[Java知识库]【尚硅谷springBoot】springBoot编写Helloworld

SpringBoot化简Spring应用开发的框架，对Spring技术栈的整合，约定大于配置，去繁从简。

优点：

●快速创建独立运行的Spring项目以及主流框架继承

●使用嵌入式的Servlet容器，应用无需打成WAR包

●starters自动依赖与版本控制

●大量的自动配置，简化开发，也可修改默认值

●无需配置XML，无代码生成，开箱即用

●准生成环境的运行时应用监控

●与云计算的天然集成

缺点：springBoot入门容易，精通难。

微服务：

一个应用是一组小型服务，可以通过HTTP的方式进行互通。

每一个功能元素最终都是一个可独立替换和可独立软件升级的软件单元。

编写Hello,world

?说明：依赖配置和Hello,wolrd代码可以参考SpringBoot官网

Spring | Spring Quickstart Guide

浏览器发送hello请求，服务器接受请求并处理，响应Hello,world字符串

1、创建一个MAVEN工程

2、导入SpringBoot相关依赖

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.0</version>
        <relativePath/>
        <!--  lookup parent from repository  -->
    </parent>

    <groupId>org.example</groupId>
    <artifactId>SpringBoot-HelloWorld</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

3、编写一个主程序，启动SpringBoot应用

package com.guigu;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
//标注一个主程序类，说明这是一个SpringBoot应用
@SpringBootApplication
public class HelloWorldMainApplication {
    public static void main(String[] args) {
        //启动Spring应用
        SpringApplication.run(HelloWorldMainApplication.class, args);
    }
}

4、编写Service，Controller

package com.guigu.controller;


import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class HelloController {
    @ResponseBody
    @RequestMapping("/hello")
    public String hello(){
            return "hello,world";
    }
}

运行

部署：

可以打成jar包后直接运行

?右击package，运行

?直接使用命令行运行jar包

仍然可以访问?

HelloWorld探究

pom文件：

父项目：用于版本控制

  <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.0</version>
        <relativePath/>
        <!--  lookup parent from repository  -->
    </parent>

他的父项目是
  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-dependencies</artifactId>
    <version>2.7.0</version>
  </parent>

进入spring-boot-dependecies可以看到有很多很多配置。

所以是由spring-boot-dependecies真正管理SpringBoot里面所有的依赖版本

spring-boot-dependecies又称为Springboot的版本仲裁中心。

所以以后导入依赖时不需要写版本；

<properties>
    <activemq.version>5.16.5</activemq.version>
    <antlr2.version>2.7.7</antlr2.version>
    <appengine-sdk.version>1.9.96</appengine-sdk.version>
    <artemis.version>2.19.1</artemis.version>
    <aspectj.version>1.9.7</aspectj.version>
    <assertj.version>3.22.0</assertj.version>
    <atomikos.version>4.0.6</atomikos.version>
    <awaitility.version>4.2.0</awaitility.version>
    <build-helper-maven-plugin.version>3.3.0</build-helper-maven-plugin.version>
    <byte-buddy.version>1.12.10</byte-buddy.version>
    <cache2k.version>2.6.1.Final</cache2k.version>
    <caffeine.version>2.9.3</caffeine.version>
    <cassandra-driver.version>4.14.1</cassandra-driver.version>
    <classmate.version>1.5.1</classmate.version>
    <commons-codec.version>1.15</commons-codec.version>
    <commons-dbcp2.version>2.9.0</commons-dbcp2.version>
    <commons-lang3.version>3.12.0</commons-lang3.version>
    <commons-pool.version>1.6</commons-pool.version>
    <commons-pool2.version>2.11.1</commons-pool2.version>
    <couchbase-client.version>3.3.0</couchbase-client.version>
    <db2-jdbc.version>11.5.7.0</db2-jdbc.version>
    <dependency-management-plugin.version>1.0.11.RELEASE</dependency-management-plugin.version>
    <derby.version>10.14.2.0</derby.version>
    <dropwizard-metrics.version>4.2.9</dropwizard-metrics.version>
    <ehcache.version>2.10.9.2</ehcache.version>
    <ehcache3.version>3.10.0</ehcache3.version>
    <elasticsearch.version>7.17.3</elasticsearch.version>
    <embedded-mongo.version>3.4.5</embedded-mongo.version>
    <flyway.version>8.5.11</flyway.version>
    <freemarker.version>2.3.31</freemarker.version>
    <git-commit-id-plugin.version>4.9.10</git-commit-id-plugin.version>
    <glassfish-el.version>3.0.4</glassfish-el.version>
    <glassfish-jaxb.version>2.3.6</glassfish-jaxb.version>
    <glassfish-jstl.version>1.2.6</glassfish-jstl.version>
    <graphql-java.version>18.1</graphql-java.version>
    <groovy.version>3.0.10</groovy.version>
    <gson.version>2.9.0</gson.version>
    <h2.version>2.1.212</h2.version>
    <hamcrest.version>2.2</hamcrest.version>
    <hazelcast.version>5.1.1</hazelcast.version>
    <hazelcast-hibernate5.version>2.2.1</hazelcast-hibernate5.version>
    <hibernate.version>5.6.9.Final</hibernate.version>
    <hibernate-validator.version>6.2.3.Final</hibernate-validator.version>
    <hikaricp.version>4.0.3</hikaricp.version>
    <hsqldb.version>2.5.2</hsqldb.version>
    <htmlunit.version>2.60.0</htmlunit.version>
    <httpasyncclient.version>4.1.5</httpasyncclient.version>
    <httpclient.version>4.5.13</httpclient.version>
    <httpclient5.version>5.1.3</httpclient5.version>
    <httpcore.version>4.4.15</httpcore.version>
    <httpcore5.version>5.1.3</httpcore5.version>
    <infinispan.version>13.0.10.Final</infinispan.version>
    <influxdb-java.version>2.22</influxdb-java.version>
    <jackson-bom.version>2.13.3</jackson-bom.version>
    <jakarta-activation.version>1.2.2</jakarta-activation.version>
    <jakarta-annotation.version>1.3.5</jakarta-annotation.version>
    <jakarta-jms.version>2.0.3</jakarta-jms.version>
    <jakarta-json.version>1.1.6</jakarta-json.version>
    <jakarta-json-bind.version>1.0.2</jakarta-json-bind.version>
    <jakarta-mail.version>1.6.7</jakarta-mail.version>
    <jakarta-management.version>1.1.4</jakarta-management.version>
    <jakarta-persistence.version>2.2.3</jakarta-persistence.version>
    <jakarta-servlet.version>4.0.4</jakarta-servlet.version>
    <jakarta-servlet-jsp-jstl.version>1.2.7</jakarta-servlet-jsp-jstl.version>
    <jakarta-transaction.version>1.3.3</jakarta-transaction.version>
    <jakarta-validation.version>2.0.2</jakarta-validation.version>
    <jakarta-websocket.version>1.1.2</jakarta-websocket.version>
    <jakarta-ws-rs.version>2.1.6</jakarta-ws-rs.version>
    <jakarta-xml-bind.version>2.3.3</jakarta-xml-bind.version>
    <jakarta-xml-soap.version>1.4.2</jakarta-xml-soap.version>
    <jakarta-xml-ws.version>2.3.3</jakarta-xml-ws.version>
    <janino.version>3.1.7</janino.version>
    <javax-activation.version>1.2.0</javax-activation.version>
    <javax-annotation.version>1.3.2</javax-annotation.version>
    <javax-cache.version>1.1.1</javax-cache.version>
    <javax-jaxb.version>2.3.1</javax-jaxb.version>
    <javax-jaxws.version>2.3.1</javax-jaxws.version>
    <javax-jms.version>2.0.1</javax-jms.version>
    <javax-json.version>1.1.4</javax-json.version>
    <javax-jsonb.version>1.0</javax-jsonb.version>
    <javax-mail.version>1.6.2</javax-mail.version>
    <javax-money.version>1.1</javax-money.version>
    <javax-persistence.version>2.2</javax-persistence.version>
    <javax-transaction.version>1.3</javax-transaction.version>
    <javax-validation.version>2.0.1.Final</javax-validation.version>
    <javax-websocket.version>1.1</javax-websocket.version>
    <jaxen.version>1.2.0</jaxen.version>
    <jaybird.version>4.0.6.java8</jaybird.version>
    <jboss-logging.version>3.4.3.Final</jboss-logging.version>
    <jdom2.version>2.0.6.1</jdom2.version>
    <jedis.version>3.8.0</jedis.version>
    <jersey.version>2.35</jersey.version>
    <jetty-el.version>9.0.52</jetty-el.version>
    <jetty-jsp.version>2.2.0.v201112011158</jetty-jsp.version>
    <jetty-reactive-httpclient.version>1.1.11</jetty-reactive-httpclient.version>
    <jetty.version>9.4.46.v20220331</jetty.version>
    <jmustache.version>1.15</jmustache.version>
    <johnzon.version>1.2.18</johnzon.version>
    <jolokia.version>1.7.1</jolokia.version>
    <jooq.version>3.14.15</jooq.version>
    <json-path.version>2.7.0</json-path.version>
    <json-smart.version>2.4.8</json-smart.version>
    <jsonassert.version>1.5.0</jsonassert.version>
    <jstl.version>1.2</jstl.version>
    <jtds.version>1.3.1</jtds.version>
    <junit.version>4.13.2</junit.version>
    <junit-jupiter.version>5.8.2</junit-jupiter.version>
    <kafka.version>3.1.1</kafka.version>
    <kotlin.version>1.6.21</kotlin.version>
    <kotlin-coroutines.version>1.6.1</kotlin-coroutines.version>
    <lettuce.version>6.1.8.RELEASE</lettuce.version>
    <liquibase.version>4.9.1</liquibase.version>
    <log4j2.version>2.17.2</log4j2.version>
    <logback.version>1.2.11</logback.version>
    <lombok.version>1.18.24</lombok.version>
    <mariadb.version>3.0.4</mariadb.version>
    <maven-antrun-plugin.version>3.0.0</maven-antrun-plugin.version>
    <maven-assembly-plugin.version>3.3.0</maven-assembly-plugin.version>
    <maven-clean-plugin.version>3.2.0</maven-clean-plugin.version>
    <maven-compiler-plugin.version>3.10.1</maven-compiler-plugin.version>
    <maven-dependency-plugin.version>3.3.0</maven-dependency-plugin.version>
    <maven-deploy-plugin.version>2.8.2</maven-deploy-plugin.version>
    <maven-enforcer-plugin.version>3.0.0</maven-enforcer-plugin.version>
    <maven-failsafe-plugin.version>2.22.2</maven-failsafe-plugin.version>
    <maven-help-plugin.version>3.2.0</maven-help-plugin.version>
    <maven-install-plugin.version>2.5.2</maven-install-plugin.version>
    <maven-invoker-plugin.version>3.2.2</maven-invoker-plugin.version>
    <maven-jar-plugin.version>3.2.2</maven-jar-plugin.version>
    <maven-javadoc-plugin.version>3.4.0</maven-javadoc-plugin.version>
    <maven-resources-plugin.version>3.2.0</maven-resources-plugin.version>
    <maven-shade-plugin.version>3.3.0</maven-shade-plugin.version>
    <maven-source-plugin.version>3.2.1</maven-source-plugin.version>
    <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
    <maven-war-plugin.version>3.3.2</maven-war-plugin.version>
    <micrometer.version>1.9.0</micrometer.version>
    <mimepull.version>1.10.0</mimepull.version>
    <mockito.version>4.5.1</mockito.version>
    <mongodb.version>4.6.0</mongodb.version>
    <mssql-jdbc.version>10.2.1.jre8</mssql-jdbc.version>
    <mysql.version>8.0.29</mysql.version>
    <nekohtml.version>1.9.22</nekohtml.version>
    <neo4j-java-driver.version>4.4.5</neo4j-java-driver.version>
    <netty.version>4.1.77.Final</netty.version>
    <okhttp.version>4.9.3</okhttp.version>
    <oracle-database.version>21.5.0.0</oracle-database.version>
    <pooled-jms.version>1.2.4</pooled-jms.version>
    <postgresql.version>42.3.5</postgresql.version>
    <prometheus-client.version>0.15.0</prometheus-client.version>
    <quartz.version>2.3.2</quartz.version>
    <querydsl.version>5.0.0</querydsl.version>
    <r2dbc-bom.version>Borca-SR1</r2dbc-bom.version>
    <rabbit-amqp-client.version>5.14.2</rabbit-amqp-client.version>
    <rabbit-stream-client.version>0.5.0</rabbit-stream-client.version>
    <reactive-streams.version>1.0.3</reactive-streams.version>
    <reactor-bom.version>2020.0.19</reactor-bom.version>
    <rest-assured.version>4.5.1</rest-assured.version>
    <rsocket.version>1.1.2</rsocket.version>
    <rxjava.version>1.3.8</rxjava.version>
    <rxjava-adapter.version>1.2.1</rxjava-adapter.version>
    <rxjava2.version>2.2.21</rxjava2.version>
    <saaj-impl.version>1.5.3</saaj-impl.version>
    <selenium.version>4.1.4</selenium.version>
    <selenium-htmlunit.version>3.61.0</selenium-htmlunit.version>
    <sendgrid.version>4.9.2</sendgrid.version>
    <servlet-api.version>4.0.1</servlet-api.version>
    <slf4j.version>1.7.36</slf4j.version>
    <snakeyaml.version>1.30</snakeyaml.version>
    <solr.version>8.11.1</solr.version>
    <spring-amqp.version>2.4.5</spring-amqp.version>
    <spring-batch.version>4.3.6</spring-batch.version>
    <spring-data-bom.version>2021.2.0</spring-data-bom.version>
    <spring-framework.version>5.3.20</spring-framework.version>
    <spring-graphql.version>1.0.0</spring-graphql.version>
    <spring-hateoas.version>1.5.0</spring-hateoas.version>
    <spring-integration.version>5.5.12</spring-integration.version>
    <spring-kafka.version>2.8.6</spring-kafka.version>
    <spring-ldap.version>2.4.0</spring-ldap.version>
    <spring-restdocs.version>2.0.6.RELEASE</spring-restdocs.version>
    <spring-retry.version>1.3.3</spring-retry.version>
    <spring-security.version>5.7.1</spring-security.version>
    <spring-session-bom.version>2021.2.0</spring-session-bom.version>
    <spring-ws.version>3.1.3</spring-ws.version>
    <sqlite-jdbc.version>3.36.0.3</sqlite-jdbc.version>
    <sun-mail.version>1.6.7</sun-mail.version>
    <thymeleaf.version>3.0.15.RELEASE</thymeleaf.version>
    <thymeleaf-extras-data-attribute.version>2.0.1</thymeleaf-extras-data-attribute.version>
    <thymeleaf-extras-java8time.version>3.0.4.RELEASE</thymeleaf-extras-java8time.version>
    <thymeleaf-extras-springsecurity.version>3.0.4.RELEASE</thymeleaf-extras-springsecurity.version>
    <thymeleaf-layout-dialect.version>3.0.0</thymeleaf-layout-dialect.version>
    <tomcat.version>9.0.63</tomcat.version>
    <unboundid-ldapsdk.version>6.0.5</unboundid-ldapsdk.version>
    <undertow.version>2.2.17.Final</undertow.version>
    <versions-maven-plugin.version>2.10.0</versions-maven-plugin.version>
    <webjars-locator-core.version>0.50</webjars-locator-core.version>
    <wsdl4j.version>1.6.3</wsdl4j.version>
    <xml-maven-plugin.version>1.0.2</xml-maven-plugin.version>
    <xmlunit2.version>2.9.0</xmlunit2.version>
  </properties>

导入的依赖：

 <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
 </dependency>

进入spring-boot-starter- web后，可以看到导入很多web模块需要的依赖，

<dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter</artifactId>
      <version>2.7.0</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-json</artifactId>
      <version>2.7.0</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
      <version>2.7.0</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>5.3.20</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>5.3.20</version>
      <scope>compile</scope>
    </dependency>
  </dependencies>

springboot将所有的功能场景都抽取处理，做成一个starters（启动器），只需要在项目里面引入starter，相关场景的所有依赖都会被导入

主程序类：

@SpringBootApplication:SpringBoot应用标注在某个类上，说明这个类是SpringBoot的主配置类，SpringBoot就应该运行这个类来启动SpringBoot应用。

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    classes = {TypeExcludeFilter.class}
), @Filter(
    type = FilterType.CUSTOM,
    classes = {AutoConfigurationExcludeFilter.class}
)}
)

@SpringBootConfiguration:SpringBoot的配置类

标注在某个类上，表示这是一个SpringBoot的配置类。

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
@Indexed
public @interface SpringBootConfiguration {
    @AliasFor(
        annotation = Configuration.class
    )
    boolean proxyBeanMethods() default true;
}

@Configuaration：配置类

@EnableAutoConfiguration：开启自动配置功能

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import({AutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {
    String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";

    Class<?>[] exclude() default {};

    String[] excludeName() default {};
}

@AutoConfigurationPackage：自动配置包

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import({Registrar.class})
public @interface AutoConfigurationPackage {
    String[] basePackages() default {};

    Class<?>[] basePackageClasses() default {};
}