详解java实现HTTP请求的三种方式

发布时间：2020-09-10 10:23:23 来源：脚本之家阅读：158 作者：君临-行者无界栏目：编程语言

目前JAVA实现HTTP请求的方法用的最多的有两种：一种是通过HTTPClient这种第三方的开源框架去实现。HTTPClient对HTTP的封装性比较不错，通过它基本上能够满足我们大部分的需求，HttpClient3.1 是 org.apache.commons.httpclient下操作远程 url的工具包，虽然已不再更新，但实现工作中使用httpClient3.1的代码还是很多，HttpClient4.5是org.apache.http.client下操作远程 url的工具包，最新的；另一种则是通过HttpURLConnection去实现，HttpURLConnection是JAVA的标准类，是JAVA比较原生的一种实现方式。

自己在工作中三种方式都用到过，总结一下分享给大家，也方便自己以后使用，话不多说上代码。

第一种方式：java原生HttpURLConnection

package com.powerX.httpClient;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class HttpClient {
  public static String doGet(String httpurl) {
    HttpURLConnection connection = null;
    InputStream is = null;
    BufferedReader br = null;
    String result = null;// 返回结果字符串
    try {
      // 创建远程url连接对象
      URL url = new URL(httpurl);
      // 通过远程url连接对象打开一个连接，强转成httpURLConnection类
      connection = (HttpURLConnection) url.openConnection();
      // 设置连接方式：get
      connection.setRequestMethod("GET");
      // 设置连接主机服务器的超时时间：15000毫秒
      connection.setConnectTimeout(15000);
      // 设置读取远程返回的数据时间：60000毫秒
      connection.setReadTimeout(60000);
      // 发送请求
      connection.connect();
      // 通过connection连接，获取输入流
      if (connection.getResponseCode() == 200) {
        is = connection.getInputStream();
        // 封装输入流is，并指定字符集
        br = new BufferedReader(new InputStreamReader(is, "UTF-8"));
        // 存放数据
        StringBuffer sbf = new StringBuffer();
        String temp = null;
        while ((temp = br.readLine()) != null) {
          sbf.append(temp);
          sbf.append("\r\n");
        }
        result = sbf.toString();
      }
    } catch (MalformedURLException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      // 关闭资源
      if (null != br) {
        try {
          br.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }

      if (null != is) {
        try {
          is.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }

      connection.disconnect();// 关闭远程连接
    }

    return result;
  }

  public static String doPost(String httpUrl, String param) {

    HttpURLConnection connection = null;
    InputStream is = null;
    OutputStream os = null;
    BufferedReader br = null;
    String result = null;
    try {
      URL url = new URL(httpUrl);
      // 通过远程url连接对象打开连接
      connection = (HttpURLConnection) url.openConnection();
      // 设置连接请求方式
      connection.setRequestMethod("POST");
      // 设置连接主机服务器超时时间：15000毫秒
      connection.setConnectTimeout(15000);
      // 设置读取主机服务器返回数据超时时间：60000毫秒
      connection.setReadTimeout(60000);

      // 默认值为：false，当向远程服务器传送数据/写数据时，需要设置为true
      connection.setDoOutput(true);
      // 默认值为：true，当前向远程服务读取数据时，设置为true，该参数可有可无
      connection.setDoInput(true);
      // 设置传入参数的格式:请求参数应该是 name1=value1&name2=value2 的形式。
      connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
      // 设置鉴权信息：Authorization: Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0
      connection.setRequestProperty("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");
      // 通过连接对象获取一个输出流
      os = connection.getOutputStream();
      // 通过输出流对象将参数写出去/传输出去,它是通过字节数组写出的
      os.write(param.getBytes());
      // 通过连接对象获取一个输入流，向远程读取
      if (connection.getResponseCode() == 200) {

        is = connection.getInputStream();
        // 对输入流对象进行包装:charset根据工作项目组的要求来设置
        br = new BufferedReader(new InputStreamReader(is, "UTF-8"));

        StringBuffer sbf = new StringBuffer();
        String temp = null;
        // 循环遍历一行一行读取数据
        while ((temp = br.readLine()) != null) {
          sbf.append(temp);
          sbf.append("\r\n");
        }
        result = sbf.toString();
      }
    } catch (MalformedURLException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      // 关闭资源
      if (null != br) {
        try {
          br.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (null != os) {
        try {
          os.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (null != is) {
        try {
          is.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      // 断开与远程地址url的连接
      connection.disconnect();
    }
    return result;
  }
}

第二种方式：apache HttpClient3.1

package com.powerX.httpClient;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.apache.commons.httpclient.DefaultHttpMethodRetryHandler;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.httpclient.params.HttpMethodParams;

public class HttpClient3 {

  public static String doGet(String url) {
    // 输入流
    InputStream is = null;
    BufferedReader br = null;
    String result = null;
    // 创建httpClient实例
    HttpClient httpClient = new HttpClient();
    // 设置http连接主机服务超时时间：15000毫秒
    // 先获取连接管理器对象，再获取参数对象,再进行参数的赋值
    httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);
    // 创建一个Get方法实例对象
    GetMethod getMethod = new GetMethod(url);
    // 设置get请求超时为60000毫秒
    getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);
    // 设置请求重试机制，默认重试次数：3次，参数设置为true，重试机制可用，false相反
    getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, true));
    try {
      // 执行Get方法
      int statusCode = httpClient.executeMethod(getMethod);
      // 判断返回码
      if (statusCode != HttpStatus.SC_OK) {
        // 如果状态码返回的不是ok,说明失败了,打印错误信息
        System.err.println("Method faild: " + getMethod.getStatusLine());
      } else {
        // 通过getMethod实例，获取远程的一个输入流
        is = getMethod.getResponseBodyAsStream();
        // 包装输入流
        br = new BufferedReader(new InputStreamReader(is, "UTF-8"));

        StringBuffer sbf = new StringBuffer();
        // 读取封装的输入流
        String temp = null;
        while ((temp = br.readLine()) != null) {
          sbf.append(temp).append("\r\n");
        }

        result = sbf.toString();
      }

    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      // 关闭资源
      if (null != br) {
        try {
          br.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (null != is) {
        try {
          is.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      // 释放连接
      getMethod.releaseConnection();
    }
    return result;
  }

  public static String doPost(String url, Map<String, Object> paramMap) {
    // 获取输入流
    InputStream is = null;
    BufferedReader br = null;
    String result = null;
    // 创建httpClient实例对象
    HttpClient httpClient = new HttpClient();
    // 设置httpClient连接主机服务器超时时间：15000毫秒
    httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000);
    // 创建post请求方法实例对象
    PostMethod postMethod = new PostMethod(url);
    // 设置post请求超时时间
    postMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000);

    NameValuePair[] nvp = null;
    // 判断参数map集合paramMap是否为空
    if (null != paramMap && paramMap.size() > 0) {// 不为空
      // 创建键值参数对象数组，大小为参数的个数
      nvp = new NameValuePair[paramMap.size()];
      // 循环遍历参数集合map
      Set<Entry<String, Object>> entrySet = paramMap.entrySet();
      // 获取迭代器
      Iterator<Entry<String, Object>> iterator = entrySet.iterator();

      int index = 0;
      while (iterator.hasNext()) {
        Entry<String, Object> mapEntry = iterator.next();
        // 从mapEntry中获取key和value创建键值对象存放到数组中
        try {
          nvp[index] = new NameValuePair(mapEntry.getKey(),
              new String(mapEntry.getValue().toString().getBytes("UTF-8"), "UTF-8"));
        } catch (UnsupportedEncodingException e) {
          e.printStackTrace();
        }
        index++;
      }
    }
    // 判断nvp数组是否为空
    if (null != nvp && nvp.length > 0) {
      // 将参数存放到requestBody对象中
      postMethod.setRequestBody(nvp);
    }
    // 执行POST方法
    try {
      int statusCode = httpClient.executeMethod(postMethod);
      // 判断是否成功
      if (statusCode != HttpStatus.SC_OK) {
        System.err.println("Method faild: " + postMethod.getStatusLine());
      }
      // 获取远程返回的数据
      is = postMethod.getResponseBodyAsStream();
      // 封装输入流
      br = new BufferedReader(new InputStreamReader(is, "UTF-8"));

      StringBuffer sbf = new StringBuffer();
      String temp = null;
      while ((temp = br.readLine()) != null) {
        sbf.append(temp).append("\r\n");
      }

      result = sbf.toString();
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      // 关闭资源
      if (null != br) {
        try {
          br.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (null != is) {
        try {
          is.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      // 释放连接
      postMethod.releaseConnection();
    }
    return result;
  }
}

第三种方式：apache httpClient4.5

package com.powerX.httpClient;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
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.HttpGet;
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;

public class HttpClient4 {

  public static String doGet(String url) {
    CloseableHttpClient httpClient = null;
    CloseableHttpResponse response = null;
    String result = "";
    try {
      // 通过址默认配置创建一个httpClient实例
      httpClient = HttpClients.createDefault();
      // 创建httpGet远程连接实例
      HttpGet httpGet = new HttpGet(url);
      // 设置请求头信息，鉴权
      httpGet.setHeader("Authorization", "Bearer da3efcbf-0845-4fe3-8aba-ee040be542c0");
      // 设置配置请求参数
      RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 连接主机服务超时时间
          .setConnectionRequestTimeout(35000)// 请求超时时间
          .setSocketTimeout(60000)// 数据读取超时时间
          .build();
      // 为httpGet实例设置配置
      httpGet.setConfig(requestConfig);
      // 执行get请求得到返回对象
      response = httpClient.execute(httpGet);
      // 通过返回对象获取返回数据
      HttpEntity entity = response.getEntity();
      // 通过EntityUtils中的toString方法将结果转换为字符串
      result = EntityUtils.toString(entity);
    } catch (ClientProtocolException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      // 关闭资源
      if (null != response) {
        try {
          response.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (null != httpClient) {
        try {
          httpClient.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }
    return result;
  }

  public static String doPost(String url, Map<String, Object> paramMap) {
    CloseableHttpClient httpClient = null;
    CloseableHttpResponse httpResponse = null;
    String result = "";
    // 创建httpClient实例
    httpClient = HttpClients.createDefault();
    // 创建httpPost远程连接实例
    HttpPost httpPost = new HttpPost(url);
    // 配置请求参数实例
    RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(35000)// 设置连接主机服务超时时间
        .setConnectionRequestTimeout(35000)// 设置连接请求超时时间
        .setSocketTimeout(60000)// 设置读取数据连接超时时间
        .build();
    // 为httpPost实例设置配置
    httpPost.setConfig(requestConfig);
    // 设置请求头
    httpPost.addHeader("Content-Type", "application/x-www-form-urlencoded");
    // 封装post请求参数
    if (null != paramMap && paramMap.size() > 0) {
      List<NameValuePair> nvps = new ArrayList<NameValuePair>();
      // 通过map集成entrySet方法获取entity
      Set<Entry<String, Object>> entrySet = paramMap.entrySet();
      // 循环遍历，获取迭代器
      Iterator<Entry<String, Object>> iterator = entrySet.iterator();
      while (iterator.hasNext()) {
        Entry<String, Object> mapEntry = iterator.next();
        nvps.add(new BasicNameValuePair(mapEntry.getKey(), mapEntry.getValue().toString()));
      }

      // 为httpPost设置封装好的请求参数
      try {
        httpPost.setEntity(new UrlEncodedFormEntity(nvps, "UTF-8"));
      } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
      }
    }
    try {
      // httpClient对象执行post请求,并返回响应参数对象
      httpResponse = httpClient.execute(httpPost);
      // 从响应对象中获取响应内容
      HttpEntity entity = httpResponse.getEntity();
      result = EntityUtils.toString(entity);
    } catch (ClientProtocolException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      // 关闭资源
      if (null != httpResponse) {
        try {
          httpResponse.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
      if (null != httpClient) {
        try {
          httpClient.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }
    return result;
  }
}

有时候我们在使用post请求时，可能传入的参数是json或者其他格式，此时我们则需要更改请求头及参数的设置信息，以httpClient4.5为例，更改下面两列配置：httpPost.setEntity(new StringEntity("你的json串")); httpPost.addHeader("Content-Type", "application/json")。

以上所述是小编给大家介绍的java实现HTTP请求的三种方式详解整合，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对亿速云网站的支持！

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