What are the ways to send HTTP requests in JAVA?

1. HttpURLConnection

Use the net provided by the JDK natively, without the need for other jar packages. The code is as follows:

import com.alibaba.fastjson.JSON;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
 
public class HttpTest1 {
 
    public static void main(String[] args) {
        HttpURLConnection con = null;
 
        BufferedReader buffer = null;
        StringBuffer resultBuffer = null;
 
        try {
            URL url = new URL("http://10.30.10.151:8012/gateway.do");
            //得到连接对象
            con = (HttpURLConnection) url.openConnection();
            //设置请求类型
            con.setRequestMethod("POST");
            //设置Content-Type，此处根据实际情况确定
            con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            //允许写出
            con.setDoOutput(true);
            //允许读入
            con.setDoInput(true);
            //不使用缓存
            con.setUseCaches(false);
            OutputStream os = con.getOutputStream();
            Map paraMap = new HashMap();
            paraMap.put("type", "wx");
            paraMap.put("mchid", "10101");
            //组装入参
            os.write(("consumerAppId=test&serviceName=queryMerchantService&params=" + JSON.toJSONString(paraMap)).getBytes());
            //得到响应码
            int responseCode = con.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                //得到响应流
                InputStream inputStream = con.getInputStream();
                //将响应流转换成字符串
                resultBuffer = new StringBuffer();
                String line;
                buffer = new BufferedReader(new InputStreamReader(inputStream, "GBK"));
                while ((line = buffer.readLine()) != null) {
                    resultBuffer.append(line);
                }
                System.out.println("result:" + resultBuffer.toString());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2. HttpClient

You need to use commons-httpclient- 3.1.jar, the maven dependencies are as follows:

<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>

The code is as follows:

import com.alibaba.fastjson.JSON;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.methods.PostMethod;
 
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
 
public class HttpTest2 {
 
    public static void main(String[] args) {
        HttpClient httpClient = new HttpClient();
        PostMethod postMethod = new PostMethod("http://10.30.10.151:8012/gateway.do");
 
        postMethod.addRequestHeader("accept", "*/*");
        //设置Content-Type，此处根据实际情况确定
        postMethod.addRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        //必须设置下面这个Header
        //添加请求参数
        Map paraMap = new HashMap();
        paraMap.put("type", "wx");
        paraMap.put("mchid", "10101");
        postMethod.addParameter("consumerAppId", "test");
        postMethod.addParameter("serviceName", "queryMerchantService");
        postMethod.addParameter("params", JSON.toJSONString(paraMap));
        String result = "";
        try {
            int code = httpClient.executeMethod(postMethod);
            if (code == 200){
                result = postMethod.getResponseBodyAsString();
                System.out.println("result:" + result);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. CloseableHttpClient

needs to use httpclient-4.5.6.jar, the maven dependencies are as follows:

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.6</version>
</dependency>

The code is as follows:

import com.alibaba.fastjson.JSON;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
 
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
public class HttpTest3 {
 
    public static void main(String[] args) {
        int timeout = 120000;
        CloseableHttpClient httpClient = HttpClients.createDefault();
        RequestConfig defaultRequestConfig = RequestConfig.custom().setConnectTimeout(timeout)
                .setConnectionRequestTimeout(timeout).setSocketTimeout(timeout).build();
        HttpPost httpPost = null;
        List<NameValuePair> nvps = null;
        CloseableHttpResponse responses = null;// 命名冲突，换一个名字，response
        HttpEntity resEntity = null;
        String result;
        try {
            httpPost = new HttpPost("http://10.30.10.151:8012/gateway.do");
            httpPost.setConfig(defaultRequestConfig);
 
            Map paraMap = new HashMap();
            paraMap.put("type", "wx");
            paraMap.put("mchid", "10101");
            nvps = new ArrayList<NameValuePair>();
            nvps.add(new BasicNameValuePair("consumerAppId", "test"));
            nvps.add(new BasicNameValuePair("serviceName", "queryMerchantService"));
            nvps.add(new BasicNameValuePair("params", JSON.toJSONString(paraMap)));
            httpPost.setEntity(new UrlEncodedFormEntity(nvps, Consts.UTF_8));
 
            responses = httpClient.execute(httpPost);
            resEntity = responses.getEntity();
            result = EntityUtils.toString(resEntity, Consts.UTF_8);
            EntityUtils.consume(resEntity);
            System.out.println("result:" + result);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                responses.close();
                httpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

4. okhttp

needs to use okhttp-3.10.0.jar, and the maven dependency is as follows:

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

The code is as follows:

import com.alibaba.fastjson.JSON;
import okhttp3.*;
 
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
 
public class HttpTest4 {
 
    public static void main(String[] args) throws IOException {
        String url = "http://10.30.10.151:8012/gateway.do";
        OkHttpClient client = new OkHttpClient();
        Map paraMap = new HashMap();
        paraMap.put("yybh", "1231231");
 
        RequestBody requestBody = new MultipartBody.Builder()
                .addFormDataPart("consumerAppId", "tst")
                .addFormDataPart("serviceName", "queryCipher")
                .addFormDataPart("params", JSON.toJSONString(paraMap))
                .build();
 
        Request request = new Request.Builder()
                .url(url)
                .post(requestBody)
                .addHeader("Content-Type", "application/x-www-form-urlencoded")
                .build();
        Response response = client
                .newCall(request)
                .execute();
        if (response.isSuccessful()) {
            System.out.println("result:" + response.body().string());
        } else {
            throw new IOException("Unexpected code " + response);
        }
    }
}

5. Socket

Use the net provided by the JDK natively, no other jar package required

The code is as follows:

import com.alibaba.fastjson.JSON;
 
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.URLEncoder;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
 
public class HttpTest6 {
 
    private static String encoding = "utf-8";
 
    public static void main(String[] args) {
        try {
            Map paraMap = new HashMap();
            paraMap.put("yybh", "12312311");
            String data = URLEncoder.encode("consumerAppId", "utf-8") + "=" + URLEncoder.encode("test", "utf-8") + "&" +
                    URLEncoder.encode("serviceName", "utf-8") + "=" + URLEncoder.encode("queryCipher", "utf-8")
                    + "&" +
                    URLEncoder.encode("params", "utf-8") + "=" + URLEncoder.encode(JSON.toJSONString(paraMap), "utf-8");
            Socket s = new Socket("10.30.10.151", 8012);
            OutputStreamWriter osw = new OutputStreamWriter(s.getOutputStream());
            StringBuffer sb = new StringBuffer();
            sb.append("POST /gateway.do HTTP/1.1\r\n");
            sb.append("Host: 10.30.10.151:8012\r\n");
            sb.append("Content-Length: " + data.length() + "\r\n");
            sb.append("Content-Type: application/x-www-form-urlencoded\r\n");
            //注，这里很关键。这里一定要一个回车换行，表示消息头完，不然服务器会等待
            sb.append("\r\n");
            osw.write(sb.toString());
            osw.write(data);
            osw.write("\r\n");
            osw.flush();
 
            //--输出服务器传回的消息的头信息
            InputStream is = s.getInputStream();
            String line = null;
            int contentLength = 0;//服务器发送回来的消息长度
            // 读取所有服务器发送过来的请求参数头部信息
            do {
                line = readLine(is, 0);
                //如果有Content-Length消息头时取出
                if (line.startsWith("Content-Length")) {
                    contentLength = Integer.parseInt(line.split(":")[1].trim());
                }
                //打印请求部信息
                System.out.print(line);
                //如果遇到了一个单独的回车换行，则表示请求头结束
            } while (!line.equals("\r\n"));
 
            //--输消息的体
            System.out.print(readLine(is, contentLength));
 
            //关闭流
            is.close();
 
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
    /*
     * 这里我们自己模拟读取一行，因为如果使用API中的BufferedReader时，它是读取到一个回车换行后
     * 才返回，否则如果没有读取，则一直阻塞，直接服务器超时自动关闭为止，如果此时还使用BufferedReader
     * 来读时，因为读到最后一行时，最后一行后不会有回车换行符，所以就会等待。如果使用服务器发送回来的
     * 消息头里的Content-Length来截取消息体，这样就不会阻塞
     *
     * contentLe 参数 如果为0时，表示读头，读时我们还是一行一行的返回；如果不为0，表示读消息体，
     * 时我们根据消息体的长度来读完消息体后，客户端自动关闭流，这样不用先到服务器超时来关闭。
     */
    private static String readLine(InputStream is, int contentLe) throws IOException {
        ArrayList lineByteList = new ArrayList();
        byte readByte;
        int total = 0;
        if (contentLe != 0) {
            do {
                readByte = (byte) is.read();
                lineByteList.add(Byte.valueOf(readByte));
                total++;
            } while (total < contentLe);//消息体读还未读完
        } else {
            do {
                readByte = (byte) is.read();
                lineByteList.add(Byte.valueOf(readByte));
            } while (readByte != 10);
        }
 
        byte[] tmpByteArr = new byte[lineByteList.size()];
        for (int i = 0; i < lineByteList.size(); i++) {
            tmpByteArr[i] = ((Byte) lineByteList.get(i)).byteValue();
        }
        lineByteList.clear();
 
        return new String(tmpByteArr, encoding);
    }
}

6. RestTemplate

RestTemplate is an HTTP request tool provided by Spring. It is much more convenient than traditional Apache and HttpCLient, and can greatly improve the writing efficiency of the client. The code is as follows:

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;
 
@Configuration
public class RestTemplateConfig {
 
    @Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory factory){
        return new RestTemplate(factory);
    }
 
    @Bean
    public ClientHttpRequestFactory simpleClientHttpRequestFactory(){
        SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
        factory.setConnectTimeout(15000);
        factory.setReadTimeout(5000);
        return factory;
    }
}
 
 
@Autowired
RestTemplate restTemplate;
 
@Test
public void postTest() throws Exception {
    MultiValueMap<String, String> requestEntity = new LinkedMultiValueMap<>();
    Map paraMap = new HashMap();
    paraMap.put("type", "wx");
    paraMap.put("mchid", "10101");
    requestEntity.add("consumerAppId", "test");
    requestEntity.add("serviceName", "queryMerchant");
    requestEntity.add("params", JSON.toJSONString(paraMap));
    RestTemplate restTemplate = new RestTemplate();
    System.out.println(restTemplate.postForObject("http://10.30.10.151:8012/gateway.do",         requestEntity, String.class));
}

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