使用Android和Servlet實現簡單交互（客戶端服務器模式）

本文介紹瞭如何使用Android與Servlet進行簡單交互，使App擁有自己的服務器。本文的技術主要是使用網絡連接來實現交互。

1.Android從服務器中下載字符串

Android端：

    /**
     * 接收服務端發送的字符串
     */
    private void getDownStr(final String s) {
        //android中無法進行耗時操作，這個操作應放在線程中
        new Thread(){
            @Override
            public void run() {

                    //從網絡上獲取str
                URL url= null;
                try {
                    url = new URL(s);
                    Log.e("a",s);
                    //獲取網絡輸入流
                     URLConnection  urlConnection=url.openConnection();
                    InputStream in= urlConnection.getInputStream();
                    Log.e("msg","出錯了");
                    //創建字符流讀取數據
                    BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(in, "utf-8"));
                    String str=bufferedReader.readLine();
                    Log.e("str",str);
                    //關閉流
                    bufferedReader.close();
                    in.close();
                    //子線程無法更改UI界面，這裏使用Handler+Message的方式進行交互
                    //創建Message對象
                    Message message=new Message();
                    message.what=1;
                    message.obj=str;
                    //發送message
                    handler.sendMessage(message);

                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }

        }.start();

    }

服務器端：

package net.xyz.connandroid;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 向客戶端傳輸字符串
 * @author lenovo
 *
 */
@WebServlet("/DownStr")
public class DownStr extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DownStr() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//設置編碼方式
	    response.setContentType("text/html;charset=utf-8");
		String str="張三：123456";
		//獲取PrinterWriter對象
		PrintWriter printWriter=response.getWriter();
		//向客戶端發送數據
		printWriter.write(str);
		System.out.println("字符串發送完畢");
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

2.Android從服務器端下載圖片

android：

/**
     * 接收服務端發送的圖片
     */
    private void getDownImg(final String s ) {
        new Thread(){
            @Override
            public void run() {
                try {
                    //獲取網絡上的資源
                    URL url=new URL(s);
                    URLConnection urlConnection=url.openConnection();
                    InputStream in=urlConnection.getInputStream();
                    //把輸入流解析成一個Bitmap對象
                    Bitmap bitmap= BitmapFactory.decodeStream(in);
                    //用message將bitmap對象顯示在客戶端
                    Message message=new Message();
                    message.what=2;
                    message.obj=bitmap;
                    handler.sendMessage(message);
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }.start();
    }

服務器：

package net.xyz.connandroid;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 向客戶端發送圖片
 */
@WebServlet("/DownImgServlet")
public class DownImgServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DownImgServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
             //設置編碼方式
		  response.setContentType("text/html;charset=utf-8");
		  //獲取本地輸入流讀取圖片，輸出流發送圖片
		  FileInputStream in=new FileInputStream("D:\\學習\\圖片\\1.jpg");
		  OutputStream out=response.getOutputStream();
		  //用字節流讀取文件
		  int len=-1;
		  while((len=in.read())!=-1) {
			  out.write(len);
		  }
		  //關閉連接
		  out.close();
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

3.客戶端向服務器上傳鍵值對信息（以url的方式傳送）

Andorid端

    /**
     * 向服務器發送鍵值對信息
     */

    private void upKeyValue(final String s) {
        new Thread(){
            @Override
            public void run() {

                try {
                    //設置鍵值對信息
                    String keyValue="?name=張三&password=123";
                    Log.e("key",s+keyValue);
                    //獲取URL對象
                    URL url=new URL(s+keyValue);

                    //打開url連接
                    url.openStream();


                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }.start();
    }

服務器端：

package net.xyz.connandroid;

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;

/**
 * 接收客戶端發送的鍵值對信息
 */
@WebServlet("/UpKeyValueServlet")
public class UpKeyValueServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public UpKeyValueServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //設置編碼方式
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		//獲取上傳的鍵值對信息
		String name=request.getParameter("name");
		String password=request.getParameter("password");
		response.getWriter().write(name+":"+password);
		System.out.println(name+":"+password);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

4.向服務器上傳字符串信息

Android端：

  /**
     * 向服務器提交敏感字符信息
     */
    private void upStr(final String s) {
        new Thread(){
            @Override
            public void run() {

                try {
                    //使用URL和httpURLConnection進行網絡連接
                    URL url=new URL(s);
                    HttpURLConnection conn= (HttpURLConnection) url.openConnection();
                    //設置編碼方式
                    conn.setRequestMethod("POST");

                    //獲取網絡輸出流
                    OutputStream outputStream=conn.getOutputStream();
                    //獲取待發送的字符串
                    String str=editText.getText().toString().trim();
                    outputStream.write(str.getBytes());
                    //必須要獲取網絡輸入流保證客戶端與服務端建立連接
                    conn.getInputStream();
                    outputStream.close();
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }.start();
    }

服務器端：

package net.xyz.connandroid;

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;

/**
 * 接收客戶端發送的敏感字符串
 */
@WebServlet("/UpStr")
public class UpStr extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public UpStr() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       //設置編碼方式
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		//獲取網絡輸入流
		InputStream in=request.getInputStream();
		//用字符流讀取數據
		BufferedReader read=new BufferedReader(new InputStreamReader(in,"utf-8"));
		String str=read.readLine();
		if(str!=null) {
			response.getWriter().write(str);
		}
		System.out.println(str);
		in.close();
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

5.向服務器端上傳圖片
Android端：

 /**
     * 向服務端上傳圖片信息
     * @param s
     */
    private void UpImg(final String s) {
        new Thread(){
            @Override
            public void run() {
                try {
                    URL url=new URL(s);
                    HttpURLConnection conn= (HttpURLConnection) url.openConnection();
                    //設置編碼方式
                    conn.setRequestMethod("POST");
                    //獲取輸入流
                    InputStream in=getResources().openRawResource(R.raw.fish);
                    //獲取網絡輸出流
                    OutputStream out=conn.getOutputStream();
                    //循環讀寫
                    int len=-1;
                    while((len=in.read())!=-1){
                        out.write(len);
                    }
                    //獲取連接
                    conn.getInputStream();
                    //關閉流
                    in.close();
                    out.close();
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }.start();
    }

服務器端：

package net.xyz.connandroid;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 獲取客戶端上傳的圖片
 */
@WebServlet("/UpImg")
public class UpImg extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public UpImg() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         //設置編碼方式
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		String path=this.getServletContext().getRealPath("/");
		//獲取網絡輸入流
		InputStream in=request.getInputStream();
		//獲取本地輸出流
		OutputStream out=new FileOutputStream(path+"b.jpg");
		//循環讀寫
		int len=-1;
		while((len=in.read())!=-1) {
			out.write(len);
		}
		//關閉流
		out.close();
		System.out.println("圖片接收完畢");
		response.getWriter().write("OK");
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}