Java实现Http请求的常用方式

一、使用Java自带的java.io和java.net包。

　　实现方式如下：

public class HttpClient {
　　　　　//1、doGet方法　
	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;
	}
　　　　　//2、doPost方法
	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(150000);
			// 设置读取主机服务器返回数据超时时间：60000毫秒
			connection.setReadTimeout(600000);

			// 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("
");
				}
				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;
	}

　　

二、使用Apache的HttpClient-4.x.Jar包。

　　Jar包Maven下载地址：https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient。

　　实现方式如下：

package com.test.http;

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;
	}
}

三、使用Apache的HttpClient-3.x.Jar包。

　　Jar包Maven下载地址：https://mvnrepository.com/artifact/commons-httpclient/commons-httpclient。

　　实现方式如下：

package com.test.http;

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;
	}
}