Android后台数据接口交互实现注册功能

　　首先，在ecplise里面新建一个叫做TestServices的web工程。在WebContent--WEB-INF--libs文件夹下导入两个jar包：mysql-connector-java-6.0.2和gson-2.3.1

mysql-connector-java-6.0.2下载链接：https://pan.baidu.com/s/1eRMByB9ERVC_T51ZBw5Q8Q 提取码: th9l

gson-2.3.1下载链接：https://pan.baidu.com/s/1NpYioUbOJTj8B1idDVupqQ提取码: 9ir9

mysql数据库表如下：

源代码如下：

DBUtils.java：

package com.xhj.db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DBUtils {
    private Connection conn;
    private String url = "jdbc:mysql://127.0.0.1:3306/test?serverTimezone=UTC"; // 指定连接数据库的URL
    private String user = "root"; // 指定连接数据库的用户名
    private String password = ""; // 指定连接数据库的密码
    private Statement sta;
    private ResultSet rs; // 打开数据库连接

    public void openConnect() {
        try {
            // 加载数据库驱动
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(url, user, password);// 创建数据库连接
            if (conn != null) {
                System.out.println("数据库连接成功"); // 连接成功的提示信息
            }
        } catch (Exception e) {
            System.out.println("ERROR: " + e.getMessage());
        }
    }

    // 获得查询user表后的数据集
    public ResultSet getUser() {
        // 创建 statement对象
        try {
            sta = conn.createStatement(); // 执行SQL查询语句
            rs = sta.executeQuery("select * from user");
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return rs;
    }

    // 判断数据库中是否存在某个用户名及其密码,注册和登录的时候判断
    public boolean isExistInDB(String username, String password) {
        boolean isFlag = false; // 创建 statement对象
        try {
            System.out.println("判断用户名密码");
            sta = conn.createStatement(); // 执行SQL查询语句
            rs = sta.executeQuery("select * from user");// 获得结果集
            if (rs != null) {
                while (rs.next()) { // 遍历结果集
                    if (rs.getString("user_name").equals(username)) {
                        if (rs.getString("user_pwd").equals(password)) {
                            isFlag = true;
                            break;
                        }
                    }
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
            isFlag = false;
        }
        return isFlag;

    }

    // 注册 将用户名和密码插入到数据库(id设置的是自增长的，因此不需要插入)
    public boolean insertDataToDB(String username, String password) {
        String sql = " insert into user ( user_name , user_pwd ) values ( " + "'" + username + "', " + "'" + password
                + "' )";
        try {
            sta = conn.createStatement();
            // 执行SQL查询语句
            return sta.execute(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    // 关闭数据库连接
    public void closeConnect() {
        try {
            if (rs != null) {
                rs.close();
            }
            if (sta != null) {
                sta.close();
            }
            if (conn != null) {
                conn.close();
            }
            System.out.println("关闭数据库连接成功");
        } catch (SQLException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }

}

BaseBean.java：

package com.xhj.domain;

public class BaseBean {
    private int code;
    private String msg;
    private Object data;

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }

}

UserBean.java：

package com.xhj.domain;

import java.io.Serializable;

public class UserBean implements Serializable{

    private int id;
    private String username;
    private String password;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }

}

LoginDateServlet.java：

package com.xhj.servlet;

import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;

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

import com.google.gson.Gson;
import com.xhj.db.DBUtils;
import com.xhj.domain.BaseBean;
import com.xhj.domain.UserBean;

public class LoginDateServlet extends HttpServlet {

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

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("request--->"+request.getRequestURL()+"===="+request.getParameterMap().toString());
        String username = request.getParameter("username"); // 获取客户端传过来的参数
        String password = request.getParameter("password");
        response.setContentType("text/html;charset=utf-8");
        if (username == null || username.equals("") || password == null || password.equals("")) {
            System.out.println("用户名或密码为空");
            return;
        } // 请求数据库
        DBUtils dbUtils = new DBUtils();
        dbUtils.openConnect();
        // 打开数据库连接
        BaseBean data = new BaseBean(); // 基类对象，回传给客户端的json对象
        UserBean userBean = new UserBean(); // user的对象
        if (dbUtils.isExistInDB(username, password)) {
            // 判断账号是否存在
            data.setCode(-1);
            data.setData(userBean);
            data.setMsg("该账号已存在");
        } else if (!dbUtils.insertDataToDB(username, password)) {
            // 注册成功
            data.setCode(0);
            data.setMsg("注册成功!!");
            ResultSet rs = dbUtils.getUser();
            int id = -1;
            if (rs != null) {
                try {
                    while (rs.next()) {
                        if (rs.getString("user_name").equals(username)
                                && rs.getString("user_pwd").equals(password)) {
                            id = rs.getInt("user_id");
                        }
                    }
                    userBean.setId(id);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            userBean.setUsername(username);
            userBean.setPassword(password);
            data.setData(userBean);
        } else {
            // 注册不成功，这里错误没有细分，都归为数据库错误
            data.setCode(500);
            data.setData(userBean);
            data.setMsg("数据库错误");
        }
        Gson gson = new Gson();
        String json = gson.toJson(data);
        // 将对象转化成json字符串
        try {
            response.getWriter().println(json);
            // 将json数据传给客户端
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            response.getWriter().close(); // 关闭这个流，不然会发生错误的
        }
        dbUtils.closeConnect(); // 关闭数据库连接}
    }

}

web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
    id="WebApp_ID" version="3.0">
  <display-name>TestServices</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  
    <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
        <servlet-name>LoginDateServlet</servlet-name>
    <servlet-class>com.xhj.servlet.LoginDateServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>LoginDateServlet</servlet-name>
    <url-pattern>/servlet/LoginDateServlet</url-pattern>
  </servlet-mapping>
  
</web-app>

　　 到这里，点击LoginDateServlet.java，运行一下

因为我们没有传输用户名和密码，所以输出用户名或密码为空。

可以这样测试一下，在地址后面添加?username=123&password=123

可以看到，注册成功，数据已经保存到了数据库中

接下来需要在Android Studio里面，新建一个叫做TestNet的工程

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.testnet.MainActivity">

    <EditText
        android:id="@+id/et_data_uname"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入用户名：" />

    <EditText
        android:id="@+id/et_data_upass"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入密码："
        android:inputType="number" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="loginGET"
        android:text="注册（GET）" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="loginPOST"
        android:text="注册（POST）" />
</LinearLayout>

activity_main.java:

package com.example.testnet;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;

import androidx.appcompat.app.AppCompatActivity;

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;

public class MainActivity extends AppCompatActivity {

    String TAG = MainActivity.class.getCanonicalName();
    private EditText et_data_uname;
    private EditText et_data_upass;
    private HashMap<String, String> stringHashMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_data_uname = (EditText) findViewById(R.id.et_data_uname);
        et_data_upass = (EditText) findViewById(R.id.et_data_upass);
        stringHashMap = new HashMap<>();
    }

    public void loginGET(View view) {
        stringHashMap.put("username", et_data_uname.getText().toString());
        stringHashMap.put("password", et_data_upass.getText().toString());
        new Thread(getRun).start();

    }

    public void loginPOST(View view) {
        stringHashMap.put("username", et_data_uname.getText().toString());
        stringHashMap.put("password", et_data_upass.getText().toString());

        new Thread(postRun).start();
    }

    /**
     * get请求线程
     */
    Runnable getRun = new Runnable() {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            requestGet(stringHashMap);
        }
    };
    /**
     * post请求线程
     */
    Runnable postRun = new Runnable() {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            requestPost(stringHashMap);
        }
    };

    /**
     * get提交数据
     *
     * @param paramsMap
     */
    private void requestGet(HashMap<String, String> paramsMap) {
        try {
            String baseUrl = "http://10.0.2.2:8080/TestServices/servlet/LoginDateServlet?";
            StringBuilder tempParams = new StringBuilder();
            int pos = 0;
            for (String key : paramsMap.keySet()) {
                if (pos > 0) {
                    tempParams.append("&");
                }
                tempParams.append(String.format("%s=%s", key, URLEncoder.encode(paramsMap.get(key), "utf-8")));
                pos++;
            }

            Log.e(TAG,"params--get-->>"+tempParams.toString());
            String requestUrl = baseUrl + tempParams.toString();
            // 新建一个URL对象
            URL url = new URL(requestUrl);
            // 打开一个HttpURLConnection连接
            HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
            // 设置连接主机超时时间
            urlConn.setConnectTimeout(5 * 1000);
            //设置从主机读取数据超时
            urlConn.setReadTimeout(5 * 1000);
            // 设置是否使用缓存  默认是true
            urlConn.setUseCaches(true);
            // 设置为Post请求
            urlConn.setRequestMethod("GET");
            //urlConn设置请求头信息
            //设置请求中的媒体类型信息。
            urlConn.setRequestProperty("Content-Type", "application/json");
            //设置客户端与服务连接类型
            urlConn.addRequestProperty("Connection", "Keep-Alive");
            // 开始连接
            urlConn.connect();
            // 判断请求是否成功
            if (urlConn.getResponseCode() == 200) {
                // 获取返回的数据
                String result = streamToString(urlConn.getInputStream());
                Log.e(TAG, "Get方式请求成功，result--->" + result);
            } else {
                Log.e(TAG, "Get方式请求失败");
            }
            // 关闭连接
            urlConn.disconnect();
        } catch (Exception e) {
            Log.e(TAG, e.toString());
        }
    }

    /**
     * post提交数据
     *
     * @param paramsMap
     */
    private void requestPost(HashMap<String, String> paramsMap) {
        try {
            String baseUrl = "http://10.0.2.2:8080/TestServices/servlet/LoginDateServlet";
            //合成参数
            StringBuilder tempParams = new StringBuilder();
            int pos = 0;
            for (String key : paramsMap.keySet()) {
                if (pos >0) {
                    tempParams.append("&");
                }
                tempParams.append(String.format("%s=%s", key, URLEncoder.encode(paramsMap.get(key), "utf-8")));
                pos++;
            }
            String params = tempParams.toString();
            Log.e(TAG,"params--post-->>"+params);
            // 请求的参数转换为byte数组
//            byte[] postData = params.getBytes();
            // 新建一个URL对象
            URL url = new URL(baseUrl);
            // 打开一个HttpURLConnection连接
            HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
            // 设置连接超时时间
            urlConn.setConnectTimeout(5 * 1000);
            //设置从主机读取数据超时
            urlConn.setReadTimeout(5 * 1000);
            // Post请求必须设置允许输出 默认false
            urlConn.setDoOutput(true);
            //设置请求允许输入 默认是true
            urlConn.setDoInput(true);
            // Post请求不能使用缓存
            urlConn.setUseCaches(false);
            // 设置为Post请求
            urlConn.setRequestMethod("POST");
            //设置本次连接是否自动处理重定向
            urlConn.setInstanceFollowRedirects(true);
            //配置请求Content-Type
//            urlConn.setRequestProperty("Content-Type", "application/json");//post请求不能设置这个
            // 开始连接
            urlConn.connect();

            // 发送请求参数
            PrintWriter dos = new PrintWriter(urlConn.getOutputStream());
            dos.write(params);
            dos.flush();
            dos.close();
            // 判断请求是否成功
            if (urlConn.getResponseCode() == 200) {
                // 获取返回的数据
                String result = streamToString(urlConn.getInputStream());
                Log.e(TAG, "Post方式请求成功，result--->" + result);
            } else {
                Log.e(TAG, "Post方式请求失败");
            }
            // 关闭连接
            urlConn.disconnect();
        } catch (Exception e) {
            Log.e(TAG, e.toString());
        }
    }

    /**
     * 将输入流转换成字符串
     *
     * @param is 从网络获取的输入流
     * @return
     */
    public String streamToString(InputStream is) {
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[1024];
            int len = 0;
            while ((len = is.read(buffer)) != -1) {
                baos.write(buffer, 0, len);
            }
            baos.close();
            is.close();
            byte[] byteArray = baos.toByteArray();
            return new String(byteArray);
        } catch (Exception e) {
            Log.e(TAG, e.toString());
            return null;
        }
    }

    /**
     * 文件下载
     *
     * @param fileUrl
     */
    private void downloadFile(String fileUrl) {
        try {
            // 新建一个URL对象
            URL url = new URL(fileUrl);
            // 打开一个HttpURLConnection连接
            HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
            // 设置连接主机超时时间
            urlConn.setConnectTimeout(5 * 1000);
            //设置从主机读取数据超时
            urlConn.setReadTimeout(5 * 1000);
            // 设置是否使用缓存  默认是true
            urlConn.setUseCaches(true);
            // 设置为Post请求
            urlConn.setRequestMethod("GET");
            //urlConn设置请求头信息
            //设置请求中的媒体类型信息。
            urlConn.setRequestProperty("Content-Type", "application/json");
            //设置客户端与服务连接类型
            urlConn.addRequestProperty("Connection", "Keep-Alive");
            // 开始连接
            urlConn.connect();
            // 判断请求是否成功
            if (urlConn.getResponseCode() == 200) {
                String filePath = "";//下载文件保存在本地的地址
                File descFile = new File(filePath);
                FileOutputStream fos = new FileOutputStream(descFile);
                ;
                byte[] buffer = new byte[1024];
                int len;
                InputStream inputStream = urlConn.getInputStream();
                while ((len = inputStream.read(buffer)) != -1) {
                    // 写到本地
                    fos.write(buffer, 0, len);
                }
            } else {
                Log.e(TAG, "文件下载失败");
            }
            // 关闭连接
            urlConn.disconnect();
        } catch (Exception e) {
            Log.e(TAG, e.toString());
        }
    }

    /**
     * 文件上传
     *
     * @param filePath
     * @param paramsMap
     */
    private void upLoadFile(String filePath, HashMap<String, String> paramsMap) {
        try {
            String baseUrl = "https://xxx.com/uploadFile";
            File file = new File(filePath);
            //新建url对象
            URL url = new URL(baseUrl);
            //通过HttpURLConnection对象,向网络地址发送请求
            HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
            //设置该连接允许读取
            urlConn.setDoOutput(true);
            //设置该连接允许写入
            urlConn.setDoInput(true);
            //设置不能适用缓存
            urlConn.setUseCaches(false);
            //设置连接超时时间
            urlConn.setConnectTimeout(5 * 1000);   //设置连接超时时间
            //设置读取超时时间
            urlConn.setReadTimeout(5 * 1000);   //读取超时
            //设置连接方法post
            urlConn.setRequestMethod("POST");
            //设置维持长连接
            urlConn.setRequestProperty("connection", "Keep-Alive");
            //设置文件字符集
            urlConn.setRequestProperty("Accept-Charset", "UTF-8");
            //设置文件类型
            urlConn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + "*****");
            String name = file.getName();
            DataOutputStream requestStream = new DataOutputStream(urlConn.getOutputStream());
            requestStream.writeBytes("--" + "*****" + "\r\n");
            //发送文件参数信息
            StringBuilder tempParams = new StringBuilder();
            tempParams.append("Content-Disposition: form-data; name=\"" + name + "\"; filename=\"" + name + "\"; ");
            int pos = 0;
            int size = paramsMap.size();
            for (String key : paramsMap.keySet()) {
                tempParams.append(String.format("%s=\"%s\"", key, paramsMap.get(key), "utf-8"));
                if (pos < size - 1) {
                    tempParams.append("; ");
                }
                pos++;
            }
            tempParams.append("\r\n");
            tempParams.append("Content-Type: application/octet-stream\r\n");
            tempParams.append("\r\n");
            String params = tempParams.toString();
            requestStream.writeBytes(params);
            //发送文件数据
            FileInputStream fileInput = new FileInputStream(file);
            int bytesRead;
            byte[] buffer = new byte[1024];
            DataInputStream in = new DataInputStream(new FileInputStream(file));
            while ((bytesRead = in.read(buffer)) != -1) {
                requestStream.write(buffer, 0, bytesRead);
            }
            requestStream.writeBytes("\r\n");
            requestStream.flush();
            requestStream.writeBytes("--" + "*****" + "--" + "\r\n");
            requestStream.flush();
            fileInput.close();
            int statusCode = urlConn.getResponseCode();
            if (statusCode == 200) {
                // 获取返回的数据
                String result = streamToString(urlConn.getInputStream());
                Log.e(TAG, "上传成功，result--->" + result);
            } else {
                Log.e(TAG, "上传失败");
            }
        } catch (IOException e) {
            Log.e(TAG, e.toString());
        }
    }

}

在TestNet--app--src--main--AndroidMainifest.xml中添加

<uses-permission android:name="android.permission.INTERNET" />

参考文章：https://blog.csdn.net/qq_34317125/article/details/80533685