一、前言
spring cloud大行其道的當下，如果不了解基本原理那么是很糾結的(看見的都是 約定大于配置 ，但是原理呢？為什么要這么做？)。spring cloud是基于spring boot快速搭建的，今天咱們就看看spring boot容器啟動流程。(本文不講解如何快速啟動spring boot，那些直接官方看即可， 官網文檔飛機票 )
二、容器啟動
spring boot一般是 指定容器啟動main方法，然后以命令行方式啟動jar包 ，如下圖：
|
1
2
3
4
5
6
|
@springbootapplicationpublic class application { public static void main(string[] args) { springapplication.run(application.class, args); } } |
這里核心關注2個東西：
1.@springbootapplication注解
2. springapplication.run()靜態方法
下面我們就分別探究這兩塊內容。
2.1 @springbootapplication注解
源碼如下：
|
1
2
3
4
5
6
7
8
9
10
|
@target(elementtype.type)@retention(retentionpolicy.runtime)@documented@inherited@springbootconfiguration@enableautoconfiguration@componentscan(excludefilters = {@filter(type = filtertype.custom, classes = typeexcludefilter.class),@filter(type = filtertype.custom, classes = autoconfigurationexcludefilter.class) })public @interface springbootapplication { |
核心注解：
@springbootconfiguration（實際就是個@configuration）：表示這是一個javaconfig配置類，可以在這個類中自定義bean,依賴關系等。-》這個是spring-boot特有的注解，常用到。
@enableautoconfiguration：借助@import的幫助，將所有符合自動配置條件的bean定義加載到ioc容器（建議放在根包路徑下，這樣可以掃描子包和類）。-》這個需要詳細深挖！
@componentscan：spring的自動掃描注解，可定義掃描范圍，加載到ioc容器。-》這個不多說，spring的注解大家肯定眼熟
其中@enableautoconfiguration這個注解的源碼：
|
1
2
3
4
5
6
7
8
|
@suppresswarnings("deprecation")@target(elementtype.type)@retention(retentionpolicy.runtime)@documented@inherited@autoconfigurationpackage@import(enableautoconfigurationimportselector.class)public @interface enableautoconfiguration { |
核心是一個enableautoconfigurationimportselector類圖如下：
核心方法在頂級接口 importselector 的 selectimports（） ，源碼如下：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
|
@overridepublic string[] selectimports(annotationmetadata annotationmetadata) {if (!isenabled(annotationmetadata)) {return no_imports;}try { //1.從meta-inf/spring-autoconfigure-metadata.properties文件中載入483條配置屬性（有一些有默認值），autoconfigurationmetadata autoconfigurationmetadata = autoconfigurationmetadataloader .loadmetadata(this.beanclassloader);annotationattributes attributes = getattributes(annotationmetadata);//2.獲取注解屬性list<string> configurations = getcandidateconfigurations(annotationmetadata,//3.獲取97個自動配置類 attributes);configurations = removeduplicates(configurations);//4.移除重復的configurations = sort(configurations, autoconfigurationmetadata);//5.排序set<string> exclusions = getexclusions(annotationmetadata, attributes);//6.獲取需要排除的checkexcludedclasses(configurations, exclusions);//7.校驗排除類configurations.removeall(exclusions);//8.刪除所有需要排除的configurations = filter(configurations, autoconfigurationmetadata);//9.過濾器onclasscondition（注解中配置的當存在某類才生效）fireautoconfigurationimportevents(configurations, exclusions);//10.觸發自動配置導入監聽事件return configurations.toarray(new string[configurations.size()]);}catch (ioexception ex) {throw new illegalstateexception(ex);}} |
這里注意3個核心方法：
1） loadmetadata 加載配置
其實就是用類加載器去加載： meta-inf/spring-autoconfigure-metadata.properties （spring-boot-autoconfigure-1.5.9.release-sources.jar） 文件中定義的配置，返回propertiesautoconfigurationmetadata（實現了autoconfigurationmetadata接口，封裝了屬性的get set方法）
2） getcandidateconfigurations 獲取默認支持的自動配置類名列表
自動配置靈魂方法， springfactoriesloader.loadfactorynames 從 meta-inf/spring.factories （spring-boot-autoconfigure-1.5.9.release-sources.jar）文件中獲取自動配置類key=enableautoconfiguration.class的配置。
|
1
2
3
4
5
6
7
8
9
10
11
12
13
|
protected list<string> getcandidateconfigurations(annotationmetadata metadata, annotationattributes attributes) {//話說這里2個入參沒啥用啊...誰來給我解釋一下... list<string> configurations = springfactoriesloader.loadfactorynames( getspringfactoriesloaderfactoryclass(), getbeanclassloader()); assert.notempty(configurations, "no auto configuration classes found in meta-inf/spring.factories. if you " + "are using a custom packaging, make sure that file is correct."); return configurations; } //返回的是enableautoconfiguration類 protected class<?> getspringfactoriesloaderfactoryclass() { return enableautoconfiguration.class; } |
實際獲取了什么？ spring.factories 文件如下，實際獲取了 # auto configure 自動配置模塊的所有類。
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
# initializersorg.springframework.context.applicationcontextinitializer=\org.springframework.boot.autoconfigure.sharedmetadatareaderfactorycontextinitializer,\org.springframework.boot.autoconfigure.logging.autoconfigurationreportlogginginitializer# application listenersorg.springframework.context.applicationlistener=\org.springframework.boot.autoconfigure.backgroundpreinitializer# auto configuration import listenersorg.springframework.boot.autoconfigure.autoconfigurationimportlistener=\org.springframework.boot.autoconfigure.condition.conditionevaluationreportautoconfigurationimportlistener# auto configuration import filtersorg.springframework.boot.autoconfigure.autoconfigurationimportfilter=\org.springframework.boot.autoconfigure.condition.onclasscondition# auto configure 這里就是全部的自動配置類org.springframework.boot.autoconfigure.enableautoconfiguration=\org.springframework.boot.autoconfigure.admin.springapplicationadminjmxautoconfiguration,\org.springframework.boot.autoconfigure.aop.aopautoconfiguration,\org.springframework.boot.autoconfigure.amqp.rabbitautoconfiguration,\org.springframework.boot.autoconfigure.batch.batchautoconfiguration,\org.springframework.boot.autoconfigure.cache.cacheautoconfiguration,\org.springframework.boot.autoconfigure.cassandra.cassandraautoconfiguration,\org.springframework.boot.autoconfigure.cloud.cloudautoconfiguration,\org.springframework.boot.autoconfigure.context.configurationpropertiesautoconfiguration,\org.springframework.boot.autoconfigure.context.messagesourceautoconfiguration,\org.springframework.boot.autoconfigure.context.propertyplaceholderautoconfiguration,\org.springframework.boot.autoconfigure.couchbase.couchbaseautoconfiguration,\org.springframework.boot.autoconfigure.dao.persistenceexceptiontranslationautoconfiguration,\org.springframework.boot.autoconfigure.data.cassandra.cassandradataautoconfiguration,\org.springframework.boot.autoconfigure.data.cassandra.cassandrarepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.couchbase.couchbasedataautoconfiguration,\org.springframework.boot.autoconfigure.data.couchbase.couchbaserepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.elasticsearchautoconfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.elasticsearchdataautoconfiguration,\org.springframework.boot.autoconfigure.data.elasticsearch.elasticsearchrepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.jpa.jparepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.ldap.ldapdataautoconfiguration,\org.springframework.boot.autoconfigure.data.ldap.ldaprepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.mongo.mongodataautoconfiguration,\org.springframework.boot.autoconfigure.data.mongo.mongorepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.neo4j.neo4jdataautoconfiguration,\org.springframework.boot.autoconfigure.data.neo4j.neo4jrepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.solr.solrrepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.redis.redisautoconfiguration,\org.springframework.boot.autoconfigure.data.redis.redisrepositoriesautoconfiguration,\org.springframework.boot.autoconfigure.data.rest.repositoryrestmvcautoconfiguration,\org.springframework.boot.autoconfigure.data.web.springdatawebautoconfiguration,\org.springframework.boot.autoconfigure.elasticsearch.jest.jestautoconfiguration,\org.springframework.boot.autoconfigure.freemarker.freemarkerautoconfiguration,\org.springframework.boot.autoconfigure.gson.gsonautoconfiguration,\org.springframework.boot.autoconfigure.h2.h2consoleautoconfiguration,\org.springframework.boot.autoconfigure.hateoas.hypermediaautoconfiguration,\org.springframework.boot.autoconfigure.hazelcast.hazelcastautoconfiguration,\org.springframework.boot.autoconfigure.hazelcast.hazelcastjpadependencyautoconfiguration,\org.springframework.boot.autoconfigure.info.projectinfoautoconfiguration,\org.springframework.boot.autoconfigure.integration.integrationautoconfiguration,\org.springframework.boot.autoconfigure.jackson.jacksonautoconfiguration,\org.springframework.boot.autoconfigure.jdbc.datasourceautoconfiguration,\org.springframework.boot.autoconfigure.jdbc.jdbctemplateautoconfiguration,\org.springframework.boot.autoconfigure.jdbc.jndidatasourceautoconfiguration,\org.springframework.boot.autoconfigure.jdbc.xadatasourceautoconfiguration,\org.springframework.boot.autoconfigure.jdbc.datasourcetransactionmanagerautoconfiguration,\org.springframework.boot.autoconfigure.jms.jmsautoconfiguration,\org.springframework.boot.autoconfigure.jmx.jmxautoconfiguration,\org.springframework.boot.autoconfigure.jms.jndiconnectionfactoryautoconfiguration,\org.springframework.boot.autoconfigure.jms.activemq.activemqautoconfiguration,\org.springframework.boot.autoconfigure.jms.artemis.artemisautoconfiguration,\org.springframework.boot.autoconfigure.flyway.flywayautoconfiguration,\org.springframework.boot.autoconfigure.groovy.template.groovytemplateautoconfiguration,\org.springframework.boot.autoconfigure.jersey.jerseyautoconfiguration,\org.springframework.boot.autoconfigure.jooq.jooqautoconfiguration,\org.springframework.boot.autoconfigure.kafka.kafkaautoconfiguration,\org.springframework.boot.autoconfigure.ldap.embedded.embeddedldapautoconfiguration,\org.springframework.boot.autoconfigure.ldap.ldapautoconfiguration,\org.springframework.boot.autoconfigure.liquibase.liquibaseautoconfiguration,\org.springframework.boot.autoconfigure.mail.mailsenderautoconfiguration,\org.springframework.boot.autoconfigure.mail.mailsendervalidatorautoconfiguration,\org.springframework.boot.autoconfigure.mobile.deviceresolverautoconfiguration,\org.springframework.boot.autoconfigure.mobile.devicedelegatingviewresolverautoconfiguration,\org.springframework.boot.autoconfigure.mobile.sitepreferenceautoconfiguration,\org.springframework.boot.autoconfigure.mongo.embedded.embeddedmongoautoconfiguration,\org.springframework.boot.autoconfigure.mongo.mongoautoconfiguration,\org.springframework.boot.autoconfigure.mustache.mustacheautoconfiguration,\org.springframework.boot.autoconfigure.orm.jpa.hibernatejpaautoconfiguration,\org.springframework.boot.autoconfigure.reactor.reactorautoconfiguration,\org.springframework.boot.autoconfigure.security.securityautoconfiguration,\org.springframework.boot.autoconfigure.security.securityfilterautoconfiguration,\org.springframework.boot.autoconfigure.security.fallbackwebsecurityautoconfiguration,\org.springframework.boot.autoconfigure.security.oauth2.oauth2autoconfiguration,\org.springframework.boot.autoconfigure.sendgrid.sendgridautoconfiguration,\org.springframework.boot.autoconfigure.session.sessionautoconfiguration,\org.springframework.boot.autoconfigure.social.socialwebautoconfiguration,\org.springframework.boot.autoconfigure.social.facebookautoconfiguration,\org.springframework.boot.autoconfigure.social.linkedinautoconfiguration,\org.springframework.boot.autoconfigure.social.twitterautoconfiguration,\org.springframework.boot.autoconfigure.solr.solrautoconfiguration,\org.springframework.boot.autoconfigure.thymeleaf.thymeleafautoconfiguration,\org.springframework.boot.autoconfigure.transaction.transactionautoconfiguration,\org.springframework.boot.autoconfigure.transaction.jta.jtaautoconfiguration,\org.springframework.boot.autoconfigure.validation.validationautoconfiguration,\org.springframework.boot.autoconfigure.web.dispatcherservletautoconfiguration,\org.springframework.boot.autoconfigure.web.embeddedservletcontainerautoconfiguration,\org.springframework.boot.autoconfigure.web.errormvcautoconfiguration,\org.springframework.boot.autoconfigure.web.httpencodingautoconfiguration,\org.springframework.boot.autoconfigure.web.httpmessageconvertersautoconfiguration,\org.springframework.boot.autoconfigure.web.multipartautoconfiguration,\org.springframework.boot.autoconfigure.web.serverpropertiesautoconfiguration,\org.springframework.boot.autoconfigure.web.webclientautoconfiguration,\org.springframework.boot.autoconfigure.web.webmvcautoconfiguration,\org.springframework.boot.autoconfigure.websocket.websocketautoconfiguration,\org.springframework.boot.autoconfigure.websocket.websocketmessagingautoconfiguration,\org.springframework.boot.autoconfigure.webservices.webservicesautoconfiguration# failure analyzersorg.springframework.boot.diagnostics.failureanalyzer=\org.springframework.boot.autoconfigure.diagnostics.analyzer.nosuchbeandefinitionfailureanalyzer,\org.springframework.boot.autoconfigure.jdbc.datasourcebeancreationfailureanalyzer,\org.springframework.boot.autoconfigure.jdbc.hikaridriverconfigurationfailureanalyzer# template availability providersorg.springframework.boot.autoconfigure.template.templateavailabilityprovider=\org.springframework.boot.autoconfigure.freemarker.freemarkertemplateavailabilityprovider,\org.springframework.boot.autoconfigure.mustache.mustachetemplateavailabilityprovider,\org.springframework.boot.autoconfigure.groovy.template.groovytemplateavailabilityprovider,\org.springframework.boot.autoconfigure.thymeleaf.thymeleaftemplateavailabilityprovider,\org.springframework.boot.autoconfigure.web.jsptemplateavailabilityprovider |
3）filter過濾器 根據 onclasscondition 注解把不滿足條件的過濾掉
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
|
private list<string> filter(list<string> configurations,autoconfigurationmetadata autoconfigurationmetadata) {long starttime = system.nanotime();string[] candidates = configurations.toarray(new string[configurations.size()]);boolean[] skip = new boolean[candidates.length];boolean skipped = false;//獲取需要過濾的自動配置導入攔截器，spring.factories配置中就一個：org.springframework.boot.autoconfigure.condition.onclassconditionfor (autoconfigurationimportfilter filter : getautoconfigurationimportfilters()) {invokeawaremethods(filter);boolean[] match = filter.match(candidates, autoconfigurationmetadata);for (int i = 0; i < match.length; i++) { if (!match[i]) { skip[i] = true; skipped = true; }}}if (!skipped) {//多條件只要有一個不匹配->skipped = true，全部匹配-》skipped = false->直接返回return configurations;}list<string> result = new arraylist<string>(candidates.length);for (int i = 0; i < candidates.length; i++) {if (!skip[i]) {//匹配-》不跳過-》添加進result result.add(candidates[i]);}}if (logger.istraceenabled()) {int numberfiltered = configurations.size() - result.size();logger.trace("filtered " + numberfiltered + " auto configuration class in " + timeunit.nanoseconds.tomillis(system.nanotime() - starttime) + " ms");}return new arraylist<string>(result);} |
2.2 springapplication .run()靜態方法
springapplication.run
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
|
public configurableapplicationcontext run(string... args) {stopwatch stopwatch = new stopwatch();stopwatch.start();configurableapplicationcontext context = null;failureanalyzers analyzers = null;configureheadlessproperty();springapplicationrunlisteners listeners = getrunlisteners(args);//1.獲取監聽器listeners.starting();-->啟動！try {applicationarguments applicationarguments = new defaultapplicationarguments( args);configurableenvironment environment = prepareenvironment(listeners,//2.準備好環境，觸發applicationenvironmentpreparedevent事件 applicationarguments);banner printedbanner = printbanner(environment);//打印啟動提示字符，默認spring的字符圖context = createapplicationcontext();//實例化一個可配置應用上下文analyzers = new failureanalyzers(context);preparecontext(context, environment, listeners, applicationarguments,//3.準備上下文 printedbanner);refreshcontext(context);//4.刷新上下文afterrefresh(context, applicationarguments);//5.刷新上下文后listeners.finished(context, null);--關閉！stopwatch.stop();if (this.logstartupinfo) { new startupinfologger(this.mainapplicationclass) .logstarted(getapplicationlog(), stopwatch);}return context;}catch (throwable ex) {handlerunfailure(context, listeners, analyzers, ex);throw new illegalstateexception(ex);}} |
1. getrunlisteners 獲取監聽器（ springapplicationrunlisteners ）
實際是 springapplicationrunlistener 類
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
|
private springapplicationrunlisteners getrunlisteners(string[] args) {class<?>[] types = new class<?>[] { springapplication.class, string[].class };return new springapplicationrunlisteners(logger, getspringfactoriesinstances(springapplicationrunlistener.class, types, this, args));}private <t> collection<? extends t> getspringfactoriesinstances(class<t> type) {return getspringfactoriesinstances(type, new class<?>[] {});}private <t> collection<? extends t> getspringfactoriesinstances(class<t> type,class<?>[] parametertypes, object... args) {classloader classloader = thread.currentthread().getcontextclassloader();// 使用set確保的字符串的唯一性set<string> names = new linkedhashset<string>(springfactoriesloader.loadfactorynames(type, classloader));// 1.載入工廠名稱集合list<t> instances = createspringfactoriesinstances(type, parametertypes,// 2.創建工廠實例classloader, args, names);annotationawareordercomparator.sort(instances);// 排序return instances;} |
1.1 載入工廠名稱（loadfactorynames）
當前類的類加載器從 meta-inf/spring.factories 文件中獲取springapplicationrunlistener類的配置
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
|
public static list<string> loadfactorynames(class<?> factoryclass, classloader classloader) { string factoryclassname = factoryclass.getname(); try { enumeration<url> urls = (classloader != null ? classloader.getresources(factories_resource_location) : classloader.getsystemresources(factories_resource_location)); list<string> result = new arraylist<string>(); while (urls.hasmoreelements()) { url url = urls.nextelement(); properties properties = propertiesloaderutils.loadproperties(new urlresource(url)); string factoryclassnames = properties.getproperty(factoryclassname); result.addall(arrays.aslist(stringutils.commadelimitedlisttostringarray(factoryclassnames))); } return result; } catch (ioexception ex) { throw new illegalargumentexception("unable to load [" + factoryclass.getname() + "] factories from location [" + factories_resource_location + "]", ex); } } |
上圖，獲取到工廠類名后，下面來看看meta-inf/spring.factories中定義了啥：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
# propertysource loadersorg.springframework.boot.env.propertysourceloader=\org.springframework.boot.env.propertiespropertysourceloader,\org.springframework.boot.env.yamlpropertysourceloader# run listeners 這里呢，看這里！！！！org.springframework.boot.springapplicationrunlistener=\org.springframework.boot.context.event.eventpublishingrunlistener# application context initializersorg.springframework.context.applicationcontextinitializer=\org.springframework.boot.context.configurationwarningsapplicationcontextinitializer,\org.springframework.boot.context.contextidapplicationcontextinitializer,\org.springframework.boot.context.config.delegatingapplicationcontextinitializer,\org.springframework.boot.context.embedded.serverportinfoapplicationcontextinitializer# application listenersorg.springframework.context.applicationlistener=\org.springframework.boot.clearcachesapplicationlistener,\org.springframework.boot.builder.parentcontextcloserapplicationlistener,\org.springframework.boot.context.fileencodingapplicationlistener,\org.springframework.boot.context.config.ansioutputapplicationlistener,\org.springframework.boot.context.config.configfileapplicationlistener,\org.springframework.boot.context.config.delegatingapplicationlistener,\org.springframework.boot.liquibase.liquibaseservicelocatorapplicationlistener,\org.springframework.boot.logging.classpathloggingapplicationlistener,\org.springframework.boot.logging.loggingapplicationlistener# environment post processorsorg.springframework.boot.env.environmentpostprocessor=\org.springframework.boot.cloud.cloudfoundryvcapenvironmentpostprocessor,\org.springframework.boot.env.springapplicationjsonenvironmentpostprocessor# failure analyzersorg.springframework.boot.diagnostics.failureanalyzer=\org.springframework.boot.diagnostics.analyzer.beancurrentlyincreationfailureanalyzer,\org.springframework.boot.diagnostics.analyzer.beannotofrequiredtypefailureanalyzer,\org.springframework.boot.diagnostics.analyzer.bindfailureanalyzer,\org.springframework.boot.diagnostics.analyzer.connectorstartfailureanalyzer,\org.springframework.boot.diagnostics.analyzer.nouniquebeandefinitionfailureanalyzer,\org.springframework.boot.diagnostics.analyzer.portinusefailureanalyzer,\org.springframework.boot.diagnostics.analyzer.validationexceptionfailureanalyzer# failureanalysisreportersorg.springframework.boot.diagnostics.failureanalysisreporter=\org.springframework.boot.diagnostics.loggingfailureanalysisreporter |
哇，都是些類全名稱，且key都是接口，value都是實現類。我們根據key=“ org.springframework.boot.springapplicationrunlistener ”查詢得到實現類value=" org.springframework.boot.context.event.eventpublishingrunlistener" 事件發布啟動監聽器 ， 一猜也知道肯定要用” 反射 ”根據類名獲取類實例，下面很快得到驗證...
1.2 創建spring工廠實例（createspringfactoriesinstances）
根據第一步得到的set<string> names（springapplicationrunlistener的唯一實現類 eventpublishingrunlistener ）生成" 事件發布啟動監聽器 " 工廠實例
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
|
@suppresswarnings("unchecked")private <t> list<t> createspringfactoriesinstances(class<t> type,class<?>[] parametertypes, classloader classloader, object[] args,set<string> names) {list<t> instances = new arraylist<t>(names.size());for (string name : names) {try { class<?> instanceclass = classutils.forname(name, classloader);// 利用反射獲取類 assert.isassignable(type, instanceclass); constructor<?> constructor = instanceclass .getdeclaredconstructor(parametertypes);// 得到構造器 t instance = (t) beanutils.instantiateclass(constructor, args);// 根據構造器和參數構造實例 instances.add(instance);}catch (throwable ex) { throw new illegalargumentexception( "cannot instantiate " + type + " : " + name, ex);}}return instances;} |
準備上下文
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
|
private void preparecontext(configurableapplicationcontext context,configurableenvironment environment, springapplicationrunlisteners listeners,applicationarguments applicationarguments, banner printedbanner) {context.setenvironment(environment);postprocessapplicationcontext(context);//單例一個beannamegenerator，把resourceloader設置進應用上下文applyinitializers(context);//執行初始化器listeners.contextprepared(context);// 監聽器執行上下文"已準備好"方法if (this.logstartupinfo) {logstartupinfo(context.getparent() == null);logstartupprofileinfo(context);} // 添加spring boot特殊單例beancontext.getbeanfactory().registersingleton("springapplicationarguments", applicationarguments);if (printedbanner != null) {context.getbeanfactory().registersingleton("springbootbanner", printedbanner);}// 載入資源set<object> sources = getsources();assert.notempty(sources, "sources must not be empty");load(context, sources.toarray(new object[sources.size()]));listeners.contextloaded(context);// 監聽器執行"上下文已加載"方法} |
刷新上下文
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
|
private void refreshcontext(configurableapplicationcontext context) {refresh(context);//核心類if (this.registershutdownhook) {try {context.registershutdownhook();//注冊關閉鉤子，容器關閉時執行}catch (accesscontrolexception ex) {// not allowed in some environments.}}}protected void refresh(applicationcontext applicationcontext) {assert.isinstanceof(abstractapplicationcontext.class, applicationcontext);((abstractapplicationcontext) applicationcontext).refresh();} |
最終執行的是abstractapplicationcontext抽象類的 refresh 方法。
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
|
public void refresh() throws beansexception, illegalstateexception {synchronized (this.startupshutdownmonitor) {//準備刷新的上下文環境，例如對系統屬性或者環境變量進行準備及驗證。preparerefresh();//啟動子類的refreshbeanfactory方法.解析xmlconfigurablelistablebeanfactory beanfactory = obtainfreshbeanfactory();//為beanfactory配置容器特性，例如類加載器、事件處理器等.preparebeanfactory(beanfactory);try { //設置beanfactory的后置處理. 空方法，留給子類拓展用。 postprocessbeanfactory(beanfactory); //調用beanfactory的后處理器, 這些后處理器是在bean定義中向容器注冊的. invokebeanfactorypostprocessors(beanfactory); //注冊bean的后處理器, 在bean創建過程中調用. registerbeanpostprocessors(beanfactory); //初始化上下文中的消息源，即不同語言的消息體進行國際化處理 initmessagesource(); //初始化applicationeventmulticaster bean,應用事件廣播器 initapplicationeventmulticaster(); //初始化其它特殊的bean， 空方法，留給子類拓展用。 onrefresh(); //檢查并向容器注冊監聽器bean registerlisteners(); //實例化所有剩余的(non-lazy-init) 單例bean. finishbeanfactoryinitialization(beanfactory); //發布容器事件, 結束refresh過程. finishrefresh();}catch (beansexception ex) { if (logger.iswarnenabled()) { logger.warn("exception encountered during context initialization - " + "cancelling refresh attempt: " + ex); } //銷毀已經創建的單例bean, 以避免資源占用. destroybeans(); //取消refresh操作, 重置active標志. cancelrefresh(ex); // propagate exception to caller. throw ex;}finally { //重置spring的核心緩存 resetcommoncaches();}}} |
刷新完上下文后
spring boot提供的2個供用戶自己拓展的接口： applicationrunner和 commandlinerunner。可以在容器啟動完畢后（上下文刷新后）執行，做一些類似數據初始化的操作。
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
|
private void callrunners(applicationcontext context, applicationarguments args) {list<object> runners = new arraylist<object>();runners.addall(context.getbeansoftype(applicationrunner.class).values());//從上下文中獲取applicationrunner類型的beanrunners.addall(context.getbeansoftype(commandlinerunner.class).values());//從上下文中獲取commandlinerunner類型的beanannotationawareordercomparator.sort(runners);//排序for (object runner : new linkedhashset<object>(runners)) {if (runner instanceof applicationrunner) { callrunner((applicationrunner) runner, args);//執行}if (runner instanceof commandlinerunner) { callrunner((commandlinerunner) runner, args);}}} |
兩個區別在于入參不同，根據實際情況自己選擇。
|
1
2
3
4
5
6
|
public interface commandlinerunner {void run(string... args) throws exception;}public interface applicationrunner {void run(applicationarguments args) throws exception;} |
commandlinerunner中執行參數是原始的 java啟動類main方法的string[] args字符串數組參數； applicationrunner中的參數經過處理提供一些方法例如:
|
1
|
list<string> getoptionvalues(string name); |
根據名稱獲取值list,java 啟動命令中 --foo=bar --foo=baz，則根據foo參數名返回list ["bar", "baz"]
三、總結
按照前面的分析，spring-boot容器啟動流程總體可劃分為2部分：
1） 執行注解 ：掃描指定范圍下的bean、載入自動配置類對應的bean加載到ioc容器。
2）man方法中具體springappliocation.run() ，全流程貫穿springapplicationevent,有6個子類：
|
1
2
3
4
5
6
|
applicationfailedevent.classapplicationpreparedevent.classapplicationreadyevent.classapplicationstartedevent.classapplicationstartingevent.classspringapplicationevent.class |
這里用到了很經典的 spring事件驅動模型 ，飛機票： spring事件驅動模型和觀察者模式
類圖如下：
如上圖，就是一個經典spring 事件驅動模型，包含3種角色：事件發布者、事件、監聽者。對應到spring-boot中就是：
1 .eventpublishingrunlistener 這個類封裝了 事件發布 ，
2. springapplicationevent 是spring-boot中定義的事件（上面說的6種事件），繼承自 applicationevent （spring中定義的）
3. 監聽者 spring-boot并沒有實現針對上述6種事件的監聽者（我沒找到...）， 這里用戶可以自己實現監聽者（上述6種事件）來注入spring boot容器啟動流程，觸發相應的事件。
例如：實現applicationlistener<applicationreadyevent>這個接口，在容器啟動完畢時最后一步listener.finished時，如果啟動沒有異常，就會執行！可以做一些數據初始化之類的操作。
總結
以上所述是小編給大家介紹的spring boot容器啟動的相關知識，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復大家的。在此也非常感謝大家對服務器之家網站的支持！
原文鏈接：http://www.cnblogs.com/dennyzhangdd/p/8028950.html
