使用HTTP协议发送GET/POST请求，可以有多种方式，以下详细介绍两种方法。
一、JDK 的 java.net 包中提供的访问 HTTP 协议功能发送GET/POST请求
1、发送get请求详细步骤
1)创建要请求的URL实例
String urlNameString = url + "?" + param;
URL realUrl = new URL(urlNameString);
2)打开和实例URL的连接
URLConnection connection = realUrl.openConnection();
3)为已打开的连接设置HTTP请求通用的属性,如accept,connection,user-agent.
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
4)在设置好属性的连接基础上,执行实际的连接,即发送请求
connection.connect();
5)获取get请求的响应头
Map> map = connection.getHeaderFields();
// 遍历所有的响应头字段
for (String key : map.keySet()) {
System.out.println(key + "--->" + map.get(key));
}
6)获取get请求的响应结果.这里可以通过BufferedReader输入流来读取URL的响应
BufferedReader in = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
也可以使用工具类IOUtils的toString方法获取响应结果.
result = IOUtils.toString(connection.getInputStream(),"utf-8");
7)关闭流,关闭连接
// 使用finally块来关闭输入流
finally {
try {
if (in != null) {
in.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
2、发送post请求详细步骤
1)创建要请求的URL实例
String urlNameString = url + "?" + param;
URL realUrl = new URL(urlNameString);
2)打开和实例URL的连接
URLConnection connection = realUrl.openConnection();
3)为已打开的连接设置HTTP请求通用的属性,如accept,connection,user-agent.
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
4)由于post请求,参数是放在body中,需要设置连接中允许写入参数
conn.setDoOutput(true);
conn.setDoInput(true);
5)获取URLConnection对象对应的输出流
PrintWriter out = new PrintWriter(conn.getOutputStream());
6)写入发送post请求需要的参数
out.print(param);
out.flush();
6)获取get请求的响应结果.这里可以通过BufferedReader输入流来读取URL的响应
BufferedReader in = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
也可以使用工具类IOUtils的toString方法获取响应结果.
List list = IOUtils.readLines(conn.getInputStream(),"UTF-8");
for(String s:list){
System.out.println(s);
}
7)关闭流,关闭连接
完整代码：
package com.sc.http;
import org.apache.commons.io.IOUtils;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;
public class HttpRequest {
/**
* 向指定URL发送GET方法的请求
*
* @param url
* 发送请求的URL
* @param param
* 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return URL 所代表远程资源的响应结果
*/
public static String sendGet(String url, String param) {
String result = "";
BufferedReader in = null;
try {
String urlNameString = url + "?" + param;
URL realUrl = new URL(urlNameString);
// 打开和URL之间的连接
URLConnection connection = realUrl.openConnection();
// 设置通用的请求属性
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 建立实际的连接
connection.connect();
// 获取所有响应头字段
Map> map = connection.getHeaderFields();
// 遍历所有的响应头字段
for (String key : map.keySet()) {
System.out.println(key + "--->" + map.get(key));
}
//定义 BufferedReader输入流来读取URL的响应
in = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
result = IOUtils.toString(connection.getInputStream(),"utf-8");
} catch (Exception e) {
System.out.println("发送GET请求出现异常！" + e);
e.printStackTrace();
}
// 使用finally块来关闭输入流
finally {
try {
if (in != null) {
in.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
return result;
}
/**
* 向指定 URL 发送POST方法的请求
*
* @param url
* 发送请求的 URL
* @param param
* 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return 所代表远程资源的响应结果
*/
public static String sendPost(String url, String param) {
PrintWriter out = null;
BufferedReader in = null;
String result = "";
try {
URL realUrl = new URL(url);
// 打开和URL之间的连接
URLConnection conn = realUrl.openConnection();
// 设置通用的请求属性
conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("connection", "Keep-Alive");
conn.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 发送POST请求必须设置如下两行
conn.setDoOutput(true);
conn.setDoInput(true);
// 获取URLConnection对象对应的输出流
out = new PrintWriter(conn.getOutputStream());
// 发送请求参数
out.print(param);
// flush输出流的缓冲
out.flush();
// 定义BufferedReader输入流来读取URL的响应
in = new BufferedReader(
new InputStreamReader(conn.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
// List list = IOUtils.readLines(conn.getInputStream(),"UTF-8");
// for(String s:list){
// System.out.println(s);
// }
} catch (Exception e) {
System.out.println("发送 POST 请求出现异常！"+e);
e.printStackTrace();
}
//使用finally块来关闭输出流、输入流
finally{
try{
if(out!=null){
out.close();
}
if(in!=null){
in.close();
}
}
catch(Exception ex){
ex.printStackTrace();
}
}
return result;
}
public static void main(String[] args) {
//发送 GET 请求
// String s=HttpRequest.sendGet("http://www.baidu.com", "key=123&v=456");
// System.out.println(s);
//发送 POST 请求
String sr=HttpRequest.sendPost("http://192.168.200.66/zabbix/screens.php", "ddreset=1");
System.out.println(sr);
}
}
二、使用org.apache.http包下的HttpClient发送GET/POST请求
HttpClient相比传统JDK自带的URLConnection，增加了易用性和灵活性。它不仅是客户端发送Http请求变得容易，而且也方便了开发人员测试接口（基于Http协议的），即提高了开发的效率，也方便提高代码的健壮性。
1、HttpClient发送get请求(无参数)详细步骤
1). 创建HttpClient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
2). 创建请求方法的实例，并指定请求URL
HttpGet get = new HttpGet("http://www.baidu.com");
3). 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。
CloseableHttpResponse response= httpclient.execute(get);
4).获取get请求的响应结果.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
HttpEntity entity = response.getEntity();
获取响应状态
int code = response.getStatusLine().getStatusCode();
System.out.println(" code "+code);
5).通过BufferedReader输入流读取响应结果
BufferedReader in = new BufferedReader(
new InputStreamReader(entity.getContent(),"UTF-8"));
String line;
String result="";
while ((line = in.readLine()) != null) {
result += line+"\n";
}
System.out.println(result);
可以使用工具类IOUtils的toString方法获取响应结果.
List list = IOUtils.readLines(entity.getContent(),"UTF-8");
for(String s:list){
System.out.println(s);
}
或者：
result=IOUtils.toString(entity.getContent(),"utf-8");
可以使用EntityUtils的toString方法获取响应结果.(推荐使用)
if(entity!=null){
System.out.println(EntityUtils.toString(entity));
}
6).释放连接,无论执行方法是否成功，都必须释放连接
完整代码：
package com.sc.http;
import java.io.IOException;
import org.apache.http.HttpEntity;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
public class HttpClientTest2 {
public static void main(String[] args) {
CloseableHttpClient httpclient = HttpClients.createDefault();
CloseableHttpResponse response = null;
HttpEntity entity=null;
try {
HttpGet get = new HttpGet("http://www.baidu.com");
response = httpclient.execute(get);
entity = response.getEntity();
int code = response.getStatusLine().getStatusCode();
System.out.println(" code "+code);
if(entity!=null){
System.out.println(EntityUtils.toString(entity));
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
EntityUtils.consume(entity);
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
2、HttpClient发送post请求详细步骤
1). 创建HttpClient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
2). 创建请求方法的实例，并指定请求URL
HttpPost post = new HttpPost("http://123.58.251.183:8080/goods/UserServlet");
3). 创建HttpEntity,模拟一个表单,用于包装参数
POST请求,参数是放在body内,所以需要构建UrlEncodedFormEntity
而UrlEncodedFormEntity需要传入的参数类型为List且List中装入的是NameValuePair类型的集合
NameValuePair是一个接口,它的实现类是BasicNameValuePair
BasicNameValuePair类的构造方法中需要传入两个参数key,value
List list = new ArrayList();
list.add(new BasicNameValuePair("method","loginMobile"));
list.add(new BasicNameValuePair("loginname","abc"));
list.add(new BasicNameValuePair("loginpass","abc"));
HttpEntity postEntity = new UrlEncodedFormEntity(list);
post.setEntity(postEntity);
4). 若需要使用例如Fidder工具抓包,就需要设置代理.(无需抓包时,可省略此步)
HttpHost proxy = new HttpHost("127.0.0.1", 8888, "http");
RequestConfig config = RequestConfig.custom().setProxy(proxy).build();
post.setConfig(config);
5). 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。
CloseableHttpResponse response= httpclient.execute(get);
6).获取get请求的响应结果.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
HttpEntity entity = response.getEntity();
获取响应状态
int code = response.getStatusLine().getStatusCode();
System.out.println(" code "+code);
7).通过BufferedReader输入流读取响应结果
BufferedReader in = new BufferedReader(
new InputStreamReader(entity.getContent(),"UTF-8"));
String line;
String result="";
while ((line = in.readLine()) != null) {
result += line+"\n";
}
System.out.println(result);
可以使用工具类IOUtils的toString方法获取响应结果.
List list = IOUtils.readLines(entity.getContent(),"UTF-8");
for(String s:list){
System.out.println(s);
}
或者：
result=IOUtils.toString(entity.getContent(),"utf-8");
可以使用EntityUtils的toString方法获取响应结果.(推荐使用)
if(entity!=null){
System.out.println(EntityUtils.toString(entity));
}
8).释放连接,无论执行方法是否成功，都必须释放连接
EntityUtils.consume(httpEntity);
closeableHttpClient.close();
完整代码：
package com.sc.http;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.NameValuePair;
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.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 HttpClientTest3 {
public static void main(String[] args) {
CloseableHttpClient closeableHttpClient = HttpClients.createDefault();
HttpPost post = new HttpPost("http://123.58.251.183:8080/goods/UserServlet");
List list = new ArrayList();
list.add(new BasicNameValuePair("method","loginMobile"));
list.add(new BasicNameValuePair("loginname","abc"));
list.add(new BasicNameValuePair("loginpass","abc"));
HttpHost proxy = new HttpHost("127.0.0.1", 8888, "http");
RequestConfig config = RequestConfig.custom().setProxy(proxy).build();
HttpEntity httpEntity = null;
try {
HttpEntity postEntity = new UrlEncodedFormEntity(list);
post.setEntity(postEntity);
//post.setConfig(config);
CloseableHttpResponse reponse = closeableHttpClient.execute(post);
httpEntity= reponse.getEntity();
System.out.println(EntityUtils.toString(httpEntity, "utf-8"));
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
EntityUtils.consume(httpEntity);
closeableHttpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}