java 发送 http 请求
概述
在java中，我们发送http请求(get、post) 主要有两种方法
- 使用Java原生HttpURLConnection
- 使用第三方库，例如 Apache的HttpClient库
HttpURLConnection
下面的代码分别是使用 get 进行 http 访问和 使用 post 进行 https 访问的例子
package com.mkyong;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.net.ssl.HttpsURLConnection;
public class HttpURLConnectionExample {
private final String USER_AGENT = "Mozilla/5.0";
public static void main(String[] args) throws Exception {
HttpURLConnectionExample http = new HttpURLConnectionExample();
System.out.println("Testing 1 - Send Http GET request");
http.sendGet();
System.out.println("\nTesting 2 - Send Http POST request");
http.sendPost();
}
// HTTP GET请求
private void sendGet() throws Exception {
String url = "http://www.google.com/search?q=mkyong";
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
//默认值我GET
con.setRequestMethod("GET");
//添加请求头
con.setRequestProperty("User-Agent", USER_AGENT);
int responseCode = con.getResponseCode();
System.out.println("\nSending 'GET' request to URL : " + url);
System.out.println("Response Code : " + responseCode);
BufferedReader in = new BufferedReader(
new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
response.append(inputLine);
}
in.close();
//打印结果
System.out.println(response.toString());
}
// HTTP POST请求
private void sendPost() throws Exception {
String url = "https://selfsolve.apple.com/wcResults.do";
URL obj = new URL(url);
HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
//添加请求头
con.setRequestMethod("POST");
con.setRequestProperty("User-Agent", USER_AGENT);
con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
String urlParameters = "sn=C02G8416DRJM&cn=&locale=&caller=&num=12345";
//发送Post请求
con.setDoOutput(true);
DataOutputStream wr = new DataOutputStream(con.getOutputStream());
wr.writeBytes(urlParameters);
wr.flush();
wr.close();
int responseCode = con.getResponseCode();
System.out.println("\nSending 'POST' request to URL : " + url);
System.out.println("Post parameters : " + urlParameters);
System.out.println("Response Code : " + responseCode);
BufferedReader in = new BufferedReader(
new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
response.append(inputLine);
}
in.close();
//打印结果
System.out.println(response.toString());
}
}
输出结果
Sending 'GET' request to URL : http://www.google.com/search?q=mkyong
Response Code : 200
Google search result...
Testing 2 - Send Http POST request
Sending 'POST' request to URL : https://selfsolve.apple.com/wcResults.do
Post parameters : sn=C02G8416DRJM&cn=&locale=&caller=&num=12345
Response Code : 200
Apple product detail...
HttpClient 第三方库
下面是两个分别封装进行纯参数 post 请求和 带文件的 post 请求例子
public String httpPost(String url, List<NameValuePair> nvpList, int requestTimeout, int connectTimeout, int socketTimeout) {
RequestConfig config = RequestConfig.custom().setConnectionRequestTimeout(requestTimeout)
.setConnectTimeout(connectTimeout).setSocketTimeout(socketTimeout).build(); //设置各种超时时间
CloseableHttpClient httpclient = HttpClients.custom().setDefaultRequestConfig(config).build(); //build httpClient
HttpPost httpPost = new HttpPost(url); //新建post请求操作类
CloseableHttpResponse response; //返回
String body;
try {
if (nvpList != null || !nvpList.isEmpty()) {
httpPost.setEntity(new UrlEncodedFormEntity(nvpList, "utf-8")); //设置post的参数
}
response = httpclient.execute(httpPost); //执行 post
HttpEntity entity = response.getEntity();
body = EntityUtils.toString(entity);
EntityUtils.consume(entity);
} catch (Exception e) {
e.printStackTrace();
}
return body;
}
public String httpPost(String url, List<NameValuePair> nvpList, final Map<String, File> files, int requestTimeout, int connectTimeout, int socketTimeout) {
RequestConfig config = RequestConfig.custom().setConnectionRequestTimeout(requestTimeout)
.setConnectTimeout(connectTimeout).setSocketTimeout(socketTimeout).build();
CloseableHttpClient httpclient = HttpClients.custom().setDefaultRequestConfig(config).build();
HttpPost httpPost = new HttpPost(url);
CloseableHttpResponse response;
String body;
try {
httpPost.setEntity(makeMultipartEntity(nvpList, files)); //根据post参数和文件生成post请求的具体信息
response = httpclient.execute(httpPost);
HttpEntity entity = response.getEntity();
body = EntityUtils.toString(entity);
EntityUtils.consume(entity);
} catch (Exception e) {
e.printStackTrace();
}
return body;
}
private static HttpEntity makeMultipartEntity(List<NameValuePair> params, final Map<String, File> files) {
MultipartEntityBuilder builder = MultipartEntityBuilder.create(); //旧版 HttpClient 使用 MultipartEntity, 已经废弃
builder.setMode(HttpMultipartMode.STRICT); //设置模式，STRICT 为默认模式(RFC 822, RFC 2045, RFC 2046 compliant), BROWSER_COMPATIBLE 为浏览器兼容模式(browser-compatible mode, i.e.), RFC6532（RFC 6532 compliant），一般选 STRICT 或者 BROWSER_COMPATIBLE
if (params != null && params.size() > 0) {
for (NameValuePair p : params) {
builder.addTextBody(p.getName(), p.getValue(), ContentType.TEXT_PLAIN.withCharset("UTF-8")); //生成参数信息
}
}
if (files != null && files.size() > 0) {
Set<Map.Entry<String, File>> entries = files.entrySet();
for (Map.Entry<String, File> entry : entries) {
builder.addBinaryBody("file", entry.getValue()); //生成文件信息，另外一种方法为使用 addPart, 那种不能随意设置 ContentType，具体可以参考后面的一个链接网站
}
}
return builder.build();
}
参考链接
如何在Java中发送HTTP GET/POST请求
HttpClient使用MultipartEntityBuilder实现多文件上传
