【HttpURLConnection】使用 HttpURLConnection 后台模拟实现 HTTP 请求

Dear 丶 2023-10-02 16:17 18阅读 0赞

[【HttpURLConnection】使用 HttpURLConnection 后台模拟实现 HTTP 请求][HttpURLConnection_ HttpURLConnection _ HTTP]  
[【HttpClient】在 SpringBoot 中使用 HttpClient 实现 HTTP 请求][HttpClient_ SpringBoot _ HttpClient _ HTTP]  
[【SpringBoot】使用 OkHttp 完成网络请求][SpringBoot_ OkHttp]

在 SpringBoot 工程中，通过 `HttpURLConnection` 类来实现 HTTP 请求吧。

类 `HttpURLConnection` 是 JDK 自带的。

它的应用场景：在自己的工程中，你想调用第三方接口（外部接口）来获取数据，那么 `HttpURLConnection` 类就可以实现。接下来通过两个小案例来进行实现吧。

开发步骤：

1.  先开发外部接口
2.  再开发内部接口
3.  在内部接口中，通过类 `HttpURLConnection` 去调用外部接口

为了测试方便，我这里就将外部接口、内部接口，全写在通过一个工程里面了哈。

### 1. 开发外部接口 ###

1、新建一个 SpringBoot 工程

2、新开发 4 个接口：这4个接口就假定为外部接口。也就是说，是在我们工程中需要调用的接口

**`HttpController`**：两个接口用于 `GET` 请求的无参请求、有参请求；另外两个接口用于 `POST` 请求的无参请求、有参请求

@RestController
    @RequestMapping("/http")
    public class HttpController {
        
    
        @Autowired
        private HttpService httpService;
    	
    	/// GET 请求/
    
        // 通过id获取用户信息
        @GetMapping("/getUserById")
        public UserVo getUserById(String id) {
        
            return httpService.getUserById(id);
        }
    
        // 获取所有用户信息
        @GetMapping("/listUsers")
        public List<UserVo> listUsers() {
        
            return httpService.listUsers();
        }
    	
    	/// POST 请求/
    
        // 通过id获取用户信息
        @PostMapping("/getUserVoById")
        public UserVo getUserVoById(String id) {
        
            return httpService.getUserById(id);
        }
    
        // 获取所有用户信息
        @PostMapping("/listUserList")
        public List<UserVo> listUserList() {
        
            return httpService.listUsers();
        }
    
    }

说明：

1.  4个接口分别按照 `get`、`post` 请求区分
2.  `get/post` 请求中的两个接口：无参：查询所有用户信息；有参：按照用户id查询用户信息

**`HttpServiceImpl`**：这里我没有连接数据库，直接使用了假数据。

@Service
    @Slf4j
    public class HttpServiceImpl implements HttpService {
        
    
        private static Map<String, UserVo> userVoMap;
    
        static {
        
            userVoMap = new HashMap<>();
            userVoMap.put("1", new UserVo("1", "zzc", "上海市"));
            userVoMap.put("2", new UserVo("2", "wzc", "北京市"));
            userVoMap.put("3", new UserVo("3", "wxc", "武汉市"));
        }
    
        @Override
        public UserVo getUserById(@RequestParam("id") String id) {
        
            return userVoMap.get(id);
        }
    
        @Override
        public List<UserVo> listUsers() {
        
            List<UserVo> userVos = new ArrayList<>();
            for (Map.Entry<String, UserVo> userVoEntry : userVoMap.entrySet()) {
        
                UserVo userVo = userVoEntry.getValue();
                userVos.add(userVo);
            }
            return userVos;
        }
    
    }

好了，到这就完成了我们外部接口的开发，接下来，就要通过类 `HttpURLConnection` 来调用这些接口了。

### 2. GET 请求 ###

在 `HttpController` 类中再开一个接口：用于 `get` 请求测试

@PostMapping("/httpUrlConnectionDoGet")
    public void httpUrlConnectionDoGet(@RequestBody HttpUrlConnectionVo httpUrlConnectionVo) {
        
        httpService.httpUrlConnectionDoGet(httpUrlConnectionVo);
    }

`HttpUrlConnectionVo`：请求Vo

@Data
    public class HttpUrlConnectionVo {
        
    
        // 请求地址
        private String uri;
    
        // 请求参数
        private Map<String, String> params;
    
        // 编码
        private String encoding;
    
    }

**`HttpServiceImpl`**：

@Override
    public void httpUrlConnectionDoGet(@RequestBody HttpUrlConnectionVo httpUrlConnectionVo) {
        
        if (StringUtil.isBlank(httpUrlConnectionVo.getEncoding())) {
        
            log.error("【发送GET请求】失败，字符编码不能为空！");
            return;
        }
        HttpUrlConnectionUtil.doGet(httpUrlConnectionVo.getUri(), httpUrlConnectionVo.getParams(), httpUrlConnectionVo.getEncoding());
    }

`HttpUrlConnectionUtil`：URLConnection工具类

@Slf4j
    @Component
    public class HttpUrlConnectionUtil {
        
    
        // 服务器ip
        public static final String IP = "http://localhost";
    
        // 端口
        public static final String PORT = ":8080";
    
        // GET请求接口带参数
        public static final String GET_URL_PARAMS = IP + PORT + "/http/getUserById";
    
        // GET请求接口不带参数
        public static final String GET_URL_NO_PARAMS = IP + PORT + "/http/listUsers";
    
        // POST请求接口带参数
        public static final String POST_URL_PARAMS = IP + PORT + "/http/getUserVoById";
    
        // POST请求接口不带参数
        public static final String POST_URL_NO_PARAMS = IP + PORT +  "/http/listUserList";
    
        // 返回成功编码
        public static final Integer RESPONSE_CODE_SUCCESS = 200;
    
        // POST请求
        public static final String METHOD_POST = "POST";
    
        private static HttpUrlConnectionConfig httpUrlConnectionConfig = ApplicationContextHolder.getContext().getBean(HttpUrlConnectionConfig.class);
    
        // 通过HttpUrlConnection发起Get请求
        public static String doGet(String uri, Map<String, String> params, String encoding) {
        
            byte[] bytes = null;
            if (MapUtil.isEmpty(params)) {
        
                uri = GET_URL_NO_PARAMS;
            } else {
        
                uri = GET_URL_PARAMS;
                try {
        
                    // 拼接参数
                    bytes = transformRequestParams(params).getBytes(encoding);
                    uri = uri + "?" + new String(bytes);
                } catch (UnsupportedEncodingException e) {
        
                    log.error("【发送GET请求】字符集转换失败，失败信息为：{}", e);
                    return null;
                }
            }
            log.info("【发送GET请求】请求地址为：{}", uri);
            URL url = null;
            HttpURLConnection connection = null;
            try {
        
                url = new URL(uri);
                // 建立连接
                connection = (HttpURLConnection)url.openConnection();
                httpUrlConnectionConfig.setConnectionProperty(connection);
                // 请求服务器
                connection.connect();
                // 获取服务器返回结果
                String responseData = getResponseData(connection, encoding);
                return responseData;
            } catch (MalformedURLException e) {
        
                log.error("【发送GET请求】创建URL失败，失败信息为：{}", e);
            } catch (IOException e) {
        
                log.error("【发送GET请求】创建连接失败，失败信息为：{}", e);
            }
            return null;
        }
    
    }

说明：

1.  此类中的常量已经定义好了外部接口的 ip、端口号。由于是本机，所有是 `localhost`。SpringBoot应用默认启动端口号为 8080
2.  此类中的常量也区分的 `get`、`post` 以及无参、有参
3.  在静态方法中使用对象：`httpUrlConnectionConfig.setConnectionProperty(connection);`

`MapUtil`：判断 Map 是否为空

public class MapUtil {
        
    
        public static boolean isEmpty(Map map) {
        
            return (map == null || map.isEmpty());
        }
    
        public static boolean isNotEmpty(Map map) {
        
            return !isEmpty(map);
        }
    
    }

`transformRequestParams()`：将 Map 格式的参数转换为字符串

// 转换请求参数
    public static String transformRequestParams(Map<String, String> params) {
        
        StringBuffer buffer = new StringBuffer();
        for (Map.Entry<String, String> entry : params.entrySet()) {
        
            buffer.append(entry.getKey()).append("=").append(entry.getValue()).append("&");
        }
        if (buffer.length() > 0) {
        
            buffer.deleteCharAt(buffer.length() - 1);
        }
        return buffer.toString();
    }

`HttpUrlConnectionConfig`：HttpUrlConnection配置

@Component
    public class HttpUrlConnectionConfig {
        
    
        public static final Integer CONNECTION_TIME_OUT = 10000;
        public static final Integer READ_TIME_OUT = 10000;
    
        // 设置连接时的属性
        public void setConnectionProperty(HttpURLConnection connection) {
        
            connection.setConnectTimeout(CONNECTION_TIME_OUT);
            connection.setReadTimeout(READ_TIME_OUT);
            connection.setRequestProperty("accept", "*/*");
            connection.setRequestProperty("connection", "close");
            connection.setRequestProperty("user-agent",
                    "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.106 Safari/537.36");
            if (HttpUrlConnectionUtil.METHOD_POST.equals(connection.getRequestMethod())) {
        
                // 设置连接输出流为true，默认false (post 请求是以流的方式隐式的传递参数)
                connection.setDoOutput(true);
                // 设置连接输入流为true
                connection.setDoInput(true);
                // 表单数据
                connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
            }
        }
    
    }

`ApplicationContextHolder`：以静态变量保存Spring ApplicationContext, 可在任何代码任何地方任何时候中取出 ApplicaitonContext

@Component
    public class ApplicationContextHolder implements ApplicationContextAware {
        
    
        private static ApplicationContext context;
    
        @Override
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        
            context = applicationContext;
        }
    
        public static ApplicationContext getContext() {
        
            return context;
        }
    
        public static Object getBean(String name) {
        
            return context != null ? context.getBean(name) : null;
        }
    
        public static <T> T getBean(Class<T> clz) {
        
            return context != null ? context.getBean(clz) : null;
        }
    
        public static <T> T getBean(String name, Class<T> clz) {
        
            return context != null ? context.getBean(name, clz) : null;
        }
    
        public static void addApplicationListenerBean(String listenerBeanName) {
        
            if (context != null) {
        
                ApplicationEventMulticaster applicationEventMulticaster = (ApplicationEventMulticaster)context.getBean(ApplicationEventMulticaster.class);
                applicationEventMulticaster.addApplicationListenerBean(listenerBeanName);
            }
        }
    
    }

`getResponseData()`：获取响应信息

// 获取响应信息
    public static String getResponseData(HttpURLConnection connection, String encoding) {
        
        BufferedReader in = null;
        StringBuffer result = new StringBuffer();
        StringBuffer errorMsg = new StringBuffer();
        try {
        
            // 调用成功
            if (RESPONSE_CODE_SUCCESS.equals(connection.getResponseCode())) {
        
                // 处理服务器响应
                in = new BufferedReader(new InputStreamReader(connection.getInputStream(), encoding));
                String line = null;
                while ((line = in.readLine()) != null) {
        
                    result.append(line);
                }
                log.info("【发送GET请求】请求成功，返回结果为：{}", result.toString());
                return result.toString();
            } else {
        
                in = new BufferedReader(new InputStreamReader(connection.getErrorStream(), encoding));
                String line = null;
                while ((line = in.readLine()) != null) {
        
                    errorMsg.append(line);
                }
                log.error("【发送GET请求】请求失败，失败信息为：{}", errorMsg.toString());
                return errorMsg.toString();
            }
        } catch (IOException e) {
        
            log.error("【发送GET请求】创建连接失败，失败信息为：{}", e);
        } finally {
        
            if (null != in) {
        
                try {
        
                    in.close();
                } catch (IOException e) {
        
                    log.error("【发送GET请求】关闭流失败，出现IO异常，异常信息为：{}", e);
                }
            }
        }
        return null;
    }

**POSTMAN 调用接口：**

1、GET 请求的无参：

![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAc2NvNTI4Mg_size_20_color_FFFFFF_t_70_g_se_x_16]  
查看控制台打印日志：  
![在这里插入图片描述][be5d295d773345b8ae65a15aacb1dac6.png]  
2、GET 请求的带参：  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAc2NvNTI4Mg_size_20_color_FFFFFF_t_70_g_se_x_16 1]  
查看控制台打印日志：  
![在这里插入图片描述][2bb39bbb76ca4e1eb0aa2f06376585bf.png]

### 3. POST 请求 ###

`HttpController`：在 `HttpController` 类中再开一个接口：用于 `post` 请求测试

@PostMapping("/httpUrlConnectionDoPost")
    public void httpUrlConnectionDoPost(@RequestBody HttpUrlConnectionVo httpUrlConnectionVo) {
        
        httpService.httpUrlConnectionDoPost(httpUrlConnectionVo);
    }

`HttpServiceImpl`：

@Override
    public void httpUrlConnectionDoPost(HttpUrlConnectionVo httpUrlConnectionVo) {
        
        if (StringUtil.isBlank(httpUrlConnectionVo.getEncoding())) {
        
            log.error("【发送POST请求】失败，字符编码不能为空！");
            return;
        }
        HttpUrlConnectionUtil.doPost(httpUrlConnectionVo.getUri(), httpUrlConnectionVo.getParams(), httpUrlConnectionVo.getEncoding());
    }

`HttpUrlConnectionUtil.doPost()`：

public static String doPost(String uri, Map<String, String> params, String encoding) {
        
        byte[] bytes = null;
        if (MapUtil.isEmpty(params)) {
        
            uri = POST_URL_NO_PARAMS;
        } else {
        
            uri = POST_URL_PARAMS;
            try {
        
                // 以字节的形式获取参数
                param = transformRequestParams(params);
                bytes = param.getBytes(encoding);
            } catch (UnsupportedEncodingException e) {
        
                log.error("【发送GET请求】字符集转换失败，失败信息为：{}", e);
                return null;
            }
        }
        log.info("【发送POST请求】请求地址为：{}", uri);
        URL url = null;
        HttpURLConnection connection = null;
        try {
        
            url = new URL(uri);
            // 1.建立连接
            connection = (HttpURLConnection)url.openConnection();
            // 【注意】这里的 POST 必须是大写，否则，会报错
            connection.setRequestMethod(METHOD_POST);
            httpUrlConnectionConfig.setConnectionProperty(connection);
            // 2.请求服务器
            connection.connect();
            // 3.拼接参数
            if (null != bytes && bytes.length > 0) {
        
                OutputStream out = connection.getOutputStream();
                out.write(bytes);
                out.close();
            }
            // 4.获取服务器返回结果
            String responseData = getResponseData(connection, encoding);
            return responseData;
        } catch (MalformedURLException e) {
        
            log.error("【发送POST请求】创建URL失败，失败信息为：{}", e);
        } catch (IOException e) {
        
            log.error("【发送POST请求】创建连接失败，失败信息为：{}", e);
        }
        return null;
    }

`post` 的有参、无参调用，跟 `get` 的一样，就是接口不同而已，可以自己试试吧。

好了，使用 `HttpURLConnection` 后台模拟实现 HTTP 请求就到这了。

[HttpURLConnection_ HttpURLConnection _ HTTP]: https://blog.csdn.net/sco5282/article/details/121457557
[HttpClient_ SpringBoot _ HttpClient _ HTTP]: https://blog.csdn.net/sco5282/article/details/121458401
[SpringBoot_ OkHttp]: https://blog.csdn.net/sco5282/article/details/128176718
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAc2NvNTI4Mg_size_20_color_FFFFFF_t_70_g_se_x_16]: https://img-blog.csdnimg.cn/da34de42fd5a415884c08b3ce6aa1ae5.png?x-oss-process=image/watermark,type_ZHJvaWRzYW5zZmFsbGJhY2s,shadow_50,text_Q1NETiBAc2NvNTI4Mg==,size_20,color_FFFFFF,t_70,g_se,x_16
[be5d295d773345b8ae65a15aacb1dac6.png]: https://img-blog.csdnimg.cn/be5d295d773345b8ae65a15aacb1dac6.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAc2NvNTI4Mg_size_20_color_FFFFFF_t_70_g_se_x_16 1]: https://img-blog.csdnimg.cn/d92835840568438d8443c86de91b7db0.png?x-oss-process=image/watermark,type_ZHJvaWRzYW5zZmFsbGJhY2s,shadow_50,text_Q1NETiBAc2NvNTI4Mg==,size_20,color_FFFFFF,t_70,g_se,x_16
[2bb39bbb76ca4e1eb0aa2f06376585bf.png]: https://img-blog.csdnimg.cn/2bb39bbb76ca4e1eb0aa2f06376585bf.png