String password = request.getParameter("password");

throw new ServletException("用户名不能为空"); }

var username = document.getElementById("username").value; if (username.trim() === "") { alert("用户名不能为空"); event.preventDefault(); // 阻止表单提交 } });

request.setAttribute("error", "用户名格式不正确"); request.getRequestDispatcher("form.jsp").forward(request, response); }

cookie.setMaxAge(60 * 60 * 24 * 7); // 设置Cookie的有效期为7天 response.addCookie(cookie);

if (cookies != null) { for (Cookie cookie : cookies) { if ("username".equals(cookie.getName())) { String username = cookie.getValue(); System.out.println("用户名：" + username); } } }

session.setAttribute("username", "user1");

System.out.println("用户名：" + username);

ServletFileUpload upload = new ServletFileUpload(factory); List items = upload.parseRequest(request); for (FileItem item : items) { if (!item.isFormField()) { String fileName = item.getName(); item.write(new File("upload/" + fileName)); } }

File file = new File(filePath); response.setContentType("application/octet-stream"); response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(file.getName(), "UTF-8")); InputStream inputStream = new FileInputStream(file); OutputStream outputStream = response.getOutputStream(); byte[] buffer = new byte[1024]; int length; while ((length = inputStream.read(buffer)) > 0) { outputStream.write(buffer, 0, length); } inputStream.close(); outputStream.close();

public class CharacterEncodingFilter implements Filter { @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { request.setCharacterEncoding("UTF-8"); response.setCharacterEncoding("UTF-8"); chain.doFilter(request, response); } }

public class MyListener implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent sce) { System.out.println("应用启动"); }

@Override public void contextDestroyed(ServletContextEvent sce) { System.out.println("应用销毁"); } }

public class MyService { public void doSomething() { System.out.println("Doing something"); } }

public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); MyService myService = context.getBean(MyService.class); myService.doSomething(); } }

public class LoggingAspect { @Before("execution(* com.example.*.*(..))") public void beforeAdvice() { System.out.println("Before method execution"); } }

public class MyService { }

public class AppConfig { @Bean public MyService myService() { return new MyService(); } }

public class MyService { @Transactional public void doSomething() { // 业务逻辑 } }

public PlatformTransactionManager transactionManager(DataSource dataSource) { return new DataSourceTransactionManager(dataSource); }

public class MyController { @RequestMapping("/hello") public String hello(Model model) { model.addAttribute("message", "Hello, Spring MVC!"); return "hello"; } }

${message}

public class MyController { @RequestMapping("/submit") public String submit(User user) { System.out.println(user.getUsername() + " : " + user.getPassword()); return "success"; } }

public void initBinder(WebDataBinder binder) { SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd"); binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true)); }

public ViewResolver viewResolver() { InternalResourceViewResolver resolver = new InternalResourceViewResolver(); resolver.setPrefix("/WEB-INF/views/"); resolver.setSuffix(".jsp"); return resolver; }

InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

UserMapper userMapper = session.getMapper(UserMapper.class); User user = userMapper.selectUserById(1); System.out.println(user.getUsername()); }

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

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

spring.datasource.url=jdbc:mysql://localhost:3306/mydatabase spring.datasource.username=username spring.datasource.password=password

port: 8081 spring: datasource: url: jdbc:mysql://localhost:3306/mydatabase username: username password: password

public String register(User user) { userService.register(user); return "redirect:/login"; }

public String login(String username, String password, Model model) { User user = userService.login(username, password); if (user != null) { model.addAttribute("user", user); return "home"; } else { model.addAttribute("error", "用户名或密码错误"); return "login"; } }

public String listProducts(Model model) { List products = productService.listProducts(); model.addAttribute("products", products); return "productList"; }

public String productDetail(@PathVariable Integer id, Model model) { Product product = productService.getProductById(id); model.addAttribute("product", product); return "productDetail"; }

public String addToCart(Integer productId, Integer quantity, HttpSession session) { Cart cart = (Cart) session.getAttribute("cart"); if (cart == null) { cart = new Cart(); } cart.addProduct(productService.getProductById(productId), quantity); session.setAttribute("cart", cart); return "redirect:/cart"; }

public String cart(HttpSession session, Model model) { Cart cart = (Cart) session.getAttribute("cart"); if (cart == null) { cart = new Cart(); } model.addAttribute("cart", cart); return "cart"; }

public String submitOrder(HttpSession session) { Cart cart = (Cart) session.getAttribute("cart"); if (cart != null) { orderService.createOrder(cart); session.removeAttribute("cart"); } return "redirect:/orders"; }

public String listOrders(Model model) { List orders = orderService.listOrders(); model.addAttribute("orders", orders); return "orderList"; }

return username.matches("^[a-zA-Z0-9_]{3,16}$"); }

return input.replace("<", "<").replace(">", ">"); }

@EnableWebSecurity public class SecurityConfig extends WebSecurityConfigurerAdapter { @Override protected void configure(HttpSecurity http) throws Exception { http .authorizeRequests() .antMatchers("/admin/**").hasRole("ADMIN") .antMatchers("/user/**").hasRole("USER") .antMatchers("/", "/register", "/login").permitAll() .anyRequest().authenticated() .and() .formLogin() .loginPage("/login") .defaultSuccessUrl("/home", true) .permitAll() .and() .logout() .permitAll(); } }

public void adminOnlyMethod() { // 只有管理员角色可以访问 }

import ReactDOM from 'react-dom';

function App() { return

Hello, React!

ReactDOM.render(, document.getElementById('root'));

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

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

public class MyService { @HystrixCommand(fallbackMethod = "fallback") public String getData() { // 调用远程服务 }

public String fallback() { return "Fallback data"; } }

COPY target/myapp.jar /app.jar ENTRYPOINT ["java", "-jar", "/app.jar"]

props.put("bootstrap.servers", "localhost:9092"); props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer"); props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer"); KafkaProducer producer = new KafkaProducer<>(props); producer.send(new ProducerRecord<>("mytopic", "key", "value")); producer.close();

JavaSparkContext sc = new JavaSparkContext(conf); JavaRDD lines = sc.textFile("data.txt"); JavaRDD filteredLines = lines.filter(line -> line.contains("keyword")); filteredLines.saveAsTextFile("output"); sc.close();

public class DataController { @GetMapping("/data") public List getData() { // 从数据库或缓存中获取分析结果 return Arrays.asList("result1", "result2"); } }