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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：
<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 * */@SpringBootApplicationpublic 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;@Componentpublic 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;@Configurationpublic 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(); }}
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