2、Spring Boot配置
阅读原文时间:2023年07月09日阅读:1

1.配置文件

SpringBoot使用一个全局的配置文件,配置文件名是固定的;

•application.properties

•application.yml

配置文件的作用:修改SpringBoot自动配置的默认值;SpringBoot在底层都给我们自动配置好;

YAML(YAML Ain't Markup Language):以数据为中心,比json、xml等更适合做配置文件;以前的配置文件;大多都使用的是xxxx.xml文件;

范例:YAML配置例子

server:

port: 8081

范例:XML配置

8081

2.YAML语法

语法: K: V:表示一对键值对(: v之间有个空格)

空格的缩进来控制层级关系;只要是左对齐的一列数据,都是同一个层级的

server:

port: 8081

path: /hello

属性和值也是大小写敏感;

(1).普通的值(数字,字符串,布尔)

​  k: v:字面直接来写;

字符串默认不用加上单引号或者双引号;

"":双引号;不会转义字符串里面的特殊字符;特殊字符会作为本身想表示的意思

name: "zhangsan \n lisi":输出;zhangsan 换行  lisi

'':单引号;会转义特殊字符,特殊字符最终只是一个普通的字符串数据

name: ‘zhangsan \n lisi’:输出;zhangsan \n  lisi

(2).对象、Map(属性和值)(键值对)

k: v:在下一行来写对象的属性和值的关系;注意缩进

对象还是k: v的方式

friends:

lastName: zhangsan

age: 20

行内写法:

friends: {lastName: zhangsan,age: 18}

(3).数组(List、Set)

用- 值表示数组中的一个元素

pets:

- cat

- dog

- pig

行内写法

pets: [cat,dog,pig]

application.yml

server:

port: 8081

person:

lastname: zhangsan

age: 18

boss: false

birth: 2020/1/1

maps: {k1: v1,k2: 12}

lists:

- lisi

- zhaoliu

- zhangsan

dog:

name: 狗狗

age: 2

javaBean:

/**

* 将配置文件中配置的每一个属性的值,映射到这个组件中

* @ConfigurationProperties: 告诉SpringBoot将本类中的所有属性和配置文件中相关的配置进行绑定 默认从全局配置文件中获取值

*      prefix="person":_配置文件中将下面的所有属性进行一一映射_

*/

@Component

@ConfigurationProperties(prefix = "person")

public class Person {

private String lastName;

private Integer age;

private Boolean boss;

private Date birth;

private Map maps;

private List lists;

private Dog dog;

可以导入配置文件处理器,以后编写配置就有提示

<dependency>

<groupId>org.springframework.bootgroupId>

<artifactId>spring-boot-configuration-processorartifactId>

<version>2.1.6.RELEASEversion>

<optional>trueoptional>

</dependency>

(1).properties配置文件在idea中默认utf-8可能会乱码

(2).@Value获取值和@ConfigurationProperties获取值比较

配置文件yml还是properties以上方式都能获取到值;

如何选择以上方式:

如果说,我们只是在某个业务逻辑中需要获取一下配置文件中的某项值,使用@Value;

如果说,我们专门编写了一个javaBean来和配置文件进行映射,我们就直接使用@ConfigurationProperties;

(3).配置文件注入值数据校验

@Component

@ConfigurationProperties(prefix = "person")

@Validated

public class Person {

/**

*

*      

*

*/

//lastName必须是邮箱格式

@Email

//@Value("${person.last-name}")

private String lastName;

//@Value("#{11*2}")

private Integer age;

//@Value("true")

private Boolean boss;

private Date birth;

private Map maps;

private List lists;

private Dog dog;

(4).@PropertySource&@ImportResource&@Bean

@PropertySource:加载指定的配置文件;

/**

* 将配置文件中配置的每一个属性的值,映射到这个组件中

* @ConfigurationProperties: 告诉SpringBoot将本类中的所有属性和配置文件中相关的配置进行绑定 默认从全局配置文件中获取值

*      prefix="person":_配置文件中将下面的所有属性进行一一映射_

*/

@PropertySource(value={"classpath:person.properties"})

@Component

@ConfigurationProperties(prefix = "person")

//@Validated

public class Person {

/**

*

* __

*

*/

//    @Value("${person.last-name}")

private String lastName;

//    @Value("#{11*2}")

private Integer age;

//    @Value("true")

private Boolean boss;

private Date birth;

private Map maps;

private List lists;

private Dog dog;

@ImportResource:导入Spring的配置文件,让配置文件里面的内容生效;

Spring Boot里面没有Spring的配置文件,我们自己编写的配置文件,也不能自动识别;

想让Spring的配置文件生效,加载进来;@ImportResource标注在一个配置类上

@ImportResource(locations = {"classpath:beans.xml"})

导入Spring的配置文件让其生效

不编写Spring的配置文件

xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

<bean id="helloService" class="com.pluto.springboot.service.HelloService">bean>

</beans>

SpringBoot推荐给容器中添加组件的方式;推荐使用全注解的方式

1)、配置类@Configuration------>Spring配置文件

2)、使用@Bean给容器中添加组件

/**

* @Configuration:指明当前类是一个配置类;就是来替代之前的Spring配置文件

*

* 在配置文件中用标签添加组件

*

*/

@Configuration

public class MyAppConfig {

//将方法的返回值添加到容器中;容器中这个组件默认的id就是方法名

@Bean

public HelloService helloService02(){

System.out.println("配置类@Bean给容器中添加组件了…");

return new HelloService();

}

}

# idea_配置文件默认为_utf-8

#����__Person��ֵ

person.last-name=张三${random.uuid}

person.age=${random.int}

person.birth=2020/1/1

person.boss=false

person.maps.k1=v1

person.maps.k2=14

person.lists=a,b,c

person.dog.name=${person.last-name}_dog

person.dog.age=15

在主配置文件编写的时候,文件名可以是   application-{profile}.properties/yml

默认使用application.properties的配置;

(1).在配置文件中指定开发环境

application.properties

server.port=8081

spring.profiles.active=dev

application-dev.properties

server.port=8083

(2).yml文档快

yml支持多文档块方式

server:

port: 8081

spring:

profiles:

active: prod

---

server:

port: 8083

spring:

profiles: dev

---

server:

port: 8088

spring:

profiles: prod

(3).激活指定profile

1).在配置文件中指定spring.profiles.active=dev

2).命令行

(1.Program arguments

(2.CMD

java -jar spring-boot-02-config-0.0.1-SNAPSHOT.jar --spring.profiles.active=dev;

(3.虚拟机参数

-Dspring.profiles.active=dev

springboot 启动会扫描以下位置的application.properties或者application.yml文件作为Spring boot的默认配置文件

–file:./config/

–file:./

–classpath:/config/

–classpath:/

优先级由高到底,高优先级的配置会覆盖低优先级的配置;

SpringBoot会从这四个位置全部加载主配置文件;它们成互补配置;

我们还可以通过spring.config.location来改变默认的配置文件位置

项目打包好以后,我们可以使用命令行参数的形式,启动项目的时候来指定配置文件的新位置;指定配置文件和默认加载的这些配置文件共同起作用形成互补配置;

通过packet生成jar包

D:\DevCode\spring-boot-02-config-02\target>java -jar spring-boot-02-config-02-0.0.1-SNAPSHOT.jar --spring.config.location=G:/application.properties

[7].外部配置加载顺序

https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#boot-features-external-config

SpringBoot也可以从以下位置加载配置; 优先级从高到低;高优先级的配置覆盖低优先级的配置,所有的配置会形成互补配置

(1).命令行

多个配置用空格分开; --配置项=值

java -jar spring-boot-02-config-02-0.0.1-SNAPSHOT.jar --server.port=8086  --server.context-path=/hello

(2)..来自java:comp/env的JNDI属性

(3),Java系统属性(System.getProperties())

(4).操作系统环境变量

(5).RandomValuePropertySource配置的random.*属性值

由jar包外向jar包内进行寻找

优先加载带profile

(6).jar包外部的application-{profile}.properties或application.yml(带spring.profile)配置文件

(7).jar包内部的application-{profile}.properties或application.yml(带spring.profile)配置文件

加载不带profile

(8).jar包外部的application.properties或application.yml(不带spring.profile)配置文件

(9).jar包内部的application.properties或application.yml(不带spring.profile)配置文件

(10).@Configuration注解类上的@PropertySource

(11).通过SpringApplication.setDefaultProperties指定的默认属性

所有支持的配置加载来源:参考官方文档

配置文件到底能写什么?怎么写?自动配置原理;

配置文件能够配置的属性参照

(1).自动配置原理

1).Spring启动的时候会自动加载主配置类,开启了自动配置功能@SpringBootApplication

2).@EnableAutoConfiguration 作用

利用AutoConfigurationImportSelector给容器中导入一些组件

查看selectImports()方法的内容

获取候选的配置

return StringUtils.toStringArray(autoConfigurationEntry.getConfigurations());

SpringFactoriesLoader.loadFactoryNames()

扫描所有jar包类路径下  META-INF/spring.factories

把扫描到的这些文件的内容包装成properties对象

从properties中获取到EnableAutoConfiguration.class类(类名)对应的值,然后把他们添加在容器中

将类路径下  META-INF/spring.factories 里面配置的所有EnableAutoConfiguration的值加入到了容器中;

# Auto Configure

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.context.ConfigurationPropertiesAutoConfiguration,\

org.springframework.boot.autoconfigure.context.LifecycleAutoConfiguration,\

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.CassandraReactiveDataAutoConfiguration,\

org.springframework.boot.autoconfigure.data.cassandra.CassandraReactiveRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.cassandra.CassandraRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.couchbase.CouchbaseDataAutoConfiguration,\

org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveDataAutoConfiguration,\

org.springframework.boot.autoconfigure.data.couchbase.CouchbaseReactiveRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.couchbase.CouchbaseRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchDataAutoConfiguration,\

org.springframework.boot.autoconfigure.data.elasticsearch.ElasticsearchRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.elasticsearch.ReactiveElasticsearchRestClientAutoConfiguration,\

org.springframework.boot.autoconfigure.data.jdbc.JdbcRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration,\

org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration,\

org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration,\

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.r2dbc.R2dbcDataAutoConfiguration,\

org.springframework.boot.autoconfigure.data.r2dbc.R2dbcRepositoriesAutoConfiguration,\

org.springframework.boot.autoconfigure.data.r2dbc.R2dbcTransactionManagerAutoConfiguration,\

org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration,\

org.springframework.boot.autoconfigure.data.redis.RedisReactiveAutoConfiguration,\

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.ElasticsearchRestClientAutoConfiguration,\

org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration,\

org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\

org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration,\

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.http.HttpMessageConvertersAutoConfiguration,\

org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration,\

org.springframework.boot.autoconfigure.influx.InfluxDbAutoConfiguration,\

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.jersey.JerseyAutoConfiguration,\

org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration,\

org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration,\

org.springframework.boot.autoconfigure.kafka.KafkaAutoConfiguration,\

org.springframework.boot.autoconfigure.availability.ApplicationAvailabilityAutoConfiguration,\

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.mongo.embedded.EmbeddedMongoAutoConfiguration,\

org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration,\

org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration,\

org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration,\

org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration,\

org.springframework.boot.autoconfigure.quartz.QuartzAutoConfiguration,\

org.springframework.boot.autoconfigure.r2dbc.R2dbcAutoConfiguration,\

org.springframework.boot.autoconfigure.rsocket.RSocketMessagingAutoConfiguration,\

org.springframework.boot.autoconfigure.rsocket.RSocketRequesterAutoConfiguration,\

org.springframework.boot.autoconfigure.rsocket.RSocketServerAutoConfiguration,\

org.springframework.boot.autoconfigure.rsocket.RSocketStrategiesAutoConfiguration,\

org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration,\

org.springframework.boot.autoconfigure.security.servlet.UserDetailsServiceAutoConfiguration,\

org.springframework.boot.autoconfigure.security.servlet.SecurityFilterAutoConfiguration,\

org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration,\

org.springframework.boot.autoconfigure.security.reactive.ReactiveUserDetailsServiceAutoConfiguration,\

org.springframework.boot.autoconfigure.security.rsocket.RSocketSecurityAutoConfiguration,\

org.springframework.boot.autoconfigure.security.saml2.Saml2RelyingPartyAutoConfiguration,\

org.springframework.boot.autoconfigure.sendgrid.SendGridAutoConfiguration,\

org.springframework.boot.autoconfigure.session.SessionAutoConfiguration,\

org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientAutoConfiguration,\

org.springframework.boot.autoconfigure.security.oauth2.client.reactive.ReactiveOAuth2ClientAutoConfiguration,\

org.springframework.boot.autoconfigure.security.oauth2.resource.servlet.OAuth2ResourceServerAutoConfiguration,\

org.springframework.boot.autoconfigure.security.oauth2.resource.reactive.ReactiveOAuth2ResourceServerAutoConfiguration,\

org.springframework.boot.autoconfigure.solr.SolrAutoConfiguration,\

org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration,\

org.springframework.boot.autoconfigure.task.TaskSchedulingAutoConfiguration,\

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.client.RestTemplateAutoConfiguration,\

org.springframework.boot.autoconfigure.web.embedded.EmbeddedWebServerFactoryCustomizerAutoConfiguration,\

org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration,\

org.springframework.boot.autoconfigure.web.reactive.ReactiveWebServerFactoryAutoConfiguration,\

org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration,\

org.springframework.boot.autoconfigure.web.reactive.error.ErrorWebFluxAutoConfiguration,\

org.springframework.boot.autoconfigure.web.reactive.function.client.ClientHttpConnectorAutoConfiguration,\

org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration,\

org.springframework.boot.autoconfigure.web.servlet.DispatcherServletAutoConfiguration,\

org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration,\

org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration,\

org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,\

org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,\

org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,\

org.springframework.boot.autoconfigure.websocket.reactive.WebSocketReactiveAutoConfiguration,\

org.springframework.boot.autoconfigure.websocket.servlet.WebSocketServletAutoConfiguration,\

org.springframework.boot.autoconfigure.websocket.servlet.WebSocketMessagingAutoConfiguration,\

org.springframework.boot.autoconfigure.webservices.WebServicesAutoConfiguration,\

org.springframework.boot.autoconfigure.webservices.client.WebServiceTemplateAutoConfiguration

每个这样的  xxxAutoConfiguration类都是容器中的一个组件,都加入到容器中;用他们来做自动配置;

3).每一个自动配置类进行自动配置功能

4).以HttpEncodingAutoConfiguration(Http编码自动配置)为例解释自动配置原理

@Configuration   //表示这是一个配置类,以前编写的配置文件一样,也可以给容器中添加组件

@EnableConfigurationProperties(HttpEncodingProperties.class)  //启动指定类的ConfigurationProperties功能;将配置文件中对应的值和HttpEncodingProperties绑定起来;并把HttpEncodingProperties加入到ioc容器中

@ConditionalOnWebApplication //Spring底层@Conditional注解(Spring注解版),根据不同的条件,如果满足指定的条件,整个配置类里面的配置就会生效;    判断当前应用是否是web应用,如果是,当前配置类生效

@ConditionalOnClass(CharacterEncodingFilter.class)  //判断当前项目有没有这个类CharacterEncodingFilter;SpringMVC中进行乱码解决的过滤器;

@ConditionalOnProperty(prefix = "spring.http.encoding", value = "enabled", matchIfMissing = true)  //判断配置文件中是否存在某个配置  spring.http.encoding.enabled;如果不存在,判断也是成立的

//即使我们配置文件中不配置pring.http.encoding.enabled=true,也是默认生效的;

public class HttpEncodingAutoConfiguration {

//他已经和SpringBoot的配置文件映射了

private final HttpEncodingProperties properties;

//只有一个有参构造器的情况下,参数的值就会从容器中拿

public HttpEncodingAutoConfiguration(HttpEncodingProperties properties) {

this.properties = properties;

}

@Bean   //给容器中添加一个组件,这个组件的某些值需要从properties中获取

@ConditionalOnMissingBean(CharacterEncodingFilter.class) //判断容器没有这个组件?

public CharacterEncodingFilter characterEncodingFilter() {

  CharacterEncodingFilter filter = new OrderedCharacterEncodingFilter();

  filter.setEncoding(this.properties.getCharset().name());

  filter.setForceRequestEncoding(this.properties.shouldForce(Type.REQUEST));

  filter.setForceResponseEncoding(this.properties.shouldForce(Type.RESPONSE));

  return filter;

}

根据当前不同的条件判断,决定这个配置类是否生效?

一但这个配置类生效;这个配置类就会给容器中添加各种组件;这些组件的属性是从对应的properties类中获取的,这些类里面的每一个属性又是和配置文件绑定的;

5).所有在配置文件中能配置的属性都是在xxxxProperties类中封装者‘;配置文件能配置什么就可以参照某个功能对应的这个属性类

@ConfigurationProperties(prefix = "spring.http.encoding")  //从配置文件中获取指定的值和bean的属性进行绑定

public class HttpEncodingProperties {

public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

springboot精髓:

1)、SpringBoot启动会加载大量的自动配置类

2)、我们看我们需要的功能有没有SpringBoot默认写好的自动配置类;

3)、我们再来看这个自动配置类中到底配置了哪些组件;(只要我们要用的组件有,我们就不需要再来配置了)

4)、给容器中自动配置类添加组件的时候,会从properties类中获取某些属性。我们就可以在配置文件中指定这些属性的值;

xxxxAutoConfigurartion:自动配置类;

给容器中添加组件

xxxxProperties:封装配置文件中相关属性;

(2).细节

1).@Conditional派生注解(Spring注解版原生的@Conditional作用)

作用:必须是@Conditional指定的条件成立,才给容器中添加组件,配置配里面的所有内容才生效;

@Conditional扩展注解

作用(判断是否满足当前指定条件)

@ConditionalOnJava

系统的java版本是否符合要求

@ConditionalOnBean

容器中存在指定Bean;

@ConditionalOnMissingBean

容器中不存在指定Bean;

@ConditionalOnExpression

满足SpEL表达式指定

@ConditionalOnClass

系统中有指定的类

@ConditionalOnMissingClass

系统中没有指定的类

@ConditionalOnSingleCandidate

容器中只有一个指定的Bean,或者这个Bean是首选Bean

@ConditionalOnProperty

系统中指定的属性是否有指定的值

@ConditionalOnResource

类路径下是否存在指定资源文件

@ConditionalOnWebApplication

当前是web环境

@ConditionalOnNotWebApplication

当前不是web环境

@ConditionalOnJndi

JNDI存在指定项

自动配置类必须在一定的条件下才能生效;

我们怎么知道哪些自动配置类生效;

我们可以通过启用  debug=true属性;来让控制台打印自动配置报告,这样我们就可以很方便的知道哪些自动配置类生效;

============================

CONDITIONS EVALUATION REPORT

============================

Positive matches: 启用的自动配置类

-----------------

AopAutoConfiguration matched:

- @ConditionalOnProperty (spring.aop.auto=true) matched (OnPropertyCondition)

AopAutoConfiguration.ClassProxyingConfiguration matched:

- @ConditionalOnMissingClass did not find unwanted class 'org.aspectj.weaver.Advice' (OnClassCondition)

- @ConditionalOnProperty (spring.aop.proxy-target-class=true) matched (OnPropertyCondition)

Negative matches:

没启用的自动配置类

-----------------

ActiveMQAutoConfiguration:

Did not match:

- @ConditionalOnClass did not find required class 'javax.jms.ConnectionFactory' (OnClassCondition)

参考文档:https://bitbucket.org/asomov/snakeyaml/wiki/Documentation#markdown-header-yaml-syntax