Android 中HttpURLConnection 的使用
首先要搭建与Android 交互的简单的网络服务端
HttpURLConnection分为两个部分,分为两个部分,请求和回复,回复的时候根据回复的内容来读取。
通过URL.openConnection来得到HttpURLConnection的对象。请求部分分为GET请求和POST 请求,POST请求更安全.都是需要设置请求时间等。
POST 请求还需要设置请求的数据，例如HashMap 来设置键值对，然后通过遍历得到具体的要提交的数据。值的部分 需要通过URLEncode来编码，
POST 请求还需要设置请求的属性，有两个属性必须要设置，Content-Type和Content-Length
POST 请求还需要通过OutputStream 来将数据提交给服务器端。
收到信息回复的时候，如果返回码为200说明正确了,这个时候我们要根据需求来决定使用哪一种输出流，如果需要保存在本地那么就使用FileOutputStream，
如果是仅仅是一次性的信息，可以使用ByteArrayOutputStream来在内存读取，然后释放就好了。
0:HttpURLConnection GET 请求，HttpURLConnection POST 请求
0.1GET 请求:
URL url = new URL("http://192.168.1.106:8080/tomcat.png");
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("GET");
httpURLConnection.setConnectTimeout(5000);
httpURLConnection.setDoInput(true);
0.2 POST 请求:
url = new URL("http://192.168.1.106:8080/ServerDemo/servlet/LoginServlert");
HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
urlConnection.setRequestMethod("POST");
urlConnection.setConnectTimeout(5000);
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);//设置可以向服务器传递数据
上面的都几乎一样，最关键的就是这里设置属性的部分，需要设置两个属性，一个是内容类型，一个是内容的长度。然后输出。
通过这里的输出，其实我们也可以是图片或者文件，这样就实现了文件的上传的功能。
urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");//设置提交的内容的类
byte[] data = sb.toString().getBytes("utf-8");//注意这里的编码utf-8
urlConnection.setRequestProperty("Content-Length", String.valueOf(data.length));//设置提交的内容的长度
//提交数据
OutputStream outputStream = urlConnection.getOutputStream();
outputStream.write(data);
outputStream.close();
请求的数据,方法一:
StringBuilder sb = new StringBuilder("username=哈哈&password=psw");
请求的数据,方法二:
HashMap
params.put("username", "哈哈");
params.put("password", "psw");
StringBuilder sb = new StringBuilder();//把要提交的 数据类型定义为 username=哈哈&password=psw的格式
for(Map.Entry
sb.append(en.getKey())
.append("=")
.append(URLEncoder.encode(en.getValue(), "utf-8"))//这里的编码别忘记了。
.append("&");
}
sb.deleteCharAt(sb.length()-1);//删除最后一个&,注意 这里是 length-1，因为是从0开始计数的。
1:接收回复信息
返回信息的读取:读取的时候因为有的数据对于我们是没有必要存储的，有的是需要存储的。需要存储的我们使用FileOutputStream 将它写入到文件中，不需要存储的我们通过ByteArrayOutputStream 在内存中读取然后释放就好了。
1.1 需要存储的我们使用FileOutputStream 将它写入到文件中
InputStream in = null;
FileOutputStream fos = null;
if (httpURLConnection.getResponseCode() == 200) {
in = httpURLConnection.getInputStream();
fos = new FileOutputStream(getCacheDir().getPath()+"a.bmp");
byte[] arr = new byte[1024];
int len = 0;
//每次读取 1024个字节，如果读取返回为-1说明到了文件的末尾，结束读取
while ((len = in.read(arr)) != -1) {
fos.write(arr, 0, len);
}
//一定要记住要关闭读取流。
in.close();
fos.close();
}
1.2 不需要存储的我们通过ByteArrayOutputStream 在内存中读取然后释放就好了。
InputStream in = null;
if(urlConnection.getResponseCode()==200){
in = urlConnection.getInputStream();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] arr = new byte[1024];
int len=0;
while((len=in.read(arr))!=-1){
bos.write(arr,0,len);
}
byte[] b = bos.toByteArray();
String ss = new String(b,"utf-8");
Log.d("kodulf",ss);
}
//关闭流
in.close();
具体的实现代码如下：
0：GET 请求
别忘了权限
例如我的电脑的ip地址是192.168.1.106，那么通过HttpURLConnection 的GET方法下载一个图片的案例如下
package tech.androidstudio.readfileshttpurlconnection;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
public class MainActivity extends AppCompatActivity implements Runnable {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Thread thread = new Thread(this);
thread.start();
}
@Override
public void run() {
try {
//配置 HttpURLConnection
//TODO 这里的ip 地址一定不能使localhost 一定要是电脑的或者是正式ip地址.
//如果写成了localhost，那么就会报错java.net.ConnectException: localhost/127.0.0.1:8080 - Connection refused
//URL url = new URL("http://localhost:8080/tomcat.png");
URL url = new URL("http://192.168.1.106:8080/tomcat.png");
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("GET");
httpURLConnection.setConnectTimeout(5000);
//Sets the flag indicating whether this URLConnection allows input. It cannot be set after the connection is established.
httpURLConnection.setDoInput(true);
//获取返回的文件
InputStream in = null;
FileOutputStream fos = null;
if (httpURLConnection.getResponseCode() == 200) {
in = httpURLConnection.getInputStream();
//一定不能直接在FileOutputStream里面写文件名，需要添加路径
//错误的写法：fos = new FileOutputStream("a.bmp");
//下面存储到内部存储的私有的cache目录里面，注意了生成的文件名是cachea.bmp
fos = new FileOutputStream(getCacheDir().getPath()+"a.bmp");
byte[] arr = new byte[1024];
int len = 0;
//每次读取 1024个字节，如果读取返回为-1说明到了文件的末尾，结束读取
while ((len = in.read(arr)) != -1) {
fos.write(arr, 0, len);
}
//一定要记住要关闭读取流。
in.close();
fos.close();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
1：POST 请求
package tech.androidstudio.readfileshttpurlconnection;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;
public class MainActivity extends AppCompatActivity implements Runnable {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Thread thread = new Thread(this);
// thread.start();
URL url = null;
try {
//定义存储要提交的数据的Map
//如果 仅仅是为了测试那么直接使用
//测试的请求+++++++++++++开始+++++++++++++++
//StringBuilder sb = new StringBuilder("username=哈哈&password=psw");
//测试的请求++++++++++++++结束++++++++++++++
//如果为了模拟真实的请求，那么就使用下面的
//模拟真实的请求+++++++++++++开始+++++++++++++++
HashMap params = new HashMap();
params.put("username", "哈哈");
params.put("password", "psw");
//把要提交的 数据类型定义为 username=哈哈&password=psw的格式
StringBuilder sb = new StringBuilder();
//通过Map的遍历的到
for(Map.Entry en:params.entrySet()){
sb.append(en.getKey())
.append("=")
.append(URLEncoder.encode(en.getValue(), "utf-8"))
.append("&");
}
//删除最后一个&,注意 这里是 length-1，因为是从0开始计数的。
sb.deleteCharAt(sb.length()-1);
//模拟真实的请求++++++++++++++结束++++++++++++++
url = new URL("http://192.168.1.106:8080/ServerDemo/servlet/LoginServlert");
HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
urlConnection.setRequestMethod("POST");
urlConnection.setConnectTimeout(5000);
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);//设置可以向服务器传递数据
//设置提交的内容的类型
urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
//设置提交的内容的长度
byte[] data = sb.toString().getBytes("utf-8");//注意这里的编码utf-8
urlConnection.setRequestProperty("Content-Length", String.valueOf(data.length));
//提交数据
OutputStream outputStream = urlConnection.getOutputStream();
outputStream.write(data);
outputStream.close();
//判断服务器端的响应码是不是200
InputStream in = null;
if(urlConnection.getResponseCode()==200){
in = urlConnection.getInputStream();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] arr = new byte[1024];
int len=0;
while((len=in.read(arr))!=-1){
bos.write(arr,0,len);
}
byte[] b = bos.toByteArray();
String ss = new String(b,"utf-8");
Log.d("kodulf",ss);
}
//关闭流
in.close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void run() {
try {
//配置 HttpURLConnection
//TODO 这里的ip 地址一定不能使localhost 一定要是电脑的或者是正式ip地址.
//如果写成了localhost，那么就会报错java.net.ConnectException: localhost/127.0.0.1:8080 - Connection refused
//URL url = new URL("http://localhost:8080/tomcat.png");
URL url = new URL("http://192.168.1.106:8080/tomcat.png");
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("GET");
httpURLConnection.setConnectTimeout(5000);
//Sets the flag indicating whether this URLConnection allows input. It cannot be set after the connection is established.
httpURLConnection.setDoInput(true);
//获取返回的文件
InputStream in = null;
FileOutputStream fos = null;
if (httpURLConnection.getResponseCode() == 200) {
in = httpURLConnection.getInputStream();
//一定不能直接在FileOutputStream里面写文件名，需要添加路径
//错误的写法：fos = new FileOutputStream("a.bmp");
//下面存储到内部存储的私有的cache目录里面，注意了生成的文件名是cachea.bmp
fos = new FileOutputStream(getCacheDir().getPath()+"a.bmp");
byte[] arr = new byte[1024];
int len = 0;
//每次读取 1024个字节，如果读取返回为-1说明到了文件的末尾，结束读取
while ((len = in.read(arr)) != -1) {
fos.write(arr, 0, len);
}
//一定要记住要关闭读取流。
in.close();
fos.close();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
+++++++++++++++++++++++++++++++++++++++++++++
Post服务端的代码可以参考搭建与Android 交互的简单的网络服务端里面的第10步
或者参考下面的,主要就是doPost
import java.io.IOException;
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 LoginServlert extends HttpServlet {
/**
* Constructor of the object.
*/
public LoginServlert() {
super();
}
/**
* Destruction of the servlet.
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet.
*
* This method is called when a form has its tag value method equals to get.
*
* @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 doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("");
out.println("");
out.println(" A Servlet ");
out.println(" ");
out.print(" This is ");
out.print(this.getClass());
out.println(", using the GET method");
out.println(" ");
out.println("");
out.flush();
out.close();
}
/**
* The doPost method of the servlet.
*
* 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");
PrintWriter out = response.getWriter();
request.setCharacterEncoding("utf-8");//请求方式是 post
//先得到客户端提交的用户名和密码
//因为客户端信息被封装在 request对象中，所以需要从request对象中获取用户名密码
String uname = request.getParameter("username");//?username= &psw=
//String uname = fun(name);
String psw = request.getParameter("password");
//验证
if(uname!=null&&uname.trim()!=""&&psw!=null&&psw.trim()!="")
{
if("哈哈".equals(uname) && "123".equals(psw))
{
out.println("登陆成功");
}
else
out.println("登陆失败");
}else{
out.println("参数有问题");
}
out.flush();
out.close();
/**
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("");
out.println("");
out.println(" A Servlet ");
out.println(" ");
out.print(" This is ");
out.print(this.getClass());
out.println(", using the POST method");
out.println(" ");
out.println("");
out.flush();
out.close();
*/
}
/**
* Initialization of the servlet.
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}