Android 实现http通信（servlet做服务器端) HttpClient、HttpURLConnection实现登录验证

一，写好服务器端

　　在eclipse或其它javaee开发工具中新建一个web项目(我这里的项目名是：Android)，建一个servlet（我这里的servlet名是:LoginServlet），模拟实现数据库，对安卓请求的数据判断，并返回（封装为json，需要json有解析json的jar包哦），servlet核心代码如下：

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        doPost(request, response);
        
    }


    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        number++;
        System.out.println("已经进入... ,第"+number+"次");
        
        request.setCharacterEncoding("utf-8");
        String name="";
        String password = "";
        name = request.getParameter("name");
        password = request.getParameter("password");
        
        String result = "";
        //模拟数据库获取数据并判断
        if ("yyc".equals(name)&&"123456".equals(password)) {
            result="success";
        }else{
            result = "error";
        }
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("result", result);
        response.getWriter().print(jsonObject);
    }

　　写完了就可以发布在Tomcat服务器上（我们这里就写一个servlet就足够了），在浏览器中，访问试试，看不能访问，免得影响后续步骤的操作。测试链接，如：http://127.0.0.1:8080/Android/servlet/LoginServlet?name=yyc&password=123456

二、Android布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <EditText
        android:id="@+id/nameEdit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="点击输入用户名"
        android:inputType="text" />

    <EditText
        android:id="@+id/passwordEdit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="点击输入密码"
        android:inputType="numberPassword" />

    <Button
    android:id="@+id/login"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="登录（HttpClient)" />

    <Button
        android:id="@+id/login1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登录(HttpURLConnection)" />

</LinearLayout>

　　从布局文件中可以看出写了两个输入框，一个输入用户名，一个输密码，两个按钮，一个用于测试HttpClient通信，一个用于测试HttpURLConnection通信。我们先来实现HttpClient吧。

三、用HttpClient实现登陆认证（不建议）

　　在这之前，先在Android模拟器的浏览器中，访问刚刚的地址，测试能不能访问，不要影响我们后面的程序。注意：这时不能通过localhost来访问了，通过ip，cmd输入ipconfig可以查看ip地址。

　　现在高版本的android要使用HttpClient的话，要在build.gradle（app）中的android标签中添加：useLibrary 'org.apache.http.legacy'，由于我们要访问网络，我们需要设置网络权限：在AndroidManifest.xml中加入网络权限：<uses-permission android:name="android.permission.INTERNET"/>

　　在android studio中新建一个类：HttpUtilsHttpClient

public class HttpUtilsHttpClient {
    //1.创建HttpClient对象
    private static HttpClient httpClient = new DefaultHttpClient();

    public static String BASE_URL= "http://你的ip地址:8080/Android";

    /**
     * GET方式
     * @param url
     * @return
     */
    public static String getRequest(String url){
        String result  = "";

        //2.创建HttpGet对象
        HttpGet httpGet= new HttpGet(url);
        try {
            //3.发送Get请求
            HttpResponse response = httpClient.execute(httpGet);
            if (response.getStatusLine().getStatusCode() == 200){
                //4.获取服务器返回的数据
                HttpEntity entity = response.getEntity();
                result  = EntityUtils.toString(entity);
            }

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

        return result ;
    }

    public static String postRequest(String url,Map<String,String> params){
        String result = "";

        HttpPost httpPost = new HttpPost(url);

        List<NameValuePair> parameters = new ArrayList<>();
        for (Map.Entry<String,String>  entry: params.entrySet()) {
            NameValuePair pair = new BasicNameValuePair(entry.getKey(),entry.getValue());
            parameters.add(pair);
        }
        try {
            httpPost.setEntity(new UrlEncodedFormEntity(parameters,"utf-8"));

            HttpResponse response = httpClient.execute(httpPost);
            if (response.getStatusLine().getStatusCode() == 200){
                //4.获取服务器返回的数据
                HttpEntity entity = response.getEntity();
                result  = EntityUtils.toString(entity);
            }
        }catch (IOException e) {
            e.printStackTrace();
        }

        return result;
    }
}

　　这个类总共两个方法getRequest故名思意就是Get请求，postRequest就是post方式请求，由于我们要传参数(name和password)，我们这里真正使用的是post请求。参数保存在一个map集合中。执行后返回String类型的参数，其实就是json字符串。

　　然后在MainActivity中调用PostRequest方法（设置url和参数），并对放回的String字符串(json)解析，做出相应的表现（Toast成功或者失败）;

private void loginButtonHttpClientOption() {
        loginButtonHttpClient.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        String url=HttpUtilsHttpClient.BASE_URL+"/servlet/LoginServlet";
                        Map<String ,String > params = new HashMap<String, String>();
                        String name=nameEdit.getText().toString();
                        String password=passwordEdit.getText().toString();
                        params.put("name",name);
                        params.put("password",password);
                        //请求，返回json
                        String result = HttpUtilsHttpClient.postRequest(url, params);
                        Message msg = new Message();
                        msg.what=0x11;
                        Bundle data=new Bundle();
                        data.putString("result",result);
                        msg.setData(data);


                        hander.sendMessage(msg);
                    }

                    Handler hander = new Handler(){
                        @Override
                        public void handleMessage(Message msg) {
                            if (msg.what==0x11){
                                Bundle data = msg.getData();
                                String key = data.getString("result");//得到json返回的json数据
//                                   Toast.makeText(MainActivity.this,key,Toast.LENGTH_LONG).show();
                                try {
                                    JSONObject json= new JSONObject(key);
                                    String result = (String) json.get("result");
                                    if ("success".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录成功",Toast.LENGTH_LONG).show();
                                    }else if("error".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录失败",Toast.LENGTH_LONG).show();
                                    }
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                }
                            }
                        }
                    };
                }).start();
            }
        });
    }

　　loginButtonHttpClientOption这个方法主要就是一个按钮的点击事件监听，设置url、获取EditText中的值后封装在map中后，我们就可以请求http了（调用HttpUtilsHttpClient.postRequest(url, params);)。
而Handler的作用是一般情况下，在主线程中我们绑定了Handler，并在事件触发上面创建新的线程用于完成某些耗时的操作（我们这里用线程访问了网络），当子线程中的工作完成之后，会对Handler发送一个完成的信号，
而Handler接收到信号后，就进行主UI界面的更新操作（我们这里直接判断并Toast）。对Handler和线程不理解的话，可以去百度搜搜其它技术贴看看。

四、使用HttpURLConnection实现登录验证（建议）
　　安卓建议我们使用这种方式，我们也不用修改build文件了，但还是需要在AndroidManifest.xml文件中加入网络权限：<uses-permission android:name="android.permission.INTERNET"/>

　　新建类：HttpUtilsHttpURLConnection

public class HttpUtilsHttpURLConnection {

    public static String BASE_URL= "http://你的ip地址:8080/Android";
    /*
     * urlStr:网址
     * parms：提交数据
     * return:网页源码
     * */
    public static  String getContextByHttp(String urlStr,Map<String,String> parms){
        StringBuilder sb = new StringBuilder();
        try{
            URL url = new URL(urlStr);
            HttpURLConnection connection = (HttpURLConnection)url.openConnection();
            connection.setRequestMethod("POST");
            connection.setReadTimeout(5000);
            connection.setConnectTimeout(5000);
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setInstanceFollowRedirects(true);

            OutputStream outputStream = connection.getOutputStream();
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
            writer.write(getStringFromOutput(parms));

            writer.flush();
            writer.close();
            outputStream.close();

            if(connection.getResponseCode() == HttpURLConnection.HTTP_OK){
                BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                String temp;
                while((temp = reader.readLine()) != null){
                    sb.append(temp);
                }
                reader.close();
            }else{
                return "connection error:" + connection.getResponseCode();
            }

            connection.disconnect();
        }catch (Exception e){
            return e.toString();
        }
        return sb.toString();
    }

    /**
     * 将map转换成key1=value1&key2=value2的形式
     * @param map
     * @return
     * @throws UnsupportedEncodingException
     */
    private static String getStringFromOutput(Map<String,String> map) throws UnsupportedEncodingException {
        StringBuilder sb = new StringBuilder();
        boolean isFirst = true;

        for(Map.Entry<String,String> entry:map.entrySet()){
            if(isFirst)
                isFirst = false;
            else
                sb.append("&");

            sb.append(URLEncoder.encode(entry.getKey(),"UTF-8"));
            sb.append("=");
            sb.append(URLEncoder.encode(entry.getValue(),"UTF-8"));
        }
        return sb.toString();
    }
}

　　这个和上面讲的那个HeepClient也没多大区别，有异曲同工之妙嘛。仔细店看看就懂了。
　　
点击事件监听代码：
　　这和上面的那个点击事件也是一样的啦，没什么好说的。同样的是设置url、获取EditText中的值后封装在map中后，请求http。返回数据并解析。

 private void loginButtonHttpURLConnectionOption() {
        loginButtonHttpURLConnection.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        String url=HttpUtilsHttpURLConnection.BASE_URL+"/servlet/LoginServlet";
                        Map<String, String> params = new HashMap<String, String>();
                        String name=nameEdit.getText().toString();
                        String password=passwordEdit.getText().toString();
                        params.put("name",name);
                        params.put("password",password);

                        String result = HttpUtilsHttpURLConnection.getContextByHttp(url,params);

                        Message msg = new Message();
                        msg.what=0x12;
                        Bundle data=new Bundle();
                        data.putString("result",result);
                        msg.setData(data);


                        hander.sendMessage(msg);
                    }

                    Handler hander = new Handler(){
                        @Override
                        public void handleMessage(Message msg) {
                            if (msg.what==0x12){
                                Bundle data = msg.getData();
                                String key = data.getString("result");//得到json返回的json
//                                   Toast.makeText(MainActivity.this,key,Toast.LENGTH_LONG).show();
                                try {
                                    JSONObject json= new JSONObject(key);
                                    String result = (String) json.get("result");
                                    if ("success".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录成功",Toast.LENGTH_LONG).show();
                                    }else if("error".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录失败",Toast.LENGTH_LONG).show();
                                    }
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                }
                            }
                        }
                    };
                }).start();
            }
        });
    }

效果图：

成功：                                                             失败：

                  

 最后贴上MainActivity的所有代码：

package com.yyc.webservice;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.HashMap;
import java.util.Map;

public class MainActivity extends AppCompatActivity {

    private EditText nameEdit,passwordEdit;
    private Button loginButtonHttpClient,loginButtonHttpURLConnection;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        init();
        loginButtonHttpClientOption();
        loginButtonHttpURLConnectionOption();

        
    }

    private void loginButtonHttpURLConnectionOption() {
        loginButtonHttpURLConnection.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        String url=HttpUtilsHttpURLConnection.BASE_URL+"/servlet/LoginServlet";
                        Map<String, String> params = new HashMap<String, String>();
                        String name=nameEdit.getText().toString();
                        String password=passwordEdit.getText().toString();
                        params.put("name",name);
                        params.put("password",password);

                        String result = HttpUtilsHttpURLConnection.getContextByHttp(url,params);

                        Message msg = new Message();
                        msg.what=0x12;
                        Bundle data=new Bundle();
                        data.putString("result",result);
                        msg.setData(data);


                        hander.sendMessage(msg);
                    }

                    Handler hander = new Handler(){
                        @Override
                        public void handleMessage(Message msg) {
                            if (msg.what==0x12){
                                Bundle data = msg.getData();
                                String key = data.getString("result");//得到json返回的json
//                                   Toast.makeText(MainActivity.this,key,Toast.LENGTH_LONG).show();
                                try {
                                    JSONObject json= new JSONObject(key);
                                    String result = (String) json.get("result");
                                    if ("success".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录成功",Toast.LENGTH_LONG).show();
                                    }else if("error".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录失败",Toast.LENGTH_LONG).show();
                                    }
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                }
                            }
                        }
                    };
                }).start();
            }
        });
    }

    private void loginButtonHttpClientOption() {
        loginButtonHttpClient.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        String url=HttpUtilsHttpClient.BASE_URL+"/servlet/LoginServlet";
                        Map<String ,String > params = new HashMap<String, String>();
                        String name=nameEdit.getText().toString();
                        String password=passwordEdit.getText().toString();
                        params.put("name",name);
                        params.put("password",password);
                        //请求，返回json
                        String result = HttpUtilsHttpClient.postRequest(url, params);
                        Message msg = new Message();
                        msg.what=0x11;
                        Bundle data=new Bundle();
                        data.putString("result",result);
                        msg.setData(data);


                        hander.sendMessage(msg);
                    }

                    Handler hander = new Handler(){
                        @Override
                        public void handleMessage(Message msg) {
                            if (msg.what==0x11){
                                Bundle data = msg.getData();
                                String key = data.getString("result");//得到json返回的json
//                                   Toast.makeText(MainActivity.this,key,Toast.LENGTH_LONG).show();
                                try {
                                    JSONObject json= new JSONObject(key);
                                    String result = (String) json.get("result");
                                    if ("success".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录成功",Toast.LENGTH_LONG).show();
                                    }else if("error".equals(result)){
                                        Toast.makeText(MainActivity.this,"登录失败",Toast.LENGTH_LONG).show();
                                    }
                                } catch (JSONException e) {
                                    e.printStackTrace();
                                }
                            }
                        }
                    };
                }).start();
            }
        });
    }

    private void init() {
        nameEdit = (EditText) findViewById(R.id.nameEdit);
        passwordEdit = (EditText) findViewById(R.id.passwordEdit);
        loginButtonHttpClient = (Button) findViewById(R.id.login);
        loginButtonHttpURLConnection= (Button) findViewById(R.id.login1);
    }
}

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