{"id":2985,"date":"2023-07-14T17:58:00","date_gmt":"2023-07-14T09:58:00","guid":{"rendered":"https:\/\/xinchewhd.com.cn\/?p=2985"},"modified":"2023-07-14T17:58:00","modified_gmt":"2023-07-14T09:58:00","slug":"%e9%9d%a2%e8%af%95%e5%ae%98%e9%97%ae%ef%bc%9aspringboot%e4%b8%ad%e6%9d%a1%e4%bb%b6%e6%b3%a8%e8%a7%a3%e5%ba%95%e5%b1%82%e5%a6%82%e4%bd%95%e5%ae%9e%e7%8e%b0%e7%9a%84%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/xinchewhd.com.cn\/index.php\/spring-boot\/%e9%9d%a2%e8%af%95%e5%ae%98%e9%97%ae%ef%bc%9aspringboot%e4%b8%ad%e6%9d%a1%e4%bb%b6%e6%b3%a8%e8%a7%a3%e5%ba%95%e5%b1%82%e5%a6%82%e4%bd%95%e5%ae%9e%e7%8e%b0%e7%9a%84%ef%bc%9f\/","title":{"rendered":"\u9762\u8bd5\u5b98\u95ee\uff1aSpringBoot\u4e2d\u6761\u4ef6\u6ce8\u89e3\u5e95\u5c42\u5982\u4f55\u5b9e\u73b0\u7684\uff1f"},"content":{"rendered":"
SpringBoot\u5185\u90e8\u63d0\u4f9b\u4e86\u7279\u6709\u7684\u6ce8\u89e3\uff1a\u6761\u4ef6\u6ce8\u89e3\uff08<\/span>Conditional Annotation\uff09<\/span>\u3002\u6bd4<\/span>\u5982<\/span><\/section>\n

@ConditionalOnBean\u3001<\/span><\/p>\n

@ConditionalOnClass\u3001<\/span><\/p>\n

@ConditionalOnExpression\u3001<\/span><\/p>\n

@ConditionalOnMissingBean\u7b49\u3002<\/span><\/p>\n

\u6761\u4ef6\u6ce8\u89e3\u5b58\u5728\u7684\u610f\u4e49\u5728\u4e8e\u52a8\u6001\u8bc6\u522b\uff08\u4e5f\u53ef\u4ee5\u8bf4\u662f\u4ee3\u7801\u81ea\u52a8\u5316\u6267\u884c\uff09<\/span>\u3002\u6bd4\u5982@ConditionalOnClass\u4f1a\u68c0\u67e5\u7c7b\u52a0\u8f7d\u5668\u4e2d\u662f\u5426\u5b58\u5728\u5bf9\u5e94\u7684\u7c7b\uff0c\u5982\u679c\u6709\u7684\u8bdd\u88ab\u6ce8\u89e3\u4fee\u9970\u7684\u7c7b\u5c31\u6709\u8d44\u683c\u88abSpring\u5bb9\u5668\u6240\u6ce8\u518c\uff0c\u5426\u5219\u4f1a\u88abskip\u3002<\/span><\/p>\n

\u6bd4\u5982FreemarkerAutoConfiguration\u8fd9\u4e2a\u81ea\u52a8\u5316\u914d\u7f6e\u7c7b\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/span><\/p>\n

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@Configuration<\/span>\n@ConditionalOnClass<\/span>({ freemarker.template.Configuration.class,<\/span>\n\t\tFreeMarkerConfigurationFactory.class })<\/span>\n@AutoConfigureAfter<\/span>(WebMvcAutoConfiguration.class)<\/span>\n@EnableConfigurationProperties<\/span>(FreeMarkerProperties.class)<\/span>\npublic<\/span> class<\/span> FreeMarkerAutoConfiguration<\/span><\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
\u8fd9\u4e2a\u81ea\u52a8\u5316\u914d\u7f6e\u7c7b\u88ab@ConditionalOnClass\u6761\u4ef6\u6ce8\u89e3\u4fee\u9970\uff0c\u8fd9\u4e2a\u6761\u4ef6\u6ce8\u89e3\u5b58\u5728\u7684\u610f\u4e49\u5728\u4e8e\u5224\u65ad\u7c7b\u52a0\u8f7d\u5668\u4e2d\u662f\u5426\u5b58\u5728freemarker.template.Configuration\u548cFreeMarkerConfigurationFactory\u8fd9\u4e24\u4e2a\u7c7b\uff0c\u5982\u679c\u90fd\u5b58\u5728\u7684\u8bdd\u4f1a\u5728Spring\u5bb9\u5668\u4e2d\u52a0\u8f7d\u8fd9\u4e2aFreeMarkerAutoConfiguration\u914d\u7f6e\u7c7b\uff1b\u5426\u5219\u4e0d\u4f1a\u52a0\u8f7d\u3002<\/span><\/p>\n
\u6761\u4ef6\u6ce8\u89e3\u5185\u90e8\u7684\u4e00\u4e9b\u57fa\u7840<\/span><\/h2>\n
\u5728\u5206\u6790\u6761\u4ef6\u6ce8\u89e3\u7684\u5e95\u5c42\u5b9e\u73b0\u4e4b\u524d\uff0c\u6211\u4eec\u5148\u6765\u770b\u4e00\u4e0b\u8fd9\u4e9b\u6761\u4ef6\u6ce8\u89e3\u7684\u5b9a\u4e49\u3002\u4ee5@ConditionalOnClass\u6ce8\u89e3\u4e3a\u4f8b\uff0c\u5b83\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/span><\/p>\n
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@Target<\/span>({ ElementType.TYPE, ElementType.METHOD })<\/span>\n@Retention<\/span>(RetentionPolicy.RUNTIME)<\/span>\n@Documented<\/span>\n@Conditional<\/span>(OnClassCondition.class)<\/span>\npublic<\/span> @interface<\/span> ConditionalOnClass {<\/span>\n  Class<?>[] value() default<\/span> {}; \/\/ \u9700\u8981\u5339\u914d\u7684\u7c7b<\/span><\/span>\n  String[] name() default<\/span> {}; \/\/ \u9700\u8981\u5339\u914d\u7684\u7c7b\u540d<\/span><\/span>\n}<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
\u5b83\u67092\u4e2a\u5c5e\u6027\uff0c\u5206\u522b\u662f\u7c7b\u6570\u7ec4\u548c\u5b57\u7b26\u4e32\u6570\u7ec4(\u4f5c\u7528\u4e00\u6837\uff0c\u7c7b\u578b\u4e0d\u4e00\u6837)\uff0c\u800c\u4e14\u88ab@Conditional\u6ce8\u89e3\u6240\u4fee\u9970\uff0c\u8fd9\u4e2a@Conditional\u6ce8\u89e3\u6709\u4e2a\u540d\u4e3avalues\u7684Class<? extends Condition>[]\u7c7b\u578b\u7684\u5c5e\u6027\u3002\u8fd9\u4e2aCondition\u662f\u4e2a\u63a5\u53e3\uff0c\u7528\u4e8e\u5339\u914d\u7ec4\u4ef6\u662f\u5426\u6709\u8d44\u683c\u88ab\u5bb9\u5668\u6ce8\u518c\uff0c\u5b9a\u4e49\u5982\u4e0b\uff1a<\/span><\/p>\n
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public<\/span> interface<\/span> Condition<\/span> {<\/span>\n  \/\/ ConditionContext\u5185\u90e8\u4f1a\u5b58\u50a8Spring\u5bb9\u5668\u3001\u5e94\u7528\u7a0b\u5e8f\u73af\u5883\u4fe1\u606f\u3001\u8d44\u6e90\u52a0\u8f7d\u5668\u3001\u7c7b\u52a0\u8f7d\u5668<\/span><\/span>\n  boolean<\/span> matches<\/span>(ConditionContext context, AnnotatedTypeMetadata metadata)<\/span><\/span>;<\/span>\n}<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
\u4e5f\u5c31\u662f\u8bf4@Conditional\u6ce8\u89e3\u5c5e\u6027\u4e2d\u53ef\u4ee5\u6301\u6709\u591a\u4e2aCondition\u63a5\u53e3\u7684\u5b9e\u73b0\u7c7b\uff0c\u6240\u6709\u7684Condition\u63a5\u53e3\u9700\u8981\u5168\u90e8\u5339\u914d\u6210\u529f\u540e\u8fd9\u4e2a@Conditional\u4fee\u9970\u7684\u7ec4\u4ef6\u624d\u6709\u8d44\u683c\u88ab\u6ce8\u518c\u3002<\/span><\/p>\n
Condition\u63a5\u53e3\u6709\u4e2a\u5b50\u63a5\u53e3<\/span><\/p>\n
ConfigurationCondition\uff1a<\/span><\/p>\n
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public<\/span> interface<\/span> ConfigurationCondition<\/span> extends<\/span> Condition<\/span> {<\/span>\n\n  ConfigurationPhase getConfigurationPhase<\/span>()<\/span><\/span>;<\/span>\n\n  public<\/span> static<\/span> enum<\/span> ConfigurationPhase {<\/span>\n\n  \tPARSE_CONFIGURATION,<\/span>\n\n  \tREGISTER_BEAN<\/span>\n  }<\/span>\n\n}<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
\u8fd9\u4e2a\u5b50\u63a5\u53e3\u662f\u4e00\u79cd\u7279\u6b8a\u7684\u6761\u4ef6\u63a5\u53e3\uff0c\u591a\u4e86\u4e00\u4e2agetConfigurationPhase\u65b9\u6cd5\uff0c\u4e5f\u5c31\u662f\u6761\u4ef6\u6ce8\u89e3\u7684\u751f\u6548\u9636\u6bb5\u3002\u53ea\u6709\u5728ConfigurationPhase\u4e2d\u5b9a\u4e49\u7684\u4e24\u79cd\u9636\u6bb5\u4e0b\u624d\u4f1a\u751f\u6548\u3002<\/span><\/p>\n
Condition\u63a5\u53e3\u6709\u4e2a\u5b9e\u73b0\u62bd\u8c61\u7c7bSpringBootCondition\uff0cSpringBoot\u4e2d\u6240\u6709\u6761\u4ef6\u6ce8\u89e3\u5bf9\u5e94\u7684\u6761\u4ef6\u7c7b\u90fd\u7ee7\u627f\u8fd9\u4e2a\u62bd\u8c61\u7c7b\u3002\u5b83\u5b9e\u73b0\u4e86matches\u65b9\u6cd5\uff1a<\/span><\/p>\n
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@Override<\/span>\npublic<\/span> final<\/span> boolean<\/span> matches<\/span>(ConditionContext context,<\/span><\/span>\n\t\tAnnotatedTypeMetadata metadata)<\/span> <\/span>{<\/span>\n  String classOrMethodName = getClassOrMethodName(metadata); \/\/ \u5f97\u5230\u7c7b\u540d\u6216\u8005\u65b9\u6cd5\u540d(\u6761\u4ef6\u6ce8\u89e3\u53ef\u4ee5\u4f5c\u7528\u7684\u7c7b\u6216\u8005\u65b9\u6cd5\u4e0a)<\/span><\/span>\n  try<\/span> {<\/span>\n  \tConditionOutcome outcome = getMatchOutcome(context, metadata); \/\/ \u62bd\u8c61\u65b9\u6cd5\uff0c\u5177\u4f53\u5b50\u7c7b\u5b9e\u73b0\u3002ConditionOutcome\u8bb0\u5f55\u4e86\u5339\u914d\u7ed3\u679cboolean\u548clog\u4fe1\u606f<\/span><\/span>\n  \tlogOutcome(classOrMethodName, outcome); \/\/ log\u8bb0\u5f55\u4e00\u4e0b\u5339\u914d\u4fe1\u606f<\/span><\/span>\n  \trecordEvaluation(context, classOrMethodName, outcome); \/\/ \u62a5\u544a\u8bb0\u5f55\u4e00\u4e0b\u5339\u914d\u4fe1\u606f<\/span><\/span>\n  \treturn<\/span> outcome.isMatch(); \/\/ \u8fd4\u56de\u662f\u5426\u5339\u914d<\/span><\/span>\n  }<\/span>\n  catch<\/span> (NoClassDefFoundError ex) {<\/span>\n  \tthrow<\/span> new<\/span> IllegalStateException(<\/span>\n  \t\t\t\"Could not evaluate condition on \"<\/span> + classOrMethodName + \" due to \"<\/span><\/span>\n  \t\t\t\t\t+ ex.getMessage() + \" not \"<\/span><\/span>\n  \t\t\t\t\t+ \"found. Make sure your own configuration does not rely on \"<\/span><\/span>\n  \t\t\t\t\t+ \"that class. This can also happen if you are \"<\/span><\/span>\n  \t\t\t\t\t+ \"@ComponentScanning a springframework package (e.g. if you \"<\/span><\/span>\n  \t\t\t\t\t+ \"put a @ComponentScan in the default package by mistake)\"<\/span>,<\/span>\n  \t\t\tex);<\/span>\n  }<\/span>\n  catch<\/span> (RuntimeException ex) {<\/span>\n  \tthrow<\/span> new<\/span> IllegalStateException(<\/span>\n  \t\t\t\"Error processing condition on \"<\/span> + getName(metadata), ex);<\/span>\n  }<\/span>\n}<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
\u57fa\u4e8eClass\u7684\u6761\u4ef6\u6ce8\u89e3<\/span><\/h2>\n
SpringBoot\u63d0\u4f9b\u4e86\u4e24\u4e2a\u57fa\u4e8eClass\u7684\u6761\u4ef6\u6ce8\u89e3\uff1a@ConditionalOnClass(\u7c7b\u52a0\u8f7d\u5668\u4e2d\u5b58\u5728\u6307\u660e\u7684\u7c7b)\u6216\u8005@ConditionalOnMissingClass(\u7c7b\u52a0\u8f7d\u5668\u4e2d\u4e0d\u5b58\u5728\u6307\u660e\u7684\u7c7b)\u3002<\/span><\/p>\n
@ConditionalOnClass\u6216\u8005<\/span><\/section>\n
@ConditionalOnMissingClass\u6ce8\u89e3\u5bf9\u5e94\u7684\u6761\u4ef6\u7c7b\u662fOnClassCondition\uff0c\u5b9a\u4e49\u5982\u4e0b\uff1a<\/span><\/p>\n
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@Order<\/span>(Ordered.HIGHEST_PRECEDENCE) \/\/ \u4f18\u5148\u7ea7\u3001\u6700\u9ad8\u7ea7\u522b<\/span><\/span>\nclass<\/span> OnClassCondition<\/span> extends<\/span> SpringBootCondition<\/span> {<\/span>\n\n  @Override<\/span><\/span>\n  public<\/span> ConditionOutcome getMatchOutcome<\/span>(ConditionContext context,<\/span><\/span><\/span>\n  \t\tAnnotatedTypeMetadata metadata)<\/span> <\/span>{<\/span>\n\n  \tStringBuffer matchMessage = new<\/span> StringBuffer(); \/\/ \u8bb0\u5f55\u5339\u914d\u4fe1\u606f<\/span><\/span>\n\n  \tMultiValueMap<String, Object> onClasses = getAttributes(metadata,<\/span>\n  \t\t\tConditionalOnClass.class); \/\/ \u5f97\u5230@ConditionalOnClass\u6ce8\u89e3\u7684\u5c5e\u6027<\/span><\/span>\n  \tif<\/span> (onClasses != null<\/span>) { \/\/ \u5982\u679c\u5c5e\u6027\u5b58\u5728<\/span><\/span>\n  \t\tList<String> missing = getMatchingClasses(onClasses, MatchType.MISSING,<\/span>\n  \t\t\t\tcontext); \/\/ \u5f97\u5230\u5728\u7c7b\u52a0\u8f7d\u5668\u4e2d\u4e0d\u5b58\u5728\u7684\u7c7b<\/span><\/span>\n  \t\tif<\/span> (!missing.isEmpty()) { \/\/ \u5982\u679c\u5b58\u5728\u7c7b\u52a0\u8f7d\u5668\u4e2d\u4e0d\u5b58\u5728\u5bf9\u5e94\u7684\u7c7b\uff0c\u8fd4\u56de\u4e00\u4e2a\u5339\u914d\u5931\u8d25\u7684ConditionalOutcome<\/span><\/span>\n  \t\t\treturn<\/span> ConditionOutcome<\/span>\n  \t\t\t\t\t.noMatch(\"required @ConditionalOnClass classes not found: \"<\/span><\/span>\n  \t\t\t\t\t\t\t+ StringUtils.collectionToCommaDelimitedString(missing));<\/span>\n  \t\t}<\/span>\n                \/\/ \u5982\u679c\u7c7b\u52a0\u8f7d\u5668\u4e2d\u5b58\u5728\u5bf9\u5e94\u7684\u7c7b\u7684\u8bdd\uff0c\u5339\u914d\u4fe1\u606f\u8fdb\u884c\u8bb0\u5f55<\/span><\/span>\n  \t\tmatchMessage.append(\"@ConditionalOnClass classes found: \"<\/span><\/span>\n  \t\t\t\t+ StringUtils.collectionToCommaDelimitedString(<\/span>\n  \t\t\t\t\t\tgetMatchingClasses(onClasses, MatchType.PRESENT, context)));<\/span>\n  \t}<\/span>\n        \/\/ \u5bf9@ConditionalOnMissingClass\u6ce8\u89e3\u505a\u76f8\u540c\u7684\u903b\u8f91\u5904\u7406(\u8bf4\u660e@ConditionalOnClass\u548c@ConditionalOnMissingClass\u53ef\u4ee5\u4e00\u8d77\u4f7f\u7528)<\/span><\/span>\n  \tMultiValueMap<String, Object> onMissingClasses = getAttributes(metadata,<\/span>\n  \t\t\tConditionalOnMissingClass.class);<\/span>\n  \tif<\/span> (onMissingClasses != null<\/span>) {<\/span>\n  \t\tList<String> present = getMatchingClasses(onMissingClasses, MatchType.PRESENT,<\/span>\n  \t\t\t\tcontext);<\/span>\n  \t\tif<\/span> (!present.isEmpty()) {<\/span>\n  \t\t\treturn<\/span> ConditionOutcome<\/span>\n  \t\t\t\t\t.noMatch(\"required @ConditionalOnMissing classes found: \"<\/span><\/span>\n  \t\t\t\t\t\t\t+ StringUtils.collectionToCommaDelimitedString(present));<\/span>\n  \t\t}<\/span>\n  \t\tmatchMessage.append(matchMessage.length() == 0<\/span> ? \"\"<\/span> : \" \"<\/span>);<\/span>\n  \t\tmatchMessage.append(\"@ConditionalOnMissing classes not found: \"<\/span><\/span>\n  \t\t\t\t+ StringUtils.collectionToCommaDelimitedString(getMatchingClasses(<\/span>\n  \t\t\t\t\t\tonMissingClasses, MatchType.MISSING, context)));<\/span>\n  \t}<\/span>\n        \/\/ \u8fd4\u56de\u5168\u90e8\u5339\u914d\u6210\u529f\u7684ConditionalOutcome<\/span><\/span>\n  \treturn<\/span> ConditionOutcome.match(matchMessage.toString());<\/span>\n\t}<\/span>\n\n  private<\/span> enum<\/span> MatchType { \/\/ \u679a\u4e3e\uff1a\u5339\u914d\u7c7b\u578b\u3002\u7528\u4e8e\u67e5\u8be2\u7c7b\u540d\u5728\u5bf9\u5e94\u7684\u7c7b\u52a0\u8f7d\u5668\u4e2d\u662f\u5426\u5b58\u5728\u3002<\/span><\/span>\n\n  \tPRESENT { \/\/ \u5339\u914d\u6210\u529f<\/span><\/span>\n  \t\t@Override<\/span><\/span>\n  \t\tpublic<\/span> boolean<\/span> matches<\/span>(String className, ConditionContext context)<\/span> <\/span>{<\/span>\n  \t\t\treturn<\/span> ClassUtils.isPresent(className, context.getClassLoader());<\/span>\n  \t\t}<\/span>\n  \t},<\/span>\n\n  \tMISSING { \/\/ \u5339\u914d\u4e0d\u6210\u529f<\/span><\/span>\n  \t\t@Override<\/span><\/span>\n  \t\tpublic<\/span> boolean<\/span> matches<\/span>(String className, ConditionContext context)<\/span> <\/span>{<\/span>\n  \t\t\treturn<\/span> !ClassUtils.isPresent(className, context.getClassLoader());<\/span>\n  \t\t}<\/span>\n  \t};<\/span>\n\n  \tpublic<\/span> abstract<\/span> boolean<\/span> matches<\/span>(String className, ConditionContext context)<\/span><\/span>;<\/span>\n\n  }<\/span>\n\n}<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
\u6bd4\u5982FreemarkerAutoConfiguration\u4e2d\u7684@ConditionalOnClass\u6ce8\u89e3\u4e2d\u6709value\u5c5e\u6027\u662ffreemarker.template.Configuration.class\u548cFreeMarkerConfigurationFactory.class\u3002\u5728OnClassCondition\u6267\u884c\u8fc7\u7a0b\u4e2d\u5f97\u5230\u7684\u6700\u7ec8ConditionalOutcome\u4e2d\u7684log message\u5982\u4e0b\uff1a<\/span><\/p>\n
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@ConditionalOnClass<\/span> classes found: freemarker.template.Configuration,org.springframework.ui.freemarker.FreeMarkerConfigurationFactory<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
\u57fa\u4e8eBean\u7684\u6761\u4ef6\u6ce8\u89e3<\/span><\/h2>\n
@ConditionalOnBean(Spring\u5bb9\u5668\u4e2d\u5b58\u5728\u6307\u660e\u7684bean)\u3001@ConditionalOnMissingBean(Spring\u5bb9\u5668\u4e2d\u4e0d\u5b58\u5728\u6307\u660e\u7684bean)\u4ee5\u53caConditionalOnSingleCandidate(Spring\u5bb9\u5668\u4e2d\u5b58\u5728\u4e14\u53ea\u5b58\u5728\u4e00\u4e2a\u6307\u660e\u7684bean)\u90fd\u662f\u57fa\u4e8eBean\u7684\u6761\u4ef6\u6ce8\u89e3\uff0c\u5b83\u4eec\u5bf9\u5e94\u7684\u6761\u4ef6\u7c7b\u662fConditionOnBean\u3002<\/span><\/p>\n
@ConditionOnBean\u6ce8\u89e3\u5b9a\u4e49\u5982\u4e0b\uff1a<\/span><\/p>\n
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@Target<\/span>({ ElementType.TYPE, ElementType.METHOD })<\/span>\n@Retention<\/span>(RetentionPolicy.RUNTIME)<\/span>\n@Documented<\/span>\n@Conditional<\/span>(OnBeanCondition.class)<\/span>\npublic<\/span> @interface<\/span> ConditionalOnBean {<\/span>\n  Class<?>[] value() default<\/span> {}; \/\/ \u5339\u914d\u7684bean\u7c7b\u578b<\/span><\/span>\n  String[] type() default<\/span> {}; \/\/ \u5339\u914d\u7684bean\u7c7b\u578b\u7684\u7c7b\u540d<\/span><\/span>\n  Class<? extends Annotation>[] annotation() default<\/span> {}; \/\/ \u5339\u914d\u7684bean\u6ce8\u89e3<\/span><\/span>\n  String[] name() default<\/span> {}; \/\/ \u5339\u914d\u7684bean\u7684\u540d\u5b57<\/span><\/span>\n  SearchStrategy search<\/span>()<\/span> default<\/span> SearchStrategy.ALL<\/span>; \/\/ \u641c\u7d22\u7b56\u7565\u3002\u63d0\u4f9bCURRENT(\u53ea\u5728\u5f53\u524d\u5bb9\u5668\u4e2d\u627e)\u3001PARENTS(\u53ea\u5728\u6240\u6709\u7684\u7236\u5bb9\u5668\u4e2d\u627e\uff1b\u4f46\u662f\u4e0d\u5305\u62ec\u5f53\u524d\u5bb9\u5668)\u548cALL(CURRENT\u548cPARENTS\u7684\u7ec4\u5408)<\/span><\/span>\n}<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
OnBeanCondition\u6761\u4ef6\u7c7b\u7684\u5339\u914d\u4ee3\u7801\u5982\u4e0b\uff1a<\/span><\/p>\n
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@Override<\/span>\npublic<\/span> ConditionOutcome getMatchOutcome<\/span>(ConditionContext context,<\/span><\/span>\n    AnnotatedTypeMetadata metadata)<\/span> <\/span>{<\/span>\n  StringBuffer matchMessage = new<\/span> StringBuffer(); \/\/ \u8bb0\u5f55\u5339\u914d\u4fe1\u606f<\/span><\/span>\n  if<\/span> (metadata.isAnnotated(ConditionalOnBean.class.getName())) {<\/span>\n    BeanSearchSpec spec = new<\/span> BeanSearchSpec(context, metadata,<\/span>\n        ConditionalOnBean.class); \/\/ \u6784\u9020\u4e00\u4e2aBeanSearchSpec\uff0c\u4f1a\u4ece@ConditionalOnBean\u6ce8\u89e3\u4e2d\u83b7\u53d6\u5c5e\u6027\uff0c\u7136\u540e\u8bbe\u7f6e\u5230BeanSearchSpec\u4e2d<\/span><\/span>\n    List<String> matching = getMatchingBeans(context, spec); \/\/ \u4eceBeanFactory\u4e2d\u6839\u636e\u7b56\u7565\u627e\u51fa\u6240\u6709\u5339\u914d\u7684bean<\/span><\/span>\n    if<\/span> (matching.isEmpty()) { \/\/ \u5982\u679c\u6ca1\u6709\u5339\u914d\u7684bean\uff0c\u8fd4\u56de\u4e00\u4e2a\u6ca1\u6709\u5339\u914d\u6210\u529f\u7684ConditionalOutcome<\/span><\/span>\n      return<\/span> ConditionOutcome<\/span>\n          .noMatch(\"@ConditionalOnBean \"<\/span> + spec + \" found no beans\"<\/span>);<\/span>\n    }<\/span>\n    \/\/ \u5982\u679c\u627e\u5230\u5339\u914d\u7684bean\uff0c\u5339\u914d\u4fe1\u606f\u8fdb\u884c\u8bb0\u5f55<\/span><\/span>\n    matchMessage.append(<\/span>\n        \"@ConditionalOnBean \"<\/span> + spec + \" found the following \"<\/span> + matching);<\/span>\n  }<\/span>\n  if<\/span> (metadata.isAnnotated(ConditionalOnSingleCandidate.class.getName())) { \/\/ \u76f8\u540c\u7684\u903b\u8f91\uff0c\u9488\u5bf9@ConditionalOnSingleCandidate\u6ce8\u89e3<\/span><\/span>\n    BeanSearchSpec spec = new<\/span> SingleCandidateBeanSearchSpec(context, metadata,<\/span>\n        ConditionalOnSingleCandidate.class);<\/span>\n    List<String> matching = getMatchingBeans(context, spec);<\/span>\n    if<\/span> (matching.isEmpty()) {<\/span>\n      return<\/span> ConditionOutcome.noMatch(<\/span>\n          \"@ConditionalOnSingleCandidate \"<\/span> + spec + \" found no beans\"<\/span>);<\/span>\n    }<\/span>\n    else<\/span> if<\/span> (!hasSingleAutowireCandidate(context.getBeanFactory(), matching)) { \/\/ \u591a\u4e86\u4e00\u5c42\u5224\u65ad\uff0c\u5224\u65ad\u662f\u5426\u53ea\u6709\u4e00\u4e2abean<\/span><\/span>\n      return<\/span> ConditionOutcome.noMatch(\"@ConditionalOnSingleCandidate \"<\/span> + spec<\/span>\n          + \" found no primary candidate amongst the\"<\/span> + \" following \"<\/span><\/span>\n          + matching);<\/span>\n    }<\/span>\n    matchMessage.append(\"@ConditionalOnSingleCandidate \"<\/span> + spec + \" found \"<\/span><\/span>\n        + \"a primary candidate amongst the following \"<\/span> + matching);<\/span>\n  }<\/span>\n  if<\/span> (metadata.isAnnotated(ConditionalOnMissingBean.class.getName())) { \/\/ \u76f8\u540c\u7684\u903b\u8f91\uff0c\u9488\u5bf9@ConditionalOnMissingBean\u6ce8\u89e3<\/span><\/span>\n    BeanSearchSpec spec = new<\/span> BeanSearchSpec(context, metadata,<\/span>\n        ConditionalOnMissingBean.class);<\/span>\n    List<String> matching = getMatchingBeans(context, spec);<\/span>\n    if<\/span> (!matching.isEmpty()) {<\/span>\n      return<\/span> ConditionOutcome.noMatch(\"@ConditionalOnMissingBean \"<\/span> + spec<\/span>\n          + \" found the following \"<\/span> + matching);<\/span>\n    }<\/span>\n    matchMessage.append(matchMessage.length() == 0<\/span> ? \"\"<\/span> : \" \"<\/span>);<\/span>\n    matchMessage.append(\"@ConditionalOnMissingBean \"<\/span> + spec + \" found no beans\"<\/span>);<\/span>\n  }<\/span>\n  return<\/span> ConditionOutcome.match(matchMessage.toString()); \/\/\u8fd4\u56de\u5339\u914d\u6210\u529f\u7684ConditonalOutcome<\/span><\/span>\n}<\/span><\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n
SpringBoot\u8fd8\u63d0\u4f9b\u4e86\u5176\u4ed6\u6bd4\u5982ConditionalOnJava\u3001ConditionalOnNotWebApplication\u3001ConditionalOnWebApplication\u3001ConditionalOnResource\u3001ConditionalOnProperty\u3001ConditionalOnExpression\u7b49\u6761\u4ef6\u6ce8\u89e3\uff0c\u6709\u5174\u8da3\u7684\u8bfb\u8005\u53ef\u4ee5\u81ea\u884c\u67e5\u770b\u5b83\u4eec\u7684\u5e95\u5c42\u5904\u7406\u903b\u8f91\u3002\u5173\u4e8e\u66f4\u591a\u9762\u8bd5\u8d44\u6599\uff0c\u516c\u4f17\u53f7Java\u7cbe\u9009\uff0c\u56de\u590djava\u9762\u8bd5\uff0c\u83b7\u53d6\u5728\u7ebf\u9762\u8bd5\u8d44\u6599\uff0c\u652f\u6301\u968f\u65f6\u968f\u5730\u5237\u9898\u3002<\/span><\/p>\n
\u5404\u79cd\u6761\u4ef6\u6ce8\u89e3\u7684\u603b\u7ed3<\/span><\/h2>\n