《Spring Boot从入门到实战》第四章习题

4.10 本章习题

1）使用IDEA手动创建一个Spring Boot项目，创建一个控制器（Controller)，模拟数据的增、删、改、查操作。

复制代码

package com.example.demo.controller;

import org.springframework.web.bind.annotation.*;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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

    private Map<Integer,String> userDatabase = new HashMap<>();

    public UserController() {
        userDatabase.put(1,"Alice");
        userDatabase.put(2,"Bob");
    }

    @GetMapping
    public List<Map.Entry<Integer,String>> getAllUsers() {
        return new ArrayList<>(userDatabase.entrySet());
    }

    @GetMapping("/{id}")
    public String user(@PathVariable Integer id) {
        return userDatabase.get(id);
    }

    @PostMapping
    public String addUser(@RequestParam Integer id, @RequestParam String name) {
        userDatabase.put(id,name);
        return "User added successfully";
    }

    @PutMapping("/{id}")
    public String updateUser(@PathVariable Integer id, @RequestParam String name) {
        if(userDatabase.containsKey(id)) {
            userDatabase.put(id,name);
            return "User updated successfully";
        }
        return "User not found";
    }

    @DeleteMapping("/{id}")
    public String deleteUser(@PathVariable Integer id) {
        if(userDatabase.containsKey(id)) {
            userDatabase.remove(id);
            return "User deleted successfully";
        }
        return "User not found";
    }

}

Postman测试结果:

新增

使用拦截器实现全局系统性能监控日志。

步骤 1：创建一个性能监控拦截器PerformanceInterceptor

复制代码

package com.example.demo.interceptor;

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

@Component
public class PerformanceInterceptor implements HandlerInterceptor {

    private static final String START_TIME = "startTime";

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        request.setAttribute(START_TIME, System.currentTimeMillis());
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        long startTime = (Long) request.getAttribute(START_TIME);
        long endTime = System.currentTimeMillis();
        long duration = endTime - startTime;
        String logMessage = String.format("Request to %s took %d ms", request.getRequestURI(), duration);
        System.out.println(logMessage);
    }
}

步骤 2：配置拦截器创建一个 WebConfig 类，并注册 PerformanceInterceptor

复制代码

package com.example.demo.config;

import com.example.demo.interceptor.PerformanceInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Autowired
    private PerformanceInterceptor performanceInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(performanceInterceptor);
    }
}

步骤 3：测试性能监控日志

使用WebMvcConfigurer自定义配置系统的静态文件路径。

步骤 1：创建 Web 配置类

复制代码

package com.example.demo.config;

import com.example.demo.interceptor.PerformanceInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/static/**")
                .addResourceLocations("classpath:/custom-static/");    
    }
}

步骤 2：创建自定义的静态资源文件夹

在项目的 src/main/resources 目录下，创建一个 custom-static 文件夹，并在其中放置静态资源文件（如图片、CSS 文件、JavaScript 文件等）。

步骤 3：访问静态资源

启动 Spring Boot 应用后，访问以下 URL 以验证静态资源是否可用

图片文件: http://localhost:8080/static/images/logo.png

这些资源将被映射到 src/main/resources/custom-static 文件夹中的文件。通过这种方式，你可以轻松自定义和管理 Spring Boot 应用中的静态资源路径。