Post方式比Get方式要復雜一點，因為該方式需要將請求的參數放在http請求的正文中，所以需要構造請求體。
步驟：
1.構造URL
URL url = new URL(PATH);
2.設置連接
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(3000);
connection.setDoInput(true);//表示從服務器獲取數據
connection.setDoOutput(true);//表示向服務器寫數據
//獲得上傳信息的字節大小以及長度
connection.setRequestMethod("POST");
//是否使用緩存
connection.setUseCaches(false);
//表示設置請求體的類型是文本類型
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
connection.setRequestProperty("Content-Length", String.valueOf(mydata.length));
connection.connect();
3.寫入請求正文
Map<String, String> params = new HashMap<String, String>();
params.put("username", "lili");
params.put("password", "123");
StringBuffer buffer = new StringBuffer();
try {//把請求的主體寫入正文！！
if(params != null&&!params.isEmpty()){
//迭代器
for(Map.Entry<String, String> entry : params.entrySet()){
buffer.append(entry.getKey()).append("=").
append(URLEncoder.encode(entry.getValue(),encode)).
append("&");
}
}
// System.out.println(buffer.toString());
//刪除最后一個字符&，多了一個;主體設置完畢
buffer.deleteCharAt(buffer.length()-1);
byte[] mydata = buffer.toString().getBytes();
//獲得輸出流，向服務器輸出數據
OutputStream outputStream = connection.getOutputStream();
outputStream.write(mydata,0,mydata.length);
4.讀取返回數據，關閉連接
//通常叫做內存流，寫在內存中的
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
String result = "";
if(inputStream != null){
try {
while((len = inputStream.read(data))!=-1){
data.toString();
outputStream.write(data, 0, len);
}
//result是在服務器端設置的doPost函數中的
result = new String(outputStream.toByteArray(),encode);
outputStream.flush();
下面上代碼：一個簡單的Demo訪問一個自建的Servlet:
package com.http.post;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;
public class HttpUtils {
private static String PATH = "http://172.24.87.47:8088/myhttp/servlet/LoginAction";
private static URL url;
public HttpUtils() {
// TODO Auto-generated constructor stub
}
static{
try {
url = new URL(PATH);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
* @param params 填寫的url的參數
* @param encode 字節編碼
* @return
*/
public static String sendPostMessage(Map<String, String> params,String encode){
StringBuffer buffer = new StringBuffer();
try {//把請求的主體寫入正文！！
if(params != null&&!params.isEmpty()){
//迭代器
for(Map.Entry<String, String> entry : params.entrySet()){
buffer.append(entry.getKey()).append("=").
append(URLEncoder.encode(entry.getValue(),encode)).
append("&");
}
}
// System.out.println(buffer.toString());
//刪除最后一個字符&，多了一個;主體設置完畢
buffer.deleteCharAt(buffer.length()-1);
byte[] mydata = buffer.toString().getBytes();
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(3000);
connection.setDoInput(true);//表示從服務器獲取數據
connection.setDoOutput(true);//表示向服務器寫數據
//獲得上傳信息的字節大小以及長度
connection.setRequestMethod("POST");
//是否使用緩存
connection.setUseCaches(false);
//表示設置請求體的類型是文本類型
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
connection.setRequestProperty("Content-Length", String.valueOf(mydata.length));
connection.connect(); //連接，不寫也可以。。？？有待了解
//獲得輸出流，向服務器輸出數據
OutputStream outputStream = connection.getOutputStream();
outputStream.write(mydata,0,mydata.length);
//獲得服務器響應的結果和狀態碼
int responseCode = connection.getResponseCode();
if(responseCode == HttpURLConnection.HTTP_OK){
return changeInputeStream(connection.getInputStream(),encode);
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return "";
}
/**
* 將一個輸入流轉換成字符串
* @param inputStream
* @param encode
* @return
*/
private static String changeInputeStream(InputStream inputStream,String encode) {
//通常叫做內存流，寫在內存中的
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
String result = "";
if(inputStream != null){
try {
while((len = inputStream.read(data))!=-1){
data.toString();
outputStream.write(data, 0, len);
}
//result是在服務器端設置的doPost函數中的
result = new String(outputStream.toByteArray(),encode);
outputStream.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return result;
}
public static void main(String[] arsg){
Map<String, String> params = new HashMap<String, String>();
params.put("username", "lili");
params.put("password", "123");
String result = sendPostMessage(params,"utf-8");
System.out.println("result->"+result);
}
}
下邊是服務端的Servlet代碼：
package com.login.manager;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginAction extends HttpServlet {
/**
* Constructor of the object.
*/
public LoginAction() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
String username = request.getParameter("username"); //傳過來的內容是：password=123&username=lili
System.out.println("username:"+username);
String pswd = request.getParameter("password");
System.out.println("password:"+pswd);
if(username.equals("張三")&&pswd.equals("123")){
//表示服務器端返回的結果
out.print("login is success!!!!");
}else{
out.print("login is fail!!!");
}
out.flush();
out.close();
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
服務端代碼使用servlet搭建的。。。
這是運行結果：
服務端的：
在服務端接收的內容是：password=123&username=lili 被它解析啦。。