spring-boot.md

spring boot 简介

SpringBoot是由Pivotal团队在2013年开始研发, 2014年4月发布第一个版本的全新开源的轻量级框架。它基于Spring4.0设计，不仅继承了Spring框架原有的优秀特性，而且还通过简化配置来进一步简化了Spring应用的整个搭建和开发过程。另外SpringBoot通过集成大量的框架使得依赖包的版本冲突，以及引用的不稳定性等问题得到了很好的解决。

依赖

Java 8+
Spring Framework 5.2.10.RELEASE+
Maven 3.3+

• Servlet 容器

名称	Servlet版本
Tomcat 9.0	4.0
Jetty 9.4	3.1
Undertow 2.0	4.0

简单使用

1. 创建maven工程

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.3.5.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
            <version>2.3.5.RELEASE</version>
        </dependency>
    </dependencies>

2. 创建Main.java, TestController.java以及application.properties

├───src
│   ├───main
│   │   ├───java
│   │   │   └───com
│   │   │       └───demo
│   │   │           │───rest
│   │   │           │   └───TestController.java
│   │   │           └───Main.java
│   │   └───resources
│           └───application.properties

3. Main.java

@SpringBootApplication
public class Main {
	public static void main(String[] args) {
		SpringApplication.run(Main.class, args);
	}
}

4. TestController.java

@RestController
public class TestController {
	
	@RequestMapping(value = "/test", method = GET, produces = APPLICATION_JSON_VALUE)
	public Map<String, String> test() {
		Map<String, String> map = new HashMap<>();
		map.put("response", "hello world");
		return map;
	}
}

5. 运行Main.java

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.4.RELEASE)

2020-11-05 16:10:15.349  INFO 17492 --- [           main] com.demo.Main                            : Starting Main on MI04-chenby with PID 17492 (C:\workspace\spring-boot-demo\target\classes started by chenby in C:\workspace\spring-boot-demo)
2020-11-05 16:10:15.351  INFO 17492 --- [           main] com.demo.Main                            : No active profile set, falling back to default profiles: default
2020-11-05 16:10:16.100  INFO 17492 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-11-05 16:10:16.107  INFO 17492 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-11-05 16:10:16.107  INFO 17492 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.38]
2020-11-05 16:10:16.166  INFO 17492 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-11-05 16:10:16.167  INFO 17492 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 760 ms
2020-11-05 16:10:16.289  INFO 17492 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-11-05 16:10:16.413  INFO 17492 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-11-05 16:10:16.421  INFO 17492 --- [           main] com.demo.Main                            : Started Main in 1.352 seconds (JVM running for 2.098)
2020-11-05 16:10:21.791  INFO 17492 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'
2020-11-05 16:10:21.792  INFO 17492 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
2020-11-05 16:10:21.795  INFO 17492 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 3 ms

6. 浏览器打开http://localhost:8080/test

{"response":"hello world"}

自动配置

1. @SpringBootApplication注解

1. @SpringBootConfiguration
2. @EnableAutoConfiguration
3. @ComponentScan

2. @EnableAutoConfiguration

├───src
│   ├───main
│   │   ├───java
│   │   └───resources
│           └───META-INF
│               └───spring.factories

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.package.MyAutoConfiguration,\
                                                               ....,\

3. MyAutoConfiguration 和 MyBean

@Configuration(proxyBeanMethods = false)
public class MyAutoConfiguration {
	@Bean
	public MyBean myBean() {
		return new MyBean();
	}
}

public class MyBean {
	public String hello() {
		return "hello world";
	}
}

debug自动配置

java -cp $CLASSPATH Main --debug

禁用自动配置

@SpringBootApplication(exclude={DataSourceAutoConfiguration.class})

优雅关闭

public class Main {
	private static final Logger LOGGER = LoggerFactory.getLogger(Main.class);
	
	@PreDestroy
	public void shutdown() {
		LOGGER.info("shutdown");
	}
	
	public static void main(String[] args) {
		SpringApplicationBuilder builder = new SpringApplicationBuilder();
		builder.sources(Main.class).registerShutdownHook(true).run(args);
	}
}

application.properties

1. 常用配置

common-application-properties

2. -Dspring.config.location=$location

file:./config/
file:./config/*/
file:./
classpath:/config/
classpath:/

3. -Dspring.profiles.active=$profile

application-$profile.properties

4. -Dspring.config.name=$name

$name.properties

类型安全的Configuration properties

@ConfigurationProperties("spring.my")
public class MyProperties {

    private boolean enabled;

    private InetAddress remoteAddress;

    public boolean isEnabled() { ... }

    public void setEnabled(boolean enabled) { ... }

    public InetAddress getRemoteAddress() { ... }

    public void setRemoteAddress(InetAddress remoteAddress) { ... }
}

@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(MyProperties.class)
public class MyConfiguration {
    @Bean
    public MyBean myBean(MyProperties properties) {
        return new MyBean(properties.isEnabled());
    }
}

#application.properties
spring.my.remote-address=127.0.0.1
spring.my.enabled=true

spring boot 条件注解

@ConditionalOnBean
@ConditionalOnClass
@ConditionalOnExpression
@ConditionalOnJava
@ConditionalOnMissingBean
@ConditionalOnMissingClass
@ConditionalOnNotWebApplication
@ConditionalOnProperty
@ConditionalOnResource
@ConditionalOnWebApplication
@ConditionalOnSingleCandidate

自建starter的几个要素

1. @Configuration 与条件注释 @Conditional**
2. 自动配置 /META-INF/spring.factories
3. 类型安全的configuration properties

非web的spring项目改造成spring-boot

@SpringBootConfiguration
@ImportResource({"classpath:your-spring-file.xml"})
public class Main {
	public static void main(String[] args) {
		SpringApplicationBuilder builder = new SpringApplicationBuilder();
		builder.sources(Main.class).registerShutdownHook(true).web(WebApplicationType.NONE).run(args);
	}
}

既有的spring mvc项目升级到spring-boot

@SpringBootConfiguration
@ImportResource({"classpath:your-spring-webmvc-file.xml"})
public class Main {
	public static void main(String[] args) {
		SpringApplicationBuilder builder = new SpringApplicationBuilder();
		builder.sources(Main.class).registerShutdownHook(true).web(WebApplicationType.SERVLET).run(args);
	}
}

Noldor项目升级过程

References

• SpringBoot 揭秘 快速构建微服务体系
• spring boot reference
• configure jetty server
• spring app migration from xml to java based config