第22章 Spring开发#

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public class BookService {
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    private HikariConfig config = new HikariConfig();
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    private DataSource dataSource = new HikariDataSource(config);
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    public Book getBook(long bookId) {
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        try (Connection conn = dataSource.getConnection()) {
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            ...
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            return book;
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        }
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    }
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}

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public class UserService {
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    private HikariConfig config = new HikariConfig();
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    private DataSource dataSource = new HikariDataSource(config);
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    public User getUser(long userId) {
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        try (Connection conn = dataSource.getConnection()) {
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            ...
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            return user;
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        }
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    }
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}

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public class CartServlet extends HttpServlet {
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    private BookService bookService = new BookService();
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    private UserService userService = new UserService();
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    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
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        long currentUserId = getFromCookie(req);
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        User currentUser = userService.getUser(currentUserId);
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        Book book = bookService.getBook(req.getParameter("bookId"));
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        cartService.addToCart(currentUser, book);
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        ...
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    }
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}

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public class HistoryServlet extends HttpServlet {
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    private BookService bookService = new BookService();
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    private UserService userService = new UserService();
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}

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public class BookService {
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    private DataSource dataSource;
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    public void setDataSource(DataSource dataSource) {
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        this.dataSource = dataSource;
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    }
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}

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<beans>
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    <bean id="dataSource" class="HikariDataSource" />
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    <bean id="bookService" class="BookService">
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        <property name="dataSource" ref="dataSource" />
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    </bean>
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    <bean id="userService" class="UserService">
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        <property name="dataSource" ref="dataSource" />
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    </bean>
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</beans>

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spring-ioc-appcontext
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├── pom.xml
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└── src
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    └── main
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        ├── java
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        │   └── com
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        │       └── itranswarp
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        │           └── learnjava
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        │               ├── Main.java
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        │               └── service
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        │                   ├── MailService.java
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        │                   ├── User.java
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        │                   └── UserService.java
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        └── resources
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            └── application.xml

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public class MailService {
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    private ZoneId zoneId = ZoneId.systemDefault();
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    public void setZoneId(ZoneId zoneId) {
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        this.zoneId = zoneId;
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    }
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    public String getTime() {
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        return ZonedDateTime.now(this.zoneId).format(DateTimeFormatter.ISO_ZONED_DATE_TIME);
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    }
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    public void sendLoginMail(User user) {
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        System.err.println(String.format("Hi, %s! You are logged in at %s", user.getName(), getTime()));
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    }
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    public void sendRegistrationMail(User user) {
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        System.err.println(String.format("Welcome, %s!", user.getName()));
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    }
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}

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public class UserService {
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    private MailService mailService;
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    public void setMailService(MailService mailService) {
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        this.mailService = mailService;
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    }
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    private List<User> users = new ArrayList<>(List.of( // users:
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            new User(1, "bob@example.com", "password", "Bob"), // bob
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            new User(2, "alice@example.com", "password", "Alice"), // alice
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            new User(3, "tom@example.com", "password", "Tom"))); // tom
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    public User login(String email, String password) {
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        for (User user : users) {
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            if (user.getEmail().equalsIgnoreCase(email) && user.getPassword().equals(password)) {
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                mailService.sendLoginMail(user);
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                return user;
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            }
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        }
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        throw new RuntimeException("login failed.");
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    }
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    public User getUser(long id) {
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        return this.users.stream().filter(user -> user.getId() == id).findFirst().orElseThrow();
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    }
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    public User register(String email, String password, String name) {
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        users.forEach((user) -> {
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            if (user.getEmail().equalsIgnoreCase(email)) {
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                throw new RuntimeException("email exist.");
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            }
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        });
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        User user = new User(users.stream().mapToLong(u -> u.getId()).max().getAsLong() + 1, email, password, name);
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        users.add(user);
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        mailService.sendRegistrationMail(user);
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        return user;
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    }
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}

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<?xml version="1.0" encoding="UTF-8"?>
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<beans xmlns="http://www.springframework.org/schema/beans"
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    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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    xsi:schemaLocation="http://www.springframework.org/schema/beans
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        https://www.springframework.org/schema/beans/spring-beans.xsd">
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    <bean id="userService" class="com.itranswarp.learnjava.service.UserService">
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        <property name="mailService" ref="mailService" />
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    </bean>
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    <bean id="mailService" class="com.itranswarp.learnjava.service.MailService" />
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</beans>

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UserService userService = new UserService();
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MailService mailService = new MailService();
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userService.setMailService(mailService);

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<bean id="dataSource" class="com.zaxxer.hikari.HikariDataSource">
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    <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/test" />
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    <property name="username" value="root" />
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    <property name="password" value="password" />
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    <property name="maximumPoolSize" value="10" />
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    <property name="autoCommit" value="true" />
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</bean>

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ApplicationContext context = new ClassPathXmlApplicationContext("application.xml");

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// 获取Bean:
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UserService userService = context.getBean(UserService.class);
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// 正常调用:
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User user = userService.login("bob@example.com", "password");

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public class Main {
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    public static void main(String[] args) {
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        ApplicationContext context = new ClassPathXmlApplicationContext("application.xml");
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        UserService userService = context.getBean(UserService.class);
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        User user = userService.login("bob@example.com", "password");
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        System.out.println(user.getName());
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    }
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}

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@Component
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public class MailService {
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    ...
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}

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@Component
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public class UserService {
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    @Autowired
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    MailService mailService;
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    ...
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}

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@Component
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public class UserService {
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    MailService mailService;
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    public UserService(@Autowired MailService mailService) {
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        this.mailService = mailService;
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    }
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    ...
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}

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@Configuration
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@ComponentScan
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public class AppConfig {
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    public static void main(String[] args) {
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        ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
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        UserService userService = context.getBean(UserService.class);
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        User user = userService.login("bob@example.com", "password");
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        System.out.println(user.getName());
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    }
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}

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ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

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spring-ioc-annoconfig
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├── pom.xml
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└── src
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    └── main
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        └── java
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            └── com
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                └── itranswarp
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                    └── learnjava
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                        ├── AppConfig.java
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                        └── service
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                            ├── MailService.java
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                            ├── User.java
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                            └── UserService.java

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@Component
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public class AppService {
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    @Value("classpath:/logo.txt")
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    private Resource resource;
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    private String logo;
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    @PostConstruct
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    public void init() throws IOException {
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        try (var reader = new BufferedReader(
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                new InputStreamReader(resource.getInputStream(), StandardCharsets.UTF_8))) {
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            this.logo = reader.lines().collect(Collectors.joining("\n"));
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        }
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    }
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}

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@Value("file:/path/to/logo.txt")
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private Resource resource;

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spring-ioc-resource
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├── pom.xml
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└── src
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    └── main
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        ├── java
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        │   └── com
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        │       └── itranswarp
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        │           └── learnjava
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        │               ├── AppConfig.java
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        │               └── AppService.java
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        └── resources
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            └── logo.txt

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@Configuration
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@ComponentScan
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@PropertySource("app.properties") // 表示读取classpath的app.properties
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public class AppConfig {
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    @Value("${app.zone:Z}")
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    String zoneId;
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    @Bean
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    ZoneId createZoneId() {
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        return ZoneId.of(zoneId);
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    }
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}

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@Value("${app.zone:Z}")
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String zoneId;

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@Bean
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ZoneId createZoneId(@Value("${app.zone:Z}") String zoneId) {
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    return ZoneId.of(zoneId);
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}

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@Component
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public class SmtpConfig {
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    @Value("${smtp.host}")
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    private String host;
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    @Value("${smtp.port:25}")
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    private int port;
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    public String getHost() {
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        return host;
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    }
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    public int getPort() {
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        return port;
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    }
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}

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@Component
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public class MailService {
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    @Value("#{smtpConfig.host}")
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    private String smtpHost;
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    @Value("#{smtpConfig.port}")
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    private int smtpPort;
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}

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@Configuration
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@ComponentScan
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public class AppConfig {
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    @Bean
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    @Profile("!test")
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    ZoneId createZoneId() {
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        return ZoneId.systemDefault();
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    }
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    @Bean
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    @Profile("test")
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    ZoneId createZoneIdForTest() {
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        return ZoneId.of("America/New_York");
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    }
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}

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-Dspring.profiles.active=test,master

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@Bean
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@Profile({ "test", "master" }) // 满足test或master
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ZoneId createZoneId() {
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    ...
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}

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@Aspect
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@Component
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public class LoggingAspect {
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    // 在执行UserService的每个方法前执行:
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    @Before("execution(public * com.itranswarp.learnjava.service.UserService.*(..))")
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    public void doAccessCheck() {
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        System.err.println("[Before] do access check...");
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    }
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    // 在执行MailService的每个方法前后执行:
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    @Around("execution(public * com.itranswarp.learnjava.service.MailService.*(..))")
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    public Object doLogging(ProceedingJoinPoint pjp) throws Throwable {
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        System.err.println("[Around] start " + pjp.getSignature());
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        Object retVal = pjp.proceed();
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        System.err.println("[Around] done " + pjp.getSignature());
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        return retVal;
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    }
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}

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@Configuration
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@ComponentScan
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@EnableAspectJAutoProxy
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public class AppConfig {
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    ...
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}

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[Before] do access check...
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[Around] start void com.itranswarp.learnjava.service.MailService.sendRegistrationMail(User)
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Welcome, test!
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[Around] done void com.itranswarp.learnjava.service.MailService.sendRegistrationMail(User)
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[Before] do access check...
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[Around] start void com.itranswarp.learnjava.service.MailService.sendLoginMail(User)
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Hi, Bob! You are logged in at 2020-02-14T23:13:52.167996+08:00[Asia/Shanghai]
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[Around] done void com.itranswarp.learnjava.service.MailService.sendLoginMail(User)

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public UserServiceAopProxy extends UserService {
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    private UserService target;
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    private LoggingAspect aspect;
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    public UserServiceAopProxy(UserService target, LoggingAspect aspect) {
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        this.target = target;
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        this.aspect = aspect;
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    }
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    public User login(String email, String password) {
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        // 先执行Aspect的代码:
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        aspect.doAccessCheck();
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        // 再执行UserService的逻辑:
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        return target.login(email, password);
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    }
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    public User register(String email, String password, String name) {
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        aspect.doAccessCheck();
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        return target.register(email, password, name);
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    }
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    ...
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}

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@Aspect
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@Component
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public class SecurityAspect {
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    @Before("execution(public * com.itranswarp.learnjava.service.*.*(..))")
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    public void check() {
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        if (SecurityContext.getCurrentUser() == null) {
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            throw new RuntimeException("check failed");
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        }
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    }
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}

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@Around("execution(public * update*(..))")
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public Object doLogging(ProceedingJoinPoint pjp) throws Throwable {
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    // 对update开头的方法切换数据源:
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    String old = setCurrentDataSource("master");
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    Object retVal = pjp.proceed();
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    restoreCurrentDataSource(old);
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    return retVal;
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}

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@Component
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public class UserService {
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    // 有事务:
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    @Transactional
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    public User createUser(String name) {
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        ...
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    }
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    // 无事务:
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    public boolean isValidName(String name) {
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        ...
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    }
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    // 有事务:
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    @Transactional
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    public void updateUser(User user) {
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        ...
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    }
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}

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@Component
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@Transactional
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public class UserService {
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    ...
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}

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@Target(METHOD)
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@Retention(RUNTIME)
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public @interface MetricTime {
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    String value();
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}

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@Component
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public class UserService {
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    // 监控register()方法性能:
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    @MetricTime("register")
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    public User register(String email, String password, String name) {
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        ...
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    }
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    ...
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}

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@Aspect
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@Component
3
public class MetricAspect {
4
    @Around("@annotation(metricTime)")
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    public Object metric(ProceedingJoinPoint joinPoint, MetricTime metricTime) throws Throwable {
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        String name = metricTime.value();
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        long start = System.currentTimeMillis();
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        try {
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            return joinPoint.proceed();
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        } finally {
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            long t = System.currentTimeMillis() - start;
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            // 写入日志或发送至JMX:
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            System.err.println("[Metrics] " + name + ": " + t + "ms");
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        }
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    }
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}

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Welcome, Bob!
2
[Metrics] register: 16ms

1
@Component
2
public class UserService {
3
    // 成员变量:
4
    public final ZoneId zoneId = ZoneId.systemDefault();
5

6
    // 构造方法:
7
    public UserService() {
8
        System.out.println("UserService(): init...");
9
        System.out.println("UserService(): zoneId = " + this.zoneId);
10
    }
11

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    // public方法:
13
    public ZoneId getZoneId() {
14
        return zoneId;
15
    }
16

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    // public final方法:
18
    public final ZoneId getFinalZoneId() {
19
        return zoneId;
20
    }
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}

1
@Component
2
public class MailService {
3
    @Autowired
4
    UserService userService;
5

6
    public String sendMail() {
7
        ZoneId zoneId = userService.zoneId;
8
        String dt = ZonedDateTime.now(zoneId).toString();
9
        return "Hello, it is " + dt;
10
    }
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}