java实现HTTP请求的四种方式

墨蓝 2022-05-12 19:20 242阅读 0赞

目前JAVA实现HTTP请求的方法用的最多的有两种：  
1、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；  
2、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。

实现过程：

GET:
    1、创建远程连接
    2、设置连接方式（get、post、put。。。）
    3、设置连接超时时间
    4、设置响应读取时间
    5、发起请求
    6、获取请求数据
    7、关闭连接
    
    POST:
    1、创建远程连接
    2、设置连接方式（get、post、put。。。）
    3、设置连接超时时间
    4、设置响应读取时间
    5、当向远程服务器传送数据/写数据时，需要设置为true（setDoOutput）
    6、当前向远程服务读取数据时，设置为true，该参数可有可无（setDoInput）
    7、设置传入参数的格式:（setRequestProperty）
    8、设置鉴权信息：Authorization:（setRequestProperty）
    9、设置参数
    10、发起请求
    11、获取请求数据
    12、关闭连接

**Java原生HttpURLConnection**

package com.ming.http;
    
    import org.springframework.lang.Nullable;
    
    import java.io.*;
    import java.net.HttpURLConnection;
    import java.net.MalformedURLException;
    import java.net.URL;
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * 文件名：  ${file_name}
     * 版权：    Copyright by ljm
     * 描述：
     * 修改人：  HuamingChen
     * 修改时间：2018/10/24
     * 跟踪单号：
     * 修改单号：
     * 修改内容：
     */
    public class HttpURLConnectionUtil {
        /**
         * http get请求
         * @param httpUrl 链接
         * @return 响应数据
         */
        public static String doGet(String httpUrl){
            //链接
            HttpURLConnection connection=null;
            InputStream is=null;
            BufferedReader br = null;
            StringBuffer result=new StringBuffer();
            try {
                //创建连接
                URL url=new URL(httpUrl);
                connection= (HttpURLConnection) url.openConnection();
                //设置请求方式
                connection.setRequestMethod("GET");
                //设置连接超时时间
                connection.setConnectTimeout(15000);
                //设置读取超时时间
                connection.setReadTimeout(15000);
                //开始连接
                connection.connect();
                //获取响应数据
                if(connection.getResponseCode()==200){
                    //获取返回的数据
                    is=connection.getInputStream();
                    if(is!=null){
                        br=new BufferedReader(new InputStreamReader(is,"UTF-8"));
                        String temp = null;
                        while ((temp=br.readLine())!=null){
                            result.append(temp);
                        }
                    }
                }
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                if(br!=null){
                    try {
                        br.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if(is!=null){
                    try {
                        is.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                connection.disconnect();// 关闭远程连接
            }
            return result.toString();
        }
    
        /**
         * post请求
         * @param httpUrl 链接
         * @param param 参数
         * @return
         */
        public static String doPost(String httpUrl, @Nullable String param) {
            StringBuffer result=new StringBuffer();
            //连接
            HttpURLConnection connection=null;
            OutputStream os=null;
            InputStream is=null;
            BufferedReader br=null;
            try {
                //创建连接对象
                URL url=new URL(httpUrl);
                //创建连接
                connection= (HttpURLConnection) url.openConnection();
                //设置请求方法
                connection.setRequestMethod("POST");
                //设置连接超时时间
                connection.setConnectTimeout(15000);
                //设置读取超时时间
                connection.setReadTimeout(15000);
                //设置是否可读取
                connection.setDoOutput(true);
                //设置响应是否可读取
                connection.setDoInput(true);
                //设置参数类型
                connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
                //拼装参数
                if(param!=null&&!param.equals("")){
                    //设置参数
                    os=connection.getOutputStream();
                    //拼装参数
                    os.write(param.getBytes("UTF-8"));
                }
                //设置权限
                //设置请求头等
                //开启连接
                //connection.connect();
                //读取响应
                if(connection.getResponseCode()==200){
                    is=connection.getInputStream();
                    if(is!=null){
                        br=new BufferedReader(new InputStreamReader(is,"UTF-8"));
                        String temp=null;
                        if((temp=br.readLine())!=null){
                            result.append(temp);
                        }
                    }
                }
                //关闭连接
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                if(br!=null){
                    try {
                        br.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if(os!=null){
                    try {
                        os.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if(is!=null){
                    try {
                        is.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                //关闭连接
                connection.disconnect();
            }
            return result.toString();
        }
    
        public static void main(String[] str){
            /*String result=HttpURLConnectionUtil.doGet("http://localhost:8080/test");
            System.out.println(result);*/
            /*Map<String, Object> map=new HashMap<>();
            map.put("1","1");
            map.put("2","2");
            map.put("3","3");
            System.out.println(HttpURLConnectionUtil.getParamStr(map));*/
        }
    }

**Apache HttpClient3.1(common)**

package com.ming.http;
    
    import java.io.BufferedReader;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.io.UnsupportedEncodingException;
    import java.util.HashMap;
    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;
    
    /**
     * 文件名：  ${file_name}
     * 版权：    Copyright by ljm
     * 描述：
     * 修改人：  HuamingChen
     * 修改时间：2018/10/24
     * 跟踪单号：
     * 修改单号：
     * 修改内容：
     */
    public class HttpClient3 {
        /**
         * get请求
         * @param url 链接
         * @return 响应参数
         */
        public static String doGet(String url) {
            // 输入流
            InputStream is = null;
            BufferedReader br = null;
            StringBuffer result=new StringBuffer();
            // 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);
            //创建请求方法
            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));
            //执行get方法
            try {
                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"));
    
                    // 读取封装的输入流
                    String temp = null;
                    while ((temp = br.readLine()) != null) {
                        result.append(temp);
                    }
                }
            } 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.toString();
        }
    
        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<Map.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);
                }
    
                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;
        }
    
        public static void main(String[] str){
           //System.out.println(HttpClient3.doGet("http://localhost:8080/test"));
            Map<String,Object> map=new HashMap<>();
            map.put("name","ming");
            System.out.println(HttpClient3.doPost("http://localhost:8080/testPost",map));
        }
    }

**Apache httpClient4.5**

package com.ming.http;
    
    import java.io.IOException;
    import java.io.UnsupportedEncodingException;
    import java.util.*;
    import java.util.Map.Entry;
    
    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;
        }
    
        public static void main(String str[]){
            System.out.println(HttpClient4.doGet("http://localhost:8080/test"));
            Map<String,Object> map=new HashMap<>();
            map.put("name","ming");
            System.out.println(HttpClient4.doPost("http://localhost:8080/testPost",map));
        }
    }

**Spring RestTemplate（比较建议使用这种方法）**

package com.ming.http;
    
    import org.springframework.http.HttpEntity;
    import org.springframework.http.HttpHeaders;
    import org.springframework.http.HttpMethod;
    import org.springframework.http.MediaType;
    import org.springframework.web.client.RestTemplate;
    
    import javax.annotation.Resource;
    
    /**
     * 文件名：  ${file_name}
     * 版权：    Copyright by ljm
     * 描述：
     * 修改人：  HuamingChen
     * 修改时间：2018/10/24
     * 跟踪单号：
     * 修改单号：
     * 修改内容：
     */
    public class HttpTemplate {
    
        public static String httpGet(String url){
            RestTemplate restTemplate=new RestTemplate();
            String result=restTemplate.exchange(url, HttpMethod.GET,null,String.class).getBody();
            return result;
        }
    
        public static String httpPost(String url,String name){
            RestTemplate restTemplate=new RestTemplate();
            return restTemplate.postForEntity(url,name,String.class).getBody();
        }
    
        public static void main(String str[]){
            //System.out.println(HttpTemplate.httpGet("http://localhost:8080/test"));
            System.out.println(HttpTemplate.httpPost("http://localhost:8080/testPost1","ming"));
        }
    }

Spring RestTemplate中几种常见的请求方式：  
[https://blog.csdn.net/u012702547/article/details/77917939/][https_blog.csdn.net_u012702547_article_details_77917939]

[https_blog.csdn.net_u012702547_article_details_77917939]: https://blog.csdn.net/u012702547/article/details/77917939/