springBoot快速入门

给maven 的settings.xml配置文件的profiles标签添加

<profile>
    <id>jdk‐1.8</id>
    <activation>
        <activeByDefault>true</activeByDefault>
        <jdk>1.8</jdk>
    </activation>
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion>
    </properties>
</profile>

★ idea中是自动集成springBoot插件

★ eclipse 需要安装一个spring ide

新建一个空白项目

 

新建一个maven quick-start模块

pom文件内容：

导入spring boot相关的依赖与Maven插件

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring‐boot‐starter‐parent</artifactId>
  <version>2.2.2.RELEASE</version>
</parent>
<dependencies>
  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring‐boot‐starter‐web</artifactId>
  </dependency>
</dependencies>
<!‐‐ 这个插件，可以将应用打包成一个可执行的jar包；‐‐>
  <build>
      <plugins>
          <plugin>
              <groupId>org.springframework.boot</groupId>
              <artifactId>spring‐boot‐maven‐plugin</artifactId>
          </plugin>
      </plugins>
  </build>

启动代码

package com.demo.boot;

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

/**
 * SpringBoot启动类：
 * 1、使用@SpringBootApplication
 * 2、提供应用程序的入口执行
 *
 */
@SpringBootApplication
public class App {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

追根溯源，Spring4演示(不再需要写配置文件)

Pom

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

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.boot.spring</groupId>
  <artifactId>spring4-demo</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>spring4-demo</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>4.3.14.RELEASE</version>
    </dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.0.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.7.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.20.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-jar-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

User类

 

package com.boot.spring;

import org.springframework.stereotype.Component;

@Component
public class User {
}

 

APP类（注解方式）

package com.boot.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Hello world!
 *
 */
public class App {
    public static void main( String[] args ) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext("com.boot.spring");
        User user = context.getBean(User.class);
        System.out.println(user);
        context.close();
    }
}

使用@Configuration注解方式

 

package com.boot.spring;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class UseConfig {

    @Bean("user")
    public User createUser() {
        return new User();
    }
}

 

使用@Configuration注解方式后的app类

package com.boot.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * Hello world!
 *
 */
public class App {
    public static void main( String[] args ) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext("com.boot.spring");
        //@Component方式创建的对象，name默认为类名的首字母小写
        User user = context.getBean("user",User.class);
        //@Configuration方式创建的对象，name默认为注解了 @Bean的方法名createUser，可以自定义名称：@Bean("user")
        //spring-boot的创建方式就是基于此实现的
        User user1 = context.getBean("user",User.class);
        System.out.println(user+","+user1);
        //打印内容：com.boot.spring.User@5e57643e,com.boot.spring.User@5e57643e
        //单例实现方式：通过key-name值相同，对象相同的方式来实现
        UseConfig useConfig = context.getBean(UseConfig.class);
        System.out.println(useConfig);
        //打印内容：com.boot.spring.UseConfig$$EnhancerBySpringCGLIB$$84f0eb4d@5e955596
        context.close();
    }
}