/*\u201d,\u201c\/server\/*\u201d\u548c\u201cshared\/*\u201d<\/code>\uff09\u53ef\u4ee5\u5b58\u653e\u516c\u7528 Java \u7c7b\u5e93\uff0c\u6b64\u5916\u8fd8\u6709\u7b2c\u56db\u7ec4 Web \u5e94\u7528\u7a0b\u5e8f\u81ea\u8eab\u7684\u76ee\u5f55<code>\u201c\/WEB-INF\/\\*\u201d<\/code>\uff0c\u628a java \u7c7b\u5e93\u653e\u7f6e\u5728\u8fd9\u4e9b\u76ee\u5f55\u4e2d\u7684\u542b\u4e49\u5206\u522b\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u653e\u7f6e\u5728 common \u76ee\u5f55\u4e2d\uff1a\u7c7b\u5e93\u53ef\u88ab Tomcat \u548c\u6240\u6709\u7684 Web \u5e94\u7528\u7a0b\u5e8f\u5171\u540c\u4f7f\u7528\uff1b<\/li><li>\u653e\u7f6e\u5728 server \u76ee\u5f55\u4e2d\uff1a\u7c7b\u5e93\u53ef\u88ab Tomcat \u4f7f\u7528\uff0c\u4f46\u5bf9\u6240\u6709\u7684 Web \u5e94\u7528\u7a0b\u5e8f\u90fd\u4e0d\u53ef\u89c1\uff1b<\/li><li>\u653e\u7f6e\u5728 shared \u76ee\u5f55\u4e2d\uff1a\u7c7b\u5e93\u53ef\u88ab\u6240\u6709\u7684 Web \u5e94\u7528\u7a0b\u5e8f\u5171\u540c\u4f7f\u7528\uff0c\u4f46\u5bf9 Tomcat \u81ea\u5df1\u4e0d\u53ef\u89c1\uff1b<\/li><li>\u653e\u7f6e\u5728<code>\/WebApp\/WEB-INF<\/code>\u76ee\u5f55\u4e2d\uff1a\u7c7b\u5e93\u4ec5\u4ec5\u53ef\u4ee5\u88ab\u6b64 Web \u5e94\u7528\u7a0b\u5e8f\u4f7f\u7528\uff0c\u5bf9 Tomcat \u548c\u5176\u4ed6 Web \u5e94\u7528\u7a0b\u5e8f\u90fd\u4e0d\u53ef\u89c1\u3002<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e3a\u4e86\u652f\u6301\u8fd9\u5957\u76ee\u5f55\u7ed3\u6784\uff0c\u5e76\u5bf9\u76ee\u5f55\u91cc\u9762\u7684\u7c7b\u5e93\u8fdb\u884c\u52a0\u8f7d\u548c\u9694\u79bb\uff0cTomcat \u81ea\u5b9a\u4e49\u4e86\u591a\u4e2a\u7c7b\u52a0\u8f7d\u5668\uff0c\u8fd9\u4e9b\u7c7b\u52a0\u8f7d\u5668\u6309\u7167\u7ecf\u5178\u7684\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\u6765\u5b9e\u73b0\uff0c\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/xmt1139057136\/xttblog\/2021\/07\/sqwp3.jpg\" alt=\"Tomcat \u7684\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\" \/><figcaption>Tomcat \u7684\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u7070\u8272\u80cc\u666f\u7684 3 \u4e2a\u7c7b\u52a0\u8f7d\u5668\u662f JDK \u9ed8\u8ba4\u63d0\u4f9b\u7684\u7c7b\u52a0\u8f7d\u5668\uff0c\u8fd9 3 \u4e2a\u52a0\u8f7d\u5668\u7684\u4f5c\u7528\u524d\u9762\u5df2\u7ecf\u4ecb\u7ecd\u8fc7\u4e86\u3002\u800c<code>CommonClassLoader<\/code>\u3001<code>CatalinaClassLoader<\/code>\u3001<code>SharedClassLoader<\/code> \u548c <code>WebAppClassLoader<\/code> \u5219\u662f Tomcat \u81ea\u5df1\u5b9a\u4e49\u7684\u7c7b\u52a0\u8f7d\u5668\uff0c\u5b83\u4eec\u5206\u522b\u52a0\u8f7d<code>\/common\/*\u3001\/server\/*\u3001\/shared\/*<\/code> \u548c <code>\/WebApp\/WEB-INF\/*<\/code> \u4e2d\u7684 Java \u7c7b\u5e93\u3002\u5176\u4e2d WebApp \u7c7b\u52a0\u8f7d\u5668\u548c Jsp \u7c7b\u52a0\u8f7d\u5668\u901a\u5e38\u4f1a\u5b58\u5728\u591a\u4e2a\u5b9e\u4f8b\uff0c\u6bcf\u4e00\u4e2a Web \u5e94\u7528\u7a0b\u5e8f\u5bf9\u5e94\u4e00\u4e2a WebApp \u7c7b\u52a0\u8f7d\u5668\uff0c\u6bcf\u4e00\u4e2a JSP \u6587\u4ef6\u5bf9\u5e94\u4e00\u4e2a Jsp \u7c7b\u52a0\u8f7d\u5668\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ece\u56fe\u4e2d\u7684\u59d4\u6d3e\u5173\u7cfb\u4e2d\u53ef\u4ee5\u770b\u51fa\uff0c<code>CommonClassLoader<\/code> \u80fd\u52a0\u8f7d\u7684\u7c7b\u90fd\u53ef\u4ee5\u88ab <code>CatalinaClassLoader<\/code> \u548c <code>SharedClassLoader<\/code> \u4f7f\u7528\uff0c\u800c <code>CatalinaClassLoader<\/code> \u548c <code>SharedClassLoader<\/code> \u81ea\u5df1\u80fd\u52a0\u8f7d\u7684\u7c7b\u5219\u4e0e\u5bf9\u65b9\u76f8\u4e92\u9694\u79bb\u3002<code>WebAppClassLoader<\/code> \u53ef\u4ee5\u4f7f\u7528 <code>SharedClassLoader<\/code> \u52a0\u8f7d\u5230\u7684\u7c7b\uff0c\u4f46\u5404\u4e2a <code>WebAppClassLoader<\/code> \u5b9e\u4f8b\u4e4b\u95f4\u76f8\u4e92\u9694\u79bb\u3002\u800c JasperLoader \u7684\u52a0\u8f7d\u8303\u56f4\u4ec5\u4ec5\u662f\u8fd9\u4e2a JSP \u6587\u4ef6\u6240\u7f16\u8bd1\u51fa\u6765\u7684\u90a3\u4e00\u4e2a Class\uff0c\u5b83\u51fa\u73b0\u7684\u76ee\u7684\u5c31\u662f\u4e3a\u4e86\u88ab\u4e22\u5f03\uff1a\u5f53\u670d\u52a1\u5668\u68c0\u6d4b\u5230 JSP \u6587\u4ef6\u88ab\u4fee\u6539\u65f6\uff0c\u4f1a\u66ff\u6362\u6389\u76ee\u524d\u7684 JasperLoader \u7684\u5b9e\u4f8b\uff0c\u5e76\u901a\u8fc7\u518d\u5efa\u7acb\u4e00\u4e2a\u65b0\u7684 Jsp \u7c7b\u52a0\u8f7d\u5668\u6765\u5b9e\u73b0 JSP \u6587\u4ef6\u7684 HotSwap \u529f\u80fd\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Spring\u52a0\u8f7d\u95ee\u9898<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Tomcat \u52a0\u8f7d\u5668\u7684\u5b9e\u73b0\u6e05\u6670\u6613\u61c2\uff0c\u5e76\u4e14\u91c7\u7528\u4e86\u5b98\u65b9\u63a8\u8350\u7684\u201c\u6b63\u7edf\u201d\u7684\u4f7f\u7528\u7c7b\u52a0\u8f7d\u5668\u7684\u65b9\u5f0f\u3002\u8fd9\u65f6\u4f5c\u8005\u63d0\u4e00\u4e2a\u95ee\u9898\uff1a\u5982\u679c\u6709 10 \u4e2a Web \u5e94\u7528\u7a0b\u5e8f\u90fd\u7528\u5230\u4e86 spring \u7684\u8bdd\uff0c\u53ef\u4ee5\u628a Spring \u7684 jar \u5305\u653e\u5230 common \u6216 shared \u76ee\u5f55\u4e0b\u8ba9\u8fd9\u4e9b\u7a0b\u5e8f\u5171\u4eab\u3002Spring \u7684\u4f5c\u7528\u662f\u7ba1\u7406\u6bcf\u4e2aweb\u5e94\u7528\u7a0b\u5e8f\u7684bean\uff0cgetBean\u65f6\u81ea\u7136\u8981\u80fd\u8bbf\u95ee\u5230\u5e94\u7528\u7a0b\u5e8f\u7684\u7c7b\uff0c\u800c\u7528\u6237\u7684\u7a0b\u5e8f\u663e\u7136\u662f\u653e\u5728 <code>\/WebApp\/WEB-INF<\/code> \u76ee\u5f55\u4e2d\u7684\uff08\u7531 WebAppClassLoader \u52a0\u8f7d\uff09\uff0c\u90a3\u4e48\u5728 CommonClassLoader \u6216 SharedClassLoader \u4e2d\u7684 Spring \u5bb9\u5668\u5982\u4f55\u53bb\u52a0\u8f7d\u5e76\u4e0d\u5728\u5176\u52a0\u8f7d\u8303\u56f4\u7684\u7528\u6237\u7a0b\u5e8f\uff08<code>\/WebApp\/WEB-INF\/<\/code>\uff09\u4e2d\u7684 Class \u5462\uff1f<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\u89e3\u7b54<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u7b54\u6848\u547c\u4e4b\u6b32\u51fa\uff1aspring 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logger.error(\"Context initialization failed\", err);\n  throw err;\n }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5177\u4f53\u8bf4\u660e\u90fd\u5728\u6ce8\u91ca\u4e2d\uff0cspring \u8003\u8651\u5230\u4e86\u81ea\u5df1\u53ef\u80fd\u88ab\u653e\u5230\u5176\u4ed6\u4f4d\u7f6e\uff0c\u6240\u4ee5\u76f4\u63a5\u7528\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u6765\u89e3\u51b3\u6240\u6709\u53ef\u80fd\u9762\u4e34\u7684\u60c5\u51b5\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e94. \u603b\u7ed3<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u901a\u8fc7\u4e0a\u9762\u7684\u4e24\u4e2a\u6848\u4f8b\u5206\u6790\uff0c\u6211\u4eec\u53ef\u4ee5\u603b\u7ed3\u51fa\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u7c7b\u52a0\u8f7d\u5668\u7684\u9002\u7528\u573a\u666f\uff1a<\/p>\n\n\n\n<ul 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id=\"bdRewardBtn\"><span><\/span><\/button><\/div> -->","protected":false},"excerpt":{"rendered":"<p>\u6458\u8981 SPI \u673a\u5236\u662f\u4ec0\u4e48\uff0c\u6709\u54ea\u4e9b\u5e94\u7528\u573a\u666f\uff0c\u53c8\u5e26\u6765\u4e86\u54ea\u4e9b\u95ee\u9898\uff1f \u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\u662f Java \u63a8\u8350\u7684\u7c7b\u52a0\u8f7d\u6a21\u578b\uff0c\u4f46\u8fdd 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