Java网络编程封装

Java 网络编程封装原理主要围绕着将底层的网络通信细节隐藏起来，提供简洁、易用且安全的高层接口，方便开发者进行网络应用开发。下面从封装的目标、常见的封装层次和具体的封装实现原理等方面详细介绍。
封装的目标
简化开发：底层的网络通信涉及到许多复杂的细节，如套接字的创建、连接的建立、数据的传输和接收等。通过封装，开发者可以使用更简单的接口来完成这些操作，无需关心底层的具体实现。
提高安全性：封装可以对网络通信的关键部分进行安全处理，例如对数据进行加密、验证等，防止数据在传输过程中被窃取或篡改。
增强可维护性和可扩展性：将网络通信的逻辑封装在独立的模块中，使得代码结构更加清晰，便于维护和扩展。当需要更改网络通信的实现方式时，只需修改封装模块的内部代码，而不会影响到使用该封装的其他部分。
常见的封装层次
套接字层封装
Java 的 java.net 包提供了基本的套接字（Socket）类，包括 Socket 和 ServerSocket，用于实现 TCP 通信，以及 DatagramSocket 用于实现 UDP 通信。这些类已经对底层的网络操作进行了一定程度的封装，但仍然需要开发者手动处理很多细节。例如，创建一个简单的 TCP 服务器：

代码如下:

package cn.ctg.common.util;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.InetAddress;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.UnknownHostException;
import java.util.Map;

import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;
import org.springframework.web.client.RestTemplate;

import cn.hutool.core.collection.CollectionUtil;
import lombok.extern.slf4j.Slf4j;

/**
 * http请求
 */
@Slf4j
public class HttpUtils {

    public static String doGet(String url) {
        return doGet(url, null);
    }

    public static String doGet(String url, Map<String, String> map) {

        String resultString = "";
        RestTemplate client = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        // 参数设置
        MultiValueMap<String, String> params = new LinkedMultiValueMap<String, String>();
        if (CollectionUtil.isNotEmpty(map)) {
            for (String key : map.keySet()) {
                params.add(key, map.get(key));
            }
        }

        try {

            // 设置表单提交
            headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
            HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<MultiValueMap<String, String>>(
                    params, headers);
            // 执行HTTP请求
            ResponseEntity<String> response = client.exchange(url, HttpMethod.GET, requestEntity, String.class);
            resultString = response.getBody();
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }

        return resultString;

    }

    public static String doPost(String url) {
        return doPost(url, null);
    }

    public static String doPost(String url, Map<String, String> map) {

        String resultString = "";
        ResponseEntity<String> response = null;
        RestTemplate client = new RestTemplate();
        HttpHeaders headers = new HttpHeaders();
        // 参数设置
        MultiValueMap<String, String> params = new LinkedMultiValueMap<String, String>();
        if (CollectionUtil.isNotEmpty(map)) {
            for (String key : map.keySet()) {
                params.add(key, map.get(key));
            }
        }

        try {

            // 请勿轻易改变此提交方式，大部分的情况下，提交方式都是表单提交
            headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
            HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<MultiValueMap<String, String>>(
                    params, headers);
            // 执行HTTP请求
            response = client.exchange(url, HttpMethod.POST, requestEntity, String.class);
            resultString = response.getBody();
        } catch (Exception e) {
            log.error(e.getMessage(), e);
        }
        return resultString;

    }

    public static String doPostJson(String url, String json) {

        String resultString = "";
        RestTemplate client = new RestTemplate();
        ResponseEntity<String> response = null;
        // 提交方式设置
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        HttpEntity<String> requestEntity = new HttpEntity<String>(json, headers);
        try {
            // 执行HTTP请求
            response = client.exchange(url, HttpMethod.POST, requestEntity, String.class);
            resultString = response.getBody();

        } catch (Exception e) {
            log.error(e.getMessage(), e);
        } finally {
            try {

            } catch (Exception e) {
                // TODO Auto-generated catch block
                log.error(e.getMessage(), e);
            }
        }
        return resultString;

    }


    /**
     * 创建http请求头
     * @param url
     * @return
     * @throws Exception
     */
    public static URLConnection FactoryCreatURLConnection(String url) throws Exception {
        URL realUrl;
        URLConnection conn = null;
        try {
            // 打开和URL之间的连接
            realUrl = new URL(url);
            conn = realUrl.openConnection();
            conn.setRequestProperty("accept", "text/plain;charset=utf-8");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=utf-8");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
        } catch (MalformedURLException e1) {
            e1.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * 判断连接是否可用
     * 
     * @param url http请求地址
     * @return
     */
    public static boolean isRearchUrl(String url) {
        return isRearchUrl(url, 3000);
    }

    /**
     * 判断连接是否可用
     * 
     * @param url http请求地址
     * @return
     */
    public static boolean isRearchUrl(String url, int timeout) {

        if (StringUtils.isEmpty(url)) {
            return false;
        }
        HttpURLConnection connection = null;
        try {
            connection = (HttpURLConnection) new URL(url).openConnection();
            // 设置超时时间
            connection.setConnectTimeout(timeout);
            connection.setReadTimeout(timeout);
            if (connection.getResponseCode() >= HttpURLConnection.HTTP_OK
                    && connection.getResponseCode() <= HttpURLConnection.HTTP_VERSION) {
                return true;
            }
        } catch (Exception e) {
            log.error(" HttpURLConnection exception happend!");
            return false;
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
        return false;
    }

    /**
     * 判断ip是否能ping通
     */
    public static boolean checkIp(String ipAddr) {
        try {
            boolean status = false;
            if (!StringUtils.isEmpty(ipAddr)) {
                int timeOut = 3000; // 超时 3秒
                status = InetAddress.getByName(ipAddr).isReachable(timeOut);
                return status;
            }
            return status;
        } catch (UnknownHostException e) {
            e.printStackTrace();
            return false;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }


}