Java 框架与库

Java 生态系统拥有丰富的框架和库，大大提高了开发效率。

Spring 全家桶

Spring Core

// 依赖注入
@Component
public class UserService {

    private UserRepository userRepository;

    @Autowired
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public User findById(Long id) {
        return userRepository.findById(id);
    }
}

Spring Boot

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

// 控制器
@RestController
@RequestMapping("/users")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/{id}")
    public User getUser(@PathVariable Long id) {
        return userService.findById(id);
    }
}

Spring Cloud

• 服务发现：Eureka
• 负载均衡：Ribbon
• 断路器：Hystrix
• 网关：Zuul
• 配置中心：Config

MyBatis

基础配置

<!-- mybatis-config.xml -->
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mydb"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

Mapper 接口

public interface UserMapper {
    @Select("SELECT * FROM users WHERE id = #{id}")
    User findById(@Param("id") Long id);

    @Insert("INSERT INTO users (name, age) VALUES (#{name}, #{age})")
    @Options(useGeneratedKeys = true, keyProperty = "id")
    void insert(User user);
}

其他常用框架

Apache Commons

• Commons Lang：提供常用工具类
• Commons Collections：增强集合类
• Commons IO：IO 操作工具

Google Guava

• 集合工具：Multimap、BiMap 等
• 缓存：LoadingCache
• 函数式编程：Function、Predicate 等

Lombok

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private Long id;
    private String name;
    private int age;
}

Hibernate

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "name", nullable = false)
    private String name;

    @Column(name = "age")
    private int age;

    // getters and setters
}