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Spring Boot

Spring Boot

概述

Spring Boot是基于Spring Framework的快速应用开发框架，通过"约定优于配置"的理念，大大简化了Spring应用的配置和部署。它提供了自动配置、起步依赖、内嵌服务器等特性，让开发者能够快速构建生产级别的Spring应用。

核心特性

1. 自动配置（Auto Configuration）

Spring Boot根据类路径中的依赖自动配置应用程序。

java 
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

// @SpringBootApplication 等价于：
// @Configuration + @EnableAutoConfiguration + @ComponentScan
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

// @SpringBootApplication 等价于：
// @Configuration + @EnableAutoConfiguration + @ComponentScan

2. 起步依赖（Starter Dependencies）

提供一站式的依赖管理，简化Maven/Gradle配置。

xml 
<!-- Web应用起步依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<!-- 数据库访问起步依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- Web应用起步依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<!-- 数据库访问起步依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

3. 内嵌服务器

无需外部服务器，应用可以独立运行。

java 
// 默认使用Tomcat，也可以切换到Jetty或Undertow
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
        // 应用启动后，内嵌Tomcat服务器开始监听8080端口
    }
}
// 默认使用Tomcat，也可以切换到Jetty或Undertow
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
        // 应用启动后，内嵌Tomcat服务器开始监听8080端口
    }
}

配置管理

application.properties/yml

properties 
# application.properties
server.port=8080
spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=password
spring.jpa.hibernate.ddl-auto=update

# 自定义配置
app.name=MyApplication
app.version=1.0.0
# application.properties
server.port=8080
spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=password
spring.jpa.hibernate.ddl-auto=update

# 自定义配置
app.name=MyApplication
app.version=1.0.0
yaml 
# application.yml
server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb
    username: root
    password: password
  jpa:
    hibernate:
      ddl-auto: update

app:
  name: MyApplication
  version: 1.0.0
# application.yml
server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/mydb
    username: root
    password: password
  jpa:
    hibernate:
      ddl-auto: update

app:
  name: MyApplication
  version: 1.0.0

配置类绑定

java 
@ConfigurationProperties(prefix = "app")
@Component
public class AppProperties {
    private String name;
    private String version;
    
    // getters and setters
}

// 使用配置
@RestController
public class InfoController {
    
    @Autowired
    private AppProperties appProperties;
    
    @GetMapping("/info")
    public Map<String, String> getInfo() {
        Map<String, String> info = new HashMap<>();
        info.put("name", appProperties.getName());
        info.put("version", appProperties.getVersion());
        return info;
    }
}
@ConfigurationProperties(prefix = "app")
@Component
public class AppProperties {
    private String name;
    private String version;
    
    // getters and setters
}

// 使用配置
@RestController
public class InfoController {
    
    @Autowired
    private AppProperties appProperties;
    
    @GetMapping("/info")
    public Map<String, String> getInfo() {
        Map<String, String> info = new HashMap<>();
        info.put("name", appProperties.getName());
        info.put("version", appProperties.getVersion());
        return info;
    }
}

多环境配置

properties 
# application.properties
spring.profiles.active=dev

# application-dev.properties
server.port=8080
spring.datasource.url=jdbc:h2:mem:devdb

# application-prod.properties
server.port=80
spring.datasource.url=jdbc:mysql://prod-server:3306/proddb
# application.properties
spring.profiles.active=dev

# application-dev.properties
server.port=8080
spring.datasource.url=jdbc:h2:mem:devdb

# application-prod.properties
server.port=80
spring.datasource.url=jdbc:mysql://prod-server:3306/proddb

常用Starter

Web开发

xml 
<!-- Web MVC -->
<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>
<!-- Web MVC -->
<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>

数据访问

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

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

测试

xml 
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>

实际应用示例

RESTful API开发

java 
@RestController
@RequestMapping("/api/users")
public class UserController {
    
    @Autowired
    private UserService userService;
    
    @GetMapping
    public List<User> getAllUsers() {
        return userService.findAll();
    }
    
    @GetMapping("/{id}")
    public ResponseEntity<User> getUserById(@PathVariable Long id) {
        User user = userService.findById(id);
        return user != null ? ResponseEntity.ok(user) : ResponseEntity.notFound().build();
    }
    
    @PostMapping
    public ResponseEntity<User> createUser(@Valid @RequestBody User user) {
        User savedUser = userService.save(user);
        return ResponseEntity.status(HttpStatus.CREATED).body(savedUser);
    }
    
    @PutMapping("/{id}")
    public ResponseEntity<User> updateUser(@PathVariable Long id, @Valid @RequestBody User user) {
        user.setId(id);
        User updatedUser = userService.update(user);
        return ResponseEntity.ok(updatedUser);
    }
    
    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
        userService.delete(id);
        return ResponseEntity.noContent().build();
    }
}
@RestController
@RequestMapping("/api/users")
public class UserController {
    
    @Autowired
    private UserService userService;
    
    @GetMapping
    public List<User> getAllUsers() {
        return userService.findAll();
    }
    
    @GetMapping("/{id}")
    public ResponseEntity<User> getUserById(@PathVariable Long id) {
        User user = userService.findById(id);
        return user != null ? ResponseEntity.ok(user) : ResponseEntity.notFound().build();
    }
    
    @PostMapping
    public ResponseEntity<User> createUser(@Valid @RequestBody User user) {
        User savedUser = userService.save(user);
        return ResponseEntity.status(HttpStatus.CREATED).body(savedUser);
    }
    
    @PutMapping("/{id}")
    public ResponseEntity<User> updateUser(@PathVariable Long id, @Valid @RequestBody User user) {
        user.setId(id);
        User updatedUser = userService.update(user);
        return ResponseEntity.ok(updatedUser);
    }
    
    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
        userService.delete(id);
        return ResponseEntity.noContent().build();
    }
}

数据访问层

java 
// Entity
@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Column(nullable = false)
    private String name;
    
    @Column(nullable = false, unique = true)
    private String email;
    
    // constructors, getters, setters
}

// Repository
@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByEmail(String email);
    List<User> findByNameContaining(String name);
    
    @Query("SELECT u FROM User u WHERE u.name = ?1")
    List<User> findByNameCustom(String name);
}

// Service
@Service
@Transactional
public class UserService {
    
    @Autowired
    private UserRepository userRepository;
    
    @Transactional(readOnly = true)
    public List<User> findAll() {
        return userRepository.findAll();
    }
    
    @Transactional(readOnly = true)
    public User findById(Long id) {
        return userRepository.findById(id).orElse(null);
    }
    
    public User save(User user) {
        return userRepository.save(user);
    }
    
    public User update(User user) {
        return userRepository.save(user);
    }
    
    public void delete(Long id) {
        userRepository.deleteById(id);
    }
}
// Entity
@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Column(nullable = false)
    private String name;
    
    @Column(nullable = false, unique = true)
    private String email;
    
    // constructors, getters, setters
}

// Repository
@Repository
public interface UserRepository extends JpaRepository<User, Long> {
    Optional<User> findByEmail(String email);
    List<User> findByNameContaining(String name);
    
    @Query("SELECT u FROM User u WHERE u.name = ?1")
    List<User> findByNameCustom(String name);
}

// Service
@Service
@Transactional
public class UserService {
    
    @Autowired
    private UserRepository userRepository;
    
    @Transactional(readOnly = true)
    public List<User> findAll() {
        return userRepository.findAll();
    }
    
    @Transactional(readOnly = true)
    public User findById(Long id) {
        return userRepository.findById(id).orElse(null);
    }
    
    public User save(User user) {
        return userRepository.save(user);
    }
    
    public User update(User user) {
        return userRepository.save(user);
    }
    
    public void delete(Long id) {
        userRepository.deleteById(id);
    }
}

监控和管理

Actuator

xml 
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
properties 
# 开启所有端点
management.endpoints.web.exposure.include=*
management.endpoint.health.show-details=always
# 开启所有端点
management.endpoints.web.exposure.include=*
management.endpoint.health.show-details=always

常用端点：

  • /actuator/health - 健康检查
  • /actuator/info - 应用信息
  • /actuator/metrics - 应用指标
  • /actuator/env - 环境变量
  • /actuator/beans - Spring Bean信息

自定义健康检查

java 
@Component
public class CustomHealthIndicator implements HealthIndicator {
    
    @Override
    public Health health() {
        // 执行健康检查逻辑
        boolean isHealthy = checkExternalService();
        
        if (isHealthy) {
            return Health.up()
                .withDetail("service", "Available")
                .build();
        } else {
            return Health.down()
                .withDetail("service", "Unavailable")
                .build();
        }
    }
    
    private boolean checkExternalService() {
        // 实际的健康检查逻辑
        return true;
    }
}
@Component
public class CustomHealthIndicator implements HealthIndicator {
    
    @Override
    public Health health() {
        // 执行健康检查逻辑
        boolean isHealthy = checkExternalService();
        
        if (isHealthy) {
            return Health.up()
                .withDetail("service", "Available")
                .build();
        } else {
            return Health.down()
                .withDetail("service", "Unavailable")
                .build();
        }
    }
    
    private boolean checkExternalService() {
        // 实际的健康检查逻辑
        return true;
    }
}

测试

单元测试

java 
@ExtendWith(SpringExtension.class)
@SpringBootTest
class UserServiceTest {
    
    @Autowired
    private UserService userService;
    
    @MockBean
    private UserRepository userRepository;
    
    @Test
    void testFindById() {
        // Given
        User user = new User("John", "[email protected]");
        when(userRepository.findById(1L)).thenReturn(Optional.of(user));
        
        // When
        User result = userService.findById(1L);
        
        // Then
        assertThat(result).isNotNull();
        assertThat(result.getName()).isEqualTo("John");
    }
}
@ExtendWith(SpringExtension.class)
@SpringBootTest
class UserServiceTest {
    
    @Autowired
    private UserService userService;
    
    @MockBean
    private UserRepository userRepository;
    
    @Test
    void testFindById() {
        // Given
        User user = new User("John", "[email protected]");
        when(userRepository.findById(1L)).thenReturn(Optional.of(user));
        
        // When
        User result = userService.findById(1L);
        
        // Then
        assertThat(result).isNotNull();
        assertThat(result.getName()).isEqualTo("John");
    }
}

集成测试

java 
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
class UserControllerIntegrationTest {
    
    @Autowired
    private TestRestTemplate restTemplate;
    
    @Test
    void testCreateUser() {
        // Given
        User user = new User("Jane", "[email protected]");
        
        // When
        ResponseEntity<User> response = restTemplate.postForEntity("/api/users", user, User.class);
        
        // Then
        assertThat(response.getStatusCode()).isEqualTo(HttpStatus.CREATED);
        assertThat(response.getBody().getName()).isEqualTo("Jane");
    }
}
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
class UserControllerIntegrationTest {
    
    @Autowired
    private TestRestTemplate restTemplate;
    
    @Test
    void testCreateUser() {
        // Given
        User user = new User("Jane", "[email protected]");
        
        // When
        ResponseEntity<User> response = restTemplate.postForEntity("/api/users", user, User.class);
        
        // Then
        assertThat(response.getStatusCode()).isEqualTo(HttpStatus.CREATED);
        assertThat(response.getBody().getName()).isEqualTo("Jane");
    }
}

Web层测试

java 
@WebMvcTest(UserController.class)
class UserControllerTest {
    
    @Autowired
    private MockMvc mockMvc;
    
    @MockBean
    private UserService userService;
    
    @Test
    void testGetUser() throws Exception {
        // Given
        User user = new User("John", "[email protected]");
        when(userService.findById(1L)).thenReturn(user);
        
        // When & Then
        mockMvc.perform(get("/api/users/1"))
                .andExpect(status().isOk())
                .andExpect(jsonPath("$.name").value("John"))
                .andExpect(jsonPath("$.email").value("[email protected]"));
    }
}
@WebMvcTest(UserController.class)
class UserControllerTest {
    
    @Autowired
    private MockMvc mockMvc;
    
    @MockBean
    private UserService userService;
    
    @Test
    void testGetUser() throws Exception {
        // Given
        User user = new User("John", "[email protected]");
        when(userService.findById(1L)).thenReturn(user);
        
        // When & Then
        mockMvc.perform(get("/api/users/1"))
                .andExpect(status().isOk())
                .andExpect(jsonPath("$.name").value("John"))
                .andExpect(jsonPath("$.email").value("[email protected]"));
    }
}

部署

打包

bash 
# Maven
mvn clean package

# Gradle
./gradlew build
# Maven
mvn clean package

# Gradle
./gradlew build

运行

bash 
# 直接运行JAR
java -jar myapp.jar

# 指定配置文件
java -jar myapp.jar --spring.config.location=classpath:/application-prod.yml

# 指定Profile
java -jar myapp.jar --spring.profiles.active=prod
# 直接运行JAR
java -jar myapp.jar

# 指定配置文件
java -jar myapp.jar --spring.config.location=classpath:/application-prod.yml

# 指定Profile
java -jar myapp.jar --spring.profiles.active=prod

Docker部署

dockerfile 
FROM openjdk:11-jre-slim

COPY target/myapp.jar app.jar

EXPOSE 8080

ENTRYPOINT ["java", "-jar", "/app.jar"]
FROM openjdk:11-jre-slim

COPY target/myapp.jar app.jar

EXPOSE 8080

ENTRYPOINT ["java", "-jar", "/app.jar"]

最佳实践

  1. 合理使用Starter：选择合适的starter，避免引入不必要的依赖
  2. 配置外部化：使用配置文件管理环境相关配置
  3. 使用Profile：为不同环境创建不同的配置文件
  4. 监控和日志：集成Actuator和日志框架
  5. 安全配置：生产环境中保护敏感端点
  6. 测试覆盖：编写充分的单元测试和集成测试
  7. 性能优化：合理配置JVM参数和连接池
  8. 文档化：使用Swagger等工具生成API文档

与微服务的关系

Spring Boot为微服务架构提供了理想的基础：

  • 独立部署：每个微服务都是独立的可执行JAR
  • 快速启动：内嵌服务器支持快速启动和停止
  • 配置管理：支持外部化配置和多环境部署
  • 监控支持：Actuator提供了丰富的监控端点

总结

Spring Boot通过自动配置、起步依赖等特性，大大简化了Spring应用的开发和部署。它让开发者能够专注于业务逻辑，而不是繁琐的配置。掌握Spring Boot是现代Java企业级开发的必备技能，也是学习Spring Cloud微服务架构的基础。