Spring Boot 3 简介

什么是Spring Boot？

Spring Boot是一个用于简化Spring应用开发的框架，它提供了一套快速开发方案，遵循"约定优于配置"的原则，让开发者能够快速搭建并运行Spring应用程序。

核心特性

1. 自动配置 (Auto-Configuration)

根据classpath中的依赖自动配置Spring应用。

2. 起步依赖 (Starter Dependencies)

预定义的依赖集合，简化Maven配置。

3. 内嵌服务器

内置Tomcat、Jetty或Undertow，无需部署WAR文件。

4. 生产就绪特性

提供监控、健康检查、指标收集等功能。

5. 无代码生成和XML配置

完全基于Java配置和注解。

Spring Boot 3 新特性

Spring Boot 3.0是一个重大版本更新，主要特性包括：

基线要求

• Java 17+：最低要求Java 17
• Spring Framework 6：基于Spring 6构建
• Jakarta EE 9+：从javax.迁移到jakarta.

核心改进

• 原生镜像支持：通过GraalVM构建原生应用
• 可观测性增强：改进的Micrometer和Micrometer Tracing集成
• 问题详情支持：RFC 7807问题详情标准支持
• 性能优化：启动时间和内存占用优化

快速开始

1. 创建项目

使用Spring Initializr：

• 访问 https://start.spring.io/
• 选择Spring Boot 3.x
• 选择Java 17+
• 添加所需依赖

或使用Maven命令：

mvn archetype:generate -DgroupId=com.example -DartifactId=demo \\
    -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

2. 项目结构

demo/
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/example/demo/
│   │   │       ├── DemoApplication.java
│   │   │       ├── controller/
│   │   │       ├── service/
│   │   │       ├── repository/
│   │   │       └── domain/
│   │   └── resources/
│   │       ├── application.yml
│   │       ├── static/
│   │       └── templates/
│   └── test/
│       └── java/
├── pom.xml
└── README.md

3. pom.xml配置

<?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>
    
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.2</version>
        <relativePath/>
    </parent>
    
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    
    <properties>
        <java.version>17</java.version>
    </properties>
    
    <dependencies>
        <!-- Web Starter -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        
        <!-- JPA Starter -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        
        <!-- MySQL Driver -->
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>
        
        <!-- Lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        
        <!-- Test -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

4. 主启动类

package com.example.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);
    }
}

5. 配置文件

application.yml:

spring:
  application:
    name: demo
  
  datasource:
    url: jdbc:mysql://localhost:3306/demo?useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
    username: root
    password: password
    driver-class-name: com.mysql.cj.jdbc.Driver
  
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    properties:
      hibernate:
        format_sql: true
        dialect: org.hibernate.dialect.MySQLDialect

server:
  port: 8080
  servlet:
    context-path: /api

logging:
  level:
    root: INFO
    com.example: DEBUG

6. 创建第一个Controller

package com.example.demo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/hello")
public class HelloController {
    
    @GetMapping
    public String hello() {
        return "Hello, Spring Boot 3!";
    }
}

7. 运行应用

mvn spring-boot:run

访问（示例运行地址，启动应用后访问）：http://localhost:8080/api/hello

常用Starter依赖

Web开发

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

<!-- WebFlux响应式Web -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

<!-- Thymeleaf模板引擎 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

数据访问

<!-- Spring Data JPA -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<!-- MyBatis -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>3.0.3</version>
</dependency>

<!-- Redis -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

<!-- MongoDB -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

安全

<!-- Spring Security -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

<!-- OAuth2 Client -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-oauth2-client</artifactId>
</dependency>

消息队列

<!-- RabbitMQ -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-amqp</artifactId>
</dependency>

<!-- Kafka -->
<dependency>
    <groupId>org.springframework.kafka</groupId>
    <artifactId>spring-kafka</artifactId>
</dependency>

监控和管理

<!-- Actuator -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

<!-- Prometheus -->
<dependency>
    <groupId>io.micrometer</groupId>
    <artifactId>micrometer-registry-prometheus</artifactId>
</dependency>

自动配置原理

@SpringBootApplication注解

@SpringBootApplication
// 等价于以下三个注解的组合：
@SpringBootConfiguration  // 标记为配置类
@EnableAutoConfiguration  // 启用自动配置
@ComponentScan           // 组件扫描
public class DemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

条件注解

Spring Boot使用条件注解来决定是否应用某个配置：

@Configuration
@ConditionalOnClass(DataSource.class) // 当类存在时
@ConditionalOnMissingBean(DataSource.class) // 当Bean不存在时
@ConditionalOnProperty(name = "spring.datasource.url") // 当属性存在时
public class DataSourceAutoConfiguration {
    
    @Bean
    public DataSource dataSource() {
        // 创建数据源
    }
}

常用条件注解：

• @ConditionalOnClass：类存在时
• @ConditionalOnMissingClass：类不存在时
• @ConditionalOnBean：Bean存在时
• @ConditionalOnMissingBean：Bean不存在时
• @ConditionalOnProperty：配置属性存在时
• @ConditionalOnWebApplication：Web应用时
• @ConditionalOnNotWebApplication：非Web应用时

自定义自动配置

1. 创建配置类：

@Configuration
@ConditionalOnClass(SomeService.class)
@EnableConfigurationProperties(SomeProperties.class)
public class SomeAutoConfiguration {
    
    @Bean
    @ConditionalOnMissingBean
    public SomeService someService(SomeProperties properties) {
        return new SomeService(properties);
    }
}

2. 创建配置属性类：

@ConfigurationProperties(prefix = "some")
@Data
public class SomeProperties {
    private boolean enabled = true;
    private String apiKey;
    private int timeout = 3000;
}

3. 注册自动配置：

在META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports文件中：

com.example.autoconfigure.SomeAutoConfiguration

配置文件

application.yml vs application.properties

# application.properties
server.port=8080
spring.datasource.url=jdbc:mysql://localhost:3306/db
spring.datasource.username=root

# application.yml (推荐)
server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/db
    username: root

多环境配置

application.yml           # 公共配置
application-dev.yml       # 开发环境
application-test.yml      # 测试环境
application-prod.yml      # 生产环境

application.yml:

spring:
  profiles:
    active: dev  # 激活dev环境

application-dev.yml:

server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/dev_db

application-prod.yml:

server:
  port: 80

spring:
  datasource:
    url: jdbc:mysql://prod-server:3306/prod_db

配置绑定

@ConfigurationProperties(prefix = "app")
@Component
@Data
public class AppProperties {
    private String name;
    private String version;
    private Server server;
    
    @Data
    public static class Server {
        private String host;
        private int port;
    }
}

app:
  name: MyApp
  version: 1.0.0
  server:
    host: localhost
    port: 8080

使用：

@Service
public class SomeService {
    
    @Autowired
    private AppProperties appProperties;
    
    public void doSomething() {
        String name = appProperties.getName();
        int port = appProperties.getServer().getPort();
    }
}

日志配置

默认日志框架

Spring Boot使用Logback作为默认日志框架。

配置日志级别

logging:
  level:
    root: INFO
    com.example: DEBUG
    org.springframework: WARN
    org.hibernate: ERROR

配置日志文件

logging:
  file:
    name: logs/app.log
    max-size: 10MB
    max-history: 30
  pattern:
    console: "%d{yyyy-MM-dd HH:mm:ss} - %msg%n"
    file: "%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n"

使用日志

import lombok.extern.slf4j.Slf4j;

@Slf4j
@Service
public class UserService {
    
    public void createUser(User user) {
        log.debug("Creating user: {}", user);
        // ...
        log.info("User created successfully: {}", user.getId());
    }
}

下一步

• Spring Boot Actuator监控
• 数据访问与JPA
• Spring Security安全
• RESTful API开发
• 测试与调试