第一个 Spring Boot 程序


#Spring Boot#


我们可以在 https://start.spring.io/ 创建项目:

# 示例 ## 项目结构 本文的项目是用它生成的,最终项目结构:
.
├── build.gradle
├── settings.gradle
└── src
    └── main
        ├── java
        │   └── demo
        │       ├── BusinessService.java
        │       ├── DemoApplication.java
        │       ├── SayHello.java
        │       └── SayHelloIml.java
        └── resources
            └── application.properties

配置文件applacation.properties 内容为空,这里可以先不关心。

build.gradle

build.gradle内容:

buildscript {
	ext {
		springBootVersion = '2.1.3.RELEASE'
	}
	repositories {
		mavenCentral()
	}
	dependencies {
		classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
	}
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'

group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = 1.8

repositories {
	maven { url 'http://mirrors.cloud.tencent.com/nexus/repository/maven-public/' }
	mavenCentral()
}

dependencies {
	compile('org.springframework.boot:spring-boot-starter')
	testCompile('org.springframework.boot:spring-boot-starter-test')
}

SayHello.java

接口 SayHello 代码:

package demo;

public interface SayHello {

    String sayHello(String name);

}

SayHelloIml.java

接口实现类 SayHelloIml 代码:

package demo;

import org.springframework.stereotype.Component;

@Component
public class SayHelloIml implements SayHello {

    @Override
    public String sayHello(String name) {
        return "Hello, " + name;
    }

}

BusinessService.java

BusinessService 类:

package demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;

@Service
public class BusinessService {

    @Autowired
    private SayHello sayHello;

    public BusinessService(){
        System.out.println("construct");
    }

    @PostConstruct
    public void postConstruct(){
        System.out.println("postConstruct");
        System.out.println(sayHello.sayHello("world"));
    }


}

@PostConstruct注解修饰的方法,会在执行构造函数后被执行。

DemoApplication.java

主程序入口 DemoApplication :

package demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

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

}

执行结果

在 IDE 中运行 DemoApplication ,输出:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.0.2.RELEASE)

2018-07-17 09:19:13.329  INFO 68004 --- [           main] demo.DemoApplication                     : Starting DemoApplication on Myhost with PID 68004 
2018-07-17 09:19:13.334  INFO 68004 --- [           main] demo.DemoApplication                     : No active profile set, falling back to default profiles: default
2018-07-17 09:19:13.409  INFO 68004 --- [           main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@3f200884: startup date [Tue Jul 17 09:19:13 CST 2018]; root of context hierarchy
construct
postConstruct
Hello, world
2018-07-17 09:19:14.045  INFO 68004 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2018-07-17 09:19:14.059  INFO 68004 --- [           main] demo.DemoApplication                     : Started DemoApplication in 1.172 seconds (JVM running for 1.718)
2018-07-17 09:19:14.062  INFO 68004 --- [       Thread-2] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@3f200884: startup date [Tue Jul 17 09:19:13 CST 2018]; root of context hierarchy
2018-07-17 09:19:14.063  INFO 68004 --- [       Thread-2] o.s.j.e.a.AnnotationMBeanExporter        : Unregistering JMX-exposed beans on shutdown

注意中间的:

construct
postConstruct
Hello, world

也可以通过 gradle bootRun运行程序。


( 本文完 )