Java中的OkHttp使用教程

目录

• 什么是OKHttp
• OkHttp基本使用
• 添加依赖
• OkHttp工具类
• 使用案例
• 发送get请求
• 发送Post请求
• 发送异步请求

什么是OKHttp

一般在Java平台上，我们会使用Apache HttpClient作为Http客户端，用于发送 HTTP 请求，并对响应进行处理。比如可以使用http客户端与第三方服务(如SSO服务)进行集成，当然还可以爬取网上的数据等。OKHttp与HttpClient类似，也是一个Http客户端，提供了对 HTTP/2 和 SPDY 的支持，并提供了连接池，GZIP 压缩和 HTTP 响应缓存功能；

OkHttp是目前非常火的网络库，它有以下特性：

1.支持HTTP/2，允许所有同一个主机地址的请求共享同一个socket连接

2.连接池减少请求延时

3.透明的GZIP压缩减少响应数据的大小

4.缓存响应内容，避免一些完全重复的请求

OkHttp基本使用

• OkHttpClient：客户端对象
• Request：访问请求，Post请求中需要包含RequestBody
• RequestBody：请求数据，在Post请求中用到
• Response：即网络请求的响应结果
• MediaType：数据类型，用来表明数据是json，image，pdf等一系列格式
• client.newCall(request).execute()：同步的请求方法
• client.newCall(request).enqueue(Callback callBack)：异步的请求方法，但Callback是执行在子线程中的，因此不能在此进行UI更新操作

官网：http://square.github.io/okhttp/

添加依赖

 <dependency>
            <groupId>com.squareup.okhttp3</groupId>
            <artifactId>okhttp</artifactId>
            <version>3.10.0</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.60</version>
        </dependency>

OkHttp工具类

package com.loginsimpl.utils;

import com.alibaba.fastjson.JSON;
import okhttp3.*;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.io.IOException;
import java.net.URLEncoder;
import java.security.SecureRandom;
import java.security.cert.X509Certificate;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

public class OkHttpUtils {
    private static volatile OkHttpClient okHttpClient = null;
    private static volatile Semaphore semaphore = null;
    private Map<String, String> headerMap;
    private Map<String, String> paramMap;
    private String url;
    private Request.Builder request;

    /**
     * 初始化okHttpClient，并且允许https访问
     */
    private OkHttpUtils() {
        if (okHttpClient == null) {
            synchronized (OkHttpUtils.class) {
                if (okHttpClient == null) {
                    TrustManager[] trustManagers = buildTrustManagers();
                    okHttpClient = new OkHttpClient.Builder()
                            .connectTimeout(15, TimeUnit.SECONDS)
                            .writeTimeout(20, TimeUnit.SECONDS)
                            .readTimeout(20, TimeUnit.SECONDS)
                            .sslSocketFactory(createSSLSocketFactory(trustManagers), (X509TrustManager) trustManagers[0])
                            .hostnameVerifier((hostName, session) -> true)
                            .retryOnConnectionFailure(true)
                            .build();
                    addHeader("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");
                }
            }
        }
    }

    /**
     * 用于异步请求时，控制访问线程数，返回结果
     *
     * @return
     */
    private static Semaphore getSemaphoreInstance() {
        //只能1个线程同时访问
        synchronized (OkHttpUtils.class) {
            if (semaphore == null) {
                semaphore = new Semaphore(0);
            }
        }
        return semaphore;
    }

    /**
     * 创建OkHttpUtils
     *
     * @return
     */
    public static OkHttpUtils builder() {
        return new OkHttpUtils();
    }

    /**
     * 添加url
     *
     * @param url
     * @return
     */
    public OkHttpUtils url(String url) {
        this.url = url;
        return this;
    }

    /**
     * 添加参数
     *
     * @param key   参数名
     * @param value 参数值
     * @return
     */
    public OkHttpUtils addParam(String key, String value) {
        if (paramMap == null) {
            paramMap = new LinkedHashMap<>(16);
        }
        paramMap.put(key, value);
        return this;
    }

    /**
     * 添加请求头
     *
     * @param key   参数名
     * @param value 参数值
     * @return
     */
    public OkHttpUtils addHeader(String key, String value) {
        if (headerMap == null) {
            headerMap = new LinkedHashMap<>(16);
        }
        headerMap.put(key, value);
        return this;
    }

    /**
     * 初始化get方法
     *
     * @return
     */
    public OkHttpUtils get() {
        request = new Request.Builder().get();
        StringBuilder urlBuilder = new StringBuilder(url);
        if (paramMap != null) {
            urlBuilder.append("?");
            try {
                for (Map.Entry<String, String> entry : paramMap.entrySet()) {
                    urlBuilder.append(URLEncoder.encode(entry.getKey(), "utf-8")).
                            append("=").
                            append(URLEncoder.encode(entry.getValue(), "utf-8")).
                            append("&");
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            urlBuilder.deleteCharAt(urlBuilder.length() - 1);
        }
        request.url(urlBuilder.toString());
        return this;
    }

    /**
     * 初始化post方法
     *
     * @param isJsonPost true等于json的方式提交数据，类似postman里post方法的raw
     *                   false等于普通的表单提交
     * @return
     */
    public OkHttpUtils post(boolean isJsonPost) {
        RequestBody requestBody;
        if (isJsonPost) {
            String json = "";
            if (paramMap != null) {
                json = JSON.toJSONString(paramMap);
            }
            requestBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), json);
        } else {
            FormBody.Builder formBody = new FormBody.Builder();
            if (paramMap != null) {
                paramMap.forEach(formBody::add);
            }
            requestBody = formBody.build();
        }
        request = new Request.Builder().post(requestBody).url(url);
        return this;
    }

    /**
     * 同步请求
     *
     * @return
     */
    public String sync() {
        setHeader(request);
        try {
            Response response = okHttpClient.newCall(request.build()).execute();
            assert response.body() != null;
            return response.body().string();
        } catch (IOException e) {
            e.printStackTrace();
            return "请求失败：" + e.getMessage();
        }
    }

    /**
     * 异步请求，有返回值  (限流的,同一时间只允许一个访问,其他等待)
     */
    public String async() {
        StringBuilder buffer = new StringBuilder("");
        setHeader(request);
        okHttpClient.newCall(request.build()).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                buffer.append("请求出错：").append(e.getMessage());
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                assert response.body() != null;
                buffer.append(response.body().string());
                getSemaphoreInstance().release();
            }
        });
        try {
            getSemaphoreInstance().acquire();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return buffer.toString();
    }

    /**
     * 异步请求，带有接口回调
     *
     * @param callBack
     */
    public void async(ICallBack callBack) {
        setHeader(request);
        okHttpClient.newCall(request.build()).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                callBack.onFailure(call, e.getMessage());
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                assert response.body() != null;
                callBack.onSuccessful(call, response.body().string());
            }
        });
    }

    /**
     * 为request添加请求头
     *
     * @param request
     */
    private void setHeader(Request.Builder request) {
        if (headerMap != null) {
            try {
                for (Map.Entry<String, String> entry : headerMap.entrySet()) {
                    request.addHeader(entry.getKey(), entry.getValue());
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 生成安全套接字工厂，用于https请求的证书跳过
     *
     * @return
     */
    private static SSLSocketFactory createSSLSocketFactory(TrustManager[] trustAllCerts) {
        SSLSocketFactory ssfFactory = null;
        try {
            SSLContext sc = SSLContext.getInstance("SSL");
            sc.init(null, trustAllCerts, new SecureRandom());
            ssfFactory = sc.getSocketFactory();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return ssfFactory;
    }

    private static TrustManager[] buildTrustManagers() {
        return new TrustManager[]{
                new X509TrustManager() {
                    @Override
                    public void checkClientTrusted(X509Certificate[] chain, String authType) {
                    }

                    @Override
                    public void checkServerTrusted(X509Certificate[] chain, String authType) {
                    }

                    @Override
                    public X509Certificate[] getAcceptedIssuers() {
                        return new X509Certificate[]{};
                    }
                }
        };
    }

    /**
     * 自定义一个接口回调
     */
    public interface ICallBack {

        void onSuccessful(Call call, String data);

        void onFailure(Call call, String errorMsg);

    }
}

使用案例

发送get请求

        String sync = OkHttpUtils.builder().url("http://localhost:9100/user/all")
                .addHeader("token", "xxxxxxx")
                .addParam("name", "xxx").addParam("pass", "xxx")
                .get()
                .sync();
        System.out.println(sync);

发送Post请求

        String sync = OkHttpUtils.builder().url("http://localhost:9100/user/all")
                .addHeader("token", "xxxxxxx")
                .addParam("name", "xxx").addParam("pass", "xxx")
                .post(true) // true 为json提交方式
                .sync();
        System.out.println(sync);

发送异步请求

需要实现ICallBack接口

//回调实现类
public class AsyncHttpServiceImpl implements OkHttpUtils.ICallBack {
    @Override
    public void onSuccessful(Call call, String data) {
        //接口正常返回的内容
        System.out.println("onSuccessful"+data);

    }

    @Override
    public void onFailure(Call call, String errorMsg) {
        //接口错误返回的内容
        System.out.println("onFailure"+errorMsg);
    }
}

发送异步请求

       OkHttpUtils.builder().url("http://localhost:9100/user/all")
                .addHeader("token", "xxxxxxx")
                .addParam("name", "xxx").addParam("pass", "xxx")
                .post(true)
                .async(new AsyncHttpServiceImpl());

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