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這期內容當中小編將會給大家帶來有關在java項目中使用java.net.URLConnection實現一個發送HTTP請求功能，文章內容豐富且以專業的角度為大家分析和敘述，閱讀完這篇文章希望大家可以有所收獲。
一、前言
如何通過Java發送HTTP請求，通俗點講，如何通過Java（模擬瀏覽器）發送HTTP請求。
Java有原生的API可用于發送HTTP請求，即java.net.URL、java.net.URLConnection，這些API很好用、很常用，但不夠簡便；
所以，也流行有許多Java HTTP請求的framework，如，Apache的HttpClient。
目前項目主要用到Java原生的方式，所以，這里主要介紹此方式。
二、運用原生Java Api發送簡單的Get請求、Post請求步驟
1.通過統一資源定位器（java.net.URL）獲取連接器（java.net.URLConnection）
2.設置請求的參數
3.發送請求
4.以輸入流的形式獲取返回內容
5.關閉輸入流
三、發送請求與接收響應流類 HttpRequestor
package me.http;
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.net.HttpURLConnection;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.URL;
import java.net.URLConnection;
import java.util.Iterator;
import java.util.Map;
public class HttpRequestor {
private String charset = "utf-8";
private Integer connectTimeout = null;
private Integer socketTimeout = null;
private String proxyHost = null;
private Integer proxyPort = null;
/**
* Do GET request
* @param url
* @return
* @throws Exception
* @throws IOException
*/
public String doGet(String url) throws Exception {
URL localURL = new URL(url);
URLConnection connection = this.openConnection(localURL);
HttpURLConnection httpURLConnection = (HttpURLConnection)connection;
httpURLConnection.setRequestProperty("Accept-Charset", charset);
httpURLConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
InputStream inputStream = null;
InputStreamReader inputStreamReader = null;
BufferedReader reader = null;
StringBuffer resultBuffer = new StringBuffer();
String tempLine = null;
//響應失敗
if (httpURLConnection.getResponseCode() >= 300) {
throw new Exception("HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode());
}
try {
inputStream = httpURLConnection.getInputStream();
inputStreamReader = new InputStreamReader(inputStream);
reader = new BufferedReader(inputStreamReader);
while ((tempLine = reader.readLine()) != null) {
resultBuffer.append(tempLine);
}
} finally {
if (reader != null) {
reader.close();
}
if (inputStreamReader != null) {
inputStreamReader.close();
}
if (inputStream != null) {
inputStream.close();
}
}
return resultBuffer.toString();
}
/**
* Do POST request
* @param url
* @param parameterMap
* @return
* @throws Exception
*/
public String doPost(String url, Map parameterMap) throws Exception {
/* Translate parameter map to parameter date string */
StringBuffer parameterBuffer = new StringBuffer();
if (parameterMap != null) {
Iterator iterator = parameterMap.keySet().iterator();
String key = null;
String value = null;
while (iterator.hasNext()) {
key = (String)iterator.next();
if (parameterMap.get(key) != null) {
value = (String)parameterMap.get(key);
} else {
value = "";
}
parameterBuffer.append(key).append("=").append(value);
if (iterator.hasNext()) {
parameterBuffer.append("&");
}
}
}
System.out.println("POST parameter : " + parameterBuffer.toString());
URL localURL = new URL(url);
URLConnection connection = this.openConnection(localURL);
HttpURLConnection httpURLConnection = (HttpURLConnection)connection;
httpURLConnection.setDoOutput(true);
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setRequestProperty("Accept-Charset", charset);
httpURLConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
httpURLConnection.setRequestProperty("Content-Length", String.valueOf(parameterBuffer.length()));
OutputStream outputStream = null;
OutputStreamWriter outputStreamWriter = null;
InputStream inputStream = null;
InputStreamReader inputStreamReader = null;
BufferedReader reader = null;
StringBuffer resultBuffer = new StringBuffer();
String tempLine = null;
try {
outputStream = httpURLConnection.getOutputStream();
outputStreamWriter = new OutputStreamWriter(outputStream);
outputStreamWriter.write(parameterBuffer.toString());
outputStreamWriter.flush();
//響應失敗
if (httpURLConnection.getResponseCode() >= 300) {
throw new Exception("HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode());
}
//接收響應流
inputStream = httpURLConnection.getInputStream();
inputStreamReader = new InputStreamReader(inputStream);
reader = new BufferedReader(inputStreamReader);
while ((tempLine = reader.readLine()) != null) {
resultBuffer.append(tempLine);
}
} finally {
if (outputStreamWriter != null) {
outputStreamWriter.close();
}
if (outputStream != null) {
outputStream.close();
}
if (reader != null) {
reader.close();
}
if (inputStreamReader != null) {
inputStreamReader.close();
}
if (inputStream != null) {
inputStream.close();
}
}
return resultBuffer.toString();
}
private URLConnection openConnection(URL localURL) throws IOException {
URLConnection connection;
if (proxyHost != null && proxyPort != null) {
Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(proxyHost, proxyPort));
connection = localURL.openConnection(proxy);
} else {
connection = localURL.openConnection();
}
return connection;
}
/**
* Render request according setting
* @param request
*/
private void renderRequest(URLConnection connection) {
if (connectTimeout != null) {
connection.setConnectTimeout(connectTimeout);
}
if (socketTimeout != null) {
connection.setReadTimeout(socketTimeout);
}
}
/*
* Getter & Setter
*/
public Integer getConnectTimeout() {
return connectTimeout;
}
public void setConnectTimeout(Integer connectTimeout) {
this.connectTimeout = connectTimeout;
}
public Integer getSocketTimeout() {
return socketTimeout;
}
public void setSocketTimeout(Integer socketTimeout) {
this.socketTimeout = socketTimeout;
}
public String getProxyHost() {
return proxyHost;
}
public void setProxyHost(String proxyHost) {
this.proxyHost = proxyHost;
}
public Integer getProxyPort() {
return proxyPort;
}
public void setProxyPort(Integer proxyPort) {
this.proxyPort = proxyPort;
}
public String getCharset() {
return charset;
}
public void setCharset(String charset) {
this.charset = charset;
}
}四、為測試方便,新建一個項目,并新建一個Servlet,接收post請求并對HttpRequestor請求響應,發出響應流
LoginServlet.java代碼:此處使用了
注解: @WebServlet("/LoginServlet") ,也可以在web.xml配置Servlet
package me.loginServlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class LoginServlet
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
System.out.println("111");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String username = request.getParameter("username");
String blog = request.getParameter("blog");
System.out.println(username);
System.out.println(blog);
response.setContentType("text/plain; charset=UTF-8");
response.setCharacterEncoding("UTF-8");
//響應流
response.getWriter().write("It is ok!");
}
}五.測試類Test.java
package me.http;
import java.util.HashMap;
import java.util.Map;
public class Test {
public static void main(String[] args) {
/* Post Request */
Map dataMap = new HashMap();
dataMap.put("username", "Nick Huang");
dataMap.put("blog", "IT");
try {
System.out.println(new HttpRequestor().doPost("http://localhost:8081/TestProgect2/LoginServlet", dataMap));
//System.out.println(new HttpRequestor().doGet("http://localhost:8081/TestProgect2/LoginServlet"));
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
/* Get Request */
}
}1.接收post請求類LoginServlet,控制臺測試結果
2.HttpRequestor接收LoginServlet返回的流
OK,完成
六.對于接收TestProgect2項目中LoginServlet.java類返回的流,在真實環境中可能是異步接收返回的流的,當一臺機器A向另外一臺機器B發送請求,B接收到A的信息,將信息處理后,需要將處理結果返回即響應返回給A,A會接收到B返回的信息
可以另外建一個Servlet類HttpListenerServlet.java來專門異步接收返回的信息
package me.http;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class HttpListenerServlet
*/
@WebServlet("/HttpListenerServlet")
public class HttpListenerServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public HttpListenerServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
InputStream inputStream = null;
inputStream = request.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
BufferedReader reader = new BufferedReader(inputStreamReader);
String tempLine = null;
StringBuffer resultBuffer=new StringBuffer();
while ((tempLine = reader.readLine()) != null) {
resultBuffer.append(tempLine);
}
System.out.println(resultBuffer.toString());
}
}上述就是小編為大家分享的在java項目中使用java.net.URLConnection實現一個發送HTTP請求功能了，如果剛好有類似的疑惑，不妨參照上述分析進行理解。如果想知道更多相關知識，歡迎關注億速云行業資訊頻道。
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