http://blog.csdn.net/wangpeng047/article/details/19624529
http://blog.csdn.net/zknxx/article/details/51598852
一、所需jar包
HttpClient 是apache 组织下面的一个用于处理HTTP 请求和响应的开源工具。所需jar包:
commons-logging-1.1.1.jar、httpclient-4.5.2.jar、httpcore-4.4.4.jar
二、使用方法
使用HttpClient发送请求、接收响应很简单,一般需要如下几步即可。
1. 创建HttpClient对象。
2. 创建请求方法的实例,并指定请求URL。如果需要发送GET请求,创建HttpGet对象;如果需要发送POST请求,创建HttpPost对象。
3. 如果需要发送请求参数,可调用HttpGet、HttpPost共同的setParams(HetpParams params)【过时,不推荐使用】方法来添加请求参数;对于HttpPost对象而言,也可调用setEntity(HttpEntity entity)方法来设置请求参数。对于HttpGet对象,可通过拼接url来添加请求参数。
4. 调用HttpClient对象的execute(HttpUriRequest request)发送请求,该方法返回一个HttpResponse。
5. 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头;
调用HttpResponse的getEntity()方法可获取HttpEntity对象,该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。
6. 释放连接。无论执行方法是否成功,都必须释放连接
三、示例
package com.learn.http;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
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 HttpSend {
public static void main(String[] args) {
// post请求百度地址,返回404
new HttpSend().post("http://www.baidu.com");
new HttpSend().get("http://www.baidu.com");
}
/**
* 发送 post请求访问本地应用并根据传递参数不同返回不同结果
*/
public void post(String url) {
// 创建默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
// 创建httppost
HttpPost httppost = new HttpPost(url);
// 创建参数队列
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
// 添加参数
// formparams.add(new BasicNameValuePair("gg", "1"));
UrlEncodedFormEntity uefEntity;
try {
//传入空参数,创建实体对象
uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8");
//设置post对象的实体对象
httppost.setEntity(uefEntity);
System.out.println("executing post request " + httppost.getURI());
//执行post请求
CloseableHttpResponse response = httpclient.execute(httppost);
try {
//获取请求结果对象
HttpEntity entity = response.getEntity();
if (entity != null) {
System.out.println("--------------------------------------");
System.out.println("Response content: " + EntityUtils.toString(entity));
System.out.println("--------------------------------------");
}
} finally {
response.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
// 关闭连接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 发送 get请求
*/
public void get(String url) {
// 创建默认的httpClient实例.
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
// 封装请求参数
List<NameValuePair> params = new ArrayList<>();
params.add(new BasicNameValuePair("cityEname", "henan"));
//转换为键值对
String str = EntityUtils.toString(new UrlEncodedFormEntity(params, "UTF-8"));
System.out.println(str);
//创建带参数get请求(示例)
HttpGet httpGet = new HttpGet(url+"?"+str);
// 创建不带参数get请求
HttpGet httpget = new HttpGet(url);
System.out.println("executing get request " + httpget.getURI());
// 执行get请求.
CloseableHttpResponse response = httpclient.execute(httpget);
try {
// 获取响应实体
HttpEntity entity = response.getEntity();
System.out.println("--------------------------------------");
// 打印响应状态
System.out.println(response.getStatusLine());
if (entity != null) {
// 打印响应内容长度
System.out.println("Response content length: " + entity.getContentLength());
// 打印响应内容
System.out.println("Response content: " + EntityUtils.toString(entity));
}
System.out.println("------------------------------------");
} finally {
response.close();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (ParseException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
// 关闭连接,释放资源
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}