java中的http请求的封装（GET、POST、form表单形式）

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。

第一种方式：java原生HttpURLConnection

package com.mobile.utils;

import com.alibaba.fastjson.JSONObject;
import org.apache.log4j.Logger;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.*;

public class HttpUtil {
    static Logger log = Logger.getLogger(HttpUtil.class);

    /**
     * 向指定URL发送GET方法的请求
     *
     * @param httpurl
     *            请求参数用?拼接在url后边，请求参数应该是 name1=value1&name2=value2 的形式。
     * @return result 所代表远程资源的响应结果
     */
    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("
");
                }
                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;
    }

    /**
     * 向指定 URL 发送POST方法的请求
     *
     * @param httpUrl
     *            发送请求的 URL
     * @param param
     *            请求参数应该是{"key":"==g43sEvsUcbcunFv3mHkIzlHO4iiUIT R7WwXuSVKTK0yugJnZSlr6qNbxsL8OqCUAFyCDCoRKQ882m6cTTi0q9uCJsq JJvxS+8mZVRP/7lWfEVt8/N9mKplUA68SWJEPSXyz4MDeFam766KEyvqZ99d"}的形式。
     * @return 所代表远程资源的响应结果
     */
    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/json");
            // 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("
");
                }
                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;
    }

    /**
     *
     * @param httpUrl  请求的url
     * @param param  form表单的参数（key,value形式）
     * @return
     */
    public static String doPostForm(String httpUrl, Map 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(form表单形式的参数实质也是key,value值的拼接，类似于get请求参数的拼接)
            os.write(createLinkString(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("
");
                }
                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;
    }
    /**
     * 把数组所有元素排序，并按照“参数=参数值”的模式用“&”字符拼接成字符串
     * @param params 需要排序并参与字符拼接的参数组
     * @return 拼接后字符串
     */
    public static String createLinkString(Map<String, String> params) {

        List<String> keys = new ArrayList<String>(params.keySet());
        Collections.sort(keys);

        StringBuilder prestr = new StringBuilder();
        for (int i = 0; i < keys.size(); i++) {
            String key = keys.get(i);
            String value = params.get(key);
            if (i == keys.size() - 1) {// 拼接时，不包括最后一个&字符
                prestr.append(key).append("=").append(value);
            } else {
                prestr.append(key).append("=").append(value).append("&");
            }
        }

        return prestr.toString();
    }


    public static void main(String[] args) {
        String url = "http://localhost:8082/api/conf/findConfList?type=1";
        String getResult = HttpUtil.doGet(url);
        System.out.println(getResult);

        url = "http://localhost:8082/api/core/login";
        JSONObject json = new JSONObject();
        json.put("key", "==g43sEvsUcbcunFv3mHkIzlHO4iiUIT R7WwXuSVKTK0yugJnZSlr6qNbxsL8OqCUAFyCDCoRKQ882m6cTTi0q9uCJsq JJvxS+8mZVRP/7lWfEVt8/N9mKplUA68SWJEPSXyz4MDeFam766KEyvqZ99d");
        String postResult = HttpUtil.doPost(url, json.toJSONString());
        System.out.println(postResult);

        url = "http://localhost:8082/api/test/testSendForm";
        Map<String,String> map = new HashMap<>();
        map.put("name", "测试表单请求");
        String formResult = HttpUtil.doPostForm(url, map);
        System.out.println(formResult);

    }

}

以上包括了get请求和post请求以及form表单请求 

第二种方式：apache HttpClient 3.1

package com.demo.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("
");
                }

                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("
");
            }

            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.mobile.utils;

import com.alibaba.fastjson.JSONObject;
import org.apache.commons.io.IOUtils;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
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.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.charset.Charset;
import java.util.*;
import java.util.Map.Entry;

public class HttpUtil {
    static Logger log = Logger.getLogger(HttpUtil.class);public static void main(String[] args) {
        String url = "http://localhost:8082/api/conf/findConfList?type=1";
        String getResult = HttpUtil.getData(url);
        System.out.println(getResult);

        url = "http://localhost:8082/api/core/login";
        JSONObject json = new JSONObject();
        json.put("key", "==g43sEvsUcbcunFv3mHkIzlHO4iiUIT R7WwXuSVKTK0yugJnZSlr6qNbxsL8OqCUAFyCDCoRKQ882m6cTTi0q9uCJsq JJvxS+8mZVRP/7lWfEVt8/N9mKplUA68SWJEPSXyz4MDeFam766KEyvqZ99d");
        String postResult = HttpUtil.postData(url, json);
        System.out.println(postResult);

        url = "http://localhost:8082/api/test/testSendForm?format=json";
        Map<String, Object> map = new HashMap<>();
        map.put("name", "测试表单请求");
        String formResult = HttpUtil.sendxwwwForm(url, map);
        System.out.println(formResult);

    }


    public static String getData(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 postData(String url, Map<String, Object> paramMap) {

        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
        HttpPost post = new HttpPost(url);
        String result = "";
        try (CloseableHttpClient closeableHttpClient = httpClientBuilder.build()) {
            // HttpEntity entity = new StringEntity(jsonStrData);
            // 修复 POST json 导致中文乱码
            HttpEntity entity = new StringEntity(paramMap.toString(), "UTF-8");
            post.setEntity(entity);
            post.setHeader("Content-type", "application/json");
            HttpResponse resp = closeableHttpClient.execute(post);
            try {
                InputStream respIs = resp.getEntity().getContent();
                byte[] respBytes = IOUtils.toByteArray(respIs);
                result = new String(respBytes, Charset.forName("UTF-8"));
            } catch (Exception e) {
                e.printStackTrace();
            }
            return result;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return result;
    }

    /**
     * form表单提交
     * @param url
     * @param paramMap
     * @return
     */
    public static String sendxwwwform(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;
    }


}

以上包括了get请求和post请求以及form表单请求 

此外还可以设置添加自定义请求头（有的接口需要登录验证）：

　　方式一：

 //设置自定义请求头
            if (headerMap != null) {
                for (Map.Entry<String, String> entry : headerMap.entrySet()) {
                    connection.setRequestProperty(entry.getKey(),entry.getValue());
                }
            }

　　方式三：

if (headers != null) {
            for (Map.Entry<String, String> entry : headers.entrySet()) {
                httpPost.addHeader(entry.getKey(),entry.getValue());
            }
        }

　　

转载自https://www.cnblogs.com/hhhshct/p/8523697.html

测试后，稍作改动及添加

httpurlconnection和httpclient区别：https://www.cnblogs.com/liushuibufu/p/4140913.html