一 . 概述

二 . OKHttp3

2.1 步骤一 : 导包

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
      <!--okhttp3-->
     <dependency>
       <groupId>com.squareup.okhttp3</groupId>
        <artifactId>okhttp</artifactId>
        <version>4.2.0</version>
     </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.60</version>
    </dependency>

2.2 步骤二 : 配置 spring-config(设定超时)

    @Bean
    public OkHttpClient okHttpClient() {
        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        builder.connectTimeout(30, TimeUnit.SECONDS)
                .readTimeout(30, TimeUnit.SECONDS)
                .writeTimeout(30,TimeUnit.SECONDS)
                .retryOnConnectionFailure(true);
        return builder.build();
    }

2.3 步骤三: 在controller层 的get请求

    @RestController
    @RequestMapping("/test")
    public String run(String url) throws IOException {
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder()
                .url(url)
                .build();
        try (Response response = client.newCall(request).execute()) {
            return response.body().string();
        }
    }

注:这样是原封不动把JSON数据返回给前端

附 post请求

public static final MediaType JSON
    = MediaType.get("application/json; charset=utf-8");

OkHttpClient client = new OkHttpClient();

String post(String url, String json) throws IOException {
  RequestBody body = RequestBody.create(JSON, json);
  Request request = new Request.Builder()
      .url(url)
      .post(body)
      .build();
  try (Response response = client.newCall(request).execute()) {
    return response.body().string();
  }
}

三 . Httpclient

3.1 步骤一导包

    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
      <groupId>org.apache.httpcomponents</groupId>
      <artifactId>httpclient</artifactId>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.60</version>
    </dependency>

3.2 步骤二 : 编写工具类HttpClientUtil

public class HttpClientUtil {

    protected final static Logger logger = LoggerFactory.getLogger(HttpClientUtil.class);

    private static PoolingHttpClientConnectionManager cm;
    private static String EMPTY_STR = "";
    private static String UTF_8 = "UTF-8";

    private static void init() {
        if (cm == null) {
            //采用绕过验证的方式处理https请求
            SSLContext sslcontext = null;
            try {
                sslcontext = createIgnoreVerifySSL();
            } catch (Exception e) {
                logger.error(e.getMessage(), e);
            }

            // 设置协议http和https对应的处理socket链接工厂的对象
            Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create()
                    .register("http", PlainConnectionSocketFactory.INSTANCE)
                    .register("https", new SSLConnectionSocketFactory(sslcontext))
                    .build();
            cm = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
            // 整个连接池最大连接数
            cm.setMaxTotal(50);
            // 每路由最大连接数，默认值是2
            cm.setDefaultMaxPerRoute(5);
        }
    }

    /**
     * 通过连接池获取HttpClient
     *
     * @return
     */
    private static CloseableHttpClient getHttpClient() {
        init();
        return HttpClients.custom().setConnectionManager(cm).build();
    }

    /**
     * get请求-不带参数
     * @param url
     * @return
     */
    public static String httpGetRequest(String url) {
        HttpGet httpGet = new HttpGet(url);
        return getResult(httpGet);
    }

    /**
     * get请求-带参数
     * @param url
     * @param params
     * @return
     * @throws URISyntaxException
     */
    public static String httpGetRequest(String url, Map<String, Object> params) throws URISyntaxException {
        URIBuilder ub = new URIBuilder();
        ub.setPath(url);
        ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
        ub.setParameters(pairs);
        HttpGet httpGet = new HttpGet(ub.build());
        return getResult(httpGet);
    }

    /**
     * get请求-带参数-带请求头信息
     * @param url
     * @param headers
     * @param params
     * @return
     * @throws URISyntaxException
     */
    public static String httpGetRequest(String url, Map<String, Object> headers, Map<String, Object> params)
            throws URISyntaxException {
        URIBuilder ub = new URIBuilder();
        ub.setPath(url);
        ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
        ub.setParameters(pairs);
        HttpGet httpGet = new HttpGet(ub.build());
        for (Map.Entry<String, Object> param : headers.entrySet()) {
            httpGet.addHeader(param.getKey(), String.valueOf(param.getValue()));
        }
        return getResult(httpGet);
    }

    /**
     * post请求-不带参数
     * @param url
     * @return
     */
    public static String httpPostRequest(String url) {
        HttpPost httpPost = new HttpPost(url);
        return getResult(httpPost);
    }

    /**
     * post请求,参数为json字符串
     * @param url
     * @param json
     * @return
     */
    public static String httpPostRequest(String url, String json) {
        HttpPost httpPost = new HttpPost(url);
        // 解决中文乱码问题
        StringEntity entity = new StringEntity(json, "UTF-8");
        entity.setContentEncoding("UTF-8");
        entity.setContentType("application/json");
        httpPost.setEntity(entity);
        return getResult(httpPost);
    }

    /**
     * post请求-参数为json字符串-带请求头信息
     * @param url
     * @param json
     * @param headers
     * @return
     */
    public static String httpPostRequest(String url, String json, Map<String, Object> headers) {
        HttpPost httpPost = new HttpPost(url);
        StringEntity entity = new StringEntity(json, "utf-8");//解决中文乱码问题
        entity.setContentEncoding("UTF-8");
        entity.setContentType("application/json");
        httpPost.setEntity(entity);
        for (Map.Entry<String, Object> param : headers.entrySet()) {
            httpPost.addHeader(param.getKey(), String.valueOf(param.getValue()));
        }
        return getResult(httpPost);
    }

    /**
     * post请求-带参数
     * @param url
     * @param params
     * @return
     * @throws UnsupportedEncodingException
     */
    public static String httpPostRequest(String url, Map<String, Object> params) throws UnsupportedEncodingException {
        HttpPost httpPost = new HttpPost(url);
        ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
        httpPost.setEntity(new UrlEncodedFormEntity(pairs, UTF_8));
        return getResult(httpPost);
    }

    /**
     * post请求-带参数-带请求头信息
     * @param url
     * @param headers
     * @param params
     * @return
     * @throws UnsupportedEncodingException
     */
    public static String httpPostRequest(String url, Map<String, Object> headers, Map<String, Object> params)
            throws UnsupportedEncodingException {
        HttpPost httpPost = new HttpPost(url);
        for (Map.Entry<String, Object> param : headers.entrySet()) {
            httpPost.addHeader(param.getKey(), String.valueOf(param.getValue()));
        }
        ArrayList<NameValuePair> pairs = covertParams2NVPS(params);
        httpPost.setEntity(new UrlEncodedFormEntity(pairs, UTF_8));

        return getResult(httpPost);
    }

    /**
     * 参数转换
     * @param params
     * @return
     */
    private static ArrayList<NameValuePair> covertParams2NVPS(Map<String, Object> params) {
        ArrayList<NameValuePair> pairs = new ArrayList<NameValuePair>();
        for (Map.Entry<String, Object> param : params.entrySet()) {
            pairs.add(new BasicNameValuePair(param.getKey(), String.valueOf(param.getValue())));
        }
        return pairs;
    }

    /**
     * 处理Http请求
     */
    private static String getResult(HttpRequestBase request) {
        CloseableHttpClient httpClient = getHttpClient();
        try {
            CloseableHttpResponse response = httpClient.execute(request);
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                // long len = entity.getContentLength();// -1 表示长度未知
                String result = EntityUtils.toString(entity);
                response.close();
                return result;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return EMPTY_STR;
    }

    /**
     * 绕过验证
     *
     * @return
     * @throws NoSuchAlgorithmException
     * @throws KeyManagementException
     */
    public static SSLContext createIgnoreVerifySSL() throws NoSuchAlgorithmException, KeyManagementException {
        SSLContext sc = SSLContext.getInstance("SSLv3");
        // 实现一个X509TrustManager接口，用于绕过验证，不用修改里面的方法
        X509TrustManager trustManager = new X509TrustManager() {
            @Override
            public void checkClientTrusted(
                    java.security.cert.X509Certificate[] paramArrayOfX509Certificate,
                    String paramString) throws CertificateException {
            }
            @Override
            public void checkServerTrusted(
                    java.security.cert.X509Certificate[] paramArrayOfX509Certificate,
                    String paramString) throws CertificateException {
            }
            @Override
            public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                return null;
            }
        };
        sc.init(null, new TrustManager[]{trustManager}, null);
        return sc;
    }
}

3.3 在controller层调用

@RestController
@RequestMapping("/remote")
public class RemoteController {
    private HttpProtocolHandler handler = new HttpProtocolHandler();
    @RequestMapping
    public Object getUser() {
        String url = "http://localhost:8080/user";
        Map<String, String> map = new HashMap<>();
        String result = HttpClientUtil.httpGetRequest(url, map);
        return result;
    }
}