在java中，特别是java web中，我们经常需要碰到的一个场景是我们需要从服务端去发送http请求，获取到数据，而不是直接从浏览器输入请求网址获得相应。比如我们想访问微信接口，获取其返回信息。
在这里需要用到java的HttpURLConnection类，此类可以模拟http请求，获取到的响应以输入流的形式被程序所取到。现将相关方法整理为工具类。
package com.m_gecko.util; import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.net.ConnectException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.List;
import java.util.Map; import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager; import org.apache.commons.io.IOUtils; public class HttpUtil {
/**
* 模拟http的get请求，获取响应（输入流），然后把输入流转为
*
* @param url
* @return
*/
public static String httpGet(String url) {
HttpURLConnection connection = null;
InputStream response = null;
try {
connection = (HttpURLConnection) new URL(url).openConnection();
connection.setConnectTimeout(10000);
connection.setReadTimeout(10000);
response = connection.getInputStream();
if (response != null) {
String nextLine = IOUtils.toString(response, "utf-8");
return nextLine;
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (response != null)
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
if (connection != null) {
connection.disconnect();
connection = null;
}
}
return null;
} /**
* 模拟http的post请求，类似上面
*
* @param url
* @return
*/
public static String httpPost(String url) {
HttpURLConnection connection = null;
InputStream response = null;
try {
connection = (HttpURLConnection) new URL(url).openConnection();
connection.setConnectTimeout(30000);
connection.setReadTimeout(30000);
// 发送POST请求必须设置如下两行
connection.setDoOutput(true);
connection.setDoInput(true);
response = connection.getInputStream();
if (response != null) {
String nextLine = IOUtils.toString(response, "utf-8");
return nextLine;
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (response != null)
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
if (connection != null) {
connection.disconnect();
connection = null;
}
}
return null;
} /**
* 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
HttpURLConnection connection = (HttpURLConnection) 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<String, List<String>> 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(), "utf-8"));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} 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
HttpURLConnection conn = (HttpURLConnection) 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(), "utf-8"));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} 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 (IOException ex) {
ex.printStackTrace();
}
}
return result;
} /**
* 向指定 URL 发送POST方法的请求
*
* @param url
* 发送请求的 URL
* @param params
* 请求的参数集合
* @return 远程资源的响应结果
*/
public static String sendPost(String url, Map<String, String> params) {
OutputStreamWriter out = null;
BufferedReader in = null;
StringBuilder result = new StringBuilder();
try {
URL realUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) realUrl
.openConnection();
// 发送POST请求必须设置如下两行
conn.setDoOutput(true);
conn.setDoInput(true);
// POST方法
conn.setRequestMethod("POST");
// 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)");
conn.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
conn.connect();
// 获取URLConnection对象对应的输出流
out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8");
// 发送请求参数
if (params != null) {
StringBuilder param = new StringBuilder();
for (Map.Entry<String, String> entry : params.entrySet()) {
if (param.length() > 0) {
param.append("&");
}
param.append(entry.getKey());
param.append("=");
param.append(entry.getValue());
// System.out.println(entry.getKey()+":"+entry.getValue());
}
System.out.println("param:" + param.toString());
out.write(param.toString());
}
// 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(), "UTF-8"));
String line;
while ((line = in.readLine()) != null) {
result.append(line);
}
} catch (Exception 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 (IOException ex) {
ex.printStackTrace();
}
}
return result.toString();
} /**
* url编码
*
* @param str
* @param charset
* @return
* @throws UnsupportedEncodingException
*/
public static String urlEncoder(String str, String charset)
throws UnsupportedEncodingException {
if (str == null) {
str = "";
}
String result = URLEncoder.encode(str, charset);
return result;
} /**
* 发送https请求
*
* @param requestUrl
* 请求地址
* @param requestMethod
* 请求方式（GET、POST）
* @param outputStr
* 提交的数据
* @return 返回微信服务器响应的信息
*/
public static String httpsRequest(String requestUrl, String requestMethod,
String outputStr) {
try {
// 创建SSLContext对象，并使用我们指定的信任管理器初始化
TrustManager[] tm = { new MyX509TrustManager() };
SSLContext sslContext = SSLContext.getInstance("SSL", "SunJSSE");
sslContext.init(null, tm, new java.security.SecureRandom());
// 从上述SSLContext对象中得到SSLSocketFactory对象
SSLSocketFactory ssf = sslContext.getSocketFactory();
URL url = new URL(requestUrl);
HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
conn.setSSLSocketFactory(ssf);
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setUseCaches(false);
// 设置请求方式（GET/POST）
conn.setRequestMethod(requestMethod);
conn.setRequestProperty("content-type",
"application/x-www-form-urlencoded");
// 当outputStr不为null时向输出流写数据
if (null != outputStr) {
OutputStream outputStream = conn.getOutputStream();
// 注意编码格式
outputStream.write(outputStr.getBytes("UTF-8"));
outputStream.close();
}
// 从输入流读取返回内容
InputStream inputStream = conn.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(
inputStream, "utf-8");
BufferedReader bufferedReader = new BufferedReader(
inputStreamReader);
String str = null;
StringBuffer buffer = new StringBuffer();
while ((str = bufferedReader.readLine()) != null) {
buffer.append(str);
}
// 释放资源
bufferedReader.close();
inputStreamReader.close();
inputStream.close();
inputStream = null;
conn.disconnect();
return buffer.toString();
} catch (ConnectException ce) {
ce.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
其中https请求所需要的信任管理器实现了X509TrustManager接口。
package com.m_gecko.util; import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import javax.net.ssl.X509TrustManager; /**
* 信任管理器
* @author xdx
*/
public class MyX509TrustManager implements X509TrustManager { // 检查客户端证书
public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
} // 检查服务器端证书
public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
} // 返回受信任的X509证书数组
public X509Certificate[] getAcceptedIssuers() {
return null;
}
}